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Effects of repeated lengthening contractions on skeletal muscle adaptations in female rats.
Willems ME; Miller GR; Stauber FD; Stauber WT
J Physiol Sci 2010 Mar; 60(2):143-150
We examined the adaptation of plantar flexor muscles of female rats to 6 weeks (5 days/week) of lengthening contractions. After repeated lengthening contractions, a decrease in myofiber area of gastrocnemius medialis (26%) was accompanied by an increase in extracellular matrix (ECM) (42%) and collagen content (30.9%) without changes in muscle mass. Decrease in myofiber area (13%) and muscle mass of soleus (19%) was associated with increased collagen content (28%) and ECM (15%). Relative number of soleus myofibers stained for fast myosin increased by 26%. For plantaris, increases in collagen content (32.3%), percent ECM (17%), and myofiber area (6%) were recorded. We also observed (1) increases (3.3%) in the collagen content of the Achilles tendon, (2) no change in the crosslink content of any of the tissues tested, and (3) no difference in the force-frequency relationship of the plantar flexor muscles. Substantial decreases in myofiber areas with increases in muscle connective tissue by 6 weeks of repeated lengthening contractions did not appear to result in isometric force loss.
Animal studies; Laboratory animals; Laboratory testing; Muscle cells; Muscle physiology; Muscles; Muscle stress; Muscle tissue; Musculoskeletal system; Myeloid tissue; Physical reactions; Physiological effects; Physiological measurements; Physiological testing; Repetitive work; Skeletal system; Statistical analysis; Author Keywords: Training; Myofiber area; Collagen; Force transmission
Mark E. T. Willems, Department of Physiology and Pharmacology, Robert C. Byrd Health Sciences Center, School of Medicine, West Virginia University, Morgantown, WV 26506-9229
Issue of Publication
Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
Journal of Physiological Sciences
West Virginia University, Morgantown, West Virginia
Page last reviewed: June 15, 2021
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