The literature has provided ample evidence that neural influence is responsible for the regulation and maintenance of muscle properties. This study, conducted on approximately 100 mice of the C57 BL/6J+/+ species investigated the differential effects of denervation on the isometric contractile properties of a fast-twitch (extensor digitorum longus) and a slow-twitoh (soleus) muscle. Adult male animals were studied at 1, 28, 84 and 210 days following unilateral section of the sciatic nerve. The muscles were stimulated in vitro at 37°C at optimal length by supramaximal square pulses. The data for all muscles in each experimental group were pooled and compared to age-matched controls. In both the denervated soleus (SOL) and extensor digitorum longus (EDL) the time-to-peak twitch tension and the half relaxation were prolonged by 28 days post-denervation and this trend continued to the oldest age groups studied. The weight of the denervated muscles was less than that of the controls. Consequently, although the force that could be generated per unit mass by the EDL was initially well maintained, all muscles showed reduced peak tetanic tension in the long term, following denervation. Even when developed tension was expressed on a per wet weight basis, soleus became weaker with increased time post-denervation. A surprising and unexpected-result was the finding that 28 days after denervation both the fast and slow-twitch muscles developed increased tension. The denervated SOL showed a marked decrease in resistance to fatigue at 1 and 28 days, whereas the EDL showed an increase in resistance to fatigue at 28 days and beyond. It was concluded that denervation affected the tension generating ability and the contraction time of the SOL more than the EDL. The fatigue response indicated that conversion of fibre types may have occurred in the EDL and to a lesser extent in the SOL. The results support the hypothesis that slow muscle may be more dependant upon neural influence than fast muscle for the maintenance of its contractile properties. Further experiments to test this hypothesis are outlined. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

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published_or_final_version / Physiology / Master / Master of Philosophy

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Thesis (M.Sc.)--York University, 2008. Graduate Programme in Kinesiology and Health Science. / Typescript. Includes bibliographical references. Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR45950

The purpose of this study was to evaluate muscle oxygenation, cardiorespiratory, and blood lactate responses to an acute bout of a high-intensity interval training (HIIT) bodyweight squat protocol (HIIT-squats) in comparison to (continuous) moderate intensity cycling exercise (MOD). On separate days, within a two week period, 15 recreationally active males (28 (4.6) years) performed: 1) incremental test to exhaustion on a cycle ergometer, 2) 30-minutes of moderate intensity cycling (MOD; 65% VO2max), and 3) HIIT-squats consisting of eight x 20 seconds of bodyweight squats performed at maximal cadence with 10-s rest intervals. During each exercise condition, oxygen consumption (VO2) and heart rate were monitored continuously, and muscle oxygenation (tissue saturation index, TSI) at the left vastus lateralis muscle was measured for 2 minutes pre-, throughout, and for 5 minutes post-exercise using Near-Infrared Spectroscopy (NIRS; Portalite, Artinis Medical Systems, Netherlands). Blood lactate was measured at pre- and one, three, and five minutes post-exercise. Mean and peak changes in TSI were similar in both HIIT-squats (mean = -14.6 (5.3)%, peak = -19.7 (5.2)%; p > 0.05) and MOD (mean = -13.2 (5.6)%, peak = -18.2 (7.6)%; p > 0.05), with peak changes in TSI occurring significantly faster in HIIT-squats (71.2 (95.2) seconds (s) after onset of exercise) than in MOD (1452.9 (647.8)s; p < 0.05). The half time of TSI recovery following HIIT-squats (T1/2TSI = 25 (7.9)s) was not significantly different post-MOD (25 (9.6)s). Mean VO2 during HIIT-squats (31.48 (4.58) ml.kg-1.min-1) was similar to MOD (33.76 (5.71) ml.kg-1.min-1), however minute ventilation (VE), respiratory exchange ratio (RER) and all post-exercise blood lactate concentrations were significantly higher in HIIT-squats compared to MOD (p < 0.05). Despite the different durations of HIIT-squats and MOD, mean and peak changes in aerobic metabolism during and after exercise were similar. Results provide evidence of both aerobic and anaerobic contributions to energy metabolism in response to HIIT-squats, and highlight possible mechanisms for the commonly reported improvements in aerobic power following chronic HIIT. / Graduate / akates@uvic.ca

Thesis (MAppSc in Physiotherapy) -- University of South Australia

Thesis (MAppSc in Physiotherapy)--University of South Australia, 1995

thesis (MAppSc in Physiotherapy)--University of South Australia, 1995