Mechanical work as predictor of force enhancement and force depression |
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| Authors: | Natalia Kosterina Håkan Westerblad Anders Eriksson |
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| Institution: | 1. KTH Mechanics, Royal Institute of Technology, Osquars backe 18, SE-100 44 Stockholm, Sweden;2. Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden;1. Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA;2. Department of Physical Therapy, University of Massachusetts Lowell, Lowell, MA, USA;3. Department of Physical Medicine & Rehabilitation, Northwestern University, Chicago, IL, USA;4. Department of Physical Therapy, Georgia State University, Atlanta, GA, USA;5. Department of Health Care Sciences, University of Texas Southwestern, Dallas, TX, USA;6. Department of Orthopaedic Surgery, Northwestern University, Chicago, IL, USA;8. Department of Orthopaedic Surgery, Northshore University HealthSystem, Evanston, IL, USA;1. Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY;2. Department of Surgery, Stony Brook Medicine, Stony Brook, NY;1. Division of Science, Pennsylvania State University, Berks Campus, USA;2. Biomechanics Laboratory, Pennsylvania State University, University Park, USA;1. Laboratoire d''Automatique, de Mécanique et d''Informatique industrielles et Humaines (LAMIH) – UMR CNRS 8201, Université de Valenciennes et du Hainaut-Cambrésis (UVHC), F-59313 Valenciennes, France;2. Laboratoire de l’Effort et du Mouvement, Haute Ecole Provinciale de Hainaut (HEPH) – Condorcet, Tournai, Belgium;3. School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, Canada;1. Ultrasound Research Laboratory, Department of Geology, University of Leicester, University Road, LE1 7RH, UK;2. Geosciences Development, Weatherford International, Gotham Road, East Leake, Leicester, LE12 6JX, UK;3. BIOS Technologies, Sighthill, Edinburgh, EH11 4BP, UK;1. School of Science and Technology, Nottingham Trent University, Nottingham NG11 8NS, UK;2. School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough LE11 3TU, UK |
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| Abstract: | The steady-state force following active muscle shortening or stretch differs from the maximum isometric force associated with the final length. This phenomenon proves that the isometric force production is not only dependent on current muscle length and length time derivative, but depends on the preceding contraction history. Isolated extensor digitorum longus and soleus muscles from mice (NMRI strain) were used to investigate the force produced by a muscle, and some parameters hypothetically influencing this history-dependent force modification. The muscles were pre-stimulated at a fixed length, then different stretch/shortening episodes were introduced, whereafter changes of the active force were recorded while the muscles were held isometrically to approach a steady-state force before de-stimulation. The mechanical work during active stretch and shortening was evaluated by integrating the product of force and ramp velocity over the length-varying period. The results show a negative linear correlation between the force modification and the mechanical work produced on or by the muscle, continuous between shortening and stretch. A corresponding modification of the passive force component following each stimulation was also observed. The conclusion is that the isometric force attained after stretch or shortening is well described by an asymptotic force which is determined by the mechanical work. |
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