Effects of 12-week Tai Chi training on soleus H-reflex and muscle strength in older adults: a pilot study

The purpose of this study was to determine the effects of 12-week Tai Chi (TC) training on the soleus (SOL) H-reflex modulation and plantarflexion muscle strength in older adults. Twenty volunteers were assigned into training (N = 14; 72.2 ± 3.7 years of age) and control (N = 6; 74.2 ± 6.1 years of age) groups. The participants in the TC group practiced Yang style TC 1 h per session, 3 sessions per week, for 12 weeks, guided by a qualified TC instructor. The ratio of the maximal peak-to-peak amplitude of SOL H-reflex (H (max)) to M-wave (M (max)) was determined during bipedal standing under four sensory conditions: stable surface and eyes open (SO), stable surface and eyes closed (SC), unstable surface and eyes open (UO), and unstable surface and eyes closed (UC). The maximal isometric plantarflexion muscle strength was also assessed by using a dynamometer. The results showed that the SOL H (max)/M (max) ratio increased significantly after the 12 weeks of TC training under the SC (37.0%), UO (33.3%) and UC (36.0%) conditions (P < 0.05). The maximal plantarflexion strength also improved significantly after training (19.8%; P < 0.05). In contrast, the control group showed no significant changes in all measurements after the 12 weeks.