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.
Highlights
Balance robustness and balance performance in perturbed unipedal standing was improved after one balance training session, with no further improvement after ten sessions.
Balance performance in unperturbed unipedal standing was improved after ten sessions
H-reflex and paired reflex depression did not change after training in unipedal or bipedal standing.
Co-contraction duration of antagonistic ankle muscles increased after ten sessions in perturbed and unperturbed unipedal standing.
Changes in co-contraction duration and excitability of ankle muscles were not exclusive causes of improved balance.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
This version of the manuscript has been revised to update the title of the article and the introduction. The title has been updated, to one-session and ten-session, instead of short-term and long-term training. The introduction has been updated to clarify the novelty of the research.