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|Title:||Effects of Training and Immobilization Upon NeuromuscuIar Function in Man|
|Authors:||Sale, Digby G.|
|Advisor:||McComas, A. J.|
|Keywords:||Medical Sciences;Medical Sciences|
|Abstract:||<p>The effects of strength training and immobilization upon neuromuscular function in man were investigated. The selected measures of neuromuscular function were voluntary strength and a number of electrophysiological measurements, including motor unit counts, motor nerve conduction velocity, reflex potentiation, and the contractile properties of isometric twitch contractions.</p> <p>Three kinds of experiments were conducted. First, subjects participated in training and immobilization experiments. Training, which consisted of maximal isometric and concentric muscle contractions and weight lifting, was performed three times per week over a period of 10-20 weeks. Relative disuse of selected muscle groups was achieved by immobilizing the elbow, wrist and thumb joints in a cast for 3-6 weeks. Second, measurements were made in selected groups of athletes (weight lifters, gymnasts, cyclists, sprinters, cross country skiers) to provide cases of long term training. Third, measurements were made on control subjects, whose results were compared to those of the athletes.</p> <p>Training resulted in an increase in voluntary strength. As cases of long term training, voluntary strength was enhanced in weight lifters and cyclists. Immobilization resulted in a decrease in voluntary strength.</p> <p>Training had no effect upon motor unit counts and the motor unit counts in the weight lifters were normal; however, the gymnasts exhibited reduced motor unit counts in distal but not proximal muscles. It was hypothesized that injury to the nerves at the wrist and ankles was responsible for the reduced motor unit counts in the gymnasts. Immobilization had no effect upon motor unit counts.</p> <p>Neither training nor immobilization caused a change in motor nerve conduction velocity in relation to the control condition; however, in one group of subjects, there was a small though significant difference between the greater post training and the lesser post immobilization values. Nerve conduction velocity was greater in weight lifters and gymnasts than in controls.</p> <p>Reflex potentiation increased following training, providing new evidence in support of the hypothesis that adaptation occurs within the nervous system in response to training. In agreement with the above finding was the enhanced reflex potentiation in the weight lifters. Immobilization caused a decrease in reflex potentiation, indicating that the nervous system is involved in the adaptation to relative disuse as well as to training.</p> <p>Muscle (triceps surac) twitch tension and contraction time were greater in weight lifters than in controls. In this same muscle, short term training resulted in an increase in twitch half relaxation-time. These findings represent the first report of a slowing of muscle contraction in response to training.</p> <p>In conclusion, the present investigation provided new evidence indicating adaptation within both the muscle and the nervous system in response to strength training and within the nervous system in response to immobilization.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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