Manuel E Hernandez1, James A Ashton-Miller, Neil B Alexander. 1. Department of Biomedical Engineering, Biomechanics Research Laboratory, Mobility Research Center, University of Michigan, 2025 Traverwood Drive, Suite E, Ann Arbor, MI 48105, USA. manueleh@umich.edu
Abstract
BACKGROUND: Downward reaching may lead to falls in older adults, but the underlying mechanisms are poorly understood. This study assessed differences between younger and older adults in postural control and losses of balance when performing a forward reach to the floor in 2 possible real-world situations, with and without full foot contact with the floor. METHODS: Healthy younger (n = 13) and older (n = 12) women reached as fast as possible to a target placed at their maximal forward reaching distance on floor, either standing on their whole foot or on the shortest base of support (BOS) that they were willing to perform a toe touch with. RESULTS: Compared with younger women, older women used a 50% larger BOS when stooping down to touch their toes and had 22% less maximal forward reaching distance on the floor. Older women were twice as likely to lose their balance as younger women while performing a rapid forward floor reach (χ(2)(2) = 3.9; p < .05; relative risk = 1.91; 95% CI = 0.99-3.72). Postural sway, measured as center of pressure excursions and center of pressure root mean square error, did not differ between younger and older women anteriorly, but posteriorly, older women decreased their sway in full foot BOS and increased their sway in forefoot BOS (Age × BOS, p < .05). Leg strength was reduced in older versus younger women and was correlated with maximal reach distance (r = .65-.71). CONCLUSIONS: Healthy older women performing a rapid maximum forward reach on the floor, particularly when using their forefoot for support, are at an increased risk for losing their balance.
BACKGROUND: Downward reaching may lead to falls in older adults, but the underlying mechanisms are poorly understood. This study assessed differences between younger and older adults in postural control and losses of balance when performing a forward reach to the floor in 2 possible real-world situations, with and without full foot contact with the floor. METHODS: Healthy younger (n = 13) and older (n = 12) women reached as fast as possible to a target placed at their maximal forward reaching distance on floor, either standing on their whole foot or on the shortest base of support (BOS) that they were willing to perform a toe touch with. RESULTS: Compared with younger women, older women used a 50% larger BOS when stooping down to touch their toes and had 22% less maximal forward reaching distance on the floor. Older women were twice as likely to lose their balance as younger women while performing a rapid forward floor reach (χ(2)(2) = 3.9; p < .05; relative risk = 1.91; 95% CI = 0.99-3.72). Postural sway, measured as center of pressure excursions and center of pressure root mean square error, did not differ between younger and older women anteriorly, but posteriorly, older women decreased their sway in full foot BOS and increased their sway in forefoot BOS (Age × BOS, p < .05). Leg strength was reduced in older versus younger women and was correlated with maximal reach distance (r = .65-.71). CONCLUSIONS: Healthy older women performing a rapid maximum forward reach on the floor, particularly when using their forefoot for support, are at an increased risk for losing their balance.