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 (V̇O2max) is typically attained at or immediately prior to the limit of tolerance (LoT). At the V̇O2max and LoT of incremental exercise, a fundamental, but unresolved, question is whether maximal evocable power can increase above the task requirement, i.e. whether there is a "power reserve" at the LoT. Using an instantaneous switch from cadence-independent 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 (4s) isokinetic power would not differ from power required by the task. Baseline isokinetic power at 80rpm (PISO; measured at the pedals) and summed integrated EMG from 5 leg muscles (∑iEMG) were measured in 12 endurance-trained men (V̇O2max=4.2±1.0 l•min(-1)). Participants then completed a ramp-incremental exercise test (20-25W•min(-1)), with instantaneous measurement of PISO and ∑iEMG at the LoT. PISO decreased from 788±103W at baseline to 391±72W at LoT, which was not different from the required ramp-incremental flywheel power (352±58W; p>0.05). At LoT, the relative reduction in PISO was greater than the relative reduction in the isokinetic ∑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.