Comparing The Physiological Responses To Single and Double Leg Cycling In Older Individuals

Abstract

Single-leg cycling allows for a greater muscle specific exercise capacity and therefore provides a greater stimulus for metabolic and vascular adaptations when compared to standard double-leg cycling. PURPOSE: The purpose of this investigation was to compare the metabolic, cardiovascular, and peripheral responses of single-leg cycling to double-leg cycling in a healthy older adult population. METHODS: Eleven healthy males (age 66±8 years) performed two cycling conditions consisting of double-leg cycling (DL) and single-leg cycling (SL) with a 97N counterweight attached to the unoccupied crank arm to replicate normal cycling biomechanics. For each condition, participants performed cycling trials (60rpm) at three different work rates (25, 50, 75 W) for 4 minutes each. Oxygen consumption (VO2), respiratory exchange ratio (RER), heart rate (HR), mean arterial pressure (MAP), femoral blood flow, rating of perceived exertion (RPE), and liking scores were recorded. RESULTS: HR was similar between DL and SL conditions at all three intensities (92±19, 102±17 and 115±17 for SL versus 91±21, 100±18 and 112±20 for DL; p≥0.160). VO2 was similar between DL and SL at 25W and 50W (p≥0.35), however at 75W VO2 was greater during the SL condition (16.1±2.7ml/kg/min) compared to DL (14.4±1.9 ml/kg/min; p= 0.037). Femoral artery blood flow was significantly greater during SL cycling for the 50W (670±287 versus 456±217ml/min; p=0.01) and 75W work rates (923±282 versus 608±270; p<0.001) but not at 25W. RER was significantly higher for SL (0.86±0.06, 0.91±0.09 and 0.97±0.09) compare to DL (0.81±0.06, 0.86±0.07 and 0.90±0.07) across all three intensities (p≤0.018). RPE and liking were similar between both conditions (p=0.065 and p=0.060, respectively). CONCLUSIONS: At least at low and moderate intensities, counterweighted single-leg cycling provides a greater peripheral stress for the same cardiovascular demand as double-leg cycling in a healthy elderly adult population. Furthermore, enjoyment of single-leg cycling was similar to double-leg. Thus, single-leg cycling with a counterweight may be an alternative exercise modality to maximize peripheral adaptations in the healthy aging population and those with central or peripheral diseases (i.e. peripheral vascular disease, diabetes, cardiovascular disease).