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  • 301.
    Seger, Jan
    et al.
    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.
    Electrically evoked eccentric and concentric torque-velocity relationships in human knee extensor muscles.2000In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 169, p. 63-69Article in journal (Refereed)
    Abstract [en]

    The torque-velocity relationship, obtained during in situ conditions in humans, demonstrates a levelling-off of eccentric torque output at the isometric torque level, at least for knee extensor actions. In contrast, the in vitro force-velocity relationship for animal muscle preparations is characterized by a sharp rise in eccentric force from isometric maximum. A force-regulating 'protective' mechanism has been suggested during maximal voluntary high-tension eccentric muscle actions. To investigate this phenomenon, maximal voluntary and three different levels of submaximal, electrically induced torques were compared during isometric and low velocity (10, 20 and 30 degrees s-1) isokinetic eccentric and concentric knee extensor actions in 10 healthy, moderately trained subjects. Eccentric torque was higher than isometric during electrically evoked, but not during maximal voluntary muscle actions. In contrast, concentric torque was significantly lower than isometric for both maximal voluntary and submaximal, electrically evoked conditions. Comparisons of normalized torques (isometric value under each condition set to 100%) demonstrated that the maximal voluntary eccentric torque had to be increased by 20%, and the isometric by 10% in order for the maximal voluntary torque-velocity curve to coincide with the electrically stimulated submaximal ones. These results support the notion that a tension-regulating mechanism is present primarily during eccentric maximal voluntary knee extensor actions.

  • 302.
    Seger, Jan
    et al.
    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.
    Muscle strength and electromyogram in boys and girls followed through puberty.2000In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 81, p. 54-61Article in journal (Refereed)
    Abstract [en]

    The main purpose of this study was to investigate the changes in anthropometric measures and muscle strength that occur during puberty in children from the age of 11 to 16 years. Special attention was paid to possible gender- and muscle action-type-specific alterations in torque/velocity and EMG/velocity characteristics. Sixteen children participated in the study (9 boys and 7 girls). Eccentric and concentric muscle strength was measured on an isokinetic dynamometer at angular velocities of 45, 90 and 180 degrees x s(-1). Simultaneously, a surface electromyogram (EMG) was recorded from the quadriceps muscle. At the age of 11, the boys and girls exhibited equal anthropometric measures and strength performance. In both genders, body measures and muscle strength increased significantly during the 5-year period, with larger increases being recorded for the boys. In addition, the boys increased selectively their eccentric torque per body mass, indicating an action-type-specific change in muscle quality. The general shape of the torque/velocity relationship exhibited an adult-like pattern both before and after puberty, and did not differ between genders. Both pre- and postpuberty, myoelectric activity was generally lower during eccentric than concentric actions, the highest values occurring for both genders in the concentric 180 degrees x s(-1) test. Ratios of eccentric to concentric torque per EMG, which reflect electromechanical efficiency, showed no significant changes with age. A significant velocity- and gender-specific change in electromechanical efficiency was observed at the highest speed at postpuberty, where the ratio for the girls was higher than for the boys.

  • 303.
    Seger, Jan
    et al.
    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.
    Muscle strength and myoelectric activity in prepubertal and adult males and females.1994In: European Journal of Applied Physiology and Occupational Physiology, ISSN 0301-5548, E-ISSN 1432-1025, Vol. 69, p. 81-87Article in journal (Refereed)
    Abstract [en]

    The compare children and adults of both genders with respect to torque-velocity, electromyogram (EMG)-velocity and torque-EMG relationships during maximal voluntary knee extensor muscle actions. Four groups of purpose of this investigation was to ten subjects each were studied comprising 11-year-old girls and boys and female and male physical education students (22-35 years). Maximal voluntary eccentric (lengthening) and concentric (shortening) actions of the knee extensors were performed at the constant velocities of 45, 90 and 180 degrees.s-1. Average values for torque and EMG activity, recorded by surface electrodes from the quadriceps muscle, were taken for the mid 40 degrees of the 80 degrees range of motion. The overall shapes of the torque- and EMG-velocity relationships were similar for all four groups, showing effects of velocity under concentric (torque decrease and EMG increase) but not under eccentric conditions. Eccentric torques were always greater than velocity-matched concentric ones, whereas the eccentric EMG values were lower than the concentric ones at corresponding velocities. Torque output per unit EMG activity was clearly higher for eccentric than for concentric conditions and the difference was of similar magnitude for all groups. Thus, the torque-EMG-velocity relationships would appear to have been largely independent of gender and to be fully developed at a prepubertal age.

  • 304. Seynnes, Olivier R
    et al.
    Bojsen-Møller, Jens
    Albracht, Kirsten
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Cronin, Neil J
    Finni, Taija
    Magnusson, S Peter
    Ultrasound-Based Testing Of Tendon Mechanical Properties: A Critical Evaluation.2015In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 118, no 2, p. 133-141Article in journal (Refereed)
    Abstract [en]

    In the past twenty years, the use of ultrasound-based methods has become a standard approach to measure tendon mechanical properties in vivo. Yet, the multitude of methodological approaches adopted by various research groups probably contributes to the large variability of reported values. The technique of obtaining and relating tendon deformation to tensile force in vivo has been applied differently, depending on practical constraints or scientific points of view. Divergence can be seen in i) methodological considerations such as the choice of anatomical features to scan and to track, force measurements or signal synchronisation and ii), in physiological considerations related to the viscoelastic behaviour or length measurements of tendons. Hence, the purpose of the present review is to assess and discuss the physiological and technical aspects connected to in vivo testing of tendon mechanical properties. In doing so, our aim is to provide the reader with a systematic, qualitative analysis of ultrasound-based techniques. Finally, a list of recommendations is proposed for a number of selected issues.

  • 305.
    Sirevåg, K
    et al.
    University of Bergen, Faculty of Psychology, Solli DPS, Nestun, Norway.
    Stavestrand, S
    Endal, T
    Sjøbø, T
    Nordhus, IH
    Pallesen, S
    Nordahl, H
    Specht, K
    Martinsen, EW
    Hammar, Å
    Mohlman, J
    Halmøy, A
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thayer, JF
    Hjelmervik, H
    Hovland, A
    Physical EXercise Augmented COGnitive Behaviour Therapy for Older Adults with Generalised Anxiety Disorder (PEXACOG)2018Conference paper (Refereed)
    Abstract [en]

    Generalised anxiety disorder (GAD) is the most prevalent severe anxiety disorder among older adults. The disorder has a pervasive influence on the lives of those affected, and is a risk factor for other severe disorders such as depression, dementia and coronary heart disease. Cognitive behaviour therapy (CBT) is the treatment of choice for this disorder, but older adults have shown reduced effect of treatment compared to working age adults. Physical exercise has been suggested as intervention to improve the effects of treatment for GAD, via its demonstrated positive effect on cognitive functioning, increased plasticity in the brain, and increased availability of neurotrophins important for extinction of fear associations. The aim of the current research project is to investigate whether augmenting CBT with physical exercise will lead to improved effects of CBT on GAD in older adults in a randomized controlled trial (RCT). Participants between 60-75 years of age with a primary diagnosis of GAD will be randomised to one of two treatment conditions. The effects of treatment will be assessed on outcome measures, biological, physiological and cognitive measures at pre- interim-, and post-treatment, and follow-up assessments at 6- and 12-months post intervention. Participants in both groups will receive five weeks of pre-treatment intervention consisting of either physical exercise or weekly telephone contact. Participants thereafter receive either ten weeks of manualised CBT for GAD combined with manualised physical exercise or ten weeks of manualised CBT for GAD combined with weekly telephone contact. We expect that the treatment effect of the physical exercise augmented CBT will be greater than that of CBT combined with weekly telephone contact, as measured by a reduction in GAD symptoms on the Penn State Worry Questionnaire and in the proportion of remitted patients. The study also aims to determining the possible beneficial and augmenting properties of physical exercise in combination with CBT, and our understanding of clinical characteristics of GAD and mechanisms involved in treatment effect. Treatment rationale, procedures and protocols will be presented in detail together with preliminary results from the initial feasibility study comprises eight participants

  • 306.
    Sirivåg, K
    et al.
    University of Bergen, Faculty of Psychology, Bergen,Solli DPS, Nesttun, Norway.
    Haukenes Stavestrand, S
    Hilde Nordhus, I
    Pallesen, S
    Sjøbø, T
    Bruun Endal, T
    Nordahl, HM
    Specht, K
    Hammar, Å
    Halmøy, A
    Martinsen, EW
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hjelmervik, H
    Mohlman, J
    Thayer, JF
    Hovland, A
    Physical exercise augmented cognitive behaviour therapy for older adults with generalised anxiety disorder (PEXACOG): Study protocol and feasibility results from a randomised controlled trial2018Conference paper (Refereed)
    Abstract [en]

    Background. Generalised anxiety disorder (GAD) is prevalent among older adults. These patients exhibit impaired response to cognitive behaviour therapy (CBT), and physical exercise has been recommended as a potential add-on intervention to improve efficacy. The current study is a randomised clinical trial that will compare CBT augmented with physical exercise, or CBT combined with attention placebo, and the current study assessing the feasibility of testing procedures and the experimental combined treatment measures.

    Methods. 4 participants were included in the feasibility study, and feasibility was assessed trough completion and attendance rates of testing and treatment sessions. Primary outcome measures were remission as assessed by an independent clinical rater using the Anxiety Disorders Interview Schedule for DSM-IV, and by symptom reduction on Penn State Worry Questionnaire. Manipulation check was assessed by physical tests of change in aerobic capacity and strength. Participants were measured on clinical, biological, physiological and neuropsychological tests at pre-, interim and post-treatment.

    Results. Completed treatment protocol for the RCT will be presented. 3 of 4 participants completed the full protocol including testing and the experimental augmented treatment. Participants completed 100% and 80% of CBT and physical exercise content, respectively. The three completers had large improvements on primary outcome and on manipulation checks.

    Conclusion. The testing procedures and experimental augmented treatment appear to be feasible. The preliminary findings indicate that this combined intervention can be efficacious.

  • 307.
    Sirivåg, K
    et al.
    Universitetet i Bergen; Solli Distriktspsykiatriske Senter (DPS), Nesttun, Norge.
    Stavestrand, SH
    Sjøbø, T
    Endal, T
    Nordhus, IH
    Pallesen, S
    Nordahl, H
    Pallesen, S
    Nordahl, H
    Mohlman, J
    Specht, K
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hammar, Å
    Halmøy, A
    Harkestad, N
    Hjelmervik, H
    Martinsen, E
    Thayer, J
    Harvey, A
    Hovland, A
    Universitetet i Bergen; Solli Distriktspsykiatriske Senter (DPS), Nesttun, Norge.
    Physical EXercise Augmented COGnitive Behaviour Therapy for Older Adults with Generalised Anxiety Disorder (PEXACOG)2016Conference paper (Refereed)
    Abstract [en]

    Generalised anxiety disorder (GAD) is the most prevalent severe anxiety disorder among older adults. The disorder has a pervasive influence on the lives of those affected, and is a risk factor for other severe disorders such as depression, dementia and coronary heart disease. Cognitive behaviour therapy (CBT) is the treatment of choice for this disorder, but older adults have shown reduced effect of treatment compared to working age adults. Physical exercise has been suggested as intervention to improve the effects of treatment for GAD, via its demonstrated positive effect on cognitive functioning, increased plasticity in the brain, and increased availability of neurotrophins important for extinction of fear associations. The aim of the current research project is to investigate whether augmenting CBT with physical exercise will lead to improved effects of CBT on GAD in older adults in a randomized controlled trial (RCT). Participants between 60-75 years of age with a primary diagnosis of GAD will be randomised to one of two treatment conditions. The effects of treatment will be assessed on outcome measures, biological, physiological and cognitive measures at pre- interim-, and post-treatment, and follow-up assessments at 6- and 12-months post intervention. Participants in both groups will receive five weeks of pre-treatment intervention consisting of either physical exercise or weekly telephone contact. Participants thereafter receive either ten weeks of manualised CBT for GAD combined with manualised physical exercise or ten weeks of manualised CBT for GAD combined with weekly telephone contact. We expect that the treatment effect of the physical exercise augmented CBT will be greater than that of CBT combined with weekly telephone contact, as measured by a reduction in GAD symptoms on the Penn State Worry Questionnaire and in the proportion of remitted patients. The study also aims to determining the possible beneficial and augmenting properties of physical exercise in combination with CBT, and our understanding of clinical characteristics of GAD and mechanisms involved in treatment effect. Treatment rationale, procedures and protocols will be presented in detail together with preliminary results from the initial feasibility study comprises eight participants.

  • 308. Sjödin, B
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Frith, K
    Karlsson, J
    Effect of physical training on LDH activity and LDH isozyme pattern in human skeletal muscle.1976In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 97, no 2, p. 150-7Article in journal (Refereed)
    Abstract [en]

    Total lactate dehydrogenase (LDH) activity and LDH isozyme pattern were studied in muscle biopsies obtained from m. vastus lateralis after 1) "aerobic" training performed as interval and extreme distance running, respectively (3 subjects); and 2) "anaerobic" training for two months, carried out as repeated maximal bursts of approximately 1 min running (6 subjects). After the "anaerobic training" no changes in LDH properties could be detected, although running performance improved. The extreme distance running resulted in a decrease in total LDH activity and an increase in relative activity of the heart specific isozymes. A relationship was also shown between the relative activity of these isozymes and the training distance covered. The relatively more aerobic prevailing during distance running as compared to "anaerobic training" were proposed to decrease muscle specific subunits and/or increase synthesis of heart specific subunits in both muscle fiber types. This suggestion was supported by isozyme analysis of lyophilized and dissected single muscle fibres.

  • 309.
    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.

  • 310. Squair, Jordan W
    et al.
    Bjerkefors, Anna
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Inglis, J Timothy
    Lam, Tania
    Carpenter, Mark G
    Cortical and vestibular stimulation reveal preserved descending motor pathways in individuals with motor-complete spinal cord injury.2016In: Journal of Rehabilitation Medicine, ISSN 1650-1977, E-ISSN 1651-2081, Vol. 48, no 7, p. 589-596Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To use a combination of electrophysiological techniques to determine the extent of preserved muscle activity below the clinically-defined level of motor-complete spinal cord injury.

    METHODS: Transcranial magnetic stimulation and vestibular-evoked myogenic potentials were used to investigate whether there was any preserved muscle activity in trunk, hip and leg muscles of 16 individuals with motor-complete spinal cord injury (C4-T12) and 16 able-bodied matched controls.

    RESULTS: Most individuals (14/16) with motor-complete spinal cord injury were found to have transcranial magnetic stimulation evoked, and/or voluntary evoked muscle activity in muscles innervated below the clinically classified lesion level. In most cases voluntary muscle activation was accompanied by a present transcranial magnetic stimulation response. Furthermore, motor-evoked potentials to transcranial magnetic stimulation could be observed in muscles that could not be voluntarily activated. Vestibular-evoked myogenic potentials responses were also observed in a small number of subjects, indicating the potential preservation of other descending pathways.

    CONCLUSION: These results highlight the importance of using multiple electrophysiological techniques to assist in determining the potential preservation of muscle activity below the clinically-defined level of injury in individuals with a motor-complete spinal cord injury. These techniques may provide clinicians with more accurate information about the state of various motor pathways, and could offer a method to more accurately target rehabilitation.

  • 311.
    Stavestrand, Silje Haukenes
    et al.
    University of Bergen, Norway.
    Sirevåg, Kristine
    University of Bergen, Norway.
    Nordhus, Inger Hilde
    University of Bergen, Norway.
    Sjøbø, Trond
    Solli DPS, Nesttun, Norway.
    Endal, Trygve Bruun
    Solli DPS, Nesttun, Norway.
    Nordahl, Hans M
    Norwegian University of Science and Technology, Trondheim, Norway..
    Specht, Karsten
    University of Bergen, Norway.
    Hammar, Åsa
    University of Bergen, Norway.
    Halmøy, Anne
    University of Bergen, Norway.
    Martinsen, Egil W
    University of Oslo, Norway.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hjelmervik, Helene
    University of Bergen, Norway.
    Mohlman, Jan
    William Paterson University, NJ, USA.
    Thayer, Julian F
    Ohio State University, OH, USA.
    Hovland, Anders
    University of Bergen, Norway.
    Physical exercise augmented cognitive behaviour therapy for older adults with generalised anxiety disorder (PEXACOG): study protocol for a randomized controlled trial.2019In: Trials, ISSN 1745-6215, E-ISSN 1745-6215, Vol. 20, no 1, article id 174Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Generalised anxiety disorder (GAD) is a frequent and severe anxiety disorder among older adults. GAD increases the risk of developing other disorders such as depression and coronary heart disease. Older adults with GAD exhibit a poorer response to cognitive behaviour therapy (CBT) compared to younger patients with GAD. The normal age-related cognitive decline can be a contributor to reduced treatment efficacy. One strategy for improving treatment efficacy is to combine CBT with adjunctive interventions targeted at improving cognitive functions. Physical exercise is a viable intervention in this regard. Increased levels of brain-derived neurotrophic factor may mediate improvement in cognitive function. The present study aims to investigate the proposed effects and mechanisms related to concomitant physical exercise.

    METHODS: The sample comprises 70 participants aged 60-75 years, who have GAD. Exclusion criteria comprise substance abuse and unstable medication; inability to participate in physical exercise; and conditions which precludes GAD as primary diagnosis. The interventions are individual treatment in the outpatient clinic at the local psychiatric hospital, with two experimental arms: (1) CBT + physical exercise and (2) CBT + telephone calls. The primary outcome measure is symptom reduction on the Penn State Worry Questionnaire. Other measures include questionnaires, clinical interviews, physiological, biological and neuropsychological tests. A subset of 40 participants will undergo magnetic resonance imaging (MRI). After inclusion, participants undergo baseline testing, and are subsequently randomized to a treatment condition. Participants attend five sessions of the add-on treatment in the pre-treatment phase, and move on to interim testing. After interim testing, participants attend 10 sessions of CBT in parallel with continued add-on treatment. Participants are tested post-intervention within 2 weeks of completing treatment, with follow-up testing 6 and 12 months later.

    DISCUSSION: This study aims to develop better treatment for GAD in older adults. Enhancing treatment response will be valuable from both individual and societal perspectives, especially taking the aging of the general population into account.

    TRIAL REGISTRATION: ClinicalTrials.gov, NCT02690441 . Registered on 24 February 2016.

  • 312. Stokes, V P
    et al.
    Lanshammar, H
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Dominant pattern extraction from 3-D kinematic data.1999In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 46, no 1, p. 100-6Article in journal (Refereed)
    Abstract [en]

    A new method for the extraction of a repeating pattern in cyclic biomechanical data is proposed--singular value decomposition pattern analysis (SVDPA). This method is based on the recent work of Kanjilal and Palit [14], [15] and can be applied to both contiguous and repeated trials without being constrained to be strictly periodic. SVDPA is a data-driven approach that does not use a preselected set of basis functions; but instead utilizes a data matrix with a special structure to identify repeating patterns. Several important features of SVDPA are described including its close relationship to the Kahunen-Loève transform. The dominant pattern is defined as the average energy component (AEC). The AEC is obtained from the SVD of the data matrix and is equivalent to the optimal [maximal signal-to-noise ratio (SNR)] ensemble average pattern. The degree of periodicity and SNR for the AEC are defined explicitly from the singular values of the data matrix. We illustrate the usefulness of SVDPA for dominant pattern extraction by applying it to the quasiperiodic three-dimensional trajectory of a marker attached to the trunk during treadmill locomotion. The AEC obtained for the normalized trajectory and error estimates at each point suggests that SVDPA could be a useful tool for the extraction of the fine details from cyclic biomechanical data.

  • 313. Stokes, V P
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Lanshammar, H
    From stride period to stride frequency.1998In: Gait & posture, Vol. 7, no 1, p. 35-38Article in journal (Refereed)
    Abstract [en]

    The stride-cycle frequency of gait data is often estimated by taking the inverse of the average stride-cycle time (stride period) over several stride-cycles. We derive the density function of the stride-cycle frequency frequency (stride frequency) and describe some of its properties. We also show the conditions under which the inverse of the mean stride period is a 'good' estimate of the mean stride frequency. Copyright 1998 Elsevier Science B.V.

  • 314.
    Stålman, Cecilia
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences. Karolinska institutet.
    Ryhed, Anna
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Godhe, Manne
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    A novel aerobic test, 5-minute-pyramid-test, useful in school to monitor VO2max2019In: AISEP International Conference 2019 Book of abstracts, 2019, p. 402-Conference paper (Other academic)
  • 315.
    Tais, Senna
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Eriksson, Martin
    KTH.
    Halvorsen, Kjartan
    KTH och Uppsala Universitet.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Effects of training with concurrent EMG feedback on Quadriceps stength and activation2012Conference paper (Refereed)
  • 316.
    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)
  • 317. Tesch, P
    et al.
    Sjödin, B
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Karlsson, J
    Muscle fatigue and its relation to lactate accumulation and LDH activity in man.1978In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 103, no 4, p. 413-20Article in journal (Refereed)
    Abstract [en]

    The lactate concentration in different muscle fibre types was determined in biopsy specimens from human vastus lateralis muscle after 30 and 60 s of maximal dynamic leg exercise. In addition, muscle fibre type distribution, total lactate dehydrogenase (LDH) activity, and isozymes of LDH were determined. In accordance with previous studies (Thorstensson and Karlsson 1976, Nilsson et al. 1977) it was found that an increasing proportion of slow twitch (ST) fibres corresponded to better sustained muscle force. Lactate was found preferentially in fast twitch (FT) fibres after 30 s, but after 60 s this difference was abolished. Differences between the two main muscle fibre types in muscle lactate, total LDH activity, and M-LDH activity were correlated to muscle fatigue. It was concluded that lactate or associated pH changes primarily in FT fibres could be one factor responsible for the impaired muscle function.

  • 318.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Effects of moderate external loading on the aerobic demand of submaximal running in men and 10 year-old boys.1986In: European Journal of Applied Physiology and Occupational Physiology, ISSN 0301-5548, E-ISSN 1432-1025, Vol. 55, no 6, p. 569-74Article in journal (Refereed)
    Abstract [en]

    The effects of moderate external loading on the aerobic demand of submaximal running were studied in habitually active adult men (29-37 yrs) and 10 year-old boys. The load was symmetrically placed around the trunk and adjusted to correspond to 10% of body weight. Running was performed on a treadmill at 8, 10 and 11 km X h-1 (2.2, 2.8 and 3.1 m X s-1). A small, but consistent decrease in net oxygen uptake (gross oxygen uptake in ml X kg-1 X min-1 minus calculated basal metabolic rate) with load was observed in both groups at all speeds, except for the men at 8 km X h-1. The decrease was larger for the boys and tended to enhance with speed. The boys had a higher net oxygen uptake than the adults at all unladen running velocities, whereas the difference in the loaded condition was significant only at the highest speed. The decrease in net oxygen uptake with load could not be directly correlated with differences in body weight or step frequency. It is hypothesized that a difference in the utilization of muscle elastic energy could underlie part of the age and load dependent changes observed in running economy.

  • 319.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    How is the normal locomotor program modified to produce backward walking?1986In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 61, no 3, p. 664-8Article in journal (Refereed)
    Abstract [en]

    The modifications occurring in the movement and muscle activity patterns of the leg when changing from forward to backward walking were studied in five healthy subjects during walking on a motor driven treadmill. Movements were recorded with a Selspot optoelectronic system and muscle activity with electromyography using surface electrodes. The movement trajectories of the leg in forward and backward walking essentially mirrored each other, even though the movements occurred in the reversed direction. The angular displacements at the hip, knee and ankle joints showed similar overall magnitude and pattern in the two situations. Most of the investigated muscles changed their pattern of activity in relation to the different movement phases. At the ankle, there was a switch between flexors and extensors with flexor activation during support in backward walking. The bursts of activity in knee extensors were prolonged and shifted to the main part of the support phase. In the hip extensors, the activity periods retained their positions relative to the leg movements, but changed function due to the reversed direction of movement. Thus, drastic changes occur in the normal locomotor program to produce a reversal of leg movements and propulsion backwards.

  • 320.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Observations on strength training and detraining.1977In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 100, no 4, p. 491-3Article in journal (Refereed)
  • 321.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arvidson, A
    Trunk muscle strength and low back pain.1982In: Scandinavian Journal of Rehabilitation Medicine, ISSN 0036-5505, E-ISSN 1940-2228, Vol. 14, no 2, p. 69-75Article in journal (Refereed)
    Abstract [en]

    The strength of the trunk muscles was measured in a group of young males with low back insufficiency (n=7) and in an age matched (19-21 yrs) healthy control group (n=8). A recently designed new application of the isokinetic technique was used to record maximal torque produced by the trunk muscles during flexion, extension and lateral flexion. Trunk muscle strength was measured during isometric contractions in different trunk positions and during slow isokinetic contractions in the whole range of motion. No significant differences between the groups were observed for trunk extension, lateral flexion or flexion with the centre of rotation at L2-L3 level. However, in the initial part of isokinetic trunk flexion with the pivot point at the hip joint the strength values for the back patients were significantly lower than for the controls. The present results demonstrate the importance of a comprehensive approach to the assessment of trunk muscle strength, including different movement velocities, body positions and pivot points. Further studies are needed to evaluate the significance of the specific weakness observed in dynamic trunk flexion strength in the back patients.

  • 322.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Carlson, H
    Fibre types in human lumbar back muscles.1987In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 131, no 2, p. 195-202Article in journal (Refereed)
    Abstract [en]

    The distribution of histochemically identified muscle fibre types was studied in biopsy samples from the two main muscles in the lumbar region of the human erector spinae, the multifidus and the longissimus, in 16 healthy subjects (nine males and seven females, age 20-30 years). Muscle fibres were classified as types I, IIA, IIB or IIC on the basis of the pH lability of their myofibrillar ATPases. There were no differences between the multifidus and the longissimus muscles in the relative occurrence of type I (62 vs. 57%), type IIA (20 vs. 22%) or type IIB fibres (18 vs. 22%), or in the absolute size of fibres (range of mean least diameters 58-66 micron). The oxidative potential (NADH-diaphorase staining intensity) was high in type I and low in type II fibres, irrespective of subgroups, in both muscles. In the females, the type I fibres occupied a relatively larger area (70-75 vs. 54-58% for the males) although the relative number of type I fibres was the same in both sexes. This was due to smaller type II fibres in the females resulting in higher type I/type II area ratios (1.70-1.90 vs. 0.88-0.92 for males). This suggests a difference in functional capacity of lumbar back muscles between males and females. On the other hand, the similarity in histochemical fibre-type distribution between the multifidus and the longissimus muscles does not give support for a functional differentiation between these two anatomically different parts of the lumbar erector spinae in man.

  • 323.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Carlson, H
    Zomlefer, M R
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Lumbar back muscle activity in relation to trunk movements during locomotion in man.1982In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 116, no 1, p. 13-20Article in journal (Refereed)
    Abstract [en]

    The function of lumbar back muscles was studied by relating their activity patterns to trunk movements in 7 healthy adult males during normal walking (1.0-2.5 m/s) and running (2.0-7.0 m/s) on a treadmill. The movements of the trunk in the sagittal and frontal planes were recorded with a Selspot optoelectronic system using infrared light emitting diodes as markers. The electromyographic (EMG) activity from the two main portions of the lumbar erector spinae muscles (Multifidus and Longissimus) was recorded bilaterally with intramuscular wire electrodes. The angular displacements of the trunk showed regular oscillations, but their shape, magnitude and relation to the step cycle were different in the two planes (sagittal and frontal) and varied with speed and mode of progression. The EMG pattern in both muscles showed a bilateral cocontraction with two main bursts of activity per step cycle starting just before each foot was placed on the ground. Relating the EMG to the movements of the trunk indicated that the main function of the lumbar erector spinae muscles is to restrict excessive trunk movements. During walking this restricting action is most evident for movements in the frontal plane, whereas in running the lumbar back muscles mainly control the movements in the sagittal plane.

  • 324.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Elwin, K
    Sjödin, B
    Karlsson, J
    Isozymes of creatine phosphokinase and myokinase in human heart and skeletal muscle.1976In: Scandinavian Journal of Clinical and Laboratory Investigation, ISSN 0036-5513, E-ISSN 1502-7686, Vol. 36, no 8, p. 821-6Article in journal (Refereed)
    Abstract [en]

    The isozyme patterns of creatine phosphokinase (CPK) and myokinase (MK) were investigated in biopsy material from human heart and skeletal muscle. The protein separation was performed on crude muscle homogenates by means of flat-bed isoelectric focusing. Two isozymes were demonstrated for each enzyme, irrespective of the sampling site. The pI values were, on the average, 9.8 (MK-1) and 8.9 (MK-2), 7.2 (CPK-1) and 6.9 (CPK-2), respectively. MK-1 and CPK-1 constituted an average of 81% and 70% of total staining density for each enzyme, respectively. The relative contribution of MK-1 differed, however. Heart muscle showed the highest values (mean 91%) and vastus lateralis the lowest (mean 74%). The mean value for soleus was 86% MK-1. Furthermore, the percentage of MK-1 present was negatively correlated with the percentage of fast twitch fibres in m. vastus lateralis (r = -0.67). No corresponding differences could be demonstrated for CPK isozyme distribution. In conclusion, it was demonstrated that MK and CPK each occurred as two isozymes in human heart and skeletal muscle, and that the relative distribution of MK isozymes, in contrast to CPK, was related to muscle fibre type composition, and thus to the metabolic profile of the muscle.

  • 325.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Grimby, G
    Karlsson, J
    Force-velocity relations and fiber composition in human knee extensor muscles.1976In: Journal of applied physiology, ISSN 0021-8987, Vol. 40, no 1, p. 12-6Article in journal (Refereed)
    Abstract [en]

    Standardized measurements of dynamic strength of the kneee extensor muscles were performed in 25 healthy male subjects (17-37 yr) by means of isokinetic contractions, i.e., knee extensions with constant angular velocities. Overall variation between double determinations of maximal torque throughout the 90 degrees arc of motion (0 degrees = fully extended leg) averaged 10% for the different constant velocities chosen. At any given angle of the knee the torque produced was higher for isometric than for dynamic contractions. Dynamic torque decreased gradually with increased speed of shortening. Peak dynamic torque was reached at knee angles in the range: 55-66 degrees, with a displacement toward smaller knee angles with higher angular velocities. Correlations were demonstrated between peak torque produced at the highest speed of muscle shortening and percent as well as relative area of fast twitch fibers in the contracting muscle. In addition muscles with a high percentage of fast twitch fibers had the highest maximal contraction speeds. These observations on intact human skeletal muscle are consistent with earlier findings in animal skeletal muscle preparations.

  • 326.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hultén, B
    von Döbeln, W
    Karlsson, J
    Effect of strength training on enzyme activities and fibre characteristics in human skeletal muscle.1976In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 96, no 3, p. 392-8Article in journal (Refereed)
    Abstract [en]

    Progressive strength training was performed 3 times a week for 8 weeks by 14 male students (19-31 yrs.). The training program consisted mainly of dynamic exercises for the leg extensors with maximal or close to maximal loads. The training caused significant improvements in dynamic and isometric strength. One repetition maximum in squats increased with 67%, Sargent jump with 22%, and maximal voluntary isometric contraction (MVC) with 13%, respectively. Body weight and leg muscle circumferences remained unchanged after training, whereas total body potassium, lean body mass and calculated total muscle mass increased, suggesting a change in body composition with training. Muscle biopsies were obtained from vastus lateralis for fibre analyses and determination of enzyme activities. There were no changes in muscle fibre composition or fibre area with training. The activities of Mg2+ stimulated ATPase, creatine phosphokinase and phosphofructokinase remained unchanged, whereas myokinase activity was increased after training from (1.41 to 1.52 moles x 10(-4) x g-1 x min-1, p less than 0.05). After training significant correlations (p less than 0.01) were demonstrated between Mg2+ stimulated ATPase activity and % fast twitch fibres (% FT) (r = 0.67), as well as between myokinase activity and % FT (r = 0.86).

  • 327.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Karlsson, J
    Fatiguability and fibre composition of human skeletal muscle.1976In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 98, no 3, p. 318-22Article in journal (Refereed)
    Abstract [en]

    The fatiguability of the quadriceps muscle was investigated in 10 male subjects (25-40 yrs), with inter-individual differences in fibre composition of their vastus lateralis muscles (range 25-65% fast twitch, FT, muscle fibres). Fatiguability was assessed as the decline in maximal force (in % of initial values) with 50 repeated isokinetic knee-extensions at fast angular velocity (3.14 rad/s). Each contraction lasted 0.5 s and the rest periods were about 0.7 s. Every subject was tested on two occasions and the standard deviation for a single determination of fatiguability was 1.4%. The decline in force after 50 contractions was on the average about 45%. The individual values varied, however, and a linear correlation was present between fatiguability and % FT fibres (r = 0.86, p less than 0.01). It was concluded that development of fatigue in human skeletal muscle performing repeated fast dynamic contractions with maximal effort was most marked in muscles with a high proportion FT fibres. This finding was in conformity with earlier results from animal skeletal muscle preparations.

  • 328.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Karlsson, J
    Viitasalo, J H
    Luhtanen, P
    Komi, P V
    Effect of strength training on EMG of human skeletal muscle.1976In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 98, no 2, p. 232-6Article in journal (Refereed)
    Abstract [en]

    The effects of an 8 weeks period of systematic progressive strength training on the EMG activity of the leg extensor muscles (vastus lateralis and rectus femoris) were investigated in 8 healthy male subjects (22-31 yrs). After training there were indications (n.s.) of a decline in integrated EMG (IEMG) during maximal isometric knee extension as well as in the IEMG vs isometric force relationship. The averaged motor unit potential (AMUP) did not demonstrate any significant changes due to the strength training regimen. In conformity with earlier findings no or only minor alterations were observed in anthropometrics, muscle enzyme activities and fibre composition. The fibre area ratio indicated a specific effect of the training stimuli on the fast twitch muscle fibres. Thus, EMG-analyses, as employed in the present study, did not provide any conclusive additional explanation as to the mechanisms behind the well established gains in muscle strength performance induced by the applied strength training program.

  • 329.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Larsson, L
    Tesch, P
    Karlsson, J
    Muscle strength and fiber composition in athletes and sedentary men.1977In: Medicine and science in sports, ISSN 0025-7990, Vol. 9, no 1, p. 26-30Article in journal (Refereed)
    Abstract [en]

    Members of Swedish national teams in track and field events (sprinting and jumping), downhill skiing, race walking, orienteering, and a group of sedentary men were studied to examine the relationship between muslce fiber characteristics in needle biopsy samples form m. vastus lateralis and muscle strength measured as peak torque during isokinectic knee extensions. In comparison with the sedentary group the following differences were found: a) percentage fast twitch fibers was lower in the endurance athetes, b) fast to slow twitch muscle fiber area ratio was higher in the track athletes, c)track athletes and downhill skier attained higher peak torque values at all angular velocities examined. The track athletes had, however, higher torque values at the fastest angular velocity as compared to the downhill skiers, whereas there was no differnce under isometric conditions. The proportion of fast twitch fibers was related to torque produced, especially at high motion velocity. The training also appeared to affect the force-velocity relationship.

  • 330.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Nilsson, J
    Carlson, H
    Zomlefer, M R
    Trunk movements in human locomotion.1984In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 121, no 1, p. 9-22Article in journal (Refereed)
    Abstract [en]

    Trunk movements in the frontal and sagittal planes were studied in 10 healthy males (18-35 yrs) during normal walking (1.0-2.5 m/s) and running (2.0-6.0 m/s) on a treadmill. Movements were recorded with a Selspot optoelectronic system. Directions, amplitudes and phase relationships to the stride cycle (defined by the leg movements) were analyzed for both linear and angular displacements. During one stride cycle the trunk displayed two oscillations in the vertical (mean net amplitude 2.5-9.5 cm) and horizontal, forward-backward directions (mean net amplitude 0.5-3 cm) and one oscillation in the lateral, side to side direction (mean net amplitude 2-6 cm). The magnitude and timing of the various oscillations varied in a different way with speed and mode of progression. Differences in amplitudes and timing of the movements at separate levels along the spine gave rise to angular oscillations with a similar periodicity as the linear displacements in both planes studied. The net angular trunk tilting in the frontal plane increased with speed from 3-10 degrees. The net forward-backward trunk inclination showed a small increase with speed up to 5 degrees in fast running. The mean forward inclination of the trunk increased from 6 degrees to about 13 degrees with speed. Peak inclination to one side occurred during the support phase of the leg on the same side. Peak forward inclination was reached at the initiation of the support phase in walking, whereas in running the peak inclination was in the opposite direction at this point. The adaptations of trunk movements to speed and mode of progression could be related to changing mechanical conditions and different demands on equilibrium control due to e.g. changes in support phase duration and leg movements.

  • 331.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Trunk muscle strength during constant velocity movements.1982In: Scandinavian Journal of Rehabilitation Medicine, ISSN 0036-5505, E-ISSN 1940-2228, Vol. 14, no 2, p. 61-8Article in journal (Refereed)
    Abstract [en]

    A new apparatus has been designed for standardized measurements of the strength of human trunk muscles utilizing the isokinetic (constant movement velocity) technique (Cybex). It is possible to measure the produced torque during maximal voluntary isometric and isokinetic contractions in the whole range of motion during flexion, extension and lateral flexion of the trunk. Effects of gravity are eliminated since the movements are performed in the horizontal plane. Torque can be measured around different centres of rotation of the body. With this experimental set-up the strength of the trunk muscles has been characterized in a group of 14 normal male subjects (18-31 yrs). The torque produced by the trunk muscles varied with movement velocity and trunk position in the arc of motion. Peak torque occurred in a position where the muscles involved were stretched. The strength of the trunk extensors exceeded that of the flexors, but the degree (ratio) varied with trunk position. The relative contribution of the hip muscles to the total torque produced with the centre of rotation at the hip joint was larger for flexors than for extensors and varied with velocity and position. It is concluded that the present technique is useful to characterize the human trunk muscles.

  • 332.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Oddsson, L
    Carlson, H
    Motor control of voluntary trunk movements in standing.1985In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 125, no 2, p. 309-21Article in journal (Refereed)
    Abstract [en]

    The pattern of activity in different trunk muscles during voluntary trunk movements was studied in the standing position in man. The electromyographic activity from ventral and dorsal trunk muscles on the left and right sides were recorded together with the movements in the sagittal and frontal planes (Selspot optoelectronic system). Movement direction, amplitude, velocity and initial posture were varied. In all movements there was a basic pattern of alternation between antagonist muscle groups. Fast movements were initiated by a sharp burst of activity, whereas slow flexions and side bendings resulted from a decrease in antigravity muscle activity. Movement amplitude was related to the magnitude of the initiating burst, and also to the time of onset of antagonist muscle activity with a braking effect. The contribution of passive internal forces in the braking of a movement was indicated by the myoelectrical pattern of activity, particularly in slow large side bendings, where ipsilateral activity was present at the end of the movement. Sagittal movements starting at different initial trunk inclinations resulted in shifts in onset time and duration between antagonist muscles. The observed modifications are specific adaptations of the motor program to balance changes in mechanical conditions, such as angular acceleration, moment arm for the gravitational force, and intrinsic forces of active and passive structures surrounding the spine and pelvis. In conclusion, the present results demonstrate that trunk movements are generated and controlled by specific patterns of muscle coordination.

  • 333.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Oddsson, Lars
    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.
    Arvidsson, Åke
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Balance in muscle strength between agonist and antagonist muscles of the trunk.1985In: Biomechanics IX: proceedings of the ninth International Congress of Biomechanics held in 1983 at Waterloo, Ontario, Canada. B / [ed] David A. Winter, 1985, p. 15-20Conference paper (Other academic)
  • 334.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Roberthson, H
    Adaptations to changing speed in human locomotion: speed of transition between walking and running.1987In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 131, no 2, p. 211-4Article in journal (Refereed)
    Abstract [en]

    The transition speed between walking and running was determined in 18 healthy males (23-38 years) of various statures (range of leg length 0.86-1.09 m) during acceleration and deceleration of different magnitudes (0.05-0.11 ms-2) on a motor-driven treadmill. The speed of the treadmill belt and the duration of the stance phases of each foot were recorded. A transition step was identified and the speed of transition was taken as the average speed value of the stance phase of that step. The overall mean value for the transition speed was 1.88 m s-1 (range 1.30-2.55). Deceleration resulted in a somewhat lower speed of transition than acceleration. There was a tendency towards increasing values for transition speed with increasing leg length. This could partly be explained by differences in natural frequency. The reasons for the switch between walking and running at a speed which is not extreme for either mode of progression are unclear. The subjective feeling that a transition will lead to a more comfortable situation might be based on previous experience combined with information from peripheral receptors and activity in central networks controlling locomotion.

  • 335.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Sjödin, B
    Karlsson, J
    Enzyme activities and muscle strength after "sprint training" in man.1975In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 94, no 3, p. 313-8Article in journal (Refereed)
    Abstract [en]

    Sprint type strength training was performed 3-4 times a week for 8 weeks by 4 healthy male students (16-18 yrs). The training was carried out on a treadmill at high speed and with high inclination. Muscle biopsies were obtained from vastus lateralis before and after the training period for histochemical classification of slow and fast twitch muscle fibres and for biochemical determination of metabolites and enzyme activities. Muscle fibre type distribution was unchanged, whereas fibre area indicated an increase for both fibre types in 3 subjects after training. The muscle enzyme activities of Mg2+ stimulated ATPase, myokinase and creatine phosphokinase increased 30, 20, and 36 percent, respectively. Muscle concentration of ATP and creatine phosphate (CP) did not change with training. Sargent's jump increased with on average 4 cm (from 47 to 51 cm), maximal voluntary contraction (MVC) with 19 kp (from 165 to 184 kp), and endurance at 50 percent of MVC with 9 s (from 47 to 56 s), respectively. After training all subjects showed a gain in body weight (mean 1.4 kg) and in thigh circumference (mean 1.5 cm) indicating a larger leg muscle volume and consequently also an increase in total ATP and CP.

  • 336.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Sjödin, B
    Tesch, P
    Karlsson, J
    Actomyosin ATPase, myokinase, CPK and LDH in human fast and slow twitch muscle fibres.1977In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 99, no 2, p. 225-9Article in journal (Refereed)
    Abstract [en]

    The enzyme activities of Mg2+ stimulated ATPase, creatine phosphokinase (CPK), myokinase (MK) and lactate dehydrogenase (LDH) were determined in pooled fast twitch (FT) and slow twitch (ST) human skeletal muscle fibers, dissected out from freeze-dried muscle biopsy material. All enzymes investigated demonstrated higher activities in FT fibres. The ratio in enzyme activity between fibre types was greatest for Mg2+ stimulated ATPase (3:1) and smallest for CPK (1.3:1). In addition, the isozyme patterns of CPK, MK and LDH were studied by means of isoelectric focusing (CPK and MK) and discelectrophoresis (LDH). A difference was observed between fibre types with respect to the isozyme distribution of MK and LDH, whereas the CPK isozyme pattern was similar in both fibre types. These results on separated human FT and ST fibres were essentially in conformity with what has earlier been indicated from experiments on mixed muscle homogenates.

  • 337.
    Tinmark, Fredrik
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet, Inst för klinisk vetenskap, intervention och teknik / Dept of Clinical Science, Intervention and Technology.
    Bimanual movement control: insights from golf ball striking2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis was to gain insight into the control of complex bimanual movements that are both fast and accurate. For this, skilled golf ball striking was used as a model in two experimental studies (I and III). The thesis also includes two methodological studies (II and IV), intended to assist in present and future investigation on bimanual movement control. Study I shows a common kinematic proximal-to-distal sequencing (PDS) pattern and speed-summation effect in skilled golf players of both genders. Using a common PDS movement strategy in golf ball striking at various endpoint speeds appears beneficial from mechanical and control points of view and could serve the purpose of providing both high speed and accuracy. In Study II a general expression for mobility was derived, which can be applied for extending the theory of mobility to double-handed grasping and manipulation. Study III found that kinematic contributions to endpoint velocity at slow, medium and fast test conditions were provided by the same subset of possible joint rotations. However, the specific subset differed between levels of expertise. The inertial behavior of the linkage arms-hands-club promoted movement parallel to and resisted movement orthogonal to the club path close to ball impact, at all endpoint speeds investigated. These findings extend previous knowledge regarding endpoint control in single-limb movements. Moreover, results regarding movement organization in Study I together with results in Study III regarding inertial behavior suggest the existence of limb configurations able to simultaneously exploit intersegmental dynamics and endpoint mobility in a proficient manner. To make the control of intersegmental dynamics in bimanual striking transparent, however, torques originating from segmental in teractions should be determined. However, when hands are placed next to each other or are overlapping it becomes challenging to find placements for standard force sensors which allow separation of right and left hand forces without altering normal behavior. As partially explored in Study IV, pressure mapping of the right hand together with inverse dynamics calculations for the golf club can potentially provide an adequate solution.

  • 338.
    Tinmark, Fredrik
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ardt, Toni
    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.
    Hellström, John
    Örebro universitet.
    Halvorsen, Kjartan
    Endpoint control in a bimanual striking task: application to the golfswing2014Article in journal (Refereed)
  • 339.
    Tinmark, Fredrik
    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.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hellström, John
    Halvorsen, Kjartan
    Endpoint mobility in bimanual manipulation: insights from golf ball striking2015In: XXV Congress of the International Society of Biomechanics: Abstract book, 2015, p. 1283-1284Conference paper (Refereed)
  • 340.
    Tinmark, Fredrik
    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.
    Halvorsen, Kjartan
    Using Motion Analysis and Pressure sensitive sensors for determining normal forces when gripping a cylinderManuscript (preprint) (Other academic)
  • 341.
    Tinmark, Fredrik
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hellström, John
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Halvorsen, Kjartan
    Contributions to club velocity in golf swings to submaximal and maximal shot distances2012In: eProceedings of the 30th Conference of the International Society of Biomechanics in Sports, 2012: Volume 3 / [ed] Bradshaw, E.J., Burnett, A., Hume, P.A., 2012, p. 81-83Conference paper (Refereed)
    Abstract [en]

    The contribution of joint rotations to endpoint velocity was investigated in golf shots to submaximal and maximal shot distances using a 41degrees of freedom (DOF) kinematic model. A subset of 16 DOFs was found to explain 97%-99% of endpoint velocity regulation at club–ball contact. The largest contributors, for both groups at every shot condition, were pelvis and torso twist rotation among the most proximal DOFs, elbow pronation/supination and wrist flexion/extension among DOFs in the left arm, and shoulder internal/external rotation and wrist flexion/extension among DOFs in the right arm. The contributions from pelvis obliquity, left wrist flexion/extension, left wrist ulnar/radial deviation and right shoulder flexion/extension differed significantly between the advanced and intermediate group.

  • 342.
    Tinmark, Fredrik
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hellström, John
    Örebro universitet.
    Halvorsen, Kjartan
    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.
    Elite golfers' kinematic sequence in full-swing and partial-swing shots2010In: Sports Biomechanics, ISSN 1476-3141, Vol. 9, no 4, p. 236-244Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate whether kinematic proximal-to-distal sequencing (PDS) and speed-summation are common characteristics of both partial and full-swing shots in golf players of different skill levels and genders. A total of 45 golfers participated, 11 male tournament professionals, 21 male and 13 female elite amateurs. They performed partial shots with a wedge to targets at three submaximal distances, 40, 55 and 70 m, and full-swing shots with a 5 iron and a driver for maximal distance. Pelvis, upper torso and hand movements were recorded in 3D with an electromagnetic tracking system (Polhemus Liberty) at 240 Hz and the magnitude of the resultant angular velocity vector of each segment was computed. The results showed a significant proximal-to-distal temporal relationship and a concomitant successive increase in maximum (peak) segment angular speed in every shot condition for both genders and levels of expertise. A proximal-to-distal utilization of interaction torques is indicated. Using a common PDS movement strategy in partial and full-swing golf shots appears beneficial from mechanical and control points of view and could serve the purpose of providing both high speed and accuracy.

  • 343. Tokuno, C D
    et al.
    Cresswell, A G
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Carpenter, M G
    Recruitment order of the abdominal muscles varies with postural task.2013In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 23, no 3, p. 349-54Article in journal (Refereed)
    Abstract [en]

    Abdominal muscle recruitment strategies in response to a postural perturbation contradict the theory that the deeper abdominal muscles are always recruited in advance of the more superficial muscles. The purpose of this study was to determine whether such contrasting muscle recruitment patterns are due to the postural task or the predictability of a postural task. Participants performed an arm raise task as well as an unpredictable and a predictable balance perturbation task (i.e. support-surface translation) while intramuscular electromyographic (EMG) recordings were obtained from the deep [transversus abdominis (TrA)] and superficial [obliquus externus (OE)] abdominal muscles. The abdominal muscle recruitment order was dependent on the postural task but not on the predictability of a postural perturbation. Whereas arm raises elicited similar EMG onset latencies in TrA and OE, the OE onset latency was 48 ms earlier than the TrA following an unpredictable translation (P = 0.003). The early OE activation persisted when the translation was made predictable to the participant (P = 0.024). These results provide evidence that the abdominal muscle recruitment order varies with the trunk stability requirements specific to each task. Rehabilitation strategies focusing on an early TrA activation to improve postural stability may not be appropriate for all everyday tasks.

  • 344.
    Tokuno, Craig
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Neural control of standing posture2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    When humans are asked to stand normally, they are not completely motionless. Rather, small amounts of body movement, termed postural sway, can be observed. Although the postural sway of standing has been well described, the manner in which this sway is neurally controlled and its influence in tasks involving postural re-stabilization are not known. Therefore, the aim of this thesis was to investigate the neural control of human standing posture, with a special emphasis on 1) whether the neuromuscular responses to an unexpected perturbation are influenced by the postural sway, 2) whether spinallymediated changes occur as a function of postural sway position and/or direction, and 3) whether the excitability of the cortical and corticospinal pathways are altered with respect to postural sway. In each study, subjects stood quietly on a force platform. For Studies I-III, the anteroposterior center of pressure (COP) signal from the force platform was monitored online such that when the position and/or velocity of the COP was of the desired magnitude and direction, a perturbation was administered to the subject. The perturbation consisted of either a sudden support surface translation (Study I) or a percutaneous electrical stimulation to the posterior tibial nerve (Studies II-IV). In Study IV, a perturbation, in the form of either a transcranial magnetic (TMS) or electric (TES) stimulation to the left motor cortex, was triggered at a random time, regardless of the COP signal. The neuromuscular responses to the mechanical, electrical or magnetic perturbations were assessed by measuring the body kinematics from a motion capture system or electromyographic (EMG) recordings from surface electrodes placed over various lower limb muscles. Specific dependent measures included the number of stepping responses, the latencies and amplitudes of the EMG recordings, the peak-to-peak amplitudes of the Hoffmann reflex (Hreflex) and M-wave from tibial nerve stimulation, as well as the peak-to-peak amplitudes of the motor evoked potentials (MEPs) elicited by TMS and TES. Study I indicated that when subjects were standing normally, the position of postural sway influenced the postural responses to an unexpected surface translation. EMG activity of various lower limb and trunk muscles were generally delayed in time and larger in amplitude when subjects were swaying in the direction opposite to the upcoming perturbation. The altered postural responses may be related to the ongoing modulation of the synaptic efficacy, as reflected by the size of the H-reflex, to the triceps surae Ia pathways. In Studies II-IV, it was found that when subjects were swaying in the forward as compared to the backward direction or position, depolarization of the soleus and medial gastrocnemius motoneurone pools, via synaptic transmission of the Ia afferents, was easier to achieve. However, this sway direction- and sway position-dependent modulation of neural excitability was limited to the spinal and corticospinal levels. Study IV revealed that TMS- and TES-evoked MEPs were similarly modulated during the naturally occurring sway of normal standing, suggesting that the excitability of the motor cortex was not dependent on postural sway. A facilitation in cortical excitability, as shown by the differential MEP response between TMS and TES, was however found during normal as compared supported (i.e. no postural sway) standing. This thesis demonstrates that human standing posture is controlled via an overall enhancement of cortical excitability, concurrently with an ongoing sway-dependent modulation of spinal and corticospinal processes. The constantly changing neural inputs to the motoneurone pool may give insight into the influence of postural sway to the neuromuscular responses to an unexpected perturbation. 

  • 345.
    Tokuno, Craig D
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Carpenter, M G
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Garland, S J
    Cresswell, Andrew G
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Control of the triceps surae during the postural sway of quiet standing.2007In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 191, no 3, p. 229-36Article in journal (Refereed)
    Abstract [en]

    AIM: The present study investigated how the triceps surae are controlled at the spinal level during the naturally occurring postural sway of quiet standing. METHODS: Subjects stood on a force platform as electrical stimuli were applied to the posterior tibial nerve when the center of pressure (COP) was either 1.6 standard deviations anterior (COP(ant)) or posterior (COP(post)) to the mean baseline COP signal. Peak-to-peak amplitudes of the H-reflex and M-wave from the soleus (SOL) and medial gastrocnemius (MG) muscles were recorded to assess the efficacy of the Ia pathway. RESULTS: A significant increase in the H(max) : M(max) ratio for both the SOL (12 +/- 6%) and MG (23 +/- 6%) was observed during the COP(ant) as compared to the COP(post) condition. The source of the modulation between COP conditions cannot be determined from this study. However, the observed changes in the synaptic efficacy of the Ia pathway are unlikely to be simply a result of an altered level of background electromyographic activity in the triceps surae. This was indicated by the lack of differences observed in the H(max) : M(max) ratio when subjects stood without postural sway (via the use of a tilt table) at two levels of background activity. CONCLUSIONS: It is suggested that the phase-dependent modulation of the triceps surae H-reflexes during the postural sway of quiet standing functions to maintain upright stance and may explain the results from previous studies, which, until now, had not taken the influence of postural sway on the H-reflex into consideration.

  • 346.
    Tokuno, Craig D
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Carpenter, Mark G
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Cresswell, Andrew G
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    The influence of natural body sway on neuromuscular responses to an unpredictable surface translation.2006In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 174, no 1, p. 19-28Article in journal (Refereed)
    Abstract [en]

    Previous research has shown that the postural configuration adopted by a subject, such as active leaning, influences the postural response to an unpredictable support surface translation. While those studies have examined large differences in postural conditions, it is of additional interest to examine the effects of naturally occurring changes in standing posture. Thus, it was hypothesized that the normal postural sway observed during quiet standing would affect the responses to an unpredictable support surface translation. Seventeen young adults stood quietly on a moveable platform and were perturbed in either the forward or backward direction when the location of the center of pressure (COP) was either 1.5 standard deviations anterior or posterior to the mean baseline COP signal. Postural responses, in the form of electromyographic (EMG) latencies and amplitudes, were recorded from lower limb and trunk muscles. When the location of the COP at the time of the translation was in the opposite, as compared to the same, direction as the upcoming translation, there was a significantly earlier onset of the antagonists (10-23%, i.e. 15-45 ms) and a greater EMG amplitude (14-39%) in four of the six recorded muscles. Stepping responses were most frequently observed during trials where the position of the COP was opposite to the direction of the translation. The results support the hypothesis that postural responses to unpredictable support surface translations are influenced by the normal movements of postural sway. The results may help to explain the large variability of postural responses found between past studies.

  • 347. Tokuno, Craig D
    et al.
    Cresswell, Andrew G
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Carpenter, Mark G
    Age-related changes in postural responses revealed by support-surface translations with a long acceleration-deceleration interval.2010In: Clinical Neurophysiology, ISSN 1388-2457, E-ISSN 1872-8952, Vol. 121, no 1, p. 109-17Article in journal (Refereed)
    Abstract [en]

    Translations with longer acceleration-deceleration intervals reveal more age-related differences in postural control, which are otherwise masked by the deceleration effects inherent to shorter translations.

  • 348.
    Tokuno, Craig D
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Garland, S Jayne
    Carpenter, Mark G
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Cresswell, Andrew G
    Sway-dependent modulation of the triceps surae H-reflex during standing.2008In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 104, no 5, p. 1359-65Article in journal (Refereed)
    Abstract [en]

    Previous research has shown that changes in spinal excitability occur during the postural sway of quiet standing. In the present study, it was of interest to examine the independent effects of sway position and sway direction on the efficacy of the triceps surae Ia pathway, as reflected by the Hoffman (H)-reflex amplitude, during standing. Eighteen participants, tested under two different experimental protocols, stood quietly on a force platform. Percutaneous electrical stimulation was applied to the posterior tibial nerve when the position and direction of anteroposterior (A-P) center of pressure (COP) signal satisfied the criteria for the various experimental conditions. It was found that, regardless of sway position, a larger amplitude of the triceps surae H-reflex (difference of 9-14%; P = 0.005) occurred when subjects were swaying in the forward compared with the backward direction. The effects of sway position, independent of the sway direction, on spinal excitability exhibited a trend (P = 0.075), with an 8.9 +/- 3.7% increase in the H-reflex amplitude occurring when subjects were in a more forward position. The observed changes to the efficacy of the Ia pathway cannot be attributed to changes in stimulus intensity, as indicated by a constant M-wave amplitude, or to the small changes in the level of background electromyographic activity. One explanation for the changes in reflex excitability with respect to the postural sway of standing is that the neural modulation may be related to the small lengthening and shortening contractions occurring in the muscles of the triceps surae.

  • 349.
    Tokuno, Craig
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Taube, W
    Cresswell, Andrew G
    Changes in cortical and corticospinal excitability during standing2007In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793Article in journal (Refereed)
  • 350. Tveit, P
    et al.
    Daggfeldt, Karl
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hetland, S
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Erector spinae lever arm length variations with changes in spinal curvature.1994In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 19, no 2, p. 199-204Article in journal (Refereed)
    Abstract [en]

    Magnetic resonance imaging was used to study the effect of different curvatures in the lumbar spine on lever arm lengths of the erector spinae musculature. Eleven subjects were instructed to simulate static lifts while lying supine in a magnetic resonance camera with the lumbar spine either in kyphosis or lordosis. A sagittal image of the spine was obtained to analyze the lumbosacral angle and to guide the imaging of transverse sections through each disc (L1/L2 to L5/S1). Images were analyzed for lever arm lengths of the erector spinae muscle (ES) and the erector spinae aponeurosis (ESA), the latter functioning as a tendon for superiorly positioned ES muscle portions. The lumbosacral angle (between superior surfaces of S1 and L4) averaged 44 degrees in the lordosed, 26 degrees in the kyphosed and 41 degrees in a neutral supine position. In lordosis, the lever arm lengths were significantly longer than in kyphosis for all levels, averaging 60-63 mm (ES) and 82-86 mm (ESA). The corresponding values for kyphosis were 49-57 mm (ES) and 67-77 mm (ESA), respectively. Thus, there was a considerable effect (10-24%) of lumbar curvature on lever arm lengths for the back extensor muscles. The change in leverage will affect the need for extensor muscle force and thus the magnitude of compression in the lumbar spine in loading situations such as lifting.

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