Abstract
BackgroundWhile the positive effect of balance training on age-related impairments in postural stability is well-documented, the neural correlates of such training adaptations in older adults remain poorly understood. This study therefore aimed to shed more light on neural adaptations in response to balance training in older adults.MethodsPostural stability as well as spinal reflex and cortical excitability was measured in older adults (65–80 years) before and after 5 weeks of balance training (n = 15) or habitual activity (n = 13). Postural stability was assessed during one- and two-legged quiet standing on a force plate (static task) and a free-swinging platform (dynamic task). The total sway path was calculated for all tasks. Additionally, the number of errors was counted for the one-legged tasks. To investigate changes in spinal reflex excitability, the H-reflex was assessed in the soleus muscle during quiet upright stance. Cortical excitability was assessed during an antero-posterior perturbation by conditioning the H-reflex with single-pulse transcranial magnetic stimulation.ResultsA significant training effect in favor of the training group was found for the number of errors conducted during one-legged standing (p = .050 for the static and p = .042 for the dynamic task) but not for the sway parameters in any task. In contrast, no significant effect was found for cortical excitability (p = 0.703). For spinal excitability, an effect of session (p < .001) as well as an interaction of session and group (p = .009) was found; however, these effects were mainly due to a reduced excitability in the control group.ConclusionsIn line with previous results, older adults’ postural stability was improved after balance training. However, these improvements were not accompanied by significant neural adaptations. Since almost identical studies in young adults found significant behavioral and neural adaptations after four weeks of training, we assume that age has an influence on the time course of such adaptations to balance training and/or the ability to transfer them from a trained to an untrained task.
Highlights
While the positive effect of balance training on age-related impairments in postural stability is well-documented, the neural correlates of such training adaptations in older adults remain poorly understood
Significant main effects of group, F (1, 24) = 7.23, p = .013 and session, F (1, 24) = 8.22, p = .008, were found but there was no interaction of the two factors
The group effect is due to a longer sway path in the control group compared to the training group while the session effect is due to a longer sway path during the postmeasurement compared to the pre-measurement
Summary
While the positive effect of balance training on age-related impairments in postural stability is well-documented, the neural correlates of such training adaptations in older adults remain poorly understood. Normal aging is accompanied by structural and functional changes in the sensory and neuromuscular systems [1, 2] which lead to decreases in postural stability [3] and eventually increase the risk for falls [4] Such age-related changes include a reduced excitability and altered modulation of spinal reflexes [5,6,7] and increases in corticospinal excitability [5, 6], indicating a shift towards a more cortically controlled processing of posture in older adults [8]. In young adults, there is evidence that improvements in postural stability after balance training can be explained by highly task-specific neural adaptations
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