Agonist-antagonist muscular co-contraction improves rapid corrective responses.

Muscular co-contraction (simultaneous activation of both agonist and antagonist muscle groups) has been observed to emerge across a range of challenging tasks. But is it beneficial? In this study we address this untested assumption by quantifying the performance benefits of muscular co-contraction when making rapid corrective responses to mechanical perturbations. Even small levels of co-contraction resulted in significant performance improvements compared to the relaxed condition in a target recapture task following a mechanical perturbation. Performance was also better when co-contracting compared to when a single muscle group was active prior to the perturbation. The performance benefits of co-contracting seem partially attributable to neural mechanisms where activation of both agonist and antagonist muscles allowed both groups to contribute to limb control via reflex responses. These findings highlight how co-contraction can greatly impact motor performance. Further, the benefit of co-contraction extends beyond just increased muscle activity providing instantaneous resistance to limb motion.