Postural steadiness during quiet stance does not associate with ability to recover balance in older women.

BACKGROUND: Fall risk depends on ability to maintain balance during daily activities, and on ability to recover balance following a perturbation such as a slip or trip. We examined whether similar neuromuscular variables govern these two domains of postural stability.
METHODS: We conducted experiments with 25 older women (mean age=78 yrs, SD=7 yrs). We acquired measures of postural steadiness during quiet stance (mean amplitude, velocity, and frequency of centre-of-pressure movement when standing with eyes open or closed, on a rigid or compliant surface). We also measured ability to recover balance using the ankle strategy after release from a forward leaning position (based on the maximum release angle where recovery was possible, and corresponding values of reaction time, rate of ankle torque generation, and peak ankle torque).
FINDINGS: We found that balance recovery variables were not strongly or consistently correlated with postural steadiness variables. The maximum release angle associated with only three of the sixteen postural steadiness variables (mean frequency in rigid, eyes open condition (r=0.36, P=.041), and mean amplitude (r=0.41, P=.038) and velocity (r=0.49, P=.015) in compliant, eyes closed condition). Reaction time and peak torque did not correlate with any steadiness variables, and rate of torque generation correlated moderately with the mean amplitude and velocity of the centre-of-pressure in the compliant, eyes closed condition (r=0.48-0.60).
INTERPRETATION: Our results indicate that postural steadiness during quiet stance is not predictive of ability to recover balance with the ankle strategy. Accordingly, balance assessment and fall prevention programs should individually target these two components of postural stability.