Effect of Tai Chi on Muscle Strength of the Lower Extremities in the Elderly

Objective： Aging is associated with a progressive decline in muscle strength, muscle mass andimpaired physical function, which reduces mobility and impairs quality of life in the elderly population. The 6-12months of exercise can enhance the muscle strength, but these improvements can only be maintained for a shortperiod. In this study, we investigated the effects of long-term Tai Chi （TC） exercise on muscle strength of lowerextremities. Methods： A cross-sectional study was conducted in 205 long-term TC practitioners （age： 60-89 years）and 205 age and gentle matched controls who did not practice TC. Each of the activity group was further dividedinto three distinct age groups： G1,60-69 years; G2, 70-79 years; and G3, 80-89 years. Hand-held dynamometerywas used to measure the maximum isometric strength of iliopsoas, quadriceps femoris, tibialis antedor andhamstrings in both sides of the participants. Unpaired t tests were performed to compare the difference of strengthbetween the TC and non-Tai Chi （NTC） groups. Multivariate analysis of variance （MANOVA） was used to comparethe lower muscle strengths among the different age groups in the TC and NTC groups. Pearson＇s correlations wereused to quantify the linear relationship between the months of TC practice and lower limbs muscle strength. Results：The inter-rater reliabilities of iliopsoas, quadriceps femoris, tibialis anterior and hamstrings were intraclass correlationcoefficient （ICC） （1,1） = 0.895 （0.862-0.920）, ICC （2,2） = 0.905 （0.874-0.928）, ICC （3,3） = 0.922 （0.898-0.941） andICC （4,4） = 0.930 （0.908-0.947）. The strength of the muscles in the TC group did not differ among different agegroups （P〉0.05）. The strength of iliopsoas, quadriceps femoris, tibialis anterior and hamstrings in TC group washigher than that in the NTC group （P〈0.05）. A correlation between muscle strength and extension of the exerciseperiod was positive （P〈0.05）. Conclusion： Results shed light on the orientation and magnitude of long-term TC inpreventing muscle strength loss with aging. TC might be a good form to slow down the trend of age-related declinein muscle strength in community-dwelling population.