Neural mechanisms underlying balance improvement with short term Tai Chi training.

BACKGROUND AND AIMS Though previous research has shown that Tai Chi reduces falls risk in older adults, no studies have examined underlying neural mechanisms responsible for balance improvement. We aimed to determine the efficacy of Tai Chi training in improving neuromuscular response characteristics underlying balance control in balance-impaired older adults. METHODS Twenty-two balance-impaired older adults were randomly divided into Tai Chi (TC) or control groups. Nineteen subjects (age 68-92, BERG 44 or less) completed the study. TC training included repetitive exercises using TC motor and biomechanical strategies, techniques, and postural elements. Control training included axial mobility exercises, balance/awareness education and stress reduction. Groups trained 1.5 hours/day, 5 days/week for 3 weeks. After post-testing the control group received TC training. Subjects walked across a force plate triggered to move forward 15 cm at 40 cm/sec at heel strike. Tibialis anterior (TA) and medial gastrocnemius (GA) responses during balance recovery were measured with electromyograms (EMGs). Four clinical measures of balance were also recorded. RESULTS TC subjects, but not controls, significantly reduced both TA response time from 148.92 +/- 45.11 ms to 98.67 +/- 17.22 ms (p < or = 0.004) and occurrence of co-contraction of antagonist muscles (p < or = 0.003) of the perturbed leg. Clinical balance measures also significantly improved after TC. CONCLUSIONS TC enhanced neuromuscular responses controlling the ankle joint of the perturbed leg. Fast, accurate neuromuscular activation is crucial for efficacious response to slips or trips.