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

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/m(2)) initially established that peak oxygen uptake ((V) over dotO(2)peak; 76 +/- 8.4%), expired ventilation ((V) over dot(E)peak; 71 +/- 6.8%), carbon dioxide production ((V) over dotCO(2)peak; 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 x (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 (V) over dot(E), (V) over dotO(2), (V) over dotCO(2), 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.