Tai Chi, a Chinese bodymind exercise, has been used in China for thousands of years for both prevention and therapeutic purposes. In the 1990s, the Western research community started to examine the effectiveness of Tai Chi interventions using scientific research design and standardized outcome measures. A number of reviews of these studies have been published. Based on an extensive literature search, this state-of-the-art review identified 25 such reviews published since 2000, provides a description of them, and summarizes what was learned from these reviews. Although there is still a need to understand more about Tai Chi interventions, especially Tai Chi's mechanism, it is concluded that Tai Chi is a very useful exercise format that can be used for a variety of chronic disease conditions. It requires no equipment and little space, and it can be practiced anytime, anywhere, and by older adults and individuals with chronic diseases. Since short forms (eg, 10 or 24 forms) have been shown to have similar benefits as longer ones, beginners should start using simple, short forms first. Like other exercise interventions, regular practice is a must to be able to gain maximal benefits. Tai Chi can be used safely as a complementary addition to conventional medical treatment, physical therapy, and rehabilitation, as well as with other exercise interventions.
Tai Chi, or more correctly Tai Chi Chuan (or Tai Ji Quan, using the current Chinese spelling system), is a Chinese body-mind exercise with a long and rich history. The Tai Chi characters in Chinese represent the Taoism or Tao philosophy, which believes that while the world is full of contrast or conflicts, it can reach harmony by balancing these contrasts or conflicts. The nature forces or rules that lead to harmony are the Tao or "way." The Tao and Tai Chi are often symbolized by a circle with 2 semicircular teardrop shapes, half white representing Yang (sun, male, fire, etc) and half black representing Ying (moon, female, water, etc;). Note that there is a black spot inside of the white shape and, similarly, there is a white spot inside of the black shape, which means that Yin and Yang are not absolute and they can change toward each other's direction. Together, the symbol represents the balance and change within the universe, nature, or even society. Chuan in Chinese means "fist," or boxing in this context. Thus, Tai Chi Chuan is in fact a boxing or martial art originally developed for self-defense. It is, however, unique because it integrates a Taoist philosophy in its principles and movements; for example, body weight is concentrated on one leg when Tai Chi Chuan practice begins, but it constantly transfers from one leg to the other. To be consistent with the terms used in the literature, TaiChi will be used throughout the text to represent "Tai Chi Chuan."
Although there are many different theories or beliefs about how Tai Chi was invented, it is generally believed that it was developed by Mr Wang-Ting Chen (17th century), a military officer during the later part of the Ming Dynasty (1368-1644 ad). Thereafter, it was passed within the Chen family for many generations in the Chen Village in He Nan Province in China until Mr Chang-Xing Chen (1771–1853 ad), a 14th-generation Chen, taught Tai Chi to Mr Lu-Chan Yang, a person outside of the Chen family. Eventually, through Mr Yang and his students' teaching and promotion, Tai Chi became popular in China, and other styles of Tai Chi, namely, Yang, Sun, and Wu(s), gradually developed. More importantly, people started to practice it for health purposes rather than fighting or self-defense. In 1956, in a major national effort, the Chinese government promoted Tai Chi by simplifying the long form of Yang style into a short 24 forms/movements, resulting in making it the most popular exercise format in China. Today, millions of people in China practice Tai Chi in parks or other open spaces every morning.
Tai Chi was introduced to the United States in the 1970s, when it was practiced by only a very small group of individuals until the publication of a study in 1996 by Dr Steven L. Wolf and his colleagues at the Emory University School of Medicine, Atlanta, Georgia. In that seminal study, they divided 162 women and 38 men with an average age of 76 years, who were free of debilitating conditions such as crippling arthritis, Parkinson disease (PD), or stroke, into 3 groups. One group was given a simplified, 10-form version of Tai Chi's more than 100 movements, one group got biofeedback-based training in balance on a movable platform, and one group received education about falls but no physical training. The Tai Chi and biofeedback groups were given 15 weeks of training, and researchers kept track of participantreported incidences of falling over 4 months. It was found that after the intervention, participants in the Tai Chi group reduced their falling risk an average 47.5% more than the other groups. Since the publication of this study, the interest in Tai Chi and its health benefits has grown and continues to grow rapidly. Hundreds of studies have been published, and interest has extended to many other health areas, such as the impact of Tai Chi on physical function, quality of life, and reducing risks of falling, cardiovascular diseases (CVDs), and so forth. In addition, many Tai Chi–related books have been published, including a few with a research focus. The purpose of this article is to provide a state-of-the-art review on the clinical implications of Tai Chi interventions. Instead of conducting another scientifically meticulous review, which has been already well reported in the literature, this article focuses on a summary of these well-done reviews published since 2000.
The reviews reported in this study were identified through extensive searches in a number of major medical and exercise science research literature search engines (eg, Academic Onefile, CINAHL, EBSCO, ERIC, Health Source, Medline, PsycINFO, Science Direct, Sportdiscus, Scopus, Web of Science, as well as Google Scholar). The keywords used included Tai Chi, Tai Chi Chuan, Tai Ji, Tai Ji Chuan, and so forth. Only reviews published in the year 2000 or later were included and examined. Based on the articles found, additional cross-reference searches were conducted. A total of 32 reviews were identified. To ensure that the findings were evidence based, only the reviews based on some type of scientific procedures, in which randomized clinical trials or controlled clinical trials were the focus of the review, were selected for this review. As a result of this culling, 25 reviews were included, described, and summarized in this study.
In the follow sections, these reviews will be described in a little more detail according to their health focuses. After providing a description of these reviews with a focus on overall health, the reviews will further be described according to diseases. Those with strong evidence will be described first including overall health, balance and control, falling, PD, osteoarthritis, rheumatoid arthritis, and psychological benefits. Then, diseases with moderate evidence, including blood pressure, cancer, CVD, and diabetes, will be described. Note that strong or moderate evidence is operationally defined by the authors based on the number of studies employed in the review and the quality of research articles used in the review. Thereafter, 2 meta-analyses on the effectiveness of Tai Chi interventions on aerobic capacity will be described. Finally, a recent review on clinical trials of both Tai Chi and Qigong for older adults will be described.
Klein and Adams critically reviewed the overall benefits of Tai Chi interventions. Seventeen studies that were either randomized controlled trials or controlled clinical trials judged to be of high rigor were selected for review, and the results produced many possible benefits from practicing Tai Chi. Seven studies produced results, indicating Tai Chi's beneficial effects on quality of life, mood, and/or stress. Other studies produced reliable results concerning increasing overall physical function and decreasing factors such as pain and blood pressure. This review highlights the wide range of benefits that practicing Tai Chi may achieve when used as an intervention tool.
The review by Wang et al covered a wide variety of chronic conditions and the influence that practicing Tai Chi may have on them. Balance, musculoskeletal conditions, hypertension, cardio-respiratory conditions, psychological conditions, endocrine and immune functions, and miscellaneous other conditions were all examined separately. Overall, 9 randomized controlled trials, 23 nonrandomized controlled trials, and 15 observational studies up to April 2002 were included in the review. According to the review, Tai Chi has the potential to improve many of the physiological and psychological aspects of chronic conditions, and it is also to promote a safe and effective intervention balance, cardiovascular fitness, and flexibility in older adults. However, according to the authors, further research should be conducted to increase the knowledge base of the subject.
Verhagen et al conducted a literature search dating through July 2001 on the effects of Tai Chi in older adults. Seven studies were selected, but a total of 9 publications are described because 3 publications were based on the results of 1 study. Three of the studies were randomized controlled trials, and the other 4 studies were controlled clinical trials. Tai Chi was shown to be effective as an aerobic exercise in reducing blood pressure, reducing the risk of falls, and increasing function in older adults. However, based on the low levels of evidence available for Tai Chi in this subgroup, the review states that no substantial claims can be made for Tai Chi practice in older adults. The review also indicates that it excluded any possible studies published in Chinese due to a language barrier, so a substantial bulk of the literature on Tai Chi may have been overlooked.
Balance and Control
Chan and Bartlett reviewed the literature on the efficacy of Tai Chi on balance and postural improvements dating through 1998. Seven articles were selected, including 3 randomized controlled trials, 3 nonrandomized controlled trials, and 1 with a group pretest/posttest study design. The studies reviewed generally support the use of Tai Chi in improving balance and postural control. Chan also included a meta-analysis, which showed that studies with more methodological rigor produced larger effect sizes in balance improvements. The authors of the review conclude that moderate evidence in support of using Tai Chi to improve balance and postural stability is available, indicating that it is a reasonable intervention for clinical use.
The review by Komagata and Newton focused on the efficacy of Tai Chi for improving balance and reducing falls in older adults. Eleven studies were selected for review and were evaluated for methodological quality. While many types of studies were used, all of the selected studies met the standards of methodological quality according to their quality index and methodological rigor scores. In the end, the authors found that Tai Chi improved balance in older adults but was not shown to be effective at reducing the rate of falls in older populations.
The review by Wayne et al analyzed the literature through June 2002 on the effects of Tai Chi on vestibulopathic postural control. Although no study was found specifically relating to vestibulopathic postural control, all studies were relevant to outcome measures associated with postural control, such as balance and falls. A total of 24 studies were selected, 10 being randomized controlled trials and 14 being nonrandomized controlled trials. Twenty of the studies produced evidence favorable to using Tai Chi to improve postural control, indicating sufficient support for Tai Chi. Support for the reduction of falls was especially strong since 8 of 10 randomized controlled trials reported fall reduction. While there are a number of methodological concerns with the studies and any conclusions should be approached carefully, the results are promising for the use of Tai Chi for elderly individuals experiencing vestibulopathic postural control.
Wu reviewed the existing literature on Tai Chi for improving balance and reducing falls in older adults. Overall, 24 articles of various levels of evidence were found on this topic. The review indicates that the results of the studies were inconsistent, making it difficult to tease out the effects of Tai Chi practice. The study indicated that factors such as duration of treatment, sample size, and age span have all been variables in Tai Chi studies related to balance and falls, but there is some evidence that supports its use. The study emphasizes the need for further research.
Harling and Simpson systematically reviewed the effects of Tai Chi practice on reducing the fear of falls and falls in those aged 60 years and older. In all, 7 randomized controlled trials were selected. The review showed that only 2 trials produced clinically significant reductions in the rate of falls, indicating weak support for Tai Chi in fall prevention; however, the study also found strong support for using Tai Chi to reduce the fear of falling. Five of the 7 studies produced clinically significant reductions in fear of falling, meaning that interventions aimed at improving an older person's self-efficacy about falls could use Tai Chi interventions.
Low et al reviewed the literature on Tai Chi and its influence on falls in elderly persons. Seven randomized controlled trials dating through August 2007 were selected, and all studies had outcome measures of fall occurrence. In the end, the data for the efficacy of Tai Chi as well as data for its noneffectiveness were almost equivalent. However, the study noted that the most rigorous studies selected in the review were in support of Tai Chi for reducing the risk of falling, although a variety of other methodological qualities of the studies may have had other unseen effects on the results. While the study asserts that more research should be conducted in this area, it does support the use of Tai Chi to prevent falls in younger, prefrail elderly individuals.
The review by Lee et al focused on the influence of Tai Chi practice in individuals with PD. The authors located 7 studies dating up to January 2008, including 3 randomized clinical trials, 1 nonrandomized controlled clinical trial, and 3 uncontrolled clinical trials were selected. While the overall consensus of the review was that more rigorous studies need to be completed to make any assertions about the use of Tai Chi for PD patients, the study did note that there is favorable evidence in support of Tai Chi with the PD population. Tai Chi improved the prevention of falls and scores on the Unified Parkinson's Disease Rating Scale compared with the exercise control group in 1 trial, but almost all other studies showed mixed or null effects of Tai Chi interventions. The review highlights the flawed designs of the current literature on the subject and recommends better designed studies be conducted in the future.
The systematic review by Lee et al determined the efficacy of Tai Chi for those with osteoarthritis. Twelve studies were included in the study, with 5 randomized controlled clinical trials and 7 nonrandomized controlled clinical trials dating up to June 2007. The review showed promising evidence in support of using Tai Chi to reduce pain associated with osteoarthritis and even reported larger effect sizes in pain reduction from Tai Chi than from other popular interventions, such as using nonsteroidal anti-inflammatory drugs. Also, the review showed that Tai Chi may be beneficial for improving balance and physical function, but the authors assert that further research needs to be conducted to support the reliability of all of the results reported in the review.
The Cochrane review by Han et al examined the effects of a Tai Chi intervention on people with rheumatoid arthritis (RA). The authors of the review located a total of 4 randomized controlled trials or clinical trials dating up to 2002 or 2003. The review mainly showed that Tai Chi statistically improved ankle plantar flexion in those with RA, but most other measures such as activities of daily living and swollen joints showed no improvements after Tai Chi interventions. None of the studies indicated any harmful effects of Tai Chi practice, and the review reported that adherence rates in the Tai Chi interventions were higher than in the controls, indicating that subjects may enjoy participating in Tai Chi over other exercises.
Lee et al systematically reviewed the effects of Tai Chi in those with rheumatoid arthritis. In all, 5 studies dating up to January 2007 were selected, including 2 randomized clinical trials and 3 nonrandomized controlled clinical trials. The review indicated that all of the included trials were of low quality, which significantly affects the results they obtained. However, some studies did show improvements in pain, fatigue, mood, depression, vitality, and disability index. It should be noted, however, that in the areas of pain and mood, other selected studies found no such improvements compared with usual activity controls.
Bone Mineral Density
The review by Wayne et al examined 6 trials dating through April 2006 to determine if Tai Chi influenced bone mineral density in postmenopausal women. Two randomized controlled trials, 2 nonrandomized prospective parallel cohort studies, and 2 cross-sectional studies met inclusion criteria, but they all were classified as having low methodological quality. This being noted, the review showed that Tai Chi is a promising intervention for maintaining postmenopausal women's bone mineral density. No significant adverse effects of practicing Tai Chi were reported, and research also indicates that Tai Chi may improve other risk factors associated with low bone mineral density. Therefore, more research needs to be conducted.
Lee et al reviewed the literature on the effectiveness of Tai Chi for osteoporosis and selected 7 articles: 5 randomized clinical trials and 2 controlled clinical trials. The published data were from studies dating through March 2007. The review mainly showed mixed results in favor of Tai Chi approaches to osteoporosis, stating that there are currently insufficient data on the subject. While a meta-analysis included in the study did show that Tai Chi interventions do increase bone mineral density compared with a no-treatment control in postmenopausal women, the results were not statistically significant.
A literature review of the psychological effects of practicing Tai Chi was conducted by Dechamps et al within the literature from January 1990 to June 2006. Overall, 14 studies were selected, with 8 randomized controlled trials and 6 nonrandomized trials in total. The review showed that Tai Chi is useful for increasing well-being and self-efficacy, as well as improving overall mood. While the study used trials including participants aged 12 to 96 years, intervention effects were most notable in those 55 years and older, including frail older adults and healthy adults. On the other hand, the review indicated that Tai Chi was no more effective than other exercises at the same intensity, but Tai Chi was a safer exercise choice for those who may be deconditioned or have exercise intolerance.
The effects of Tai Chi on blood pressure were systematically reviewed in the literature through January 2007 by Yeh et al. They located 26 relevant studies including 9 randomized controlled trials, 13 nonrandomized controlled studies, and 4 observational studies. Among the studied reviewed, 85% reported reductions in blood pressure in those who practiced Tai Chi, but the study quality varied, and 2 of the most rigorous studies showed that blood pressure was not affected by Tai Chi practice. In all of the studies, Tai Chi was shown to be safe, with no studies reporting adverse effects. Since study quality varied, solid statements cannot be made with regard to Tai Chi practice for those with high blood pressure, but the results indicate some potential for the use of Tai Chi in the future.
A systematic review was conducted by Lee et al to determine the efficacy of Tai Chi treatment in those with breast cancer as a complement to traditional cancer treatment. Four studies were selected, with 3 randomized controlled trials and 1 nonrandomized controlled trial dating up to October 2006. Various findings were noted among the studies, including improved self-esteem and health-related quality of life, improved functions in activities of daily life, and increased shoulder range of motion. While these findings are promising, the review authors suggest using caution when evaluating such results because of the paucity of the available literature (only 4 studies were included) and the flaws (such as small sample size, inadequate study design, and poor reporting) within the available studies.
The review by Mansky et al examined the effects of Tai Chi on various populations including elderly patients, cancer survivors, and those with CVD; 20 randomized controlled trials were selected. Once the studies were further subdivided into their respective categories (eg, elderly patients, cancer survivors, and patients with CVD), the review noted the limited evidence with respect to each category but also highlighted the future potential of Tai Chi in such populations. The review particularly focuses on the possible benefits of Tai Chi for cancer survivors since Tai Chi has been shown to increase immune response as well as psychological function, but only 2 randomized controlled studies have been conducted with cancer survivors. Both studies show improvements in either quality of life or functional capacity, but further research should be undertaken before any solid conclusions can be made about the usefulness of Tai Chi for cancer patients.
The review by Lee et al examined the effects of Tai Chi on CVD and associated risk factors in the literature through March 2007. Nine randomized controlled studies were selected, and support for the use of Tai Chi to reduce blood pressure was found. Four randomized controlled trials found that blood pressure was significantly reduced compared with no-treatment controls, while 2 other studies found no difference between Tai Chi and aerobic exercise interventions. The review indicates that the evidence is inconclusive because of the small number of trials but also notes that evidence is encouraging in support of using Tai Chi for reduction of hypertension.
Very recently, Yeh et al conducted a review of Tai Chi for patients with cardiovascular conditions and risk factors. A total of 29 studies met inclusion criteria, including 9 randomized controlled trials, 14 nonrandomized studies, and 6 observational trials. The study subjects included patients with coronary heart disease, heart failure, CVD, and CVDRF (hypertension, dyslipidemia, impaired glucose metabolism). Tai Chi interventions ranged from 8 weeks to 3 years, and the sample size ranged from 5 to 207. Most studies reported improvement with Tai Chi intervention, such as reduction in blood pressure and increase in exercise capacity. In addition, no adverse effects were reported. The authors concluded that Tai Chi may be a beneficial adjunctive therapy for patients with CVD and CVDRF.
The review by Lee et al attempted to determine the effects of Tai Chi on type 2 diabetes by examining the literature through May 2007. A total of 5 studies were included: 2 randomized controlled trials and 3 nonrandomized clinical trials. The results of the studies were mixed and conflicting, with some showing greater improvements in blood glucose levels compared with exercise, and others showing no effects from Tai Chi interventions. Overall, the review states that there is insufficient evidence in support of Tai Chi for type 2 diabetes. Note, however, that only the abstract of this review was published.
Taylor-Piliae and Froelicher conducted a meta-analysis of the efficacy of Tai Chi in improving aerobic capacity, locating 7 qualified studies for analysis, with 2 randomized controlled trials, 2 quasiexperimental studies, and 3 crosssectional studies. Large and significant effect sizes were noted in the crosssectional studies, while nonsignificant effect sizes were found in the randomized controlled trials and quasi-experimental studies. Studies comparing sedentary people to Tai Chi participants also noted larger effects when Tai Chi was practiced for at least 1 year. The authors of the review concluded that Tai Chi could be used as an alternative form of aerobic exercise and recommends further inquiry into this area.
Taylor-Piliae recently performed a follow-up study to update the above meta-analysis. The study added an additional 7 studies to the analysis through June 2007, including 3 experimental studies (randomized controlled trials and quasiexperimental studies), 3 cross-sectional studies, and 1 prospective cohort study (14 studies in total). Much like the original meta-analysis, statistically significant and large effect sizes were noted in the cross-section studies (effect size = 1.33), meaning that subjects experienced significant aerobic improvements from practicing Tai Chi in the studies. On the other hand, small effect sizes were found within the experimental studies (effect size = 0.38). The review concludes that Tai Chi is an effective aerobic exercise to use in interventions.
Tai Chi and Older Adults
Rogers et al recently reviewed both Tai Chi and Qigong, which is another form of Chinese body-mind exercise, clinical trials in older adults. Among 36 studies reviewed, 31 were Tai Chi studies. The authors focused their reviews on the outcomes of Tai Chi interventions on balance and falls, physical function, cardiovascular health, psychological outcomes, and disease outcomes and concluded that a Tai Chi intervention may help older adults improve physical function and reduce blood pressure, fall risk, depression, and anxiety. The authors called for more research on potential benefits of meditative aspects of Tai Chi and their possible contribution to successful aging.
Limitations of Tai Chi Research and Reviews
While these reviews provide rich and updated information on the benefits and potential of Tai Chi interventions, several limitations, both in the original research and reviews, were noticed. For the original research, the most significant limitation is the control of the dose. The dose of the Tai Chi intervention includes Tai Chi style employed, frequency, and duration and length of the intervention. Although most of the interventions used the Yang style, the forms varied greatly from study to study, ranging from only a few forms to 108 forms. In addition, many studies did not even mention the key information concerning the intervention's Tai Chi dose, rather simply stating that Tai Chi exercises were employed. Reported frequency, duration, and length of the interventions also greatly varied. While a variation in any exercise intervention is expected, variation to such a large degree makes it hard to generalize in practice, especially in therapeutic settings.
The second limitation related to Tai Chi studies is that few studies explore the mechanism of Tai Chi. Why did Tai Chi sometimes work better than a typical exercise intervention? How could Tai Chi lead to the improvement of disease conditions? Will one specific form of a style of Tai Chi be more effective than another? How important is the sequence of a set of forms? Without understanding these basic questions, it will be very difficult to use Tai Chi in a quantitative way in clinical application or an intervention.
For the conducted reviews, the variation is also a problem: while some used meta-analysis, others employed systematic or general reviews; some used 1 database, and others used more than 20 databases; some included only randomized clinical trials, and others employed several types of interventions. Inclusion and exclusion of the studies are also not consistent. In fact, some of the selection criteria have been questioned. For example, Yeh et al questioned the methodological quality of the review by Han et al, which provided one of the most solid pieces of evidence about Tai Chi benefits for those with rheumatoid arthritis. Yeh et al believed that the selection criteria (mixed intervention methods were included) in that study were not appropriate and that the use of the Jadad rating scale for this type of intervention was also a poor indicator of study quality within complementary medicine. Another limitation in these reviews is that, except for a few, most of the reviews were limited to only publications in English. As already pointed out by some of the authors (eg, Verhagen et al), most Tai Chi research has been conducted in China and other parts of Asia and published in non-English journals. Without including this research and those publications, some important information on Tai Chi research and its clinical applications may be missing.
Based on the things we learned from these reviews, it seems that we can reasonably derive the following general implications regarding Tai Chi and its applications to clinical practice:
1. Tai Chi is a very useful exercise format that can be used for a variety chronic disease conditions. It requires no equipment and little space, and it can be practiced anytime and anywhere;
2. Because of its low- to moderate-intensity characteristics and slow and relaxed nature, Tai Chi can be practiced by anyone, including both older adults and individuals with chronic diseases.
3. Start simple. Learning some long forms of Tai Chi could be challenging, especially for older adults without any previous experience. Since short forms have shown similar benefits as the longer forms, beginners should begin with short forms first.
4. Practice daily if possible. Like other exercise interventions, practicing regularly is a must to be able to gain maximal benefits. In fact, people in China practice Tai Chi every day for both therapeutic and prevention purposes.
5. Use Tai Chi as a complementary addition to both conventional medical treatment and physical therapy or rehabilitation, as well as with other exercise intervention methods (eg, walking).
Tai Chi has a long and rich history of being used as an effective therapy and for prevention purposes. Since the 1990s, researchers in Western medical communities have examined the effectiveness of Tai Chi interventions in clinical applications. The reviews described in this article provide a summary of the latest cumulative evidence on Tai Chi interventions. While some of the findings are not consistent and more research is needed, especially concerning the mechanism and dose-response issues of Tai Chi interventions, clinical practitioners should take advantage of the information learned thus far and start to integrate this simple, yet effective, means of exercise into both their therapeutic and prevention applications.
Weimo Zhu, PhD, Shangyi Guan, MS; Yubing Yang, PhD
American Journal of Lifestyle Medicine