Limb Load Asymmetry and Postural Steadiness in Young, Elderly, and Elderly Fallers

Abstract

Limb load asymmetries (differences in average vertical ground reaction forces under each foot during quiet stance) have been found to increase with age, as have other parameters related to postural steadiness. However, further differentiation amongst the elderly with a history of unexplained falls is unclear. PURPOSE: The goal of this investigation was to determine if limb load asymmetries differ between elderly fallers and non-fallers as well as if relationships exist between levels of asymmetry and measures of postural steadiness. METHODS: Eleven young (23 +/− 3yrs), 17 elderly non-fallers (73 +/− 8yrs), and 12 elderly fallers (77 +/− 7yrs) volunteered for assessment of postural control during quiet stance with feet together but on separate force platforms. Eight randomized trials (4 with eyes open: VIS; 4 with eyes closed: NOVIS) of 60s duration were completed in a single visit. In addition to the average vertical ground reaction force, the anterior/ posterior and medial/lateral (M/L) center of pressure sway, path length, maximum velocity, and standard deviation under each foot were calculated. RESULTS: The average limb load asymmetry increased with age (p = 0.047 VIS; p = 0.028 NOVIS) with the young producing a 5% difference (47.5 vs 52.5% bodyweight) between sides and the elderly a 9% difference (45.5 vs 54.5% bodyweight). No limb load asymmetry difference existed between the elderly fallers and non-fallers (p>0.8). The level of limb load asymmetry was correlated with side-to-side M/L path length differences in the entire group (r = 0.835 VIS; r = 0.649 NOVIS). No side-to-side differences existed between the young and elderly in the postural control parameters, though M/L path length (VIS & NOVIS), M/L sway (NOVIS), and M/L standard deviation (NOVIS) approached significance (0.05 < p < 0.1). However, there was a significant 95% increase in the side-to-side difference in M/L standard deviation from the elderly non-fallers to fallers (p = 0.037). CONCLUSION: While side-to-side differences in vertical ground reaction forces and postural steadiness parameters change with age, further changes to separate an elderly faller from a non-faller are less pronounced. However, side-to-side differences do exist between these two elderly populations, suggesting that they may play a role in balance and fall prevention.