Postural responses are delayed with ageing but responsive to exercise

By Steven Phu

Slips and trips are the most common causes of falls in ambulant older people, with the rapid activation and coordination of muscles being essential to recover balance following such postural disturbances. For falls prevention, balance (e.g. standing on one leg, tandem walking) and strengthening exercises are highly effective but often lack task specificity. In comparison, reactive balance training directly practices fall circumstances by inducing repeated perturbations such as slips and trips. Although there is accumulating evidence that these more task-specific interventions also prevent falls in older people, the underlying mechanisms remain unclear. For example, we do not know whether postural responses after an unpredictable perturbation are delayed with ageing and if these postural responses can be improved by exercise and/or reactive balance training interventions. Therefore, we performed a systematic review to determine the impact of ageing and interventions (both exercise and reactive balance training) on postural responses following unpredictable perturbations.

After searching the literature for studies assessing delay in muscle activation (onset latency) following an unpredictable perturbation, we compared postural responses of young versus older adults, regular exercisers versus non exercisers and the effects of interventions with (randomised control trials) and without (uncontrolled clinical trials) a control group (Figure 1). Through meta-analysis, we found evidence for significant delays in postural responses in older versus young adults. We also found evidence for faster postural response in regular exercisers (i.e. those who reported continued participation in exercise for at least a year). Finally, in data from controlled trials, we found postural responses were improved after medium (2 to 6 weeks) and long term (≥6 weeks) interventions regardless of the training mode (exercise or reactive balance training). In contrast, short-term interventions over one or two days did not improve postural responses.

In summary, our systematic review and meta-analysis provided evidence for age-related decline and exercise-induced improvement in postural responses following unpredictable perturbations. There was insufficient evidence to determine the ideal modality of intervention (exercise or reactive balance training) to improve postural responses, however, the data suggested interventions lasting at least 2 weeks were required to achieve improvements.

Figure 1. Summary of meta-analysis findings examining onset latency (milliseconds) in response to postural perturbations

Publication

Phu S, Sturnieks DL, Lord SR, Okubo Y. Impact of ageing, fall history and exercise on postural reflexes following unpredictable perturbations: A systematic review and meta-analyses. Mech Ageing Dev. 2022;203:111634. doi: 10.1016/j.mad.2022.111634

https://doi.org/10.1016/j.mad.2022.111634

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