Inter-limb 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 (\(DOM_L\)\(_E\)\(_G\)) and non-dominant (\(NDOM_L\)\(_E\)\(_G\)) legs have similar aerobic capacity and that 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 (\(V̇O_2\)\(_p\)\(_e\)\(_a\)\(_k\)), maximal lactate steady-state (\(MLSS_p\)), and profiles of local deoxygenation [HHb] would be different in the \(DOM_L\)\(_E\)\(_G\) compared with the \(NDOM_L\)\(_E\)\(_G\). Twelve participants performed a series of double-leg and counterweighted single-leg \(DOM_L\)\(_E\)\(_G\) and \(NDOM_L\)\(_E\)\(_G\)\(i)\) ramp-exercise tests, and \(ii)\) 30-min constant-load trials. \(V̇O_2\)\(_p\)\(_e\)\(_a\)\(_k\) was greater in the \(DOM_L\)\(_E\)\(_G\) than in the \(NDOM_L\)\(_E\)\(_G\) (2.87±0.42 vs 2.70±0.39 L·min-1; P<0.05). The difference in \(V̇O_2\)\(_p\)\(_e\)\(_a\)\(_k\) persisted even after accounting for lean mass (P<0.05). Similarly, \(MLSS_p\) was greater in the \(DOM_L\)\(_E\)\(_G\) than in the \(NDOM_L\)\(_E\)\(_G\) (118±31 vs 109±31 W; P<0.05). Furthermore, the amplitude of the [HHb] signal during ramp-exercise was larger in the \(DOM_L\)\(_E\)\(_G\) than in the \(NDOM_L\)\(_E\)\(_G\) 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 \(V̇O_2\)\(_p\)\(_e\)\(_a\)\(_k\) 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 \(DOM_L\)\(_E\)\(_G\) than in the \(NDOM_L\)\(_E\)\(_G\), and that superior peripheral adaptations of \(DOM_L\)\(_E\)\(_G\) may underpin these differences.