The influence of lower leg configurations on muscle force variability |
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| Institution: | 1. Department of Applied Physiology and Kinesiology, University of Florida, United States;2. Health, Human Performance, and Recreation, Baylor University, United States;3. Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, United States;1. Department of Medicine, Surgery and Neuroscience, Rheumatology Unit, University of Siena, Policlinico Le Scotte, Viale Bracci 1, 53100 Siena, Italy;2. Department of Medical Biotechnologies, University of Siena, Policlinico Le Scotte, Viale Bracci 1, 53100 Siena, Italy;3. Section of Orthopedics and Traumatology, Department of Medicine, Surgery and Neurosciences, University of Siena, Viale Bracci 1, 53100 Siena, Italy;1. Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, Jiangsu 213164, China;2. School of Automation and Information Engineering, Sichuan University of Science and Engineering, Zigong 614000, China;3. Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China;1. Division of Applied Mechanics, Department of Mechanical Engineering, École Polytechnique, Montreal, Quebec, Canada;2. Occupational Health and Safety Research Institute Robert-Sauvé, Montreal, Quebec, Canada;1. Texas Scottish Rite Hospital for Children, Dallas, TX;2. Orthopedic Surgery Department at UT Southwestern Medical Center, Dallas, TX;1. Electrical and Computer Engineering Department, University of British Columbia, Vancouver, Canada;2. Faculty of Dentistry, University of British Columbia, Vancouver, Canada;3. Department of Computer Science, University of Saskatchewan, Saskatoon, Canada |
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| Abstract: | The maintenance of steady contractions is required in many daily tasks. However, there is little understanding of how various lower limb configurations influence the ability to maintain force. The purpose of the current investigation was to examine the influence of joint angle on various lower-limb constant force contractions. Nineteen adults performed knee extension, knee flexion, and ankle plantarflexion isometric force contractions to 11 target forces, ranging from 2 to 95% maximal voluntary contraction (MVC) at 2 angles. Force variability was quantified with mean force, standard deviation, and the coefficient of variation of force output. Non-linearities in force output were quantified with approximate entropy. Curve fitting analyses were performed on each set of data from each individual across contractions to further examine whether joint angle interacts with global functions of lower-limb force variability. Joint angle had significant effects on the model parameters used to describe the force-variability function for each muscle contraction (p < 0.05). Regularities in force output were more explained by force level in smaller angle conditions relative to the larger angle conditions (p < 0.05). The findings support the notion that limb configuration influences the magnitude and regularities in force production. Biomechanical factors, such as joint angle, along with neurophysiological factors should be considered together in the discussion of the dynamics of constant force production. |
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| Keywords: | Joint position Force control Approximate entropy |
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