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bioRxiv · 10.1101/2020.10.01.322313

The underlying mechanisms of improved balance aftershort- and long-term training in older adults

Alizadehsaravi, L.·Koster, R.·Muijres, W.·Maas, H.·Bruijn, S. M.·van Dieen, J. H.
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Abstract

Training improves balance control in older adults, but the time course and neural mechanisms underlying these improvements are unclear. We studied balance robustness and performance, H-reflex gains, paired reflex depression, and co-contraction duration in ankle muscles after one and ten training sessions in 22 older adults (+65yrs). Mediolateral balance robustness, time to balance loss in unipedal standing on a platform with decreasing rotational stiffness, improved (33%) after one session, with no further improvement after ten sessions. Balance performance, absolute mediolateral center of mass velocity, improved (18.75%) after one session in perturbed unipedal standing and (18.18%) after ten sessions in unperturbed unipedal standing. Co-contraction duration of soleus/tibialis anterior increased (16%) after ten sessions. H-reflex gain and paired reflex depression excitability did not change. H-reflex gains were lower, and soleus/tibialis anterior co-contraction duration was higher in participants with more robust balance after ten sessions, and co-contraction duration was higher in participants with better balance performance at several time-points. Changes in robustness and performance were uncorrelated with changes in co-contraction duration, H-reflex gain, or paired reflex depression. In older adults, balance robustness improved over a single session, while performance improved gradually over multiple sessions. Changes in co-contraction and excitability of ankle muscles were not exclusive causes of improved balance. HighlightsO_LIBalance robustness and balance performance in perturbed unipedal standing was improved after one balance training session, with no further improvement after ten sessions. C_LIO_LIBalance performance in unperturbed unipedal standing was improved after ten sessions C_LIO_LIH-reflex and paired reflex depression did not change after training in unipedal or bipedal standing. C_LIO_LICo-contraction duration of antagonistic ankle muscles increased after ten sessions in perturbed and unperturbed unipedal standing. C_LIO_LIChanges in co-contraction duration and excitability of ankle muscles were not exclusive causes of improved balance. C_LI

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Alizadehsaravi, L., Koster, R., Muijres, W., Maas, H., Bruijn, S. M., van Dieen, J. H.. 2020-10-02. The underlying mechanisms of improved balance aftershort- and long-term training in older adults. https://doi.org/10.1101/2020.10.01.322313

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