Tai Chi Practice Differentially Affected Strength, Sensory Input, And Postural Control Among Adults Under/over 75

PURPOSE: Tai Chi practice can improve muscle strength, plantar tactile sensation, kinesthesia, and postural control. However, it remains unclear whether Tai Chi produced the same effects among older adults over and under 75 years. This study investigated the effect of 16 weeks of Tai Chi practice on muscle strength, plantar tactile sensation, kinesthesia, and postural control among older adults over and under 75 years of age. METHODS: Thirty-nine older adults participated in the study, divided into 60-75 years old group (n = 24, 13 females, 68.1 ± 3.5 years, 161.6 ± 7.9 cm, 63.3 ± 9.0 kg) and 76-90 years old group (n = 15, 7 females, 84.5 ± 3.4 years, 157.4 ± 6.1 cm, 60.6 ± 7.4 kg). They completed 16 weeks of Tai Chi practice, with four sessions each week in the community. The muscle strength, plantar tactile sensation, kinesthesia, and center of pressure root mean square in anteroposterior (CoP-RMSap) and mediolateral (CoP-RMSml) directions were measured at weeks 0 (W0) and 17 (W17), respectively. Mixed-model two-way ANOVAs were used for data analyses. Cohen's d (d) values provided evidence of small (0.2), medium (0.5), and large (0.8) effect sizes. RESULTS: Significant interactions were detected for fifth metatarsal head tactile sensation (p = 0.036, η2p = 0.127), ankle dorsiflexion (p = 0.001, η2p = 0.310) / plantarflexion (p < 0.001, η2p = 0.449) kinesthesia, and CoP-RMSml (p = 0.009, η2p = 0.196). The post-hoc tests indicated that the fifth metatarsal head tactile sensation (p = 0.003, d = 0.92, W0: 4.54 ± 0.40, W17: 4.16 ± 0.43) and ankle dorsiflexion (p < 0.001, d = 1.28, W0: 6.22 ± 2.66, W17: 3.53 ± 1.33) / plantarflexion (p < 0.001, d = 1.46, W0: 8.30 ± 3.53, W17: 4.16 ± 1.92) kinesthesia thresholds decreased from W0 to W17 only in the 76-90 years old group, while remaining unchanged in the 60-75 years old group. Additionally, CoP-RMSml decreased in both groups (60-75 years old: p = 0.031, d = 0.38, W0: 3.26 ± 0.27, W17: 3.16 ± 0.26; 76-90 years old: p < 0.001, d = 0.86, W0: 3.31 ± 0.35, W17: 3.01 ± 0.35). CONCLUSION: After 16 weeks of Tai Chi practice, muscle strength, plantar tactile sensation, kinesthesia, and postural control were significantly improved among older adults. In addition, Tai Chi practice improved plantar tactile sensation, kinesthesia, and postural control to a greater extent among older adults aged over 75 years.