Gymnastik- och idrottshögskolan, GIH

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  • 1.
    Askling, Carl M
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tengvar, Magnus
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Acute hamstring injuries in Swedish elite sprinters and jumpers: a prospective randomised controlled clinical trial comparing two rehabilitation protocols.2014In: British Journal of Sports Medicine, ISSN 0306-3674, E-ISSN 1473-0480, Vol. 48, no 7, p. 532-9Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Hamstring strain is a common injury in sprinters and jumpers, and therefore time to return to sport and secondary prevention become of particular concern.

    OBJECTIVE: To compare the effectiveness of two rehabilitation protocols after acute hamstring injury in Swedish elite sprinters and jumpers by evaluating time needed to return to full participation in the training process.

    STUDY DESIGN: Prospective randomised comparison of two rehabilitation protocols.

    METHODS: Fifty-six Swedish elite sprinters and jumpers with acute hamstring injury, verified by MRI, were randomly assigned to one of two rehabilitation protocols. Twenty-eight athletes were assigned to a protocol emphasising lengthening exercises, L-protocol, and 28 athletes to a protocol consisting of conventional exercises, C-protocol. The outcome measure was the number of days to return to full training. Re-injuries were registered during a period of 12 months after return.

    RESULTS: Time to return was significantly shorter for the athletes in the L-protocol, mean 49 days (1SD±26, range 18-107 days), compared with the C-protocol, mean 86 days (1SD±34, range 26-140 days). Irrespective of protocol, hamstring injuries where the proximal free tendon was involved took a significantly longer time to return than injuries that did not involve the free tendon, L-protocol: mean 73 vs 31 days and C-protocol: mean 116 vs 63 days, respectively. Two reinjuries were registered, both in the C-protocol.

    CONCLUSIONS: A rehabilitation protocol emphasising lengthening type of exercises is more effective than a protocol containing conventional exercises in promoting time to return in Swedish elite sprinters and jumpers.

  • 2.
    Bjerkefors, Anna
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Rosén, Johanna S
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Three-Dimensional Kinematics and Power Output in Elite Para-Kayakers and Elite Able-Bodied Flat-Water Kayakers.2019In: Journal of Applied Biomechanics, ISSN 1065-8483, E-ISSN 1543-2688, p. 93-100Article in journal (Refereed)
    Abstract [en]

    Trunk, pelvis and leg movement are important for performance in sprint kayaking. Para-kayaking is a new Paralympic sport in which athletes with trunk and/or leg impairment compete in three classification groups. The purpose of this study was to identify how physical impairments impact on performance by examining: differences in three-dimensional joint range of motion (RoM) between 10 (4 females, 6 males) elite able-bodied kayakers and 41 (13 females, 28 males) elite para-kayakersfrom the three classification groups, and which joint angles were correlated with power output during high intensity kayak ergometer paddling. There were significant differences in RoM between the able-bodied kayakers and the three para-kayak groups for the shoulders (flexion, rotation: able-bodied kayakers<para-kayakers), trunk and pelvis (rotation: able-bodied kayakers>para-kayakers) and legs (hip, knee, ankle flexion: able-bodied kayakers>para-kayakers) during paddling. Furthermore, athletes with greater impairment exhibited lower trunk and leg RoM compared to those with less impairment. Significant positive correlations were observed for both males and females between power output and peak shoulder and trunk flexion, trunk and pelvis rotation RoM and hip, knee and ankle flexion RoM. This information is important for understanding how key kinematic and kinetic variables for para-kayaking performance vary between athletes from different classification groups.

  • 3.
    Bjerkefors, Anna
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Rosén, Johanna S
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Zakaria, Pascal
    Swedish School of Sport and Health Sciences, GIH.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Three-dimensional kinematic analysis and power output of elite flat-water kayakers.2018In: Sports Biomechanics, ISSN 1476-3141, E-ISSN 1752-6116, Vol. 17, no 3, p. 414-427Article in journal (Refereed)
    Abstract [en]

    The purpose was to examine power output and three-dimensional (3D) kinematic variables in the upper limbs, lower limbs and trunk in elite flat-water kayakers during kayak ergometer paddling. An additional purpose was to analyse possible changes in kinematics with increased intensity and differences between body sides. Six male and four female international level flat-water kayakers participated. Kinematic and kinetic data were collected during three tasks; low (IntL), high (IntH) and maximal (IntM) intensities. No differences were observed in any joint angles between body sides, except for shoulder abduction. Significantly greater range of motion (RoM) values were observed for IntH compared to IntL and for IntM compared to IntL in trunk and pelvis rotation, and in hip, knee and ankle flexion. The mean maximal power output was 610 ± 65 and 359 ± 33 W for the male and female athletes, respectively. The stroke frequencies were significantly different between all intensities (IntL 59.3 ± 6.3; IntH 108.0 ± 6.8; IntM 141.7 ± 18.4 strokes/min). The results showed that after a certain intensity level, the power output must be increased by other factors than increasing the joint angular RoM. This information may assist coaches and athletes to understand the relationship between the movement of the kayaker and the paddling power output.

  • 4.
    Bojsen-Møller, Emil
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Dunstan, D W
    Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    The effect of breaking up prolonged sitting on paired associative stimulation-induced plasticity.2020In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 238, p. 2497-2506Article in journal (Refereed)
    Abstract [en]

    Paired associative stimulation (PAS) can induce plasticity in the motor cortex, as measured by changes in corticospinal excitability (CSE). This effect is attenuated in older and less active individuals. Although a single bout of exercise enhances PAS-induced plasticity in young, physically inactive adults, it is not yet known if physical activity interventions affect PAS-induced neuroplasticity in middle-aged inactive individuals. Sixteen inactive middle-aged office workers participated in a randomized cross-over design investigating how CSE and short-interval intracortical inhibition (SICI) were affected by PAS preceded by 3 h of sitting (SIT), 3 h of sitting interrupted every 30 min by 3 min of frequent short bouts of physical activity (FPA) and 2.5 h of sitting followed by 25 min of moderate-intensity exercise (EXE). Transcranial magnetic stimulation was applied over the primary motor cortex (M1) of the dominant abductor pollicis brevis to induce recruitment curves before and 5 min and 30 min post-PAS. Linear mixed models were used to compare changes in CSE using time and condition as fixed effects and subjects as random effects. There was a main effect of time on CSE and planned within-condition comparisons showed that CSE was significantly increased from baseline to 5 min and 30 min post-PAS, in the FPA condition, with no significant changes in the SIT or EXE conditions. SICI decreased from baseline to 5 min post-PAS, but this was not related to changes in CSE. Our findings suggest that in middle-aged inactive adults, FPAs may promote corticospinal neuroplasticity. Possible mechanisms are discussed.

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  • 5.
    Bojsen-Møller, Emil
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Activity breaks during prolonged sitting enhance responses to paired associative stimulation2019In: Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation, Volume 12, Issue 2, 466, Elsevier, 2019, Vol. 12, no 2Conference paper (Refereed)
  • 6.
    Crommert, Martin Eriksson
    et al.
    Örebro University.
    Bjerkefors, Anna
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ekblom, Maria M
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Abdominal Muscle Activation During Common Modifications of the Trunk Curl-Up Exercise.2021In: Journal of Strength and Conditioning Research, ISSN 1064-8011, E-ISSN 1533-4287, Vol. 35, no 2, p. 428-435Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to investigate effects of common modifications of trunk curl-up exercise on the involvement of the abdominal muscles, particularly the deepest muscle layer, transversus abdominis (TrA). Ten healthy females performed five different variations of the trunk curl-up at a standardized speed, varying the exercise by assuming three different arm positions and applying left and right twist. Indwelling fine-wire electromyography (EMG) electrodes were used to record from TrA, obliquus internus (OI), obliquus externus (OE) and rectus abdominis (RA) unilaterally on the right side. Increasing the load by changing the arm position during a straight trunk curl-up increased the EMG of all abdominal muscles. OI and TrA showed higher activation during right twist compared to left twist whereas OE displayed the opposite pattern. RA did not show any change in activation level between twisting directions. The apparent load dependency on the activation level of all muscles and the twisting direction dependency of all muscles except RA are in keeping with the fiber orientation of the muscles. Notably, also TrA, with a less obvious mechanical role with regards to fiber orientation, increased activation with load during the straight trunk curl-up. However, the highest activation level of TrA during the trunk curl-up was only 40 % of a maximum contraction, thus it might not be the most suitable strength training exercise for this muscle.

  • 7.
    da Silva, Julio Cézar Lima
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Rönquist, Gustaf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Grundström, Helene
    Danderyds Hospital.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Effect of increasing workload on knee extensor and flexor muscular activity during cycling as measured with intramuscular electromyography.2018In: PLOS ONE, E-ISSN 1932-6203, Vol. 13, no 8, article id e0201014Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to describe the effect of increasing workload on individual thigh muscle activation during a 20 minute incremental cycling test. Intramuscular electromyographic signals were recorded from the knee extensors rectus femoris, vastus lateralis, vastus medialis and vastus intermedius and the knee flexors semimembranosus, semitendinosus, and the short and long heads of the biceps femoris during increasing workloads. Mean activation levels were compared over the whole pedaling cycle and the crank angles at which onset and offset of activation and peak activity occurred were identified for each muscle. These data were compared between three workloads. EMG activation level significantly increased (p<0.05) with increasing workload in the rectus femoris, vastus medialis, vastus lateralis, vastus intermedius, biceps femoris long head, semitendinosus and semimembranosus but not in the biceps femoris short head. A significant change in activation timing was found for the rectus femoris, vastus lateralis, vastus medialis and semitendinosus. Of the knee flexors only the short head of the biceps femoris had its peak activity during the upstroke phase at the two highest workloads indicating a unique contribution to knee flexion.

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  • 8.
    da Silva, Julio Cézar Lima
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Rönquist, Gustaf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Quadriceps and hamstring muscle activity during cycling as measured with intramuscular electromyography.2016In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 116, no 9, p. 1807-1817Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The aim of this study was to describe thigh muscle activation during cycling using intramuscular electromyographic recordings of eight thigh muscles, including the biceps femoris short head (BFS) and the vastus intermedius (Vint).

    METHODS: Nine experienced cyclists performed an incremental test (start at 170 W and increased by 20 W every 2 min) on a bicycle ergometer either for a maximum of 20 min or to fatigue. Intramuscular electromyography (EMG) of eight muscles and kinematic data of the right lower limb were recorded during the last 20 s in the second workload (190 W). EMG data were normalized to the peak activity occurring during this workload. Statistical significance was assumed at p ≤ 0.05.

    RESULTS: The vastii showed a greater activation during the 1st quadrant compared to other quadrants. The rectus femoris (RF) showed a similar activation, but with two bursts in the 1st and 4th quadrants in three subjects. This behavior may be explained by the bi-articular function during the cycling movement. Both the BFS and Vint were activated longer than, but in synergy with their respective agonistic superficial muscles.

    CONCLUSION: Intramuscular EMG was used to verify muscle activation during cycling. The activation pattern of deep muscles (Vint and BFS) could, therefore, be described and compared to that of the more superficial muscles. The complex coordination of quadriceps and hamstring muscles during cycling was described in detail.

  • 9.
    Edwards, John
    et al.
    ICF Paracanoe Committee, Canada.
    Bjerkefors, Anna
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Rosén, Johanna S
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Paracanoe2019In: Canoeing / [ed] Don McKenzie, Bo Berglund, Hoboken, NJ: Wiley-Blackwell, 2019, p. 106-115Chapter in book (Other academic)
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  • 10.
    Ekblom, Maria
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska Institutet.
    Bojsen-Möller, Emil
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Day-to day variations in physical activity patterns affect corticospinal excitability on the following day2019In: Brain Stimulation March-April 2019, vol 12, issue 2, Elsevier, 2019, Vol. 12, no 2, p. 468-, article id 437Conference paper (Other academic)
  • 11.
    Ekblom, Maria
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden..
    Bojsen-Møller, Emil
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Blom, Victoria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Department of Psychology, Stockholm University, Stockholm, Sweden..
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Moberg, Marcus
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Pontén, Marjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Wang, Rui
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Acute effects of physical activity patterns on plasma cortisol and brain-derived neurotrophic factor in relation to corticospinal excitability.2022In: Behavioural Brain Research, ISSN 0166-4328, E-ISSN 1872-7549, Vol. 430, article id 113926Article in journal (Refereed)
    Abstract [en]

    Brain-derived neurotrophic factor (BDNF) and cortisol are both capable of modulating synaptic plasticity, but it is unknown how physical activity-induced changes in their plasma levels relate to corticospinal plasticity in humans. Sixteen inactive middle-aged men and women participated in three separate interventions consisting of 3hours prolonged sitting (SIT); 3hours sitting interrupted every 30minutes with frequent short physical activity breaks (FPA); and 2.5hours prolonged sitting followed by 25minutes of moderate intensity exercise (EXE). These 3hour sessions were each followed by a 30min period of paired associative stimulation over the primary motor cortex (PAS). Blood samples were taken and corticospinal excitability measured at baseline, pre PAS, 5min and 30min post PAS. Here we report levels of plasma BDNF and cortisol over three activity conditions and relate these levels to previously published changes in corticospinal excitability of a non-activated thumb muscle. There was no interaction between time and condition in BDNF, but cortisol levels were significantly higher after EXE compared to after SIT and FPA. Higher cortisol levels at pre PAS predicted larger increases in corticospinal excitability from baseline to all subsequent time points in the FPA condition only, while levels of BDNF at pre PAS did not predict such changes in any of the conditions. Neither BDNF nor cortisol modified changes from pre PAS to the subsequent time points, suggesting that the increased corticospinal excitability was not mediated though an augmented effect of the PAS protocol. The relationship between cortisol and plasticity has been suggested to be U-shaped. This is possibly why the moderately high levels of cortisol seen in the FPA condition were positively associated with changes AURC, while the higher cortisol levels seen after EXE were not. A better understanding of the mechanisms for how feasible physical activity breaks affect neuroplasticity can inform the theoretical framework for how work environments and schedules should be designed. DATA AVAILABILITY: Data are available from the corresponding author upon reasonable request.

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  • 12.
    Fernström, Maria
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Heiland, Emerald G
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Department of Surgical Sciences, Medical Epidemiology, Uppsala University Uppsala Sweden.
    Kjellenberg, Karin
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Pontén, Marjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Nyberg, Gisela
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Department of Global Public Health, Karolinska Institutet, Stockholm, Sweden.
    Helgadóttir, Björg
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Division of Insurance Medicine, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Effects of prolonged sitting and physical activity breaks on measures of arterial stiffness and cortisol in adolescents2023In: Acta Paediatrica, ISSN 0803-5253, E-ISSN 1651-2227, Vol. 112, no 5, p. 1011-1018Article in journal (Refereed)
    Abstract [en]

    Aim

    In adults, prolonged periods of sitting have been linked to acute negative effects on vascular structure and function. The aim of this study was to evaluate the acute effects of physical activity (PA) breaks during prolonged sitting on arterial stiffness, cortisol and psychological factors in adolescents.

    Methods

    Adolescents underwent different short (3-min) breaks starting every 20 min, during 80 min of sitting on three separate days. Breaks were (A) social seated breaks (SOC), (B) low-intensity simple resistance activity PA breaks (SRA) and (C) moderate-intensity step-up PA breaks (STEP). The arterial stiffness measures were augmentation index (AIx), AIx@75 and pulse wave velocity (PWV). Cortisol was measured from saliva. Psychological factors were self-reported.

    Results

    Eleven girls and six boys (average age 13.6 ± 0.7 years) participated, with average baseline heart rates of 72 ± 11 bpm, systolic/diastolic blood pressure 111 ± 7/64 ± 6 mmHg and cortisol 10.9 ± 5.8 nmoL/L. PWV, cortisol and psychological factors did not change after any of the conditions. AIx@75 increased significantly (4.9 ± 8.7–9.2 ± 13.2) after the STEP intervention compared with SOC and SRA (time × condition p < 0.05).

    Conclusion

    Arterial stiffness increased after prolonged sitting with frequent, short step-up activity breaks. The results indicate potential important intensity-dependent effects of physical activity on vascular regulation in youth.

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  • 13.
    Gago, Paulo
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ekblom, Maria M
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Post activation potentiation can be induced without impairing tendon stiffness.2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 11, p. 2299-2308Article in journal (Refereed)
    Abstract [en]

    PURPOSE: This study aimed to investigate conditioning effects from a single 6-s plantar flexion maximal voluntary isometric contraction (MVIC) on Achilles tendon stiffness (ATS) and twitch properties of the triceps surae in athletes.

    METHODS: Peak twitch (PT), rate of torque development (RTD), rising time (RT10-90%) and half relaxation time (HRT) were measured from supramaximal twitches evoked in the plantar flexors of 10 highly trained athletes. Twitches were evoked before and at seven occasions during 10 min of recovery after a 6-s MVIC. In a second session, but at identical post-conditioning time points, ATS was measured at 30 and 50 % of MVIC (ATS30% and ATS50%) using an ultrasonography-based method.

    RESULTS: The magnitude and duration of the conditioning MVIC on muscle contractile properties were in accordance with previous literature on post activation potentiation (PAP), i.e., high potentiation immediately after MVIC, with significant PAP for up to 3 min after the MVIC. While PT and RTD were significantly enhanced (by 60.6 ± 19.3 and 90.1 ± 22.5 %, respectively) and RT10-90% and HRT were reduced (by 10.1 ± 7.7 and 18.7 ± 5.6 %, respectively) after conditioning, ATS remained unaffected.

    CONCLUSIONS: Previous studies have suggested that changes in stiffness after conditioning may interfere with the enhancements in twitch contractile properties. The present study, however, provided some evidence that twitch enhancements after a standard PAP can be induced without changes in ATS. This result may suggest that athletes can use this protocol to enhance muscle contractile properties without performance deficits due to changes in ATS.

  • 14.
    Gago, Paulo
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Toni
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Post activation potentiation electromechanical delay and achilles tendon stiffness in athletes2014Conference paper (Refereed)
  • 15.
    Gago, Paulo
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Toni
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tarrassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Post activation potentiation and Achilles tendon stiffness in power athletes2013Conference paper (Refereed)
  • 16. Gullstrand, Lennart
    et al.
    Lindberg, Thomas
    Cardinale, Daniele
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology, Research group for Mitokondriell funktion och metabolisk kontroll.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Bjerkefors, Anna
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Validation of a kayak ergometer power output2013Conference paper (Refereed)
    Abstract [en]

    Introduction

    It is of a significant interest that ergometers used for evaluating elite athletes are valid and reliable. In this study the aim was to investigate how well displayed power output on a widely used kayak ergometer, DS, (Dansprint ApS, DK) related to a validation setup. Previously Gore et al. (2013) described the accuracy of 12 of the same ergometer using a motor driven calibration rig simulating power between 50 up to 450 W. They found that the ergometers underestimated true mean power with 21-23%. The reference rig simulated a 1 dimensional (1D) movement; this study however, is based on 3D analysis, which was hypothesized to better describe real paddling movement’s and allow more precise power calculations.

    Methods

    Two male national team kayakers took part in the study performing workloads from 70 up to 500 W (+30 W/stage) two times with 3 days between the measurement sessions. They were instructed to target the desired workloads displayed during 35 s bouts. The reference method included a ProReflex optoelectronic system (Qualisys AB, Gothenburg, Sweden) and force transducers (LCM 200, Futek Inc, Ca, US). The force transducers were connected with the rope from ergometer flywheel close to each end of the ergometer paddle to continuously measure force during the bouts of work. The kinematic set-up included eight cameras placed around the ergometer and two reflective markers were attached close to each force transducer.

    Results

    The reference method used here showed that the validated ergometer underestimated power with 37.7 % over the whole measured range compared to the reference method. The difference was systematic (r2=0.989) and the linear regression model could be applied (DS power = -2.362+0.628*x). When applying a 1D analysis of the collected data, it coincided with the results from Gore et al. (2013).

    Discussion

    The data suggest that 1. The measurement solution and/or calculation for describing power output in the DS have limitations. 2. The testing rig referred to in the Introduction (Gore et al. 2013) do not fully estimate true power and 3. The reference method used here is suggested to more exactly represent true paddling power as it includes a 3D movement analysis and close to original paddling simulation set-up. Both reference methods (1D and 3D analysis) show linear differences vs. the DS ergometer, giving an option to adjust the displayed power to a true power produced by elite-athletes.

  • 17.
    Hegyi, Andras
    et al.
    University of Jyväskylä, Finland.
    Peter, Annamaria
    University of Jyväskylä, Finland.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Finni, Taija
    University of Jyväskylä, Finland.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Cronin, Neil J.
    University of Jyväskylä, Finland.
    Ankle joint angle influences hamstring fine-wire and high-density electromyography activity in ramp isometric knee flexions2019Conference paper (Refereed)
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  • 18.
    Heiland, Emerald G
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Fernström, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    English, Coralie
    University of Newcastle, NSW, Australia..
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    ABBaH: Activity Breaks for Brain Health: A Protocol for a Randomized Crossover Trial2020In: Frontiers in Human Neuroscience, E-ISSN 1662-5161, Vol. 14, article id 273Article in journal (Refereed)
    Abstract [en]

    Introduction: Extended periods of sitting may have detrimental effects on brain health. However, the effects of breaking up prolonged sedentary periods with frequent, short physical activity bouts on mechanisms to improve brain health remain unclear. Therefore, this study aims to investigate the immediate effects of uninterrupted sitting and frequent, short bouts of physical activity on cerebral blood flow and cognitive function in the prefrontal cortex in middle-aged adults. Methods: This is a protocol article to describe a randomized crossover study. We will collect data from 13 healthy adults, aged between 40 and 60 years old, with a body mass index <35 kg/m(2). Participants will be required to come into the laboratory on three occasions, sit for 3 h, and perform a different type of break for 3 min every 30 min at each visit in a random order, being either: (1) a social break; (2) brisk walk on a treadmill; or (3) simple resistance activities. Before and after each experimental condition, cerebral blood flow (primary outcome) will be measured using functional near-infrared spectroscopy (fNIRS), with short-separation channels, and working memory (1-, 2-, and 3-back on the computer) will be assessed. The following additional secondary outcomes will be collected: psychological factors (questionnaires); arterial stiffness; salivary cortisol levels; and blood glucose levels. Conclusion: The results from this randomized crossover study will determine the effects of uninterrupted sitting and frequent, short bouts of physical activity on cerebral blood flow and cognitive performance. Publication of this study protocol emphasizes the importance of registration and publication of protocols in the field of sedentary behavior research.

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  • 19.
    Heiland, Emerald G
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Uppsala University, Sweden.
    Kjellenberg, Karin
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Fernström, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Nyberg, Gisela
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska institutet, Stockholm, Sweden.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska institutet, Stockholm, Sweden.
    Helgadóttir, Björg
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska institutet, Stockholm, Sweden.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    ABBaH teens: Activity Breaks for Brain Health in adolescents2022In: Trials, E-ISSN 1745-6215, Vol. 23, no 1, article id 22Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Physical activity breaks are widely being implemented in school settings as a solution to increase academic performance and reduce sitting time. However, the underlying physiological mechanisms suggested to improve cognitive function from physical activity and the frequency, intensity, and duration of the breaks remain unknown. This study will investigate the effects of frequent, short physical activity breaks during prolonged sitting on task-related prefrontal cerebral blood flow, cognitive performance, and psychological factors. Additionally, the moderating and mediating effects of arterial stiffness on changes in cerebral blood flow will be tested.

    METHODS: This is a protocol for a randomized crossover study that will recruit 16 adolescents (13-14 years old). Participants will undergo three different conditions in a randomized order, on three separate days, involving sitting 80 min with a different type of break every 17 min for 3 min. The breaks will consist of (1) seated social breaks, (2) simple resistance activities, and (3) step-up activities. Before and after the 80-min conditions, prefrontal cerebral blood flow changes will be measured using functional near-infrared spectroscopy (primary outcome), while performing working memory tasks (1-, 2-, and 3-back tests). Arterial stiffness (augmentation index and pulse wave velocity) and psychological factors will also be assessed pre and post the 80-min interventions.

    DISCUSSION: Publication of this protocol will help to increase rigor in science. The results will inform regarding the underlying mechanisms driving the association between physical activity breaks and cognitive performance. This information can be used for designing effective and feasible interventions to be implemented in schools.

    TRIAL REGISTRATION: www.ClinicalTrials.gov , NCT04552626 . Retrospectively registered on September 21, 2020.

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  • 20.
    Heiland, Emerald G.
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Kjellenberg, Karin
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Nyberg, Gisela
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Helgadóttir, Björg
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Acute effects of nitrate and breakfast on working memory and cerebral blood flow in adolescents: a randomized crossover trial2023Conference paper (Other academic)
    Abstract [en]

    Purpose: Beneficial acute effects of dietary nitrate have been demonstrated on working memory in adults, with changes in cerebral blood flow (CBF) being a potential mechanism. However, these effects have not been studied in adolescents. Moreover, having breakfast compared to skipping may also exhibit positive effects on working memory. Therefore, this randomized crossover trial investigated the acute effects of nitrate and breakfast on working memory and changes in task-related CBF in adolescents.  Methods: This trial will recruit at least 43 adolescents (13–15 years old). There were three experimental breakfast conditions: (1) none, (2) regular, and (3) regular breakfast with high nitrate in the form of concentrated beetroot juice. Working memory (1-, 2-, 3-back tests) and task-related CBF (prefrontal cortex oxygenated and deoxygenated-hemoglobin changes estimated using functional near-infrared spectroscopy) were measured immediately after breakfast and 130 min later. The data collection for this study is ongoing, thus results for 35 adolescents are presented here and due to blinding of the researcher we are unable to report at this time in which condition these effects occurred, but will be revealed by the time of the conference, as well as for the results on changes in CBF.  Results: Preliminary results from the ongoing study showed that from pretest to posttest there was a statistically significant improvement in reaction time in all three conditions for all three n-back tests, but no intervention effects. Accuracy, however, improved from pretest to posttest in only one condition, for all three nback tests (β [95% confidence interval] from linear mixed-effects models with subject as random effect: 1-back 2.8[1.2-4.3], 2-back 2.6[0.9-4.2], 3-back 3.6[2.2-5.0]), and there was a tendency towards an intervention effect between this breakfast condition and another on the accuracy of the 3-back test (P for time-by-condition interaction 0.07).   Conclusions: The results from this study will increase our understanding into the effects of breakfast and its composition (i.e., nitrate-rich) on acutely improving working memory in adolescents and the potential mechanisms. In turn, the results will inform on whether policies on providing breakfast in schools should be considered to improve students' cognitive performance.

  • 21.
    Heiland, Emerald G
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Fernström, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    English, Coralie
    School of Health Sciences and Priority Research Centre for Stroke and Brain Injury, University of Newcastle, Callaghan, NSW, Australia.; Centre for Research Excellence in Stroke Recovery and Rehabilitation, Florey Institute of Neuroscience and Hunter Medical Research Institute, Callaghan, NSW, Australia..
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Department of Neuroscience, Karolinska Institutet, Solna, Sweden..
    Frequent, Short Physical Activity Breaks Reduce Prefrontal Cortex Activation but Preserve Working Memory in Middle-Aged Adults: ABBaH Study.2021In: Frontiers in Human Neuroscience, E-ISSN 1662-5161, Vol. 15, article id 719509Article in journal (Refereed)
    Abstract [en]

    Prolonged sitting is increasingly common and may possibly be unfavorable for cognitive function and mood. In this randomized crossover study, the effects of frequent, short physical activity breaks during prolonged sitting on cognitive task-related activation of the prefrontal cortex were investigated. The effects on working memory, psychological factors, and blood glucose were also examined, and whether arterial stiffness moderated prefrontal cortex activation. Thirteen subjects (mean age 50.5 years; eight men) underwent three 3-h sitting conditions, interrupted every 30-min by a different 3-min break on separate, randomized-ordered days: seated social interactions (SOCIAL), walking (WALK), or simple resistance activities (SRA). Arterial stiffness was assessed at baseline. Before and after each 3-h condition, psychological factors (stress, mood, sleepiness, and alertness) were assessed through questionnaires and functional near-infrared spectroscopy (fNIRS) was used to measure changes in prefrontal oxygenated hemoglobin (Oxy-Hb), indicative of cortical activation, while performing working memory tasks [1- (baseline), 2-, and 3-back]. Blood glucose levels were continuously measured throughout the conditions. Results revealed no significant changes in Oxy-Hb during the 2-back compared with the 1-back test in any condition, and no time-by-condition interactions. During the 3-back test, there was a significant decrease in Oxy-Hb compared with the 1-back after the WALK condition in the right prefrontal cortex, but there were no time-by-condition interactions, although 3-back reaction time improved only in the WALK condition. Mood and alertness improved after the WALK condition, which was significantly different from the SOCIAL condition. Arterial stiffness moderated the effects, such that changes in Oxy-Hb were significantly different between WALK and SOCIAL conditions only among those with low arterial stiffness. Blood glucose during the interventions did not differ between conditions. Thus, breaking up prolonged sitting with frequent, short physical activity breaks may reduce right prefrontal cortex activation, with improvements in some aspects of working memory, mood, and alertness. Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT04137211.

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  • 22.
    Kjellenberg, Karin
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Heiland, Emerald G.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Fernström, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Nyberg, Gisela
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Helgadóttir, Björg
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Effects of physical activity breaks on working memory and oxygenated hemoglobin in adolescents: Results from the AbbaH teen study2023Conference paper (Other academic)
  • 23.
    Kjellenberg, Karin
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Heiland, Emerald G.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Fernström, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Nyberg, Gisela
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Helgadóttir, Björg
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Short, frequent physical activity breaks improve working memory in adolescents during prolonged sitting (AbbaH teen study)2023Conference paper (Other academic)
    Abstract [en]

    Purpose: Physical activity breaks in schools have been suggested as a promising strategy to acutely improve cognitive performance in children and adolescents. Most previous studies have explored the effects of single physical activity bouts, but they are infeasible in a school setting (e.g. long duration/high-intensity or requiring equipment/space). Further, studies investigating the underlying physiological mechanisms in adolescents arel acking. Therefore, the aim of this study was to investigate the effects of short, frequent physical activity breaks of different intensities on adolescents’ working memory (WM) and cerebral blood flow (CBF) during prolonged sitting.

    Methods: This randomized crossover study was performed in adolescents (13-15 years of age). In 80-minute sessions, one of the following types of breaks was performed four times in three minutes durations on three different days: simple resistance training (SRA), step-up at a pre-determined pace (STEP), or remaining seated (SOCIAL). Before and after each session, WM (accuracy and reaction time during the 1,2,3-back test) were measured, with simultaneous measurement of task-related CBF (assessed by prefrontal oxygenation using functional near-infrared spectroscopy). Analysis of CBF is ongoing and will be presented at the conference.

    Results: A total of 17 students participated (mean age 13.6 years, 11 girls). In the most demanding task (3-back) the following results were seen: improvement in reaction time following SRA (-30.1, p=0.04) and STEP (-34.3 ms, p=0.05) and no improvement following prolonged sitting. We also found a moderating effect (p <0.01) of WM performance at baseline (using a mean split), such that students with poor WM significantly improved their accuracy and reaction time following the higher-intensity breaks (STEP) while students with high performance did not.

    Conclusion: We found that implementing physical activity breaks of both moderate and high intensities was beneficial for WM performance. For students with low WM performance, high-intensity breaks were more beneficial. Implementing physical activity breaks during periods of prolonged sitting, such as long school classes could improve the students’ cognitive performance. However, future studies should investigate if these breaks are feasible, acceptable, and beneficial to implement in the school setting.

  • 24.
    Körting, Clara
    et al.
    Royal Institute of Technology, Stockholm, Sweden.
    Schlippe, Marius
    Royal Institute of Technology, Stockholm, Sweden.
    Petersson, Sven
    Karolinska Institutet, Stockholm, Sweden..
    Pennati, Gaia Valentina
    Karolinska Institutet, Stockholm, Sweden..
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska Institutet, Stockholm, Sweden..
    Finni, Taija
    University of Jyväskylä, Jyväskylä, Finland.
    Zhao, Kangqiao
    Royal Institute of Technology, Stockholm, Sweden.
    Wang, Ruoli
    Royal Institute of Technology, Stockholm, Sweden.
    In vivo muscle morphology comparison in post-stroke survivors using ultrasonography and diffusion tensor imaging.2019In: Scientific Reports, E-ISSN 2045-2322, Vol. 9, no 1, article id 11836Article in journal (Refereed)
    Abstract [en]

    Skeletal muscle architecture significantly influences the performance capacity of a muscle. A DTI-based method has been recently considered as a new reference standard to validate measurement of muscle structure in vivo. This study sought to quantify muscle architecture parameters such as fascicle length (FL), pennation angle (PA) and muscle thickness (tm) in post-stroke patients using diffusion tensor imaging (DTI) and to quantitatively compare the differences with 2D ultrasonography (US) and DTI. Muscle fascicles were reconstructed to examine the anatomy of the medial gastrocnemius, posterior soleus and tibialis anterior in seven stroke survivors using US- and DTI-based techniques, respectively. By aligning the US and DTI coordinate system, DTI reconstructed muscle fascicles at the same scanning plane of the US data can be identified. The architecture parameters estimated based on two imaging modalities were further compared. Significant differences were observed for PA and tm between two methods. Although mean FL was not significantly different, there were considerable intra-individual differences in FL and PA. On the individual level, parameters measured by US agreed poorly with those from DTI in both deep and superficial muscles. The significant differences in muscle parameters we observed suggested that the DTI-based method seems to be a better method to quantify muscle architecture parameters which can provide important information for treatment planning and to personalize a computational muscle model.

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  • 25.
    Nilsson, Jonna
    et al.
    Aging Research Center, Karolinska Institutet and Stockholm University, Stockholm, Sweden.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Lebedev, Alexander
    Aging Research Center, Karolinska Institutet and Stockholm University, Stockholm, Sweden.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Moberg, Marcus
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Lövdén, Martin
    Aging Research Center, Karolinska Institutet and Stockholm University, Stockholm, Sweden.
    Acute increases in brain-derived neurotrophic factor in plasma following physical exercise relates to subsequent learning in older adults.2020In: Scientific Reports, E-ISSN 2045-2322, Vol. 10, no 1, article id 4395Article in journal (Refereed)
    Abstract [en]

    Multidomain lifestyle interventions represents a promising strategy to counteract cognitive decline in older age. Brain-derived neurotrophic factor (BDNF) is essential for experience-dependent plasticity and increases following physical exercise, suggesting that physical exercise may facilitate subsequent learning. In a randomized-controlled trial, healthy older adults (65-75 years) completed a 12-week behavioral intervention that involved either physical exercise immediately before cognitive training (n = 25; 13 females), physical exercise immediately after cognitive training (n = 24; 11 females), physical exercise only (n = 27; 15 females), or cognitive training only (n = 21; 12 females). We hypothesized that cognition would benefit more from cognitive training when preceded as opposed to followed by physical exercise and that the relationship between exercise-induced increases in peripheral BDNF and cognitive training outcome would be greater when cognitive training is preceded by physical exercise. Greater increases of plasma BDNF were associated with greater cognitive training gains on trained task paradigms, but only when such increases preceded cognitive training (ß = 0.14, 95% CI [0.04, 0.25]). Average cognitive training outcome did not differ depending on intervention order (ß = 0.05, 95% CI [-0.10, 0.20]). The study provides the first empirical support for a time-critical but advantageous role for post-exercise increases in peripheral BDNF for learning at an interindividual level in older adults, with implications for future multidomain lifestyle interventions.

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  • 26.
    Olivo, Gaia
    et al.
    University of Gothenburg, Sweden; Karolinska Institutet, Stockholm, Sweden.
    Nilsson, Jonna
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska Institutet, Stockholm, Sweden.
    Garzón, Benjamín
    University of Gothenburg, Sweden; Karolinska Institutet, Stockholm, Sweden.
    Lebedev, Alexander
    Karolinska Institutet, Stockholm, Sweden.
    Wåhlin, Anders
    Umeå University, Umeå, Sweden..
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Lövdén, Martin
    University of Gothenburg, Sweden; Karolinska Institutet, Stockholm, Sweden.
    Higher VO2max is associated with thicker cortex and lower grey matter blood flow in older adults.2021In: Scientific Reports, E-ISSN 2045-2322, Vol. 11, no 1, article id 16724Article in journal (Refereed)
    Abstract [en]

    VO2max (maximal oxygen consumption), a validated measure of aerobic fitness, has been associated with better cerebral artery compliance and measures of brain morphology, such as higher cortical thickness (CT) in frontal, temporal and cingular cortices, and larger grey matter volume (GMV) of the middle temporal gyrus, hippocampus, orbitofrontal cortex and cingulate cortex. Single sessions of physical exercise can promptly enhance cognitive performance and brain activity during executive tasks. However, the immediate effects of exercise on macro-scale properties of the brain's grey matter remain unclear. We investigated the impact of one session of moderate-intensity physical exercise, compared with rest, on grey matter volume, cortical thickness, working memory performance, and task-related brain activity in older adults. Cross-sectional associations between brain measures and VO2max were also tested. Exercise did not induce statistically significant changes in brain activity, grey matter volume, or cortical thickness. Cardiovascular fitness, measured by VO2max, was associated with lower grey matter blood flow in the left hippocampus and thicker cortex in the left superior temporal gyrus. Cortical thickness was reduced at post-test independent of exercise/rest. Our findings support that (1) fitter individuals may need lower grey matter blood flow to meet metabolic oxygen demand, and (2) have thicker cortex.

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  • 27.
    Olivo, Gaia
    et al.
    Karolinska Institutet, Stockholm, Sweden.
    Nilsson, Jonna
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology. Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska Institutet, Stockholm, Sweden.
    Garzón, Benjamín
    Karolinska Institutet, Stockholm, Sweden ; University of Gothenburg, Sweden.
    Lebedev, Alexander
    Karolinska Institutet, Stockholm, Sweden.
    Wåhlin, Anders
    Umeå University, Sweden.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Lövdén, Martin
    Karolinska Institutet, Stockholm, Sweden ; University of Gothenburg, Sweden.
    Immediate effects of a single session of physical exercise on cognition and cerebral blood flow: A randomised controlled study of older adults2021In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 225, article id 117500Article in journal (Refereed)
    Abstract [en]

    Background

    Regular physical activity is beneficial for cognitive performance in older age. A single bout of aerobic physical exercise can transiently improve cognitive performance. Researchers have advanced improvements in cerebral circulation as a mediator of long-term effects of aerobic physical exercise on cognition, but the immediate effects of exercise on cognition and cerebral perfusion are not well characterized and the effects in older adults are largely unknown.

    Methods

    Forty-nine older adults were randomized to a 30-minutes aerobic exercise at moderate intensity or relaxation. Groups were matched on age and cardiovascular fitness (VO2 max). Average Grey Matter Blood Flow (GMBF), measured by a pulsed arterial-spin labelling (pASL) magnetic resonance imaging (MRI) acquisition, and working memory performance, measured by figurative n-back tasks with increasing loads were assessed before and 7 minutes after exercising/resting.

    Results

    Accuracy on the n-back task increased from before to after exercising/resting regardless of the type of activity. GMBF decreased after exercise, relative to the control (resting) group. In the exercise group, higher n-back performance after exercise was associated with lower GMBF in the right hippocampus, left medial frontal cortex and right orbitofrontal cortex, and higher cardiovascular fitness was associated with lower GMBF.

    Conclusion

    The decrease of GMBF reported in younger adults shortly after exercise also occurs in older adults and relates to cardiovascular fitness, potentially supporting the link between cardiovascular fitness and cerebrovascular reactivity in older age.

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  • 28.
    Peter, A
    et al.
    Neuromuscular Research Center, University of Jyväslylä, Finland.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Finni, T
    Neuromuscular Research Center, University of Jyväslylä, Finland.
    Hegyi, A
    Neuromuscular Research Center, University of Jyväslylä, Finland.
    Cronin, N
    Neuromuscular Research Center, University of Jyväslylä, Finland.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Surface compared to fine-wire electromyography activity of lower leg muscles at different walking speeds.2019Conference paper (Refereed)
    Abstract [en]

    Summary: Surface and fine-wire electromyography activity of flexor hallucis longus, soleus, medial and lateral gastrocnemius and tibialis anterior muscles was measured simultaneously during walking at four different speeds to examine whether signals recorded with the two methods exhibit similar signal characteristics. We found statistical differences between methods at all walking speeds in soleus and tibialis anterior, at all speeds except fast walking in flexor hallucis longus, and at faster speeds in lateral gastrocnemius. No differences were found in medial gastrocnemius at any speed or in lateral gastrocnemius at slow and preferred speed walking.

  • 29.
    Peter, Annamaria
    et al.
    University of Jyväskylä, Finland.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Finni, Taija
    University of Jyväskylä, Finland.
    Hegyi, Andras
    University of Jyväskylä, Finland.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Cronin, Neil
    University of Jyväskylä, Finland.
    Effect of footwear on plantar flexor fine-wire electromyography activity in walking.2019In: Footwear Science. 2019 Supplement, Vol. 11, p S120-S121: Proceedings of the Fourteenth Footwear Biomechanics Symposium (Kananaskis, Canada, 2019), Taylor & Francis, 2019, Vol. 11, p. S120-S121Conference paper (Other academic)
  • 30.
    Péter, Annamária
    et al.
    University of Jyväskylä, Jyväskylä, Finland.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet, Sweden.
    Hegyi, András
    University of Jyväskylä, Jyväskylä, Finland.
    Finni, Taija
    University of Jyväskylä, Jyväskylä, Finland.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Cronin, Neil
    University of Jyväskylä, Jyväskylä, Finland.
    Grundström, Helen
    Capio S:t Göran's Hospital, Stockholm, Sweden.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet, Sweden.
    Comparing Surface and Fine-Wire Electromyography Activity of Lower Leg Muscles at Different Walking Speeds.2019In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 10, article id 1283Article in journal (Refereed)
    Abstract [en]

    Ankle plantar flexor muscles are active in the stance phase of walking to propel the body forward. Increasing walking speed requires increased plantar flexor excitation, frequently assessed using surface electromyography (EMG). Despite its popularity, validity of surface EMG applied on shank muscles is mostly unclear. Thus, we examined the agreement between surface and intramuscular EMG at a range of walking speeds. Ten participants walked overground at slow, preferred, fast, and maximum walking speeds (1.01 ± 0.13, 1.43 ± 0.19, 1.84 ± 0.23, and 2.20 ± 0.38 m s-1, respectively) while surface and fine-wire EMG activities of flexor hallucis longus (FHL), soleus (SOL), medial gastrocnemius (MG) and lateral gastrocnemius (LG), and tibialis anterior (TA) muscles were recorded. Surface and intramuscular peak-normalised EMG amplitudes were compared for each muscle and speed across the stance phase using Statistical Parametric Mapping. In FHL, we found differences around peak activity at all speeds except fast. There was no difference in MG at any speed or in LG at slow and preferred speeds. For SOL and LG, differences were seen in the push-off phase at fast and maximum walking speeds. In SOL and TA, surface EMG registered activity during phases in which intramuscular EMG indicated inactivity. Our results suggest that surface EMG is generally a suitable method to measure MG and LG EMG activity across several walking speeds. Minimising cross-talk in FHL remains challenging. Furthermore, SOL and TA muscle onset/offset defined by surface EMG should be interpreted cautiously. These findings should be considered when recording and interpreting surface EMG of shank muscles in walking.

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  • 31.
    Péter, Annamária
    et al.
    University of Jyväskylä, Finland.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Hegyi, András
    University of Jyväskylä, Finland.
    Finni, Taija
    University of Jyväskylä, Finland.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska institutet, Stockholm, Sweden.
    Alkjær, Tine
    University of Copenhagen, Denmark..
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Rönquist, Gustaf
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Cronin, Neil
    University of Jyväskylä, Finland; Bath University, UK..
    Effect of footwear on intramuscular EMG activity of plantar flexor muscles in walking.2020In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 55, article id 102474Article in journal (Refereed)
    Abstract [en]

    One of the purposes of footwear is to assist locomotion, but some footwear types seem to restrict natural foot motion, which may affect the contribution of ankle plantar flexor muscles to propulsion. This study examined the effects of different footwear conditions on the activity of ankle plantar flexors during walking. Ten healthy habitually shod individuals walked overground in shoes, barefoot and in flip-flops while fine-wire electromyography (EMG) activity was recorded from flexor hallucis longus (FHL), soleus (SOL), and medial and lateral gastrocnemius (MG and LG) muscles. EMG signals were peak-normalised and analysed in the stance phase using Statistical Parametric Mapping (SPM). We found highly individual EMG patterns. Although walking with shoes required higher muscle activity for propulsion than walking barefoot or with flip-flops in most participants, this did not result in statistically significant differences in EMG amplitude between footwear conditions in any muscle (p > 0.05). Time to peak activity showed the lowest coefficient of variation in shod walking (3.5, 7.0, 8.0 and 3.4 for FHL, SOL, MG and LG, respectively). Future studies should clarify the sources and consequences of individual EMG responses to different footwear.

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  • 32.
    Péter, Annamária
    et al.
    Univ Jyväskylä, Finland.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics. Karolinska Inst, Dept CLINTEC, Stockholm, Sweden.
    Hegyi, András
    Univ Nantes, Lab Movement Interact Performance, Nantes, France.
    Finni, Taija
    Univ Jyväskylä, Finland.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska Inst, Dept Neurosci, Stockholm, Sweden.
    Alkjær, Tine
    Univ Copenhagen, Dept Biomed Sci, Copenhagen, Denmark.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Rönquist, Gustaf
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Cronin, Neil
    Univ Gloucestershire, Sch Sport & Exercise, Cheltenham, Glos, England.
    Intramuscular EMG amplitudes do not necessarily diverge from surface EMG amplitudes over time. Response to Letter to the Editor2022In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 64, article id 102662Article in journal (Other academic)
  • 33.
    Regan, Callum
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska Institutet, Huddinge, Sweden..
    Heiland, Emerald G.
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Uppsala University, Uppsala, Sweden.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Kjellenberg, Karin
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Larsen, Filip J
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Walltott, Hedda
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Fernström, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health.
    Nyberg, Gisela
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska Institutet, Solna, Sweden.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska Institutet, Solna, Sweden.
    Helgadóttir, Björg
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska Institutet, Solna, Sweden.
    Acute effects of nitrate and breakfast on working memory, cerebral blood flow, arterial stiffness, and psychological factors in adolescents: Study protocol for a randomised crossover trial.2023In: PLOS ONE, E-ISSN 1932-6203, Vol. 18, no 5, article id e0285581Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Inorganic nitrate has been shown to acutely improve working memory in adults, potentially by altering cerebral and peripheral vasculature. However, this remains unknown in adolescents. Furthermore, breakfast is important for overall health and psychological well-being. Therefore, this study will investigate the acute effects of nitrate and breakfast on working memory performance, task-related cerebral blood flow (CBF), arterial stiffness, and psychological outcomes in Swedish adolescents.

    METHODS: This randomised crossover trial will recruit at least 43 adolescents (13-15 years old). There will be three experimental breakfast conditions: (1) none, (2) low-nitrate (normal breakfast), and (3) high-nitrate (concentrated beetroot juice with normal breakfast). Working memory (n-back tests), CBF (task-related changes in oxygenated and deoxygenated haemoglobin in the prefrontal cortex), and arterial stiffness (pulse wave velocity and augmentation index) will be measured twice, immediately after breakfast and 130 min later. Measures of psychological factors and salivary nitrate/nitrite will be assessed once before the conditions and at two-time points after the conditions.

    DISCUSSION: This study will provide insight into the acute effects of nitrate and breakfast on working memory in adolescents and to what extent any such effects can be explained by changes in CBF. This study will also shed light upon whether oral intake of nitrate may acutely improve arterial stiffness and psychological well-being, in adolescents. Consequently, results will indicate if nitrate intake from beetroot juice or if breakfast itself could acutely improve cognitive, vascular, and psychological health in adolescents, which can affect academic performance and have implications for policies regarding school meals.

    TRIAL REGISTRATION: The trial has been prospectively registered on 21/02/2022 at https://doi.org/10.1186/ISRCTN16596056. Trial number: ISRCTN16596056.

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  • 34.
    Rosén, Johanna S
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Goosey-Tolfrey, Victoria L
    Loughborough University, UK.
    Mason, Barry S
    Loughborough University, UK.
    Hutchinson, Michael J
    Loughborough University, UK.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Bjerkefors, Anna
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The impact of impairment on kinematic and kinetic variables in Va'a paddling: Towards a sport-specific evidence-based classification system for Para Va'a.2019In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 37, no 17, p. 1942-1950Article in journal (Refereed)
    Abstract [en]

    Para Va'a is a new Paralympic sport in which athletes with trunk and/or leg impairment compete over 200 m. The purpose of this study was to examine the impact of impairment on kinematic and kinetic variables during Va'a ergometer paddling. Ten able-bodied and 44 Para Va'a athletes with impairments affecting: trunk and legs (TL), legs bilaterally (BL) or leg unilaterally (UL) participated. Differences in stroke frequency, mean paddling force, and joint angles and correlation of the joint angles with paddling force were examined. Able-bodied demonstrated significantly greater paddling force as well as knee and ankle flexion ranges of movement (ROM) on the top hand paddling side compared to TL, BL and UL. Able-bodied, BL and UL demonstrated greater paddling force and trunk flexion compared to TL, and UL demonstrated larger bottom hand paddling side knee and ankle flexion ROM compared to BL. Significant positive correlations were observed for both male and female athletes between paddling force and all trunk flexion angles and ROM in the trunk and pelvis rotation and bottom hand paddling side hip, knee and ankle flexion. The results of this study are important for creating an evidence-based classification system for Para Va'a.

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  • 35.
    Spiegl, Ondrej
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The effects of new Edea and Graf figure skating boots and used Graf boots on the kinetics and kinematics of landing after simulated on-ice jumps2019In: Footwear Science, ISSN 1942-4280, E-ISSN 1942-4299, Vol. 11, no 2, p. 121-129Article in journal (Refereed)
    Abstract [en]

    An increase in training intensity and the number of active participants and competitors in figure skating has been accompanied by an increasing frequency of injuries. The aim of this study was to investigate whether different brands of skates as well as the usage of the skates modify the kinetics and kinematics of the landing impact from a jump. New Graf Edmonton (NG), old used Graf Edmonton (OG) and new Edea Concerto (NE) skates were compared. Twelve participants completed six jump trials from 30 cm and 50 cm high boxes, respectively in all three skates and landed on a section of artificial ice placed on a laboratory floor. Landing kinematics (Oqus4 system, Qualisys, Sweden) and kinetics (force plate: Kistler, Switzerland; insoles: Pedar, Novel, Germany) were examined. Each participant acted as their own control for statistical comparison between the skates. The results confirmed that the kinetics and kinematics of the landing are affected by wearing different skates. During landing impacts in NG, participants had significantly greater dorsiflexion at initial contact (IC) and peak dorsiflexion of the ankle, peak flexion of the knee and also greater in-skate plantar forces (PF) than in NE, which may increase the risk of injury. In OG, participants had significantly greater peak flexion of knee and longer time from IC to first peak dorsiflexion (TP) of the ankle than in NG. The differences observed may be due to the different construction designs, such as height of the heel, used materials, and stiffness of the skates, which may affect injury occurrence.

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  • 36.
    Spiegl, Ondrej
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Lundgren, L E
    Halmstad University, Sweden.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Comparison of lightweight and traditional figure skating blades, a prototype blade with integrated damping system and a running shoe in simulated figure skating landings and take-offs2021In: Footwear Science, ISSN 1942-4280, E-ISSN 1942-4299, Vol. 13, p. S53-S55Article in journal (Other academic)
  • 37.
    Spiegl, Ondrej
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Lundgren, Lina E
    Rydberg Laboratory of Applied Sciences, Halmstad University, Halmstad, Sweden.
    Neuman, Daniel
    Department of Physics, Royal Institute of Technology, Stockholm, Sweden.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics. Karolinska Institute, Stockholm, Sweden..
    Comparison of lightweight and traditional figure skating blades, a prototype blade with integrated damping system and a running shoe in simulated figure skating landings and vertical countermovement jumps, and evaluation of dampening properties of the prototype blade.2022In: Sports Biomechanics, ISSN 1476-3141, E-ISSN 1752-6116, p. 1-22Article in journal (Refereed)
    Abstract [en]

    To date, there is no empirical evidence suggesting greater jump heights or cushioned landings when using figure skating (FS) blades of different mass and design. This study examined the effect of lightweight (Gold Seal Revolution from John Wilson) and traditional (Apex Supreme from Jackson Ultima and Volant from Riedell) blades, a new prototype blade with an integrated damping system (damping blade) in two different damping configurations, and running shoes (Runfalcon from Adidas) on kinetics and kinematics during simulated on-ice landings from 0.6 m and maximal countermovement jumps on synthetic ice, and measured dampening properties of the damping blade. Seventeen participants executed trials in the six footwear conditions blinded to the different blades and acted as their own control for statistical comparison. There were no differences between the lightweight and traditional blades on the maximal vertical ground reaction force during the landing. Image analysis showed a damping effect in the damping blade that significantly decreased the landing load for all participants (mean 4.38 ± 0.68 bodyweight) (p ≤ 0.006), on average between 10.1 and 14.3% compared to lightweight and traditional blades (4.87 ± 1.01 to 5.11 ± 0.88 bodyweight). The maximal jump height achieved was the same in all FS blades.

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  • 38.
    Tarassova, Olga
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Karolinska institutet, Stockholm, Sweden.
    Moberg, Marcus
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Lövdén, Martin
    Aging Research Center, Karolinska Institutet and Stockholm University, Stockholm, Sweden..
    Nilsson, Jonna
    Swedish School of Sport and Health Sciences, GIH, Department of Physical Activity and Health. Aging Research Center, Karolinska Institutet and Stockholm University, Stockholm, Sweden..
    Peripheral BDNF Response to Physical and Cognitive Exercise and Its Association With Cardiorespiratory Fitness in Healthy Older Adults.2020In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 11, article id 1080Article in journal (Refereed)
    Abstract [en]

    Physical exercise (PE) has been shown to improve brain function via multiple neurobiological mechanisms promoting neuroplasticity. Cognitive exercise (CE) combined with PE may show an even greater effect on cognitive function. Brain-derived neurotrophic factor (BDNF) is important for neuroplastic signaling, may reduce with increasing age, and is confounded by fitness. The source and physiological role of human peripheral blood BDNF in plasma (pBDNF) is thought to differ from that in serum (sBDNF), and it is not yet known how pBDNF and sBDNF respond to PE and CE. A training intervention study in healthy older adults investigated the effects of acute (35 min) and prolonged (12 weeks, 30 sessions) CE and PE, both alone and in combination, on pBDNF and sBDNF. Cross-sectional associations between baseline pBDNF, sBDNF and cardiorespiratory fitness (CRF) were also investigated. Participants (65-75 years) were randomly assigned to four groups and prescribed either CE plus 35 min of rest (n = 21, 52% female); PE [performed on a cycle ergometer at moderate intensity (65-75% of individual maximal heart rate)] plus 35 min of rest (n = 27, 56% female); CE plus PE (n = 24, 46% female), or PE plus CE (n = 25, 52% female). Groups were tested for CRF using a maximal treadmill ergometer test (VO2peak); BDNF levels (collected 48 h after CRF) during baseline, after first exercise (PE or CE) and after second exercise (PE, CE or rest); and cognitive ability pre and post 12-week training. At both pre and post, pBDNF increased after CE and PE (up to 222%), and rest (∼67%), whereas sBDNF increased only after PE (up to 18%) and returned to baseline after rest. Acute but not prolonged PE increased both pBDNF and sBDNF. CE induced acute changes in pBDNF only. Baseline pBDNF was positively associated with baseline sBDNF (n = 93, r = 0.407, p < 0.001). No changes in CRF were found in any of the groups. Baseline CRF did not correlate with baseline BDNF. Even though baseline pBDNF and sBDNF were associated, patterns of changes in pBDNF and sBDNF in response to exercise were explicitly different. Further experimental scrutiny is needed to clarify the biological mechanisms of these results.

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  • 39.
    Tarassova, Olga
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Halvorsen, Kjartan
    Åberg, Anna Christina
    Uppsala Universitet.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Balance mechanisms in children with and without motor coordination difficulties2012In: Balance mechanisms in children with and without motor coordination difficulties, 2012Conference paper (Refereed)
  • 40.
    Wang, Ruoli
    et al.
    Royal Institute of Technology, Stockholm, Sweden; Karolinska Institutet, Stockholm, Sweden..
    Yan, Shiyang
    Royal Institute of Technology, Stockholm, Sweden; Sichuan University, Chengdu, China..
    Schlippe, Marius
    Royal Institute of Technology, Stockholm, Sweden..
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Pennati, Gaia Valentina
    Karolinska Institutet, Stockholm, Sweden.
    Lindberg, Frida
    Royal Institute of Technology, Stockholm, Sweden..
    Körting, Clara
    Royal Institute of Technology, Stockholm, Sweden..
    Destro, Antea
    Royal Institute of Technology, Stockholm, Sweden..
    Yang, Luming
    Sichuan University, Chengdu, China..
    Shi, Bin
    Sichuan University, Chengdu, China..
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics. Karolinska Institutet, Stockholm, Sweden.
    Passive Mechanical Properties of Human Medial Gastrocnemius and Soleus Musculotendinous Unit.2021In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, Vol. 2021, article id 8899699Article in journal (Refereed)
    Abstract [en]

    The in vivo characterization of the passive mechanical properties of the human triceps surae musculotendinous unit is important for gaining a deeper understanding of the interactive responses of the tendon and muscle tissues to loading during passive stretching. This study sought to quantify a comprehensive set of passive muscle-tendon properties such as slack length, stiffness, and the stress-strain relationship using a combination of ultrasound imaging and a three-dimensional motion capture system in healthy adults. By measuring tendon length, the cross-section areas of the Achilles tendon subcompartments (i.e., medial gastrocnemius and soleus aspects), and the ankle torque simultaneously, the mechanical properties of each individual compartment can be specifically identified. We found that the medial gastrocnemius (GM) and soleus (SOL) aspects of the Achilles tendon have similar mechanical properties in terms of slack angle (GM: -10.96° ± 3.48°; SOL: -8.50° ± 4.03°), moment arm at 0° of ankle angle (GM: 30.35 ± 6.42 mm; SOL: 31.39 ± 6.42 mm), and stiffness (GM: 23.18 ± 13.46 Nmm-1; SOL: 31.57 ± 13.26 Nmm-1). However, maximal tendon stress in the GM was significantly less than that in SOL (GM: 2.96 ± 1.50 MPa; SOL: 4.90 ± 1.88 MPa, p = 0.024), largely due to the higher passive force observed in the soleus compartment (GM: 99.89 ± 39.50 N; SOL: 174.59 ± 79.54 N, p = 0.020). Moreover, the tendon contributed to more than half of the total muscle-tendon unit lengthening during the passive stretch. This unequal passive stress between the medial gastrocnemius and the soleus tendon might contribute to the asymmetrical loading and deformation of the Achilles tendon during motion reported in the literature. Such information is relevant to understanding the Achilles tendon function and loading profile in pathological populations in the future.

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  • 41.
    Yan, S
    et al.
    Royal Institute of Technology, Stockholm, Sweden.
    Schlippe, M
    Royal Institute of Technology, Stockholm, Sweden.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Pennati, G V
    Karolinska institutet, Stockholm, Sweden.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Yang, L
    Sichuan University, Chengdu, China.
    Shi, B
    Sichuan University, Chengdu, China.
    Wang, R
    Royal Institute of Technology, Stockholm, Sweden.
    P 158 - A method to estimate passive mechanical properties of the soleus and gastrocnemius aspects of Achilles tendon.2018In: ESMAC 2018 abstracts: special issue of Gait & Posture, 2018, Vol. 65 Suppl 1, p. 501-502, article id S0966-6362(18)31146-9Conference paper (Refereed)
  • 42.
    Zhou, Guang-Quan
    et al.
    Southeast University, Nanjing, China.
    Zhang, Yi
    Southeast University, Nanjing, China.
    Wang, Ruo-Li
    Karolinska Institute & Royal Institute of Technology, Stockholm.
    Zhou, Ping
    Southeast University, Nanjing, China.
    Zheng, Yong-Ping
    The Hong Kong Polytechnic University, Hung Hom, Hong Kong.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska Institute.
    Chen, Qiang
    Southeast University, Nanjing, China.
    Automatic Myotendinous Junction Tracking in Ultrasound Images with Phase-Based Segmentation.2018In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, article id 3697835Article in journal (Refereed)
    Abstract [en]

    Displacement of the myotendinous junction (MTJ) obtained by ultrasound imaging is crucial to quantify the interactive length changes of muscles and tendons for understanding the mechanics and pathological conditions of the muscle-tendon unit during motion. However, the lack of a reliable automatic measurement method restricts its application in human motion analysis. This paper presents an automated measurement of MTJ displacement using prior knowledge on tendinous tissues and MTJ, precluding the influence of nontendinous components on the estimation of MTJ displacement. It is based on the perception of tendinous features from musculoskeletal ultrasound images using Radon transform and thresholding methods, with information about the symmetric measures obtained from phase congruency. The displacement of MTJ is achieved by tracking manually marked points on tendinous tissues with the Lucas-Kanade optical flow algorithm applied over the segmented MTJ region. The performance of this method was evaluated on ultrasound images of the gastrocnemius obtained from 10 healthy subjects (26.0±2.9 years of age). Waveform similarity between the manual and automatic measurements was assessed by calculating the overall similarity with the coefficient of multiple correlation (CMC).<italic> In vivo</italic> experiments demonstrated that MTJ tracking with the proposed method (CMC = 0.97±0.02) was more consistent with the manual measurements than existing optical flow tracking methods (CMC = 0.79±0.11). This study demonstrated that the proposed method was robust to the interference of nontendinous components, resulting in a more reliable measurement of MTJ displacement, which may facilitate further research and applications related to the architectural change of muscles and tendons. [ABSTRACT FROM AUTHOR]

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  • 43.
    Åberg, A.C.
    et al.
    Dalarna University, Falun, Sweden.
    Åhman, H.B.
    Uppsala University, Sweden.
    Olsson, F.
    Uppsala University, Sweden.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Cedervall, Y.
    Uppsala University, Sweden.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Giedraitis, V.
    Uppsala University, Sweden.
    Halvorsen, K.
    Uppsala University, Sweden.
    Gait parameters during the Timed Up-and-Go dual-task test: A validation study of video-recorded data2020In: ESMAC 2020 Abstracts, Gait & Posture September 2020, 81, Supplement 1:2-3, Elsevier, 2020, Vol. 81, no Supplement 1, p. 2-3Conference paper (Other academic)
  • 44.
    Åberg, Anna Cristina
    et al.
    Uppsala University, Sweden; Dalarna University, Sweden.
    Olsson, Fredrik
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Åhman, Hanna Bozkurt
    Uppsala University, Sweden.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Physiology, Nutrition and Biomechanics. Karolinska Insitutet, Sweden.
    Giedraitis, Vilmantas
    Uppsala University, Sweden; Dalarna University, Sweden.
    Berglund, Lars
    Uppsala University, Sweden; Dalarna University, Sweden.
    Halvorsen, Kjartan
    Dalarna University, Sweden ; Tecnologico de Monterrey, Atizapan, Mexico.
    Extraction of gait parameters from marker-free video recordings of Timed Up-and-Go tests: Validity, inter- and intra-rater reliability.2021In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 90, p. 489-495, article id S0966-6362(21)00279-4Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: We study dual-task performance with marker-free video recordings of Timed Up-and-Go tests (TUG) and TUG combined with a cognitive/verbal task (TUG dual-task, TUGdt).

    RESEARCH QUESTION: Can gait parameters be accurately estimated from video-recorded TUG tests by a new semi-automatic method aided by a technique for human 2D pose estimation based on deep learning?

    METHODS: Thirty persons aged 60-85 years participated in the study, conducted in a laboratory environment. Data were collected by two synchronous video-cameras and a marker-based optoelectronic motion capture system as gold standard, to evaluate the gait parameters step length (SL), step width (SW), step duration (SD), single-stance duration (SSD) and double-stance duration (DSD). For reliability evaluations, data processing aided by a deep neural network model, involved three raters who conducted three repetitions of identifying anatomical keypoints in recordings of one randomly selected step from each of the participants. Validity was analysed using 95 % confidence intervals (CI) and p-values for method differences and Bland-Altman plots with limits of agreement. Inter- and intra-rater reliability were calculated as intraclass correlation coefficients (ICC) and standard errors of measurement. Smallest detectable change was calculated for inter-rater reliability.

    RESULTS: Mean ddifferences between video and the motion capture system data for SW, DSD, and SSD were significant (p < 0.001). However, mean differences for all parameters were small (-6.4%-13.0% of motion capture system) indicating good validity. Concerning reliability, almost all 95 % CI of the ICC estimates exceeded 0.90, indicating excellent reliability. Only inter-rater reliability for SW (95 % CI = 0.892;0.973) and one rater's intra-rater reliability for SSD (95 % CI = 0.793;0.951) were lower, but still showed good to excellent reliability.

    SIGNIFICANCE: The presented method for extraction of gait parameters from video appears suitable for valid and reliable quantification of gait. This opens up for analyses that may contribute to the knowledge of cognitive-motor interference in dual-task testing.

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  • 45.
    Åberg, Anna Cristina
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Halvorsen, Kjartan
    School of Technology and Health, KTH-Royal Institute of Technology, Stockholm, Sweden.
    Calculations of mechanisms for balance control during narrow and single-leg standing in fit older adults: A reliability study.2011In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 34, no 3, p. 352-7Article in journal (Refereed)
    Abstract [en]

    For older people balance control in standing is critical for performance of activities of daily living without falling. The aims were to investigate reliability of quantification of the usage of the two balance mechanisms M1 ‘moving the centre of pressure’ and M2 ‘segment acceleration’ and also to compare calculation methods based on a combination of kinetic (K) and kinematic (Km) data, (K–Km), or Km data only concerning M2. For this purpose nine physically fit persons aged 70–78 years were tested in narrow and single-leg standing. Data were collected by a 7-camera motion capture system and two force plates. Repeated measure ANOVA and Tukey's post hoc tests were used to detect differences between the standing tasks. Reliability was estimated by ICCs, standard error of measurement including its 95% CI, and minimal detectable change, whereas Pearson's correlation coefficient was used to investigate agreement between the two calculation methods. The results indicated that for the tasks investigated, M1 and M2 can be measured with acceptable inter- and intrasession reliability, and that both Km and K–Km based calculations may be useful for M2, although Km data may give slightly lower values. The proportional M1:M2 usage was approximately 9:1, in both anterio-posterior (AP) and medio-lateral (ML) directions for narrow standing, and about 2:1 in the AP and of 1:2 in the ML direction in single-leg standing, respectively. In conclusion, the tested measurements and calculations appear to constitute a reliable way of quantifying one important aspect of balance capacity in fit older people.

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