The effects of short-term and long-term experiences on co-contraction of lower extremity postural control muscles during continuous, multi-directional support-surface perturbations.

While reactive balance control in response to single perturbations in quiet standing is relatively well understood, some occupational environments (e.g. maritime environments) expose workers to continuous, multi-directional challenges to balance and postural control, which require workers to respond to the current perturbation, as well as anticipate coming perturbations. Investigation of muscle activation patterns during continuous, multi-directional perturbations, and the role of previous experience, is warranted to better understand postural control strategies in these types of environments. This study aimed to identify changes in co-contraction in the lower extremity postural control muscles during multi-directional support-surface perturbations as a result of short-term and long-term experience. Twenty-five participants (12 with minimal experience (novice), 13 with ≥6 months experience working in moving maritime environments (experienced)) were exposed to five 5-minute trials of continuous support-surface perturbations. Muscle activity was recorded from six muscles bilaterally. Co-contraction indices were calculated for selected muscle pairings and compared between groups and trials. Co-contraction decreased across trials, and was lower in the experienced group relative to the novice group. These findings provide insight into the influence of previous experience on muscle activation during reactive balance control, and suggest that increased co-contraction may be a potential mechanism of the increased risk of workplace fatigue, falls, and injury in novice maritime workers. The development and refinement of training programs targeting novice workers may be a potential avenue to reduce fall and injury risk in maritime environments.