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Title: Temperature and in vivo human skeletal muscle function and metabolism
Author: Gray, Stuart R.
ISNI:       0000 0001 3513 7451
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2007
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Increasing the temperature of the exercising muscle, passively or actively, leads to alterations in the contractile properties of the muscle, importantly an increase in power output. There is limited information, however, regarding the metabolic changes, if any, occurring within the muscle at higher temperatures and how these are related to the contractile changes occurring within the muscle and how such changes may, or may not, affect the efficiency of the working muscles. The greater power output produced during maximal sprint cycling, after a passive increase in Tm, was associated with an increase in the rate of anaerobic ATP turnover and muscle fibre conduction velocity. Further investigation revealed that this greater anaerobic ATP turnover within the muscle was the result of a greater activity of type HA fibres in the cadence range of 160-180 revs. min⁻¹. When the external power output of the muscle remains constant during more prolonged cycling exercise, performed at 60 revs. min⁻¹, there was also a greater rate of anaerobic ATP turnover in the first 2 min of exercise, with no differences in the remainder of exercise after passive elevation of Tm. There were no differences in the aerobic energy contribution or the kinetics of the V0₂ response between T. conditions. These changes led to a decrease in mechanical efficiency in the first 2 min of exercise, which was associated with a tendency for a greater PCr degradation in type I fibres. When T. was elevated via prior intense exercise there was decrease in mechanical efficiency, during 6 min of heavy exercise, at both 60 and 120 revs. min⁻¹. There was also a greater "absolute" primary amplitude and decrease in the slow component after prior exercise, with the response being greater at 120 revs. min⁻¹. The present research has demonstrated that whilst an increase in T. leads to a greater power output, during maximal exercise, mechanical efficiency is reduced as exercise progresses beyond a few seconds. Furthermore, at faster pedal rates T. affects type IIA fibres whilst at slower pedal rates (60 revs. min⁻¹) there appears to be a preferential effect on type I fibres, highlighting the velocity specific effect of Tm.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral