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 (DOMLEG) and nondominant legs (NDOMLEG) 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 singleleg cycling, this study explored whether peak O₂ consumption (VO_2peak), maximal lactate steady-state (MLSS_p), and profiles of local deoxygenation [HHb] would be different in the DOMLEG compared with the NDOMLEG. Twelve participants performed a series of double- leg and counterweighted single-leg DOMLEG and NDOM_LEG ramp-exercise tests and 30-min constant-load trials. VO_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 VO_2peak persisted even after accounting for lean mass (P < 0.05). Similarly, MLSSp 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 DOMLEG than in the NDOMLEG 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 VO_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.