Interlimb differences in parameters of aerobic function and local profiles of deoxygenation during double-leg and counterweighted single-leg cycling.

It is typically assumed that in the context of double-leg cycling, dominant (DOM _LEG ) and nondominant legs (NDOM _LEG ) have similar aerobic capacity and both contribute equally to the whole body physiological responses. However, there is a paucity of studies that have systematically investigated maximal and submaximal aerobic performance and characterized the profiles of local muscle deoxygenation in relation to leg dominance. Using counterweighted single-leg cycling, this study explored whether peak O ₂ consumption (V̇o _2peak ), maximal lactate steady-state (MLSS _p ), and profiles of local deoxygenation [HHb] would be different in the DOM _LEG compared with the NDOM _LEG . Twelve participants performed a series of double-leg and counterweighted single-leg DOM _LEG and NDOM _LEG ramp-exercise tests and 30-min constant-load trials. V̇o _2peak was greater in the DOM _LEG than in the NDOM _LEG (2.87 ± 0.42 vs. 2.70 ± 0.39 L/min, P < 0.05). The difference in V̇o _2peak persisted even after accounting for lean mass ( P < 0.05). Similarly, MLSS _p was greater in the DOM _LEG than in the NDOM _LEG (118 ± 31 vs. 109 ± 31 W; P < 0.05). Furthermore, the amplitude of the [HHb] signal during ramp exercise was larger in the DOM _LEG than in the NDOM _LEG during both double-leg (26.0 ± 8.4 vs. 20.2 ± 8.8 µM, P < 0.05) and counterweighted single-leg cycling (18.5 ± 7.9 vs. 14.9 ± 7.5 µM, P < 0.05). Additionally, the amplitudes of the [HHb] signal were highly to moderately correlated with the mode-specific V̇o _2peak values (ranging from 0.91 to 0.54). These findings showed in a group of young men that maximal and submaximal aerobic capacities were greater in the DOM _LEG than in the NDOM _LEG and that superior peripheral adaptations of the DOM _LEG may underpin these differences. NEW & NOTEWORTHY It is typically assumed that the dominant and nondominant legs contribute equally to the whole physiological responses. In this study, we found that the dominant leg achieved greater peak O ₂ uptake values, sustained greater power output while preserving whole body metabolic stability, and showed larger amplitudes of deoxygenation responses. These findings highlight heterogeneous aerobic capacities of the lower limbs, which have important implications when whole body physiological responses are examined.