Evaluation of the effects of balance training in the elderly on spinal cord excitability.
H-Reflex; Balance; Aging; Balance Training; Elderly.
Population aging is increasing. In Brazil, the elderly represent 10.9% of the population. This demographic change implies challenges in healthcare, disease prevention, and fall prevention in the elderly population. Investigating spinal cord excitability using spinal reflexes from specific interventions is crucial for understanding the neurophysiological alterations resulting from aging. Objective: To evaluate changes in spinal cord excitability using the H-reflex (evoked in the soleus muscle) of different amplitudes located on the ascending limb of the recruitment curve (RC) after balance exercise circuit (BEC) training. To compare the effects of voluntary contraction of the plantar flexors between elderly and young individuals. Methods: The sample consisted of 17 elderly individuals (65 ± 6 years) for analysis before (PRE CIRC) and after (POS CIRC) the BEC intervention; for the study of voluntary contraction effects, 16 young (24.0 ± 4.8 years) and 15 elderly (69.1 ± 5.2 years) participated. To assess spinal cord excitability, the electrical stimulation technique was used to evoke the H-reflex. Results: The study did not show significant differences in HTH, H50, H100, and HMAX parameters, suggesting that there were no changes in spinal cord excitability, i.e., there was no neuromuscular adaptive response to BEC in elderly individuals. Voluntary activation produced an increase in the amplitude of the H-reflex for both groups (elderly and young) (p<0.05), however, there were no significant differences in reflex facilitation levels between the groups. Both groups showed a significant increase in MMAX amplitude due to contraction, with a significant reduction observed in the elderly group (p=0.003), but without a significant interaction between age and muscle activation factors (p=0.062). Conclusion: Specific training in the BEC for the elderly showed a limited impact on spinal cord excitability, maintaining the stability of the H-reflex amplitude parameters. The results underscored the predominant influence of descending pathways during voluntary contractions, representing a methodological contribution to the use of the H-reflex with contraction for comparing effects of different interventions between young and elderly individuals.