Does functional performance and upper body strength predict upper extremity reaction and movement time in older women?

Background: Reaction time to initiate upper limb movement and movement time to place hands on the landing surface may be important factors in forward fall landing and impact, contributing to injury reduction. The aim was to investigate the relationship of physical function and upper body strength to upper limb reaction and movement time in older female participants. Methods: 75 female participants (72 ± 8 yrs) performed 5 arm response trials. Reaction time (signal to initiation of movement), and movement time (initial movement to contact), were collected using 3D motion capture. Additional variables were: handgrip; sit-to-stand; shoulder flexion and elbow extension strength measured by hand-held dynamometry; one-legged balance; fall risk; and physical activity scores. Prediction variables for reaction and movement time were determined in separate backward selection multiple regression analyses. Significance was set at P<0.05. Findings: Significant regression equations for RT (r2 = .08, P = 0.013) found a relationship between stronger handgrip (Beta = -.002) and faster reaction time, accounting for 8% variance. For movement time (r2 = .06, P= .036) greater shoulder flexion strength (Beta = -.04) was related to faster movement time, explaining 6% variance. Stronger SF strength was related to a decrease in MT by 4%. Discussion: A relationship between arm strength measures and faster upper body reaction and movement time was shown, with 10-20% higher strength associated with a 5% faster response time. Even though this was a relatively weak relationship, given that strength is a modifiable component this provides a potential avenue for future intervention efforts. This in turn could have an impact on forward fall landing and potential reduction of injury risk.