Single- Versus Double-Leg Cycling: Small Muscle Mass Exercise Improves Exercise Capacity to a Greater Extent in Older Compared With Younger Population

Manipulating the amount of muscle mass engaged during exercise can noninvasively inform the contribution of central cardiovascular and peripheral vascular-oxidative functions to endurance performance. To better understand the factors contributing to exercise limitation in older and younger individuals, exercise performance was assessed during single-leg and double-leg cycling. 16 older (67 +/- 5 years) and 14 younger (35 +/- 5 years) individuals performed a maximal exercise using single-leg and double-leg cycling. The ratio of single-leg to double-leg cycling power (Ratio(Power SL/DL)) was compared between age groups. The association between fitness (peak oxygen consumption, peak power output, and physical activity levels) and Ratio(Power SL/DL) was explored. The Ratio(Power SL/DL) was greater in older compared with younger individuals (1.14 +/- 0.11 vs. 1.06 +/- 0.08, p = .041). The Ratio(Power SL/DL) was correlated with peak oxygen consumption (r = .886, p < .001), peak power output relative to body mass (r = .854, p < .001), and levels of physical activity (r = .728, p = .003) in the younger but not older subgroup. Reducing the amount of muscle mass engaged during exercise improved exercise capacity to a greater extent in older versus younger population and may reflect a greater reduction in central cardiovascular function compared with peripheral vascular-oxidative function with aging.