The purpose of this study was to determine the impact of cycling cadence on cardiorespiratory and hemodynamic responses to exercise. Eleven cyclists (age=27±6yrs; VO2max=60.8±3.7ml/kg/min completed four 6-min cycling trials at 10% below gas exchange threshold while pedaling at 60rpm, 90rpm, 120rpm, and a freely chosen cadence (FCC, 94.3±6.9rpm), in randomized order. An oesophageal catheter was used to assess the work of breathing (Wb) and diaphragmatic electromyography (EMGdi). Blood flow index (BFI) was determined on four leg muscles using near-infrared spectroscopy and venous injection of indocyanine green dye. VO2 increased with each increase in cadence despite a fixed work rate (p<0.05). Wb and EMGdi were significantly greater at 120rpm compared to all other conditions (p<0.05). A significant main effect was observed for BFI in three of the four muscles, where 120rpm was higher than 60rpm and 90rpm in the vastus medialis (9.1±3.8 vs. 7.1±1.8 and 6.8±2.5 mol/s, respectively, both p<0.05) and semitendinosus (4.8±3.1 vs. 3.4±1.5 and 3.2±1.4 mol/s, respectively, both p<0.05). The gastrocnemius was higher at 120rpm compared to 60rpm, 90rpm and FCC (8.1±2.0 vs.4.1±1.5, 5.4±2.1 and 5.9±2.0 mol/s respectively, all p<0.01). No difference in BFI was found in the vastus lateralis (p=0.06). High cadence cycling is metabolically inefficient and increases leg muscle blood flow, Wb and EMGdi relative to slower cadences. Despite this finding, cyclists select a relatively high FCC, which may be a strategy to minimize peripheral muscle fatigue and perceived leg discomfort at the expense of reduced metabolic and respiratory muscle efficiency.
© Copyright 2018 Applied Physiology, Nutrition, and Metabolism. Canadian Science Publishing. Alle Rechte vorbehalten.