Changes in exercise hyperpnea are more attributable to limb movement frequency than pedal loading

The significance of limb movement frequency in determining ventilation during exercise remains a contested topic in respiratory research. We used two sinusoidal exercise protocols on a cycle ergometer to separately assess the effects of limb movement frequency i.e. cadence (CP) and pedal load (LP) on ventilation. During the first test, cadence was altered sinusoidally while pedal load remained constant. In the second test, pedal load changed sinusoidally while cadence was constant. Variables were fitted to a sinusoid with parameters amplitude, mean, period, and phase angle lag. Five participants completed both protocols. Mean (SD) cadence amplitudes differed between protocols (CP: 23.5 (0.67) rpm, LP: 0.47 (0.3) rpm, p<0.001). The phase lag angles for ventilation also differed, with sinusoidal cadence significantly smaller than sinusoidal load (CP: 23.7 (12.7) deg., LP: 48.1 (14.6) deg., p= 0.023). However the mean ventilation was not different between tests (CP: 44.5 (3.9) L/min, LP: 46.8 (4.2) L/min, p=0.99). VO 2 and VCO 2 did not differ between tests; eliminating the possibility that changes in ventilatory response between protocols resulted from differences in metabolism. Therefore we concluded that changes in exercise hyperpnea are more attributable to limb movement frequency than pedal loading. Funding provided by the Faculty of Kinesiology and Physical Education at the University of Toronto