How Tai Chi improves balance: biomechanics of recovery to a walking slip in impaired seniors.

BACKGROUND AND AIMS: This study examined the effect of Tai Chi (TC) training on biomechanical responses to large, fast walking perturbations in balance-impaired seniors. METHODS: Twenty-two seniors (age 68-92, BERG 44 or less) with surgical interventions to knees, hips, and back were randomly divided into control or TC groups. Groups trained 1.5h/day, 5 days/week for 3 weeks. Controls received TC training after post-control testing. Subjects walked across a force plate triggered to move forward 15cm at 40cm/s at right heel strike (RHS). Kinematics, center of pressure (COP) and center of mass (COM) responses were measured. RESULTS: TC but not control training significantly reduced tripping (p<or=0.005), medial cross-step distance (p<or=0.038), and increased use of swing leg heel strike (p<or=0.001). COM anterior-posterior (A/P) path significantly increased after TC (p<or=0.017) but not control training. TC training showed a trend toward increased COM-COP A/P angular separation at RHS (p<0.067). CONCLUSIONS: Tai Chi training significantly enhanced balance responses by more efficacious use of mechanisms controlling stepping strategies of the swing leg. COM A/P path significantly increased after TC implying improved ability to tolerate unsteadiness. COM-COP A/P separation angle at RHS increased suggesting a longer step and increased mechanical loading at the hip.