Physiological responses of young and elderly men to prolonged exercise at critical power

Summary

The critical power (CP) of a muscle group or individual may represent the highest rate of work which can be performed for an extended period. We investigated this concept in young (n = 13, 24.5 years) and elderly (n = 12, 70.7 years) active men by first determining CP and then comparing responses elicited by 24 min of cycle exercise at power outputs (ω) corresponding to CP. Values from the final 2 min of the 24-min ride were expressed relative to maximal values established in a ramp test. CP for the elderly was only 65% that for the young, but on a relative basis, it was significantly higher both in terms of ω (67 vs 62% of ω_max) and oxygen consumption ($\dot VO_2$) (91.5 vs 85.2% of maximum oxygen consumption). There were no group differences in relative values for ventilation ($\dot V_E$), heart rate or respiratory exchange ratio (R). During the 24-min ride,$\dot VO_2$ andR achieved a plateau in both groups, while$\dot V_E$, blood lactate and arterialPCO₂ continued to change in the young. It was concluded that CP can be determined in active elderly men, but that CP may not represent a true non-fatiguing work rate in either young or elderly men.