TITLE

Influence of passive lower-body heating on muscle metabolic perturbation and high-intensity exercise tolerance in humans

AUTHOR(S)
Bailey, Stephen; Wilkerson, Daryl; Fulford, Jonathan; Jones, Andrew
PUB. DATE
October 2012
SOURCE
European Journal of Applied Physiology;Oct2012, Vol. 112 Issue 10, p3569
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The purpose of this investigation was to determine the influence of heat stress on the dynamics of muscle metabolic perturbation during high-intensity exercise. Seven healthy males completed single-legged knee-extensor exercise until the limit of tolerance on two separate occasions. In a randomized order the subjects underwent 40 min of lower-body immersion in warm water at 42°C prior to exercise (HOT) or received no prior thermal manipulation (CON). Following the intervention, muscle metabolism was measured at rest and throughout exercise using P-MRS. The tolerable duration of high-intensity exercise was reduced by 36% after passive heating (CON: 474 ± 146 vs. HOT: 303 ± 76 s; P = 0.005). Intramuscular pH was lower over the first 60 s of exercise (CON: 7.05 ± 0.02 vs. HOT: 7.00 ± 0.03; P = 0.019) in HOT compared to CON. The rate of muscle [PCr] degradation during exercise was greater in the HOT condition (CON: −0.17 ± 0.08 vs. HOT: −0.25 ± 0.10% s; P = 0.006) and pH also tended to change more rapidly in HOT ( P = 0.09). Muscle [PCr] (CON: 26 ± 14 vs. HOT: 29 ± 10%), [Pi] (CON: 504 ± 236 vs. HOT: 486 ± 186%) and pH (CON: 6.84 ± 0.13 vs. HOT: 6.80 ± 0.14; P > 0.05) were not statistically different at the limit of tolerance ( P > 0.05 for all comparisons). These results suggest that the reduced time-to-exhaustion during high-intensity knee-extensor exercise following lower-body heating might be related, in part, to accelerated rates of change of intramuscular [PCr] and pH towards 'critical' values that limit muscle function.
ACCESSION #
79824319

 

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