Effects of unstable resistance training combined with high-definition transcranial direct current stimulation on proprioception, balance and fall risks in the elderly: a randomized controlled trial study

OBJECTIVE: This study examined the combined effects of unstable resistance training (URT) and high-definition transcranial direct current stimulation (tDCS) on proprioception, balance, and fall risk in community-dwelling older adults, targeting both central neural drive and peripheral neuromuscular adaptations. METHOD: Ninety older adults (mean age 66.2 ± 3.3 years) were recruited and randomly assigned to five groups: (1) URT + a-tDCS, (2) URT + s-tDCS, (3) URT, (4) stable resistance training (SRT) and (5) a health education control group (HALE). All participants underwent an 8-week intervention (three sessions per week, 30 min per session). Participants in the URT + a-tDCS group received 2 mA stimulation for 20 min concurrently with URT sessions. Assessments of ankle proprioception, balance and fall risk were conducted at baseline and post-intervention. RESULT: Eight weeks of URT + a-tDCS significantly improved proprioception at dorsiflexion and plantarflexion, compared with URT + s-tDCS, URT, SRT and baseline (P < 0.05). URT + s-tDCS and URT enhanced proprioception at plantarflexion than baseline (P = 0.033; P = 0.021). Balance measurements (i.e. COP displacement, COP ellipse area and sway velocity index) under stable and unstable surfaces were significantly improved after URT + a-tDCS, compared with other three training modalities and baseline. The fall-risk declined significantly after URT + a-tDCS compared with HALE and baseline (P < 0.05). The change in sway velocity index was positively related to the change in proprioception at plantarflexion after 8-week URT intervention (R² = 0.378, P = 0.015). CONCLUSION: The combined URT and a-tDCS intervention demonstrated synergistic effects, producing statistically significant improvements in proprioceptive acuity and balance parameters among older adults. This integrated intervention offers a promising approach to fall prevention and highlights the importance of targeting both central and peripheral mechanisms in rehabilitation strategies.