Effect of cardiac-locomotor coupling on the metabolic efficiency of pedalling

Coupling between cardiac and locomotor rhythms (CLC) has been reported while subjects exercise at cadences that are natural to them. The hypothesis that oxygen consumption (VO2) would be lower when subjects pedalled at the rate producing 1:1 coupling of heart and pedalling rates than when they pedalled at noncoupled rates was tested with 12 men on a cycle ergometer. At a moderate power output based on their VO2max, subjects pedalled at six different pedalling rates while VO2 and heart rate were measured. The pedalling rates were the preferred frequency, frequencies 15 and 30% above and below the preferred frequency, and the 1:1 coupled frequency. In 8 of the 12 subjects it was possible to fit their data with significant regression equations relating VO2 to pedalling rate, but in no subject was the 1:1 coupled state energetically beneficial, suggesting that any functional significance of CLC is unrelated to metabolic efficiency.