Effectiveness of Tai Chi exercise in improving aerobic capacity: a meta-analysis.

PURPOSE: Meta-analysis involves the integration of several studies with small sample sizes, enabling the investigator to summarize research results into useful clinical information. Tai Chi exercise has recently gained the attention of Western researchers as a potential form of aerobic exercise. A goal of this meta-analysis was to estimate the effect of Tai Chi exercise on aerobic capacity.
METHODS: A computerized search of 7 databases was done using key words and all languages. Sixteen study elements were critically appraised to determine study quality. D-STAT software was used to calculate the standardized mean differences (ESsm) and the 95% confidence intervals (CI), using means and standard deviations (SD) reported on aerobic capacity expressed as peak oxygen uptake (VO2peak) (mL x kg(-1) x min(-1)).
RESULTS: Of 441 citations obtained, only 7 focused on aerobic capacity in response to Tai Chi exercise (4 experimental and 3 cross-sectional). Older adults including those with heart disease participated (n = 344 subjects); on average men were aged 55.7 years (SD = 12.7) and women 60.7 years (SD = 6.2). Study quality scores ranged from 22 to 28 (mean = 25.1, SD = 2.0). Average effect size for the cross-sectional studies was large and statistically significant (ESsm = 1.01; CI = +0.37, +1.66), while in the experimental studies the average effect size was small and not significant (ESsm = 0.33; CI = -0.41, +1.07). Effect sizes of aerobic capacity in women (ESsm = 0.83; CI = -0.43, +2.09) were greater than those for men (ESsm = 0.65; CI = -0.04, +1.34), though not statistically significant. Aerobic capacity was higher in subjects performing classical Yang style (108 postures) Tai Chi (ESsm = 1.10; CI = +0.82, +1.38), a 52-week Tai Chi exercise intervention (ESsm = 0.94; C = +0.06, +1.81), compared with sedentary subjects (ESsm = 0.80; CI = +0.19, +1.41).
CONCLUSIONS: This meta-analysis suggests that Tai Chi may be an additional form of aerobic exercise. The greatest benefit was seen from the classical Yang style of Tai Chi exercise when performed for 1-year by sedentary adults with an initial low level of physical activity habits. Recommendations for future research are provided and the effect sizes generated provide information needed for sample size calculations. Randomized clinical trials in diverse populations, including those with chronic diseases, would expand the current knowledge about the effect of Tai Chi on aerobic capacity.