title: Effect of Tai Chi on muscle strength of the lower extremities in the elderly.
abstract: OBJECTIVE
  Aging is associated with a progressive decline in muscle strength, muscle mass and impaired physical function, which reduces mobility and impairs quality of life in the elderly population. The 6-12 months of exercise can enhance the muscle strength, but these improvements can only be maintained for a short period. In this study, we investigated the effects of long-term Tai Chi (TC) exercise on muscle strength of lower extremities.
  
  
  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 divided into three distinct age groups: G1, 60-69 years; G2, 70-79 years; and G3, 80-89 years. Hand-held dynamometery was used to measure the maximum isometric strength of iliopsoas, quadriceps femoris, tibialis anterior and hamstrings in both sides of the participants. Unpaired t tests were performed to compare the difference of strength between the TC and non-Tai Chi (NTC) groups. Multivariate analysis of variance (MANOVA) was used to compare the lower muscle strengths among the different age groups in the TC and NTC groups. Pearson's correlations were used 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 correlation coeffificient (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) and ICC (4,4) = 0.930 (0.908-0.947). The strength of the muscles in the TC group did not differ among different age groups (P>0.05). The strength of iliopsoas, quadriceps femoris, tibialis anterior and hamstrings in TC group was higher than that in the NTC group (P<0.05). A correlation between muscle strength and extension of the exercise period was positive (P<0.05).
  
  
  CONCLUSIONS
  Results shed light on the orientation and magnitude of long-term TC in preventing muscle strength loss with aging. TC might be a good form to slow down the trend of age-related decline in muscle strength in community-dwelling population.
authors.affiliation: Department of Geriatric Rehabilitation, Chinese People's Liberation Army General Hospital, Beijing, 100853, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhou
authors.affiliation: Department of Geriatric Rehabilitation, Chinese People's Liberation Army General Hospital, Beijing, 100853, China. pengnan301@163.com.
authors.forename: Nan
authors.initials: N
authors.lastname: Peng
authors.affiliation: Institute of Clinical Pharmacology, Peking University First Hospital, Beijing, 100191, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Dai
authors.affiliation: Yuquanlu Clinic, Chinese People's Liberation Army, Beijing, 100037, China.
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Li
authors.affiliation: Beijisi Clinic, Chinese People's Liberation Army, Beijing, 100083, China.
authors.forename: Rong-Guang
authors.initials: RG
authors.lastname: Shi
authors.affiliation: Physical Medicine and Rehabilitaion/Extended Care, Atlanta VAMC, Decatur, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D015203:Reproducibility of Results; D026302:Tai Ji
keywords: Tai Chi; lower-extremity; muscle strength