A comparison of critical power and the respiratory compensation point at slower and faster pedaling cadences.

We investigated whether pedal cadence (60 vs 100 rpm) affects oxygen uptake (V̇O2) and power output (PO) at two indexes of the heavy-to-severe-intensity domain boundary (i.e., critical power [CP] and respiratory compensation point [RCP]) and their correspondence. Fourteen adults (7 females, 23±2 yrs) cycled at 60 and 100 rpm during: i) a "Step-Ramp-Step" protocol to identify V̇O2 and PO at RCP; ii) 4-5 exhaustive constant-PO bouts for CP identification; and iii) a constant-power bout at CP to identify V̇O2 at CP. Separate two-way repeated measures ANOVA assessed whether V̇O2 and PO were affected by index (CP vs RCP) and cadence (60 vs 100 rpm). The V̇O2 was not affected by index (mean difference [MD]=73±197 mL·min-1; p=0.136) but there was an index x cadence interaction (p=0.014), such that V̇O2 was higher at 100 vs 60 rpm for CP (MD=142±169 mL·min-1; p=0.008) but not RCP (p=0526).. The PO was affected by cadence (MD=13±9 W; p<0.001) and index (MD=8±11 W; p=0.016), with no cadence x index interaction (p=0.168). The systematic bias in PO confirms cadence-specificity of CP and RCP. The relationship between these indexes and their change in unison in PO suggests a mechanistic link between these two heavy-to-severe domain boundary candidates.