High internal load but low power output in indoor cycling classes

Abstract

While several studies have described the internal load of indoor cycling, only three have assessed pedaling power, all under simulated conditions or with participants aware of the outcomes. The present study analyzed internal and external load during real indoor cycling classes conducted by different instructors. Eleven trained men participated in 130 sessions in which heart rate (HR) and pedaling power were recorded. Results showed high internal load, with mean and peak HR values of ∼81% and ∼94% HRmax, respectively, consistent with intensities classified as “hard” to “very hard.” In contrast, external load was modest, with mean power output of 110–120 W (∼50% maximal aerobic power, MAP) and peak values only slightly exceeding MAP (334 W; <120% MAP). Theoretical power estimated from HR–power regressions (PWC-170 test) was ∼25% higher than the real values obtained. A typical session lasted ∼50 min, with ∼4 min dedicated to warm-up and cool-down and the remainder to the main phase. In conclusion, these findings highlight a systematic decoupling between internal and external load in indoor cycling, underscoring the importance of incorporating structured high-intensity intervals to better align mechanical stimulus with cardiovascular demand.