Enhancing Five Times Sit-to-Stand Test outcomes in older adults through unstable resistance training combined with tDCS: a functional and electromyographic study

The Five Times Sit-to-Stand Test (FTSST) is a pivotal measure of functional mobility and independence in older adults, reflecting the ability to perform essential daily activities. Age-related declines in lower limb strength and balance are major contributors to poor FTSST performance. This study aimed to investigate the effects of an 8-week intervention combining unstable resistance training with transcranial direct current stimulation (tDCS) on FTSST outcomes. Fifty-four older adults (aged 60–70 years) were randomly assigned to three groups: Unstable resistance training combined with active tDCS (Active tDCS group) or sham tDCS (Sham tDCS group), and a control group without any intervention. Forty-five participants ( n = 15 per group) completed the 8-week intervention and were included in the final analysis. FTSST duration, isokinetic knee extension torque, center of pressure (COP) area of 1-min single-leg stance, and surface electromyography (sEMG) signals from seven lower limb muscles during FTSST test were assessed before and after the intervention. Group differences were analyzed using repeated‑measures ANOVA and analysis of covariance (ANCOVA) with Bonferroni correction. The Active tDCS group showed significantly greater improvements than the Sham tDCS group in FTSST total time ( p = 0.05, Cohen’s d = 0.72) and knee extension strength ( p = 0.011, d = 1.10). Both training groups outperformed the control group in all functional outcomes (all p < 0.05). ANCOVA revealed that active tDCS provided additional benefits in agonist muscle efficiency during both concentric and eccentric phases, whereas the reduction in antagonist co‑activation was similar between the two training groups. Unstable resistance training combined with either active or sham tDCS can both improve the FTSST outcomes. Specifically, the active tDCS may bring additional training gains on the basis of unstable resistance training. The improvement of FTSST outcomes may be related to the enhanced capacity of the neuromuscular system to produce maximal muscle force and maintain movement stability as a result of training adaptations.