Effects of Different Strength Levels on the Ability of Older Adults to Recover from Backward or Forward Balance Losses

Falls in older adults are an important concern due to the potential injuries associated with falling. Decreases in muscle strength as a result of natural aging could impair the ability of older adults to prevent either a backward or forward fall. Two musculoskeletal models were used to predict the effect of progressive aging-related losses in muscle strength on the ability to recover (i.e. restore static balance) after recovery step touchdown following a backward or forward balance loss. Additionally, the model-predicted effect of strength training selected muscle groups on the ability to recover after step touchdown following a backward balance loss was determined. The ability to recover was determined by mapping the boundary of the feasible region for balance recovery, with shifts in the boundary associated with changes in this ability. It was found that as healthy older adults age into their 60’s, 70’s, and 80’s, typical aging-related losses in strength progressively decreased the ability to recover from both backward and forward balance losses. There was an observed larger effect of strength declines on balance recovery at older ages, and these effects were mainly due to declines in reestablishing center of mass stability. Simulated strength training of the ankle dorsiflexors improved the ability to recover after a backward balance loss, but strength training the knee extensors and/or hip extensors did not. These results suggest that strength training that includes the dorsiflexors should be included in fall prevention programs and should be emphasized in older adults representative of those beyond their 60’s