Abstract

Cycling cadence (RPM)-related differences in blood lactate concentration (BLC) increase with increasing exercise intensity, whilst corresponding divergences in oxygen uptake (VO2) and carbon dioxde production (VCO2) decrease. We tested the hypothesis, that a higher RPM reduces the fraction (%) of the VO2 used for carbohydrate oxidation (relCHO) at a given BLC. Eight males (23.9 +/- 1.6 yrs; 177 +/- 3 cm; 70.3 +/- 3.4 kg) performed incremental load tests at 50 and 100 RPM. BLC, VO2 and VCO2 were measured. At respiratory exchange ratios (RER) <1, relCHO were calculated and the constant determining 50% relCHO (kCHO) was approximated as a function of the BLC. At submaximal workload, VO2 and RER were lower (p<0.001) at 50 than at 100 RPM. No differences were observed in VO2peak (3.96 +/- 0.22 vs. 4.00 +/ 0.25 l min-1) and RERpeak (1.18 +/- 0.02 vs. 1.15 +/- 0.02). BLC was lower (p<0.001) at 50 than at 100 RPM irrespective of cycling intensity. At 50 RPM, kCHO (4.2 +/- 1.4 (mmol l-1)3) was lower (p<0.05) than at 100 RPM (5.9 +/- 1.9 (mmol l-1)3). This difference in kCHO reflects a reduced CHO oxidation at a given BLC at 100 than at 50 RPM. At a low exercise intensity, a higher cycling cadence can substantially reduce the reliance on CHO at a given metabolic rate and/or BLC. Verf.-Referat