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Effect of muscle temperature on rate of oxygen uptake during exercise in humans at different contraction frequencies
1
Centre for Biophysical and Clinical Research into Human Movement,
Manchester Metropolitan University, Hassall Road, Alsage, Alsager ST7 2HL,
UK
2
Institute for Fundamental and Clinical Human Movement Sciences, Vrije
University, Amsterdam, The Netherlands
*
Present address: Applied Physiology Group, Strathclyde Institute for
Biomedical Sciences, University of Strathclyde, Southbrae Drive, Glasgow G13
1PP, UK
Present address: Biomedical Sciences, University Medical School, Foresterhill,
Aberdeen, AB25 2ZD, UK
(e-mail: richard.ferguson{at}strath.ac.uk )
Accepted 14 January 2002
The effect of elevated human muscle temperature on energy turnover was
investigated during cycling exercise (at 85 % of
O2max) at a
contraction frequency of 60 revs min-1. Muscle temperature was
passively elevated prior to exercise by immersion of the legs in a hot water
bath (42 °C). During exercise at this low pedalling rate, total energy
turnover was higher (P<0.05) when muscle temperature was elevated
compared with normal temperature (70.4±3.7 versus
66.9±2.4 kJ min-1, respectively). Estimated net mechanical
efficiency was found to be lower when muscle temperature was elevated. A
second experiment was conducted in which the effect of elevated human muscle
temperature on energy turnover was investigated during cycling exercise (at 85
% of O2max) at a
contraction frequency of 120 revs min-1. Under the conditions of a
high pedalling frequency, an elevated muscle temperature resulted in a lower
energy turnover (P<0.05) compared with the normal muscle
temperature (64.9±3.7 versus 69.0±4.7 kJ
min-1, respectively). The estimated net mechanical efficiency was
therefore higher when muscle temperature was elevated. We propose that, in
these experiments, prior heating results in an inappropriately fast rate of
cross-bridge cycling when exercising at 60 revs min-1, leading to
an increased energy turnover and decreased efficiency. However, at the faster
pedalling rate, the effect of heating the muscle shifts the
efficiency/velocity relationship to the right so that cross-bridge detachment
is more appropriately matched to the contraction velocity and, hence, energy
turnover is reduced.
Key words: contraction velocity, temperature, cycling exercise, human, efficiency/velocity relationship
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