International Journal of Exercise Science 13(2): 1487-1500, 2020. Single-leg cycling (SLC) allows for a greater muscle specific exercise capacity and therefore provides a greater stimulus for metabolic and vascular adaptations compared to double-leg cycling (DLC). The purpose of this investigation was to compare the cardiovascular, peripheral, and metabolic responses of counterweighted (10kg) SLC to DLC in a healthy older male population. Eleven males (56-86 years) performed two cycling modalities consisting of DLC and SLC. For each modality, participants performed 4-minute cycling trials (60rpm) at three work rates (25, 50, 75W). Repeated measures ANOVAs and paired samples T-test (α=0.05) were used to assess differences in physiological and perceptual responses. Heart rate (100±21 vs. 103±20bpm), oxygen uptake (12.1±3.6 vs. 11.7±2.8mL*kg-1*min-1) and mean arterial pressure (104±13 vs. 108±12mmHg) were not different between DLC and SLC, respectively. Femoral blood flow was greater during SLC at 50W (741.4±290.3 vs. 509.0±230.8mL/min) and 75W (993.8±236.2 vs. 680.6±278.0mL/min) (p≤0.01). Furthermore, carbohydrate oxidation during SLC was 30-40% greater than DLC across work rates (p≤0.011). Whole body rating of perceived exertion (RPE) at 25 and 50W were not different (p=0.065), however, whole body RPE at 75W and leg RPE were higher for SLC at all intensities (p≤0.018). Liking scores were not different between cycling modalities (p=0.060). At low and moderate intensities, SLC provides a greater peripheral stress with no difference in cardiovascular responses compared to DLC in a healthy older adult male population. Thus, SLC may be a feasible exercise modality to maximize peripheral adaptations for healthy and diseased (i.e. peripheral vascular disease/cardiovascular disease) older population
