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 (V̇O ₂ ) 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 years) cycled at 60 and 100 rpm during: (i) a "step-ramp-step" protocol to identify V̇O ₂ and PO at RCP; (ii) 4-5 exhaustive constant-PO bouts for CP identification; and (iii) a constant-power bout at CP to identify V̇O ₂ at CP. Separate two-way repeated measures Analysis of variance assessed whether V̇O ₂ and PO were affected by index (CP vs. RCP) and cadence (60 vs. 100 rpm). The V̇O ₂ was not affected by index (mean difference (MD) = 73 ± 197 mL·min ^-1 ; p  = 0.136) but there was an index × cadence interaction ( p  = 0.014), such that V̇O ₂ was higher at 100 versus 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 × 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.
Competing Interests: The authors declare there are no competing interests.