Hemodynamic responses to increasing cycle cadence in 11-year old boys: Role of the skeletal muscle pump

Previous studies in adults have indicated a rise in the metabolic cost of i ncreasing cycling cadence at constant work rates. This study examined the m etabolic and cardiovascular responses to pedaling rates of 41, 63, and 83 r pm at both zero-load and 50-watts load in 12 prepubertal boys. Increasing c adence from 41 to 83 rpm produced a 52.9% and 23.1% rise in gross energy ex penditure in the two work conditions, respectively, despite the constant ex ternal work rate. This augmented energy expenditure was accounted for entir ely by internal work, as no changes in work metabolic cost (difference betw een loaded and unloaded cycling) were observed as cadence increased. The ri se in energy expenditure with higher pedaling rate during the zero load and 50 watt conditions was accompanied by increases in both heart rate and str oke volume. Arterial venous oxygen difference did not change with increased cadence but was significantly higher with loaded cycling, suggesting that skeletal muscle pump effectiveness is negatively influenced by increased lo ad but not by increased pedaling rate.