Physiological responses underlying the perception of effort during moderate and heavy intensity cycle ergometry

This study examined patterns of responses for physiological and perceptual variables during cycle ergometry at a constant rate of perceived exertion (RPE) within the moderate and heavy exercise intensity domains. Nineteen (mean age 21.3 ± 0.5 years; 43.4 ± 2.0 mL·kg^{−1·min−1} VO_2Peak) moderately trained cyclists performed an incremental test to exhaustion and two 60 min constant RPE rides at the RPE corresponding to the gas exchange threshold (RPEGET) and 15% above the GET (RPEGET+15%). Oxygen consumption (VO₂), respiratory exchange ratio (RER), heart rate (HR), minute ventilation (V_E), breathing frequency (F_b), and power output (PO) were monitored throughout the rides. Polynomial regression analyses showed VO₂, RER, HR, and V_E (correlation = −0.85 to −0.98) tracked the decreases in PO required to maintain a constant RPE. Only F_b tracked RPE during the moderate and heavy intensity rides. Repeated measures ANOVAs indicated that VO₂ during the 60 min rides at RPEGET was not different (p > 0.05) from VO₂ at GET from the incremental test to exhaustion. Thus, monitoring intensity using an RPE associated with the GET is sustainable for up to 60 min of cycling exercise and a common mechanism may mediate F_b and the perception of effort during moderate and heavy intensity cycle ergometry.