No reserve in isokinetic cycling power at intolerance during ramp incremental exercise in endurance-trained men

During whole body exercise in health, maximal oxygen uptake ((V) over dot O-2max) is typically attained at or immediately before the limit of tolerance (LoT). At the (V) over dot O-2max and LoT of incremental exercise, a fundamental, but unresolved, question is whether maximal evocable power can be increased above the task requirement, i.e., whether there is a "power reserve" at the LoT. Using an instantaneous switch from cadence-independent (hyperbolic) to isokinetic cycle ergometry, we determined maximal evocable power at the limit of ramp-incremental exercise. We hypothesized that in endurance-trained men at LoT, maximal (4 s) isokinetic power would not differ from the power required by the task. Baseline isokinetic power at 80 rpm (Piso; measured at the pedals) and summed integrated EMG from five leg muscles (Sigma iEMG) were measured in 12 endurance-trained men ((V) over dot O-2max = 4.2 +/- 1.0 l/min). Participants then completed a ramp incremental exercise test (20-25 W/min), with instantaneous measurement of P-iso and Sigma iEMG at the LoT. P-iso decreased from 788 +/- 103 W at baseline to 391 +/- 72 W at LoT, which was not different from the required ramp-incremental flywheel power (352 +/- 58 W; P > 0.05). At LoT, the relative reduction in P-iso was greater than the relative reduction in the isokinetic Sigma iEMG (50 +/- 9 vs. 63 +/- 10% of baseline; P < 0.05). During maximal ramp incremental exercise in endurance-trained men, maximum voluntary power is not different from the power required by the task and is consequent to both central and peripheral limitations in evocable power. The absence of a power reserve suggests both the perceptual and physiological limits of maximum voluntary power production are not widely dissociated at LoT in this population.