Abstract
Extensively unilateral recruitment for daily activities may determine performance asymmetries in favor of the preferred side eliciting functional adaptation. Our study evaluated asymmetries in elbow torque output between preferred and non-preferred limbs. Eighteen subjects performed maximal elbow flexor and extensor isometric contractions at five different elbow joint angles (0º, 30º, 60º, 90º, 120º) and five different angular velocities (60, 120, 180, 240, 300º.s-1) on an isokinetic dynamometer. Higher flexor torque in favor of preferred arm was observed at 90º of flexion (p<0.05), which also corresponded to the highest torque produced (p<0.05). The fact that joint angle influenced torque asymmetries, whereas angular velocity did not, suggest that the observed asymmetry is likely related to preferential recruitment of elbow flexors at a 90º joint angle for daily tasks requiring high levels of force production. Muscle functional adaptation to frequent stimuli at this joint angle in healthy subjects may explain these results.
Highlights
Preference and performance are associated, which means that performance of preferred limb is usually more successful than that observed for the contralateral limb (SERRIEN et al, 2006)
The fact that joint angle influenced torque asymmetries, whereas angular velocity did not, suggest that the observed asymmetry is likely related to preferential recruitment of elbow flexors at a 90o joint angle for daily tasks requiring high levels of force production
Among the plausible explanations to these results are changes in muscle fiber composition towards a prevalence of slow twitch type I fibers in the preferred side (FUGL-MEYER et al, 1982), which would occur associated with reduced firing rates in the preferred side (ADAM et al, 1998). Consistent with these findings is the shorter fatigue recovery time of elbow flexor muscles from the preferred arm (WILLIAMS et al, 2002). These results suggested that limb preference, especially for the upper limb, may be associated with neuromuscular advantages in favor of the preferred side
Summary
Preference and performance are associated, which means that performance of preferred limb is usually more successful than that observed for the contralateral limb (SERRIEN et al, 2006). Among the plausible explanations to these results are changes in muscle fiber composition towards a prevalence of slow twitch type I fibers in the preferred side (FUGL-MEYER et al, 1982), which would occur associated with reduced firing rates in the preferred side (ADAM et al, 1998). Consistent with these findings is the shorter fatigue recovery time of elbow flexor muscles from the preferred arm (WILLIAMS et al, 2002). These results suggested that limb preference, especially for the upper limb, may be associated with neuromuscular advantages in favor of the preferred side
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