To compare the cardiorespiratory responses, blood lactate concentration and perceived exertion between 1-leg cycling and arm cranking. Comparison of exercise modalities. Hospital. Fourteen men who had undergone knee surgery were evaluated during rehabilitation. Not applicable. Each patient performed 2 maximal graded tests: 1-leg cycling and arm cranking exercise, with a 7-day interval. Respiratory gas exchange, heart rate, blood lactate concentration, and the ratings of perceived exertion (RPE) were measured. Peak power output, peak minute ventilation, peak oxygen uptake (Vo(2)peak), and peak heart rate did not differ significantly between 1-leg cycling and arm cranking. The first and second ventilatory thresholds occurred at above 40% and 72% of Vo(2)peak, respectively, in both tests. The maximal lactate concentrations and the RPE values were significantly higher during arm cranking (+10%, +12%, respectively, P<.05) compared with corresponding 1-leg cycling values. The maximal cardiorespiratory values were not different between arm cranking and 1-leg cycling. However, the RPE and blood lactate concentration were lower when the exercise was performed with the lower limb. Thus 1-leg cycling may be more easily tolerated than arm cranking by patients participating in aerobic conditioning after knee surgery.