Effects Of Cycling Cadence And Power Output Oscillation On Time To Exhaustion And Metabolic Energy

At high intensity, cycling at high cadence (RPM) results in reduced, unchanged or higher time to exhaustion (TTE) depending on cycling experience. High oscillations of power output (OSC) reduce TTE. OSC increase the freely chosen RPM. Combined effects of changes in RPM and OSC on TTE and aerobic (WAER) and glycolytic (WGLY) metabolic energy are unknown. PURPOSE: To test the hypotheses that WGLY is independent of OSC and that a higher RPM reduces an OSC-related decrease in TTE and WAER at average power output corresponding to the peak oxygen uptake (P-VO2PEAK). METHODS: 14 male cyclists (age: 28.2±5.0 yrs, height: 182.4±5.5 cm, body mass: 76.8±8.6 kg) performed an incremental load test to determine P-VO2PEAK and time to exhaustion tests (TTE) at RPMs of 50 and 90 min-1 and with constant P-VO2PEAK (TTE50_C and TTE90_C) and oscillations of P-VO2PEAK with an amplitude of 25% and a period of 30 s (TTE50_OSC and TTE90_OSC), respectively. WAER and WGLY were calculated by indirect calorimetry based on net oxygen uptake and net blood lactate increase and oxygen lactate equivalent. RESULTS: TTE50_OSC (306±64 s) was lower than TTE50_C (366±70 s; p=0.021) and TTE90_C (410±110 s, p=0.002). No differences between TTE90_OSC (371±101 s) and TTE50_C and TTE90_C were found (all p>0.05). WAER50_OSC (408.5±106.0 kJ) was lower than WAER50_C (499.0±107.0 kJ; p=0.027) and WAER90_C (586.7±174.6 kJ, p<0.001). No differences between WAER90_OSC (526.6±176.6 kJ) and WAER50_C and WAER90_C were found (all p>0.05). OSC had no effect on WGLY (p>0.05). WGLY_90_C (76.0±11.3 kJ) and WGLY_90_OSC (74.8±15.4 kJ) were higher (all p<0.05) than WGLY_50_C (67.4±12.1 kJ) and WGLY_50_OSC (64.0±13.8 kJ). CONCLUSIONS: OSC decreased TTE at an RPM of 50 min-1 which was prevented by an RPM of 90 min-1. At average power output corresponding to VO2PEAK, differences in WAER reflect OSC-effects on TTE. Higher WGLY at higher RPM does not explain the advantage in performance at higher RPM in terms of TTE at OSC.