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  • 1.
    Andersson, Eva
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Swärd, L
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Trunk muscle strength in athletes.1988In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 20, no 6, p. 587-93Article in journal (Refereed)
    Abstract [en]

    Maximal voluntary strength of the trunk muscles was measured in 57 male elite athletes (soccer players, wrestlers, tennis players, and gymnasts), 14 female elite gymnasts, and in a normal group of 87 conscripts. Mean ages in the different groups ranged from 18-22 yr. An isokinetic (constant velocity) technique was used to record maximal torque produced by trunk and hip muscles during flexion, extension, and lateral flexion over the range of motion. The constant angular velocities used were 15 deg.s-1 and 30 deg.s-1, respectively. Isometric strength was measured in a straight body position (0 deg. of flexion). The measurements were made with the subjects in a horizontal position with the pivot point at the hip and at the lumbar (L2-L3) level. All male athlete groups showed higher peak torque values than the normals. The differences were largest in hip extension and trunk flexion. The male gymnasts also showed significantly higher peak values in hip flexion as compared to all other categories. There was no difference in strength per kg body weight between female gymnasts and untrained males, except in trunk extension. The position for peak torque occurred earlier in the movements for the athletes, especially for the gymnasts in extension movements and for the tennis players in flexion movements. In isometric contractions essentially the same strength differences were present as in the slow isokinetic contractions. In lateral flexion wrestlers and tennis players showed significantly higher strength in movements toward the nondominant side. Thus, differences were present between the athletes and the normals, some of which appeared to be sport specific and related to long-term systematic training.(ABSTRACT TRUNCATED AT 250 WORDS)

  • 2. Andersson, Helena
    et al.
    Raastad, Truls
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Paulsen, Gøran
    Garthe, Ina
    Kadi, Fawzi
    Neuromuscular fatigue and recovery in elite female soccer: effects of active recovery.2008In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 40, no 2, p. 372-80Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To investigate the time course of recovery from neuromuscular fatigue and some biochemical changes between two female soccer matches separated by an active or passive recovery regime. METHODS: Countermovement jump (CMJ), sprint performance, maximal isokinetic knee flexion and extension, creatine kinase (CK), urea, uric acid, and perceived muscle soreness were measured in 17 elite female soccer players before, immediately after, 5, 21, 45, 51, and 69 h after a first match, and immediately after a second match. Eight players performed active recovery (submaximal cycling at 60% of HRpeak and low-intensity resistance training at < 50% 1RM) 22 and 46 h after the first match. RESULTS: In response to the first match, a significant decrease in sprint performance (-3.0 +/- 0.5%), CMJ (-4.4 +/- 0.8%), peak torque in knee extension (-7.1 +/- 1.9%) and flexion (-9.4 +/- 1.8%), and an increase in CK (+ 152 +/- 28%), urea (15 +/- 2), uric acid (+ 11 +/- 2%), and muscle soreness occurred. Sprint ability was first to return to baseline (5 h) followed by urea and uric acid (21 h), isokinetic knee extension (27 h) and flexion (51 h), CK, and muscle soreness (69 h), whereas CMJ was still reduced at the beginning of the second match. There were no significant differences in the recovery pattern between the active and passive recovery groups. The magnitude of the neuromuscular and biochemical changes after the second match was similar to that observed after the first match. CONCLUSION: The present study reveals differences in the recovery pattern of the various neuromuscular and biochemical parameters in response to a female soccer match. The active recovery had no effects on the recovery pattern of the four neuromuscular and three biochemical parameters.

  • 3.
    Apró, William
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
    Wang, Li
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Research group for Mitokondriell funktion och metabolisk kontroll.
    Pontén, Marjan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Blomstrand, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
    Sahlin, Kent
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Research group for Mitokondriell funktion och metabolisk kontroll.
    Endurance Exercise Does Not Impair mTOR Signalling After Resistance Exercise: D-58 Thematic Poster - Skeletal Muscle Cell Signaling: JUNE 2, 2011 3:15 PM - 5:15 PM: ROOM: 3042011In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 43, no 5, p. 52-Article in journal (Other academic)
    Abstract [en]

    Resistance exercise is known to stimulate muscle hypertrophy and this effect is mainly mediated by the mammalian target of rapamycin (mTOR) pathway. In contrast, endurance exercise results in a divergent phenotypic response which to a large extent is mediated by adenosine monophosphate-activated protein kinase (AMPK). Research indicates that molecular interference may exist, possibly through an inhibitory effect on mTOR signalling by AMPK, when these two modes of exercise are combined.

    PURPOSE: To investigate the impact of subsequent endurance exercise on resistance exercise induced mTOR signalling.

    METHODS: In a randomized and cross-over fashion, ten male subjects performed either heavy resistance exercise (R) or heavy resistance exercise followed by endurance exercise (RE) on two separate occasions. The R protocol consisted of thirteen sets of leg press exercise with 3 minutes of recovery allowed between each set. In the RE session, resistance exercise was followed by 15 minutes recovery after which 30 min of cycling was initiated at an intensity equal to 70 % of the subjects' maximal oxygen consumption. Muscle biopsies were collected before, 1 and 3 hours after resistance exercise in both trials. Samples were analyzed for several signalling proteins in the mTOR pathway using western blot technique.

    RESULTS: Phosphorylation of mTOR increased approx. twofold at 1 h post resistance exercise and remained elevated at the 3 h time point (p< 0.01) with no difference between the two trials. Phosphorylation of p70S6k, a downstream target of mTOR, was increased about 6-and18-fold at 1 h and 3 h post resistance exercise (p< 0.01). There was no difference in p70S6k phosphorylation at any time point between the two trials. Phosphorylation of the eukaryotic elongation factor eEF2 was decreased 3- to 4-fold at both time points post resistance exercise (p< 0.01) with no difference between trials. Phosphorylation of AMPK was unchanged at the 1 h time point but decreased approximately 30 % from pre-exercise values in both trials at 3 h post resistance exercise (p< 0.01).

    CONCLUSIONS: The signalling response following heavy resistance exercise is not blunted by subsequent endurance exercise. Supported by the Swedish National Centre for Research in Sports.

  • 4. Bergh, U
    et al.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Åstrand, PO
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Maximal oxygen uptake "classical" versus "contemporary" viewpoints.2000In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 32, no 1, p. 85-8Article in journal (Refereed)
    Abstract [en]

    In two articles Timothy Noakes proposes a new physiological model in which skeletal muscle recruitment is regulated by a central "govenor," specifically to prevent the development of a progressive myocardial ischemia that would precede the development of skeletal muscle anaerobiosis during maximal exercise. In this rebuttal to the Noakes' papers, we argue that Noakes has ignored data supporting the existing hypothesis that under normal conditions cardiac output is limiting maximal aerobic power during dynamic exercise engaging large muscle groups.

  • 5. Cornish, Rahchell S
    et al.
    Bolam, Kate A
    School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, Australia.
    Skinner, Tina L
    Effect of caffeine on exercise capacity and function in prostate cancer survivors.2015In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 47, no 3, p. 468-75Article in journal (Refereed)
    Abstract [en]

    PURPOSE: This study aimed to examine the acute effect of caffeine on exercise capacity, exercise-related fatigue, and functional performance in prostate cancer survivors.

    METHODS: In this randomized, placebo-controlled, double-blind crossover study, 30 prostate cancer survivors (age, 70.3 ± 7.7 yr; body mass, 80.5 ± 13.0 kg; mean ± SD) consumed 6.04 ± 0.16 mg·kg(-1) of anhydrous caffeine or a placebo 1 h before completing a battery of exercise capacity and functional performance tests. Testing sessions were separated by 3-4 wk. Immediate fatigue and perceived exertion were measured directly pre- and postexercise at both testing sessions.

    RESULTS: Caffeine increased exercise capacity by 7.93 s (+3.0%; P = 0.010); however, postexercise fatigue and perception of exertion were comparable with the placebo session (P = 0.632 and P = 0.902, respectively). Increases in isometric grip strength trended toward significance in both dominant (+2.9%; P = 0.053) and nondominant (+2.1%; P = 0.061) hands in the caffeine trial compared with placebo. Caffeine ingestion did not result in improvements in performance for any of the remaining functional measures, including the timed up-and-go test, repeated chair stands, 6-m fast walk, and 6-m backward tandem walk. Systolic blood pressure and HR were significantly increased (P = 0.006 and P = 0.040, respectively) upon completion of the testing battery when compared with placebo.

    CONCLUSIONS: Consumption of caffeine 1 h before exercise induced improvements in exercise capacity and muscular strength in prostate cancer survivors. However, there was no change in exercise-related fatigue when compared with placebo despite reduction in timed performance of the 400-m walk. Caffeine seems to enhance exercise tolerance through improved performance with no subsequent increase in fatigue or perception of exertion and may be an appropriate strategy to promote exercise participation in prostate cancer survivors.

  • 6.
    Ekblom, Maria M Nordlund
    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.
    Effects of prolonged vibration on H-reflexes, muscle activation, and dynamic strength.2011In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 43, no 10, p. 1933-9Article in journal (Refereed)
    Abstract [en]

     Neural activation is generally lower during maximal voluntary lengthening compared with shortening and isometric muscle actions, but the mechanisms underlying these differences are unclear. In maximal voluntary isometric actions, reduced Ia-afferent input induced by prolonged tendon vibration has been shown to impair neural activation and strength.

    PURPOSE: This study aimed to investigate whether reducing Ia-afferent input influences neural activation in maximal voluntary dynamic muscle actions and, if so, whether it affects shortening and lengthening muscle actions differently.

    METHODS: Eight women participated in three familiarization sessions and two randomly ordered experiments. In one experiment, 30-min vibration at 100 Hz was applied to the Achilles tendon to decrease Ia-afferent input as measured by the H-reflex. In the control experiment, rest substituted the vibration. Root mean square EMG from plantar and dorsiflexor muscles and plantar flexor strength were measured during maximal voluntary plantar flexor shortening and lengthening actions (20°·s(-1)) before and after vibration and rest, respectively. Soleus H-reflexes and M-waves were elicited before each set of strength tests.

    RESULTS: The vibration caused a decrease in H-reflex amplitude by, on the average, 33%, but root mean square EMG and plantar flexor strength remained largely unaffected in both action types.

    CONCLUSIONS: The findings suggest that Ia-afferent input may not substantially contribute to maximal voluntary dynamic muscle strength of the plantar flexor muscles, as tested here, and thus, the results do not support the notion that Ia-afferent excitation would contribute differently to neural activation in maximal voluntary lengthening and shortening muscle actions.

  • 7.
    Gago, Paulo
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Marques, Mário C
    Marinho, Daniel A
    Ekblom, Maria M
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Passive Muscle Length Changes Affect Twitch Potentiation in Power Athletes.2014In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 46, no 7, p. 1334-1342Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION: A conditioning maximal voluntary muscle action (MVC) has been shown to induce post-activation potentiation, i.e. improved contractile muscle properties, when muscles are contracted isometrically. It is still uncertain how the contractile properties are affected during ongoing muscle length changes. The purpose of this study was to investigate the effects of a 6 s conditioning MVC on twitch properties of the plantar flexors during ongoing muscle length changes.

    METHODS: Peak twitch, rate of torque development (RTD) and relaxation (RTR), rising time and half relaxation time (HRT) were measured from supramaximal twitches evoked in the plantar flexors of 11 highly trained athletes. Twitches were evoked prior to a 6 s MVC and subsequently on 8 different occasions during a 10-minute recovery, for five different modes: fast lengthening, slow lengthening, isometric, fast shortening and slow shortening of the plantar flexors.

    RESULTS: The magnitude and duration of effects from the conditioning MVC were significantly different between modes. Peak twitch, RTD and RTR significantly increased for all modes but more so for twitches evoked during fast and slow shortening as compared to lengthening. Rising time was reduced in the lengthening modes, but slightly prolonged in the shortening modes. HRT was significantly reduced for all modes except fast lengthening.

    CONCLUSION: The findings show that the effects of a conditioning MVC on twitch contractile properties are dependent on direction and velocity of ongoing muscle length changes. This may imply that functional enhancements from a conditioning MVC might be expected to be greatest for concentric muscle actions, but are still present in isometric and eccentric parts of a movement.

  • 8.
    Gejl, Kasper Degn
    et al.
    University of Southern Denmark.
    Thams, Line
    University of Southern Denmark.
    Hansen, Mette
    Aarhus University, Aarhus, Denmark.
    Rokkedal-Lausch, Torben
    Aalborg University, Aalborg, Denmark.
    Plomgaard, Peter
    Rigshospitalet, Copenhagen, Denmark.
    Nybo, Lars
    University of Copenhagen, Copenhagen Denmark.
    Larsen, Filip J
    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. Karolinska Institute.
    Cardinale, Daniele A
    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.
    Jensen, Kurt
    University of Southern Denmark.
    Holmberg, Hans-Christer
    Mid Sweden University, Östersund, Sweden.
    Vissing, Kristian
    Aarhus University, Aarhus, Denmark.
    Ørtenblad, Niels
    University of Southern Denmark.
    No Superior Adaptations to Carbohydrate Periodization in Elite Endurance Athletes.2017In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 49, no 12, p. 2486-2497Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The present study investigated the effects of periodic CHO restriction on endurance performance and metabolic markers in elite endurance athletes.

    METHODS: Twenty-six male elite endurance athletes (VO2max: 65.0 ml O2[BULLET OPERATOR]kg[BULLET OPERATOR]min) completed 4 weeks of regular endurance training, while matched and randomized into two groups training with (Low) or without (High) carbohydrate (CHO) manipulation three days a week. The CHO manipulation days consisted of a 1-hr high intensity bike session in the morning, recovery for 7 hrs while consuming isocaloric diets containing either high CHO (414±2.4 g) or low CHO (79.5±1.0 g), and a 2-hr moderate bike session in the afternoon with or without CHO. VO2max, maximal fat oxidation and power output during a 30-min time trial (TT) were determined before and after the training period. The TT was undertaken after 90 mins of intermittent exercise with CHO provision before the training period and both CHO and placebo after the training period. Muscle biopsies were analyzed for glycogen, citrate synthase (CS) and β-hydroxyacyl-coenzyme A dehydrogenase (HAD) activity, carnitine palmitoyltransferase (CPT1b) and phosphorylated acetyl-CoA carboxylase (pACC).

    RESULTS: The training effects were similar in both groups for all parameters. On average, VO2max and power output during the 30-min TT increased by 5 ± 1% (P<0.05) and TT performance was similar after CHO and placebo during the preload phase. Training promoted overall increases in glycogen content (18 ± 5%), CS activity (11 ± 5%) and pACC (38 ± 19%) (P<0.05) with no differences between groups. HAD activity and CPT1b protein content remained unchanged.

    CONCLUSION: Superimposing periodic CHO restriction to 4 weeks of regular endurance training had no superior effects on performance and muscle adaptations in elite endurance athletes.

  • 9. Gejl, Kasper
    et al.
    Hvid, Lars G
    Frandsen, Ulrik
    Jensen, Kurt
    Sahlin, Kent
    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.
    Ortenblad, Niels
    Muscle Glycogen Content Modifies SR Ca2 + Release Rate in Elite Endurance Athletes.2014In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 46, no 3, p. 496-505Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The aim of the present study was to investigate the influence of muscle glycogen content on sarcoplasmic reticulum (SR) function and peak power output (Wpeak) in elite endurance athletes.

    METHODS: Fourteen highly trained male triathletes (VO2max 66.5 ± 1.3 ml O2 kg min), performed 4h of glycogen depleting cycling exercise (HRmean 73 ± 1% of maximum). During the first 4h recovery, athletes received either water (H2O) or carbohydrate (CHO), separating alterations in muscle glycogen content from acute changes affecting SR function and performance. Thereafter, all subjects received CHO enriched food for the remaining 20h recovery.

    RESULTS: Immediately following exercise, muscle glycogen content and SR Ca release rate was reduced to 32 ± 4% (225 ± 28 mmol kg dw) and 86 ± 2% of initial levels, respectively (P < 0.01). Glycogen markedly recovered after 4h recovery with CHO (61 ± 2% of pre) and SR Ca release rate returned to pre-exercise level. However, in the absence of CHO during the first 4h recovery, glycogen and SR Ca release rate remained depressed, with normalization of both parameters at the end of the 24h recovery after receiving a CHO enriched diet. Linear regression demonstrated a significant correlation between SR Ca release rate and muscle glycogen content (P < 0.01, r = 0.30). The 4h cycling exercise reduced Wpeak by 5.5-8.9% at different cadences (P < 0.05) and Wpeak was normalized after 4h recovery with CHO whereas Wpeak remained depressed (P < 0.05) following water provision. Wpeak was fully recovered after 24h in both the H2O and the CHO group.

    CONCLUSION: In conclusion, the present results suggest that low muscle glycogen depresses muscle SR Ca release rate, which may contribute to fatigue and delayed recovery of Wpeak 4 hours post exercise.

  • 10. Kalsen, Anders
    et al.
    Hostrup, Morten
    Söderlund, Karin
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology, Björn Ekblom's research group.
    Karlsson, Sebastian
    Backer, Vibeke
    Bangsbo, Jens
    Inhaled Beta2-agonist Increases Power Output and Glycolysis during Sprinting in Men.2016In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 48, no 1, p. 39-48Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The aim of the present study was to investigate the effect of the beta2-agonist terbutaline (TER) on power output and muscle metabolism during maximal sprint cycling.

    METHODS: In a randomized double-blind crossover design, nine moderately trained men (VO2max: 4.6±0.2 L[BULLET OPERATOR]min) conducted a 10-s cycle sprint after inhalation of either 15 mg TER or placebo (PLA). A muscle biopsy was collected before and <10 s after the sprint, and analyzed for metabolites.

    RESULTS: Mean and peak power during the sprint were 8.3±1.1 and 7.8±2.5 % higher (P<0.05) in TER than in PLA, respectively. Moreover, net rate of glycogenolysis (6.5±0.8 vs. 3.1±0.7 mmol glucosyl units kg dw s) and glycolysis (2.4±0.2 vs. 1.6±0.2 mmol glucosyl units kg dw s) were higher (P<0.05) in TER than in PLA. After the sprint, ATP was reduced in PLA (P<0.05), but not in TER. During the sprint, there was no difference in breakdown of phosphocreatine (PCr) between treatments. Estimated anaerobic ATP utilization was 9.2 ±4.0 % higher (P<0.05) in TER than in PLA. After the sprint, ATP was lowered (P <0.05) by 25.7±7.3 % in type II fibers in PLA with no reduction in TER. Before the sprint, PCr was 24.5±7.2 % lower (P <0.05) in type II fibers in TER than in PLA. In PLA, breakdown of PCr was 50.2±24.8 % higher (P <0.05) in type II than in type I fibers with no difference in TER.

    CONCLUSION: The present study shows that a terbutaline-induced increase in power output is associated with increased rates of glycogenolysis and glycolysis in skeletal muscles. Furthermore, as terbutaline counteracted a reduction in ATP in type II fibers, terbutaline may postpone fatigue development in these fibers.

  • 11. Krustrup, Peter
    et al.
    Söderlund, Karin
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Mohr, Magni
    Bangsbo, Jens
    Slow-twitch fiber glycogen depletion elevates moderate-exercise fast-twitch fiber activity and O2 uptake.2004In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 36, no 6, p. 973-82Article in journal (Refereed)
    Abstract [en]

    PURPOSE: We tested the hypotheses that previous glycogen depletion of slow-twitch (ST) fibers enhances recruitment of fast-twitch (FT) fibers, elevates energy requirement, and results in a slow component of VO2 during moderate-intensity dynamic exercise in humans. METHODS: Twelve healthy, male subjects cycled for 20 min at approximately 50% VO2max with normal glycogen stores (CON) and with exercise-induced glycogen depleted ST fibers (CHO-DEP). Pulmonary VO2 was measured continuously and single fiber, muscle homogenate, and blood metabolites were determined repeatedly during each trial. RESULTS: ST fiber glycogen content decreased (P < 0.05) during CON (293 +/- 24 to 204 +/- 17 mmol x kg d.w.), but not during CHO-DEP (92 +/- 22 and 84 +/- 13 mmol x kg d.w.). FT fiber CP and glycogen levels were unaltered during CON, whereas FT fiber CP levels decreased (29 +/- 7%, P < 0.05) during CHO-DEP and glycogen content tended to decrease (32 +/- 14%, P = 0.07). During CHO-DEP, VO2 was higher (P < 0.05) from 2 to 20 min than in CON (0-20 min:7 +/- 1%). Muscle lactate, pH and temperature, ventilation, and plasma epinephrine were not different between trials. From 3 to 20 min of CHO-DEP, VO2 increased (P <0.05) by 5 +/- 1% from 1.95 +/- 0.05 to 2.06 +/- 0.08 L x min but was unchanged during CON. In this exercise period, muscle pH and blood lactate were unaltered in both trials. Exponential modeling revealed a slow component of VO2 equivalent to 0.12 +/- 0.04 L x min during CHO-DEP. CONCLUSION: This study demonstrates that previous glycogen depletion of ST fibers enhances FT fiber recruitment, elevates O2 cost, and causes a slow component of VO2 during dynamic exercise with no blood lactate accumulation or muscular acidosis. These findings suggest that FT fiber recruitment elevates energy requirement of dynamic exercise in humans and support an important role of active FT fibers in producing the slow component of VO2

  • 12. Liu, Anmin
    et al.
    Nester, Christopher
    Jones, Richard
    Lundgren, Paul
    Lundberg, Arne
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Wolf, Peter
    The Effect of an Antipronation Foot Orthosis on Ankle and Subtalar Kinematics2012In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 44, no 12, p. 2384-91Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION/PURPOSE:

    The aim of this study was to describe the effect of an anti pronation foot orthosis on motion of the heel relative to the leg and explore the individual contributions of the ankle and subtalar joints to this effect.

    METHODS:

    Five subjects were investigated using invasive intracortical pins to track the movement of the tibia, talus and calcaneus during walking with and without a foot orthosis.

    RESULTS:

    The anti pronation foot orthosis produced small and unsystematic reductions in eversion and abduction of the heel relative to the leg at various times during stance. Changes in calcaneus-tibia motion were comparable to those described in the literature (1-3°). Changes at both the ankle and subtalar joints contributed to this orthotic effect. However, the nature and scale of changes was highly variable between subjects. Peak angular position, range of motion and angular velocity in frontal and transverse planes were affected to different degrees in different subjects. In some cases changes occurred mainly at the ankle, in other cases changes occurred mainly at the subtalar joint.

    CONCLUSION:

    The changes in ankle and subtalar kinematics in response to the foot orthosis contradict existing orthotic paradigms that assume that changes occur only at the subtalar joint. The kinematic changes due to the orthosis are indicative of a strong interaction between the often common function of the ankle and subtalar joints.

  • 13.
    Mattsson, C. Mikael
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Ståhlberg, Marcus
    Institutionen för Medicin, Enheten för kardiologi, Karolinska Universitetssjukhuset.
    Larsen, Filip
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Braunschweig, Frieder
    Institutionen för Medicin, Enheten för kardiologi, Karolinska Universitetssjukhuset.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Late cardiovascular drift observable during ultra endurance exercise.2011In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 43, no 7, p. 1162-1168Article in journal (Refereed)
    Abstract [en]

    Introduction: The present study investigates the adaptation of the central circulation to ultraenduranceexercise, including the relative contributions of changes in stroke volume (SV) andarterio-venous oxygen difference (a-v O2 diff) to the increased oxygen pulse (VO2/HR).Methods: We evaluated subjects undergoing 12h of mixed exercise at controlled intensity(n=8) and a 53h Adventure race (n=20). Heart rate (HR), oxygen uptake (VO2), and cardiacoutput determined using non-invasive gas rebreathing (CORB) were measured during cyclingat fixed work rate after 0, 4, 8, 12 hours, and 0, 20, and 53 hours of continuous exercise in the12 and 53 h protocol, respectively.Results and Conclusion: The central circulation changed in several steps in response to ultraenduranceexercise. Compared to initial levels, VO2 was increased at every time-point measured.The increase was attributed to peripheral adaptations, confirmed by a close correlation betweenchange in VO2 and change in a-v O2 diff. The first step of the circulatory response was typical ofnormal (early) cardiovascular drift, with increased HR and concomitantly decreased SV andVO2/HR, occurring over the first 4-6 h. The second step, which continued until approximately 12h, included reversed HR-drift, with normalization of SV and VO2/HR. When exercise continueduntil 50 h late cardiovascular drift was noted, characterized by increased VO2/HR, (indicatingmore efficient energy distribution), decreased peripheral resistance, increased stroke volume, anddecreased work of the heart. Since cardiac output was maintained at all time points we interpretthe changes as physiologically appropriate adaptations to ultra-endurance exercise.

  • 14. Neovius, Martin
    et al.
    Uddén, Joanna
    Hemmingsson, Erik
    Karolinska institutet.
    Assessment of change in body fat percentage with DXA and eight-electrode BIA in centrally obese women.2007In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 39, no 12, p. 2199-203Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To compare estimates of change in percent body fat (Delta%BF) between DXA and BIA8 in abdominally obese women.

    METHODS: Six-month longitudinal study of 106 women (baseline: age 48.2 +/- 7.6 yr; BMI 30.4 +/- 2.9 kg.m; %BFDXA 45.8 +/- 3.6%) participating in an exercise-oriented behavior-change program (walking and bicycling). Fatness was measured by DXA and Tanita BC-418 (BIA8). Agreement between methods was assessed, and regression analysis was used to find predictors of the deviation between methods for estimating changes in fat mass percentage.

    RESULTS: The methods differed significantly, both at baseline and follow-up (-5.0 and -4.4%BF, respectively; both P < 0.001). The mean Delta%BF was -1.1 +/- 2.5%BFDXA and -0.5 +/- 2.2%BFBIA8 (mean difference between methods 0.6 +/- 1.8%BF; P < 0.001; 95% limits of agreement -3.0 to 4.2%BF), with a range of -14.8 to 3.3%BFDXA and -9.4 to 3.5%BFBIA8. Approximately 49% of the variation in the difference between methods was explained by variations in age (beta = -0.05; P = 0.006), DeltaBMI (beta = 0.98; P < 0.001), and Delta%BFDXA (beta = -0.71; P < 0.001), indicating that the larger the change, the greater the discrepancy between methods.

    CONCLUSION: The difference between methods regarding Delta%BF was statistically significant, but it was of small magnitude. However, with increasing Delta%BF, increasing discrepancies were observed, implying that the BIA equipment may have limited validity for detecting larger fat losses. Both clinicians and researchers may benefit from awareness of this potential limitation.

  • 15.
    Nolan, Lee
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Patritti, Benjamin L
    Simpson, Kathy J
    A biomechanical analysis of the long-jump technique of elite female amputee athletes.2006In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 38, no 10, p. 1829-35Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The purpose of this study was to investigate whether female lower-limb amputees conform to the established long-jump model and to compare the kinematics of the approach and take-off phases for elite female transfemoral and transtibial amputee long jumpers. METHODS: Eight female transfemoral and nine female transtibial amputee athletes were videotaped (sagittal plane movements at 50 Hz) from third-to-last step to take-off during the 2004 Paralympic Games long-jump finals. After digitizing and reconstruction of 2D coordinates, key variables were calculated at each stride and during contact with the take-off board. Additionally, approach speed during the run-up of each jump was recorded (100 Hz) using a laser Doppler device (LDM 300 C Sport, Jenoptik Laser, Jena, Germany). RESULTS: The transfemoral amputees had a consistently higher center of mass height on the last three steps before take-off than the transtibial amputees. However, at touch-down onto the take-off board, they lowered their center of mass excessively so that from touch-down to take-off, they were actually lower than the transtibial amputees. This resulted in a greater negative vertical velocity at touch-down and may have inversely affected their jump performance. CONCLUSION: Female transtibial athletes conformed to the long-jump model, although adaptations to this technique were displayed. Female transfemoral athletes, however, exhibited no relationship between take-off speed and distance jumped, which may be attributable to their excessive lowering of their center-of-mass height at touch-down onto the take-off board. It is recommended that coaches and athletes proceed with caution when trying to replicate techniques used by able-bodied athletes because adaptations to the constraints of a prosthesis should be considered.

  • 16.
    Schantz, Peter
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology, The Research Unit for Movement, Health and Environment.
    Stigell, Erik
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology, The Research Unit for Movement, Health and Environment.
    A criterion method for measuring route distance in physically active commuting.2009In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 41, no 2, p. 472-8Article in journal (Refereed)
    Abstract [en]

    PURPOSE: There is a need for accurate, reliable, and feasible methods for determining route distances in physically active transportation. The aim of this study, therefore, was to scrutinize if distances of commuting routes drawn by physically active commuters and measured with a digital curvimetric distance measurement device could serve such a purpose. METHODS: Participants were recruited when walking or bicycling in the inner urban area of Stockholm, Sweden. Questionnaires and individually adjusted maps were sent twice to the participants (n = 133). Commuting routes from home to work were drawn on the maps. These were measured using a digital curvimetric distance measurer that was carefully controlled for validity and reproducibility. Marked points of origin and destination were checked for validity and reproducibility using stated addresses and address geocoding systems. Nineteen participants were followed with a global positioning system (GPS) to control for validity of drawn routes. An analysis of the effect on distance measurements of any deviations between GPS route tracings and drawn routes was undertaken. RESULTS: No order effects were noted on distance measurements, and the test-retest intraclass correlation coefficient was 0.999 (P

  • 17. Svedenhag, Jan
    et al.
    Seger, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Running on land and in water: comparative exercise physiology1992In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 24, no 10, p. 1155-1160Article in journal (Refereed)
    Abstract [en]

    The effect of water immersion on cardiorespiratory and blood lactate responses during running was investigated. Wearing a buoyant vest, 10 trained runners (mean age 26 yr) ran in water at four different and specified submaximal loads (target heart rates 115, 130, 145, and 155-160 beats.min-1) and at maximal exercise intensity. Oxygen uptakes (VO2), heart rates, perceived exertion, and blood lactate concentrations were measured. Values were compared with levels obtained during treadmill running. For a given VO2, heart rate was 8-11 beats.min-1 lower during water running than during treadmill running, irrespective of exercise intensity. Both the maximal oxygen uptake (4.03 vs 4.60 1 x min-1) and heart rate (172 vs 188 beats.min-1) were lower during water running. Perceived exertion (legs and breathing) and the respiratory exchange ratio (RER) were higher during submaximal water running than during treadmill running, while ventilation (1 x min-1) was similar. The blood lactate concentrations were consistently higher in water than on the treadmill, both when related to VO2 and to %VO2max. Partly in conformity with earlier cycle ergometer studies, these data suggest that immersion induces acute cardiac adjustments that extend up to the maximal exercise level. Furthermore, both the external hydrostatic load and an altered running technique may add to an increased anaerobic metabolism during supported water running.

  • 18.
    Wang, Li
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Research group for Mitokondriell funktion och metabolisk kontroll.
    Psilander, Niklas
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Research group for Mitokondriell funktion och metabolisk kontroll.
    Tonkonogi, Michail
    Ding, Shuzhe
    Sahlin, Kent
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Research group for Mitokondriell funktion och metabolisk kontroll.
    Similar expression of oxidative genes after interval and continuous exercise.2009In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 41, no 12, p. 2136-44Article in journal (Refereed)
    Abstract [en]

    PURPOSE: There is a debate whether interval or traditional endurance training is the most effective stimulus of mitochondrial biogenesis. Here, we compared the effects of acute interval exercise (IE) or continuous exercise (CE) on the muscle messenger RNA (mRNA) content for several genes involved in mitochondrial biogenesis and lipid metabolism. METHODS: Nine sedentary subjects cycled for 90 min with two protocols: CE (at 67% VO2max) and IE (12 s at 120% and 18 s at 20% of VO2max). The duration of exercise and work performed with CE and IE was identical. Muscle biopsies were taken before and 3 h after exercise. RESULTS: There were no significant differences between the two exercise protocols in the increases in VO2 and HR, the reduction in muscle glycogen (35%-40% with both protocols) or the changes in blood metabolites (lactate, glucose, and fatty acids). The mRNA content for major regulators of mitochondrial biogenesis [peroxisome proliferator-activated receptor (PPAR) gamma coactivator 1alpha (PGC-1alpha), PGC-1-related coactivator, PPARbeta/delta] and of lipid metabolism [pyruvate dehydrogenase kinase isozyme 4 (PDK4)] increased after exercise, but there was no significant difference between IE and CE. However, the mRNA content for several downstream targets of PGC-1alpha increased significantly only after CE, and mRNA content for nuclear respiratory factor 2 was significantly higher after CE (P < 0.025 vs IE). CONCLUSIONS: The present findings demonstrate that, when the duration of exercise and work performed is the same, IE and CE influence the transcription of genes involved in oxidative metabolism in a similar manner.

  • 19. Westing, Stephen
    et al.
    Seger, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Isoacceleration: a new concept of resistive exercise1991In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 23, no 5, p. 631-635Article in journal (Refereed)
    Abstract [en]

    This study presents the concept of constant (iso-) accelerative and decelerative exercise and compares concentric and eccentric torque output during isoaccelerative and isodecelerative movements with that during comparable constant velocity (isokinetic) conditions. Twelve men (19-42 yr) performed maximal voluntary concentric and eccentric knee extensions at velocities of 120 and 240 degrees.s-1 (isokinetic) and at accelerations of 180 and 720 degrees.s-2 (both isoaccelerative and isodecelerative) between 10 degrees and 90 degrees knee angles. At 50 degrees, the 180 and 720 degrees.s-2 tests had velocities of 120 and 240 degrees.s-1, respectively, and thus torque comparisons could be made at a corresponding position and velocity. No difference was seen among the isoaccelerative, isodecelerative, or isokinetic angle- and velocity-specific torques for either the concentric or eccentric tests (P greater than 0.05). The results demonstrated that, under conditions of maximal voluntary effort, movement speed as such (within the range studied) was the essential determinant of muscle force--not whether this speed was attained during accelerative, decelerative, or constant velocity movements. As a testing and training modality, the controlled acceleration technique, particularly eccentric deceleration and concentric accleration, appears to offer advantages as compared with existing methods, since it more faithfully reflects the contraction conditions during natural strength-requiring movements.

  • 20.
    Åstrand, PO
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    J.B. Wolffe Memorial Lecture. "Why exercise?".1992In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 24, no 2, p. 153-62Article in journal (Refereed)
    Abstract [en]

    There is a pronounced plasticity and adaptability in the structural and/or functional properties of cells, tissues, and organ systems in the human body when exposed to various stimuli. While there is unanimous agreement that regular exercise is essential for optimal function of the human body, it is evident that extrinsic factors, such as diet and exercise habits, are reflected in the morbidity and mortality statistics, especially in the aged. Aging is obligatorily associated with reduced maximal aerobic power and reduced muscle strength, i.e., with reduced physical fitness. As a consequence of diminished exercise tolerance, a large and increasing number of elderly persons will be living below, at, or just above "thresholds" of physical ability, needing only a minor intercurrent illness to render them completely dependent. Physical training can readily produce a profound improvement of functions essential for physical fitness in old age. Adaptability to regular physical activity serves to cause less disruption of the cell's "milieu interieur" and minimizes fatigue, thereby enhancing performance and the economy of energy output during exercise.

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