Effect of contraction history on torque deficits by stretches of active rat skeletal muscles.
Can J Appl Physiol 2002 Aug; 27(4):323-335
Effects of contraction history on torque deficits by stretches of active skeletal muscles were examined. After three contractions using maximal and submaximal activation (80 and 20 Hz) at an ankle position of 40 (i.e., long muscle length) and with maximal activation at 120 (i.e., short muscle length), the isometric and stretch torques (15 stretches) of rat plantar flexor muscles (bout 1) were measured. Controls were unconditioned. Stretches (i.e., ankle rotation from 90 to 40, velocity: 50 s-1) were imposed on maximal isometric contractions at 90 (i.e., preloaded stretches). All groups performed a second bout following 2 hours of rest after bout 1. After maximal contractions at long muscle length, preload torque at 90 and stretch torque at 40 for stretch 1 of bout 1 were 25% and 18% lower than the other groups. However, for all groups, bout 1 ended and bout 2 began and ended with similar isometric and stretch torques. Stretches early in bout 2, with preloads similar to stretches in bout 1, had greater stretch torques resulting in larger torque deficits. Torque deficits, possibly caused by damage to muscle structures and excitation-contraction uncoupling, were not prevented by a history of isometric contractions. Different contraction histories can result in similar isometric torques but different stretch torques.
Laboratory-animals; Animals; Animal-studies; Muscles; Musculoskeletal-system; Skeletal-system; Injuries; Muscle-tissue
Department of Biochemistry, P.O. Box 9142, West Virginia University Health Sciences Center, Morgantown, WV 26506-9142
Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
Canadian Journal of Applied Physiology
West Virginia University, Morgantown, West Virginia