A systematic review of upper extremity responses during reactive balance perturbations in aging

Background: Balance responses to perturbations often involve the arms in an attempt to either restore balance or protect against impact. Although a majority of research has been dedicated to understanding age-related changes in lower limb balance responses, there is a growing body of evidence supporting age-related changes in arm responses. This systematic review aimed to summarize differences in arm responses between older and younger adults under conditions requiring counterbalancing, reaching to grasping, and protection against impact. Methods: Following a systematic review and critical appraisal of the literature, data regarding the arm response in studies comparing young and older adults was extracted. The resulting articles were also assessed for quality to determine risk of bias. Results: Fifteen high quality studies were identified. The majority of these studies reported delayed onsets in muscle activation, differences in arm movement strategies, delayed movement timing, increased impact forces, and greater grasp errors in older compared to young adults. These differences were also identified under varied visual and cognitive conditions. Conclusions: The studies included in this review demonstrate age-related differences in arm responses regardless of the direction and nature of the perturbation. These differences could provide insight into developing more targeted rehabilitation and fall prevention strategies. More research is needed to assess whether the identified age-related differences are a necessary compensation or a contributory factor to balance impairments and fall risk in older adults