Physiological responses to incremental, interval, and continuous counterweighted single-leg and double-leg cycling at the same relative intensities

Abstract

Purpose: We compared physiological responses to incremental, interval, and continuous counterweighted single-leg and double-leg cycling at the same relative intensities. The primary hypothesis was that the counterweight method would elicit greater normalized power (i.e., power/active leg), greater electromyography (EMG) responses, and lower cardiorespiratory demand.

Methods: Graded-exercise tests performed by 12 men (age: 21 ± 2 years; BMI: 24 ± 3 kg/m²) initially established that peak oxygen uptake ([Formula: see text]; 76 ± 8.4%), expired ventilation ([Formula: see text]; 71 ± 6.8%), carbon dioxide production ([Formula: see text]; 71 ± 6.8%), heart rate (HRpeak; 91 ± 5.3%), and power output (PPO; 56 ± 3.6%) were lower during single-leg compared to double-leg cycling (main effect of mode; p < 0.05). On separate days, participants performed four experimental trials, which involved 30-min bouts of either continuous (50% PPO) or interval exercise [4 × (5-min 65% PPO + 2.5 min 20% PPO)] in a single- or double-leg manner.

Results: Double-leg interval and continuous cycling were performed at greater absolute power outputs but lower normalized power outputs compared to single-leg cycling (p < 0.001). The average EMG responses from the vastus lateralis and vastus medialis were similar across modes (p > 0.05), but semitendinosus was activated to a greater extent for single-leg cycling (p = 0.005). Single-leg interval and continuous cycling elicited lower mean [Formula: see text], [Formula: see text], [Formula: see text], HR and ratings of perceived exertion compared to double-leg cycling (p < 0.05).

Conclusions: Counterweighted single-leg cycling elicits lower cardiorespiratory and perceptual responses than double-leg cycling at greater normalized power outputs.

Keywords: Cardiorespiratory; Counterweight; Electromyography; Exercise; High-intensity interval training; Moderate-intensity continuous training; One-legged cycling; Perceived exertion; Unilateral.