Dynamic postural stability is not impaired by moderate-intensity physical activity in healthy or balance-impaired older people

Older people are increasingly being encouraged to be more physically active but this may lead to physiological fatigue, tiredness and other effects, which, at high levels, can adversely alter postural stability. However, older adults rarely perform physical activity at high intensities. This study aimed to determine whether a single bout of moderate-intensity physical activity, similar to that experienced during daily living, alters dynamic postural stability, particularly among those at risk of falling. Thirty-one healthy young, 33 healthy older and 21 balance-impaired older, adults performed a rapid, voluntary step-up task before and immediately after a 14 min, self-paced, moderate-intensity physical activity protocol. Timing of step components from vertical ground reaction forces, mediolateral displacement of center of pressure, and onset and amplitude of hip abductor muscle activity were recorded during the step task. All groups demonstrated the same changes after the activity, with slightly shorter weight-shift phase duration, smaller displacement of the center of pressure towards the stance leg during weight shifting, and earlier onset of stance leg gluteus medius activity. These changes indicate improved coordination of the step task after activity. Thus this study showed that dynamic postural stability is not adversely affected immediately following moderate-intensity physical activity, even among balance-impaired elderly.