Human critical power-oxygen uptake relationship at different pedalling frequencies

Critical power (CP) is lower at faster rather than slower pedalling frequencies and traditionally reported in watts (W). Faster pedalling frequencies also engender a greater metabolic rate (V-O2) at low work rates, but with progressive increases in power output, the initial difference in. V-O2 between fast and slower pedalling frequencies is reduced. We tested the hypothesis that CP represents a unique metabolic rate for any given individual which would be similar at different pedalling frequencies. Eleven collegiate athletes (five cross-country runners, END; six sprinters, SPR), aged 18-23 years, performed exhaustive rides at either 60 or 100 r.p.m. on separate days for the determination of the pedal rate-specific CP. The V-O2 at CP (CP-V-O2) was determined from an 8 min ride at the CP for each pedal frequency. The group mean CP was significantly lower at 100 r.p.m. (189 +/- 50 W) compared to 60 r.p.m. (207 +/- 53 W, P < 0.05). However, the group mean CP-V-O2 values at 60 (2.53 +/- 0.60 l min(-1)) and 100 r.p.m. (2.58 +/- 0.53 l min(-1)) were not significantly different. Critical power was significantly higher in the END athletes (242 +/- 50 W at 60 r.p.m.; 221 +/- 56 W at 100 r.p.m.) compared to SPR athletes at both pedal frequencies (177 +/- 38 W at 60 r.p.m.; 162 +/- 27 W at 100 r.p.m., P < 0.05), but the CP-V-O2 was not (P > 0.05). However, when the CP-V-O2 VO2 was scaled to body weight, the END athletes had a significantly greater CP-V-O2 (41.3 +/- 4.1 ml min(-1) kg(-1) at 60 r.p.m.; 40.8 +/- 5.5 ml min(-1) kg(-1) at 100 r.p.m.) compared to the SPR athletes at both pedal frequencies (27.7 +/- 4.6 ml min(-1) kg(-1) at 60 r.p.m.; 29.4 +/- 2.8 ml min(-1) kg(-1) at 100 r.p.m., P < 0.05). We conclude that CP represents a specific metabolic rate (V-O2) which can be achieved at different combinations of power outputs and pedalling frequencies.