Effect of 12 Weeks of Tai Chi Training on Soleus Hoffmann Reflex and Control of Static Posture in Older Adults

Chen Y-S, Zhou S. Cartwright C. Effect of 12 weeks of Tai Chi training on soleus Hoffmann reflex and control of static posture in older adults. Arch Phys Med Rehabil 2011;92:886-91. Objective: To investigate the effect of 12 weeks of Tai Chi training on soleus (SOL) Hoffmann reflex (H-reflex) modulation and postural control in standing under 4 sensory conditions in older adults. Design: Experimental research design with pre- and post-training tests in a training group and a control group. Setting: University biomechanics laboratory. Participants: Community-dwelling older adults (N=34) were assigned to a training (n=20; mean +/- SD age, 72.9+/-4.4y) and a control (n=14; mean +/- SD age, 72.9+/-6.5y) group. Intervention: Tai Chi participants attended a 1-hour session of Yang style Tai Chi, 3 sessions a week, for 12 weeks, while control participants maintained their regular daily activities during the same period. Main Outcome Measures: SOL H-reflex (maximal amplitudes of H-reflex [H(max)] and M-wave [M(max)] waves) and mean displacement of the center of pressure (COP) in the anterior-posterior (COP(A-P)) and medial-lateral (COP(M-L)) directions were measured during bipedal standing, with the feet placed on a forceplate and the heels 6cm apart, under 4 sensory conditions: stable surface with eyes open, stable surface with eyes closed, unstable surface with eyes open, and unstable surface with eyes closed. Results: SOL H(max)/M(max) ratio in the Tai Chi group was upregulated significantly in all 4 sensory tasks after the 12-week Tai Chi training (P<.05). No significant change in COP measurements (mean displacement of COP(A-P) and COP(M-L)) was found in either the Tai Chi or control group after the 12-week period. Conclusions: An increase in SOL H(max)/M(max) ratio during static postural tasks is observed after 12 weeks of Tai Chi training in older adults under all 4 sensory conditions. However, training-induced changes in H-reflex were not accompanied by improvement of performance in the static postural control tasks.