Published in:
01-04-2015 | Original Article
Intramuscular determinants of the ability to recover work capacity above critical power
Published in: European Journal of Applied Physiology | Issue 4/2015
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Purpose
The primary purpose of this investigation was to compare the recovery of the W′ to the recovery of intramuscular substrates and metabolites using 31P- and 1H-magnetic resonance spectroscopy.
Methods
Ten healthy recreationally trained subjects were tested to determine critical power (CP) and W′ for single-leg-extensor exercise. They subsequently exercised in the bore of a 1.5-T MRI scanner at a supra-CP work rate. Following exhaustion, the subjects rested in place for 1, 2, 5 or 7 min, and then repeated the effort. The temporal course of W′ recovery was estimated, which was then compared to the recovery of creatine phosphate [PCr], pH, carnosine content, and to the output of a novel derivation of the W′
BAL model.
Results
W′ recovery closely correlated with the predictions of the novel model (r = 0.97, p = 0.03). [PCr] recovered faster \(\left( {t \frac{ 1}{ 2}\;{ = }\; 3 8 {\text{s}}} \right)\) than W′
\(\left( {t\frac{ 1}{ 2}\;{ = }\; 2 3 2 {\text{s}}} \right)\) The W′ available for the second exercise bout was directly correlated with the difference between [PCr] at the beginning of the work bout and [PCr] at exhaustion (r = 0.99, p = 0.005). Nonlinear regression revealed an inverse curvilinear relationship between carnosine concentration and the W′
t
1/2 (r
2 = 0.55).
Conclusion
The kinetics of W′ recovery in single-leg-extensor exercise is comparable to that observed in whole-body exercise, suggesting a conserved mechanism. The extent to which the recovery of the W′ can be directly attributed to the recovery of [PCr] is unclear. The relationship of the W′ to muscle carnosine content suggests novel future avenues of investigation.