Influence of elevated muscle temperature on metabolism during
intense, dynamic exercise.
Febbraio, M. A., M. F. Carey, R. J. Snow, C. G. Stathis, and M.
Hargreaves.
Exercise Metabolism Unit, Victoria University of Technology,
Footscray, 3011, Department of Human Movement Science, Royal
Melbourne Institute of Technology, Bundoora, 3083 and The University
of Melbourne, Parkville, 3052, Australia
APStracts 3:0174R, 1996.
This study examined the effects of elevated muscle temperature on
muscle metabolism during exercise. Seven active, but untrained, men
completed two cycle ergometer trials for 2 min at a workload
estimated to require 115% VO2 max either without pre-treatment (CT)
or after having their thigh wrapped in a heating blanket for 60 min
prior to exercise (HT). Heating of the limb increased (P<0.01)
muscle temperature (T[mu]) and resulted in a difference in T[mu]
between the two trials before (ae = 1.9 +/- 0.1oC, P<0.01) and
after exercise (ae = 0.6 +/- 0.2oC, P<0.05). Heating of the limb
did not affect rectal temperature or plasma catecholamines. In
addition, these parameters were not different between CT and HT
either before or after exercise. No differences in resting
intramuscular concentrations of the adenine nucleotides (ATP, ADP,
AMP) or their degradation products (inosine 5'-monophosphate,
ammonia), lactate, glycogen, creatine phosphate and creatine were
observed between HT and CT. During exercise, the magnitude of ATP
degradation and inosine 5'-monophosphate and ammonia accumulation was
higher (P<0.05) in HT compared with CT. Although pre-exercise
concentrations of glycogen and lactate were not different between the
two trials, post-exercise lactate concentration was higher
(P<0.05) and glycogen lower (P<0.05) in HT compared with
CT. In addition, net muscle glycogen utilization was higher
(P<0.05) in HT. It is concluded that an elevated muscle
temperature per se increases muscle glycogenolysis, glycolysis and
high energy phosphate degradation during exercise. These alterations
may be the result of an increased rate of ATP turnover associated
with the exercise and/or changes in the anaerobic/aerobic
contribution to ATP resynthesis.
Received 4 December 1995; accepted in final form 22 April 1996.
APS Manuscript Number R761-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96