Effect of fluid ingestion on muscle metabolism during prolonged
exercise.
Hargreaves, Mark, Peter Dillo, Damien Angus, and Mark Febbraio.
Department of Physiology, The University of Melbourne, Parkville,
3052 and Department of Human Movement Science, RMIT, Bundoora, 3083,
Australia
APStracts 2:0471A, 1995.
Five trained men were studied during 2 hr of cycling exercise at 67%
VO2 peak at 20-22 C to examine the effect of fluid ingestion on
muscle metabolism. On one occasion, subjects completed this exercise
without fluid ingestion (NF) while on the other, they ingested a
volume of distilled, deionised water that prevented loss of body mass
(FR). No differences in oxygen uptake during exercise were observed
between the two trials. Heart rate was lower (P<0.01) throughout
exercise when fluid was ingested and rectal temperature after 2 hr of
exercise was lower (FR: 38.0 0.2 vs. NF: 38.6 0.2 C, P<0.01), as was
muscle (vastus lateralis) temperature (FR: 38.5 0.4 vs. NF: 39.1 0.5
C, P<0.05). Resting muscle ATP, CP, creatine, glycogen and lactate
levels were similar in the two trials, as were the post-exercise ATP,
CP and creatine levels. In contrast, muscle glycogen was higher
(P<0.05) and muscle lactate lower (P<0.05) after 2 hr exercise in FR
compared with NF. Net muscle glycogen utilization during exercise was
reduced by 16% when fluid was ingested (FR: 318 46 vs. NF: 380 53
mmol.kg-1 d.w., P<0.05). These results indicate that fluid
ingestion reduces muscle glycogen use during prolonged exercise which
may account, in part, for the improved performance previously
observed with fluid ingestion.
Received 25 August 1995; accepted in final form 23 October 1995.
APS Manuscript Number A931-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95