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  1. Taylor-Piliae, Ruth E. RN, CNS, MN
  2. Froelicher, Erika S. RN, MPH, PhD, FAAN


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 ([latin capital V with dot above]o2peak) (mL [middle dot] kg-1 [middle dot] 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.


Tai Chi exercise, though practiced in China for hundreds of years, has only recently gained the interest of researchers in Western countries as an alternative form of exercise. 1-3 Recently, improvements in cardiorespiratory function, 4-6 balance, 7-9 muscular strength, 10-12 flexibility, 5,13,14 relaxation 15,16 and mood state 15,17-19 have been associated with Tai Chi. Additionally, reduction in blood pressure, 3,20 and improvement in aerobic capacity 2 in patients with heart disease have been reported. Tai Chi requires no special facility or expensive equipment and can be performed either individually or in groups. Tai Chi movements are suited for persons of all ages, regardless of previous exercise experience and aerobic capacity. 14,21 Tai Chi is a low impact, low to moderate intensity exercise incorporating elements of balance, strength, flexibility, relaxation, and body alignment. Features of Tai Chi exercise include weight-shifting between right and left legs, knee flexion, straight and extended head and trunk, rotation, and asymmetrical diagonal arm and leg movements with bent knees. 22,23 The exercise intensity of Tai Chi is variable and can be adjusted by the height of the postures, duration of the practice session, and training style. 22,23 Tai Chi is performed in a semisquat position. A high-squat posture and short-training session are well suited for deconditioned persons, including those with heart disease and older adults. 22,23 The exercise intensity of Tai Chi, height of the postures, and duration are all likely to affect overall improvements in aerobic capacity. However, there is a paucity of literature on the aerobic benefits of Tai Chi exercise.


Lan and colleagues 22 reported the exercise intensity during performance of the classical Yang style among experienced Tai Chi practitioners to be at 55% of the subjects' peak oxygen uptake. Zhuo and colleagues 24 reported the estimated energy costs of performing the classical Yang style of Tai Chi to be 4.1 metabolic equivalents (METs), with work intensity not exceeding 50% of an individual's maximum oxygen uptake. Schneider and Leung 25 reported that the exercise intensity of performing Tai Chi was 4.6 METs. Zhuo and colleagues 24 have also reported that the energy cost for performing a simplified form of Tai Chi requires an average of 2.9 METs with a maximum oxygen uptake at less than 40%. Energy requirements for Tai Chi Chih, a simplified form of Tai Chi, were reported by Fontana 26 to range from 1.5 to 2.6 METs, 26 depending on whether the subject was sitting or standing. There seems to be a wide range of exercise intensities associated with Tai Chi performance, ranging from 1.5 to 4.6 METs.


Maximum oxygen consumption ([latin capital V with dot above]o2max) is considered the best measure of aerobic capacity and provides important information about cardiorespiratory function. 27,28 [latin capital V with dot above]o2max is the greatest amount of oxygen a person can take in from inspired air while performing dynamic exercise involving a large part of total muscle mass. 27 [latin capital V with dot above]o2max is considered the gold standard for determining aerobic capacity, 27,28 though not feasible or appropriate for some patient populations. Aerobic capacity is derived from gas exchange during exercise testing and is difficult to obtain in older populations and those with compromised cardiopulmonary functioning. In high risk or diseased populations, it may be more appropriate to obtain [latin capital V with dot above]o2peak if symptoms such as angina, deconditioning or other factors prevent subjects from achieving maximum oxygen consumption levels. 27,28 Oxygen consumption derived from [latin capital V with dot above]o2peak during exercise testing is most accurate when measured directly from expired gases. 27,28 Another term to express oxygen consumption is metabolic equivalents. 27,28 One metabolic equivalent (MET) is a unit of resting oxygen uptake (~3.5 mL of O2 per kilogram of body weight per minute [mL [middle dot] kg-1 [middle dot] min-1]). 29 In this meta-analysis, [latin capital V with dot above]o2peak in mL [middle dot] kg-1 [middle dot] min-1 is used as the measure of aerobic capacity.


The effect of Tai Chi exercise on aerobic capacity is important to know if clinicians want to recommend Tai Chi as an alternative form of aerobic exercise. The majority of the published studies examining cardiorespiratory responses to Tai Chi exercise by measuring aerobic capacity have small sample sizes. A meta-analysis involves the integration of several studies with small or large sample sizes, enabling the investigator to summarize the research results into useful clinical information. Therefore, the purpose of this meta-analysis was to estimate the extent to which Tai Chi exercise affects aerobic capacity.