Introduction

Despite the fact that physical activity is associated with a decrease in morbidity and several health benefits, few people at any age engage in daily physical activity [1, 2]. Daily moderate physical activity is recommended to improve general health, as vigorous exercise is considered as a barrier to exercise among people with a sedentary lifestyle [1].

Tai Chi Chuan (TC) or Taiji is a traditional Chinese form of exercise based on martial arts. TC practice is a light-to-moderate intensity exercise [3, 4]. The “Chuan” term is often omitted in the literature and means “boxing.” Literally, TC means the supreme ultimate boxing or “Yin and Yang boxing.” In the TC philosophy, Yin refers to shadow, soft and feminine, whereas Yang is the light, hard and masculine part [5]. TC boxing was codified between the Ming (1368–1644) and the beginning of the Quing dynasties (1644–1911). TC forms are characterized as slow circular controlled sequences of movements, which slightly differ between TC schools.

Physical exercise has a number of psychological benefits, such as reduction in mood disturbance, improvement of quality of life, well-being, and self-efficacy [6–8]. Studies [9, 10] have provided evidence that a psychological variable like self-efficacy predicts behavioral adhesion. Perceived self-efficacy refers to beliefs in one’s capabilities to organize and execute the courses of action required to produce given attainments [11, p 2]. Moreover, among sedentary people, mental health, well-being, and outcome expectations may influence exercise adhesion [10, 12, 13]. The increasing number of TC practitioners and health-related publications calls for an update of the scientific evidence supporting psychological benefits and exercise adhesion related to TC practice. However, despite its popularity, the mental health effects of TC are still unclear [14]. The goals of this systematic review are (1) to review the body of literature assessing the health benefits of TC and (2) to provide a systematic critical analysis of the evidence based on the mental/psychological health effects of TC practice among different populations. The conclusions of this review may result in rehabilitation initiatives and new directions for research.

Materials and methods

Literature research

The literature research was conducted as a systematic search from January 1990 to June 2006 using electronic databases including: Ebsco Host, Wiley Interscience, Taylor & Francis, Blackwell Publishing, PubMed, and Science Direct. Searches were limited by keywords: ‘Tai Chi Chuan’ or ‘Taiji’, ‘mental health’, ‘self-efficacy’, ‘well-being’, ‘self-esteem’, ‘mood’, and ‘depression’. Then, titles and abstracts related to TC practice and mental/psychological health and well-being were preselected. Furthermore, a general perspective about TC health effects from previous reviews is included in this present review.

Study selection

Studies were assessed using the Scottish Intercollegiate Guidelines Network 50 [15, 16]. Each paper identified as relevant was appraised independently by two reviewers. They agreed on a methodological quality rating using the methodology and hierarchy of study types published elsewhere [15, 16]. The reviewers’ agreement score measured using the formula \( \frac{{agreement - disagreement}} {{number{\text{ }}of{\text{ }}decision}} \) was 0.98. The hierarchy criteria are presented in Table 1. Methodological quality was rated using published criteria [15, 16] presented in Table 2.

Table 1 Level of evidence (with permission from the SIGN, from section 6 of the SIGN50, 2004) [15, 16]
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Table 2 Grades of recommendation (reproduced with the permission of the SIGN group)
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Inclusion and exclusion criteria

Studies were excluded for any of the following reasons: (1) if the principal aim of the study was not to assess the mental and psychological health effects of TC; (2) if intervention procedure and outcomes were not adequately described; (3) if no definition/description of TC exercises was provided.

Inclusion criteria were studies with principal objective to assess the effect of TC practice on self-efficacy, well-being, and mental/psychological health.

Results

Overview of previous reviews

The historical perspective provided by examining previous reviews substantiates the conclusion about TC efficacy and directions for research being guided by emerging knowledge. A total of nine reviews from 2000 to 2006 were found [4, 14, 17–23], including more than 4,000 participants in 72 trials. Twenty were randomized controlled trials and 50 nonrandomized trials. On the whole, the main countries of origin of publications were China for 48.8%, the USA, 41.7% followed by Australia and Canada. The nonrandomized studies mainly come from China.

The length of the studies (n = 72) varied from 1 to 156 weeks, the most reported intervention frequency being 12 weeks (15% of trials) followed by 8 weeks (10% of trials). The duration of TC practice varied from 5 to 90 min per session for one to six sessions a week. The most frequent duration/frequency was 60 min twice a week (18.5% of trials). Most of the studies (40%) used the traditional Yang style of 108 movements, whereas 15% of trials used a simplified form comprising between 5 and 24 movements.

The number of subjects varied from 1 to 256 for an age ranging between 21 and 92. The minimal mean age was 50 for 76% of the studies (n = 72). At the gender level, the sex ratio was rarely reported; among 65% of trials with a mixed gender population, only 20% reported the sex ratio.

Reviews published between 2001 and 2006 suggest that TC practice provided health benefits among adults and elderly [17, 19, 21, 23]. Results from balance and postural control studies showed moderate evidence concerning the efficacy of TC on reduction in falls and improving postural control. Nevertheless, a significant reduction in fear of falling and an overall functional improvement were found [18, 20, 22]. On the other hand, none of the studies reviewed in these reviews assessed the effects of TC on institutionalized elders with or without cognitive impairments.

Analysis of the psychological effects of Tai Chi practice

Few studies have provided information about the psychological effects of TC, yet the relaxing and beneficial nature of TC exercise still requires clarification [14]. In light of the above review conclusions, two main aspects based on studies from 1990 to June 2006 are discussed here: (1) the relationship between psychological factors and adhesion; (2) TC expert guidance when the information is available, with the modeling approach serving as a reference [24]. A total of 67 references were obtained. Based on title and abstract, 20 articles were selected. Of these 20, three studies were rejected because the intervention was a combination of exercises, did not mainly comprise TC exercises, or was not clearly described, whereas three other studies were not included because psychological health was not the main outcome. Thus, details of 14 studies are presented according to study design in Tables 3 and 4 [3, 25–38]. A total of eight randomized controlled studies and six nonrandomized ones were, thus, considered in this analysis. A detailed analysis of four high quality trials is presented below.

Table 3 Characteristics of randomized controlled trials
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Table 4 Characteristics of nonrandomized controlled trials
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Details of high quality trials

Brown et al. [37] studied the cognitive effects of exercise on psychological benefits. Out of a total of 163 sedentary healthy older adults (aged 40–69 years), 135 participants finished the intervention consisting of three sessions a week for 16 weeks. Participants were randomly assigned to one of the five experimental procedures: (1) moderate intensity walking (MW), 65–75% of heart rate reserve (HRR), 30–40 min; (2) low intensity walking (LW), 45–55% of HRR, 40–50 min; (3) low intensity walking plus relaxation response (LWR, relaxation tape), 40–50 min; (4) mindful exercise (ME) Tai Chi exercises, 45 min; (5) control. The ME group received instructions from an exercise leader, whereas the walking groups autonomously used an indoor walking track. The dependent measures for the psychological change were mood, self-esteem, life satisfaction, and personality inventories. The results showed that women in the ME group achieved a significant decrease in anger and total mood disturbances than those in the LW and LWR groups. Compared to the LW and LWR subjects, women in the ME group also showed a greater decrease in confusion, depression, and tension in the profile of mood states. For men, the MW procedure had more positive effects on mood than the other procedures, and all four procedures had more favorable effects at 16 weeks.

Li et al. [3] studied TC effects on self-efficacy and exercise adhesion. Low-active and independent older adults (n = 98), 65–96 years old (mean 73.2 ± 4.91 year) were randomly assigned to two groups, TC or control (waiting list for TC course after the trial). Participants in the TC procedure followed a 6-month program of 60 min of TC Yang (24 movements) twice a week. Cognitive functions were not assessed either before or after the intervention. During the TC course, participants were instructed to replicate the motions, postures, and movement at the speed of the instructor. No information was given concerning the effect of age on the time to learn the TC forms. Dependent measures were exercise barriers and performance self-efficacy. Class attendance was also recorded as an exercise-behavior outcome. Results showed a general improvement in TC exercise self-efficacy. Class compliance was predicted by both dimensions of self-efficacy. Regression coefficients of barriers and performance efficacy suggested that exercise adherence was significantly related to self-efficacy cognitions [3].

Two trials from the Atlanta Frailty and Injuries: Cooperative Studies on Intervention Techniques (FICSIT) examined the psychosocial and health effects of TC practice [33, 35]. Subjects (n = 200) with a mean age of 76.2 years of age were independent and community living. They were randomly assigned to one of the three groups: a 15-week course of TC Yang style (n = 72), computerized balance training (n = 64), or education (n = 64). Subjects with severe cognitive impairments (not defined) or Parkinson’s disease were excluded. The TC group met twice weekly, and the balance training and control groups met once weekly. The practitioners reproduced the motions and speed of the movements from the expert demonstrations. No information was given for the time needed to learn the TC form. It was found that those who participated in TC had a 48% reduction in the risk of falls, reduced their fear of falling, and improved their well-being. A trend of a higher increase in self-efficacy and overall improvement was found in favor of the TC group, but this was not statistically significant.

Commentary

The majority of the randomized controlled studies reviewed here concerned TC benefits in adults aged 55 and older. This is also among such population that research has shown tangible results. Few nonrandomized studies have targeted TC effects on younger and middle-aged people [26, 27, 30]. However, the effects noted should be interpreted cautiously considering the lack of information on the description of the experimental settings and interventions used. For some authors, the intensity component of exercise could mediate adhesion [3, 31, 37]. People who do not like intense exercise or the deconditioned ones might benefit more from TC exercise [4, 26, 37, 38].

Analyses according to gender have been almost entirely absent from TC research. One study [37] that did investigate gender differences demonstrated that men may benefit more from walking exercises in terms of mood improvements, whereas this effect was observed after TC practice in women.

The majority of studies have described the psychological benefits of TC practice. Time is an important factor in physical and psychological interventions. The length of studies varied from 5 to 26 weeks, so the long-term effects of TC practice are still unknown. The relationship between length and frequency of exercise and psychological effects was not addressed in most of the studies. Moreover, as TC is classified as a form of moderate intensity exercise [4], it is important to take into account public health recommendations about exercise [1]. In the present review, one study used an intervention procedure according to the recommendations [25]. In addition, a dose/response effect of exercise on mood has recently been demonstrated [39, 40]. Tsang et al. [41] showed a positive relation between length and the frequency of TC practice on balance, which could explain most of the inconsistency found in studies where there were few sessions per week.

An effect of incorporation of TC activity on patients’ lifestyle after the intervention has also been found [34, 37], underlining the need for further investigation into the adhesion mechanisms related to TC practice. Besides the effects of the intervention length and the volume of practice, the role of the expert guidance and the conditions in which the TC training are given should be taken into account when assessing its beneficial effects.

Studies that directly compared TC with other forms of exercise undertaken at the same intensity are not numerous [33, 35, 37, 38]. Others [3, 25, 27–30, 32–35, 37, 38] have shown beneficial effects of TC practice on mood, well-being, self-efficacy, and exercise participation. However, the results observed in TC practice were not statistically significant compared to other exercises of equivalent intensity. In addition, studies comparing TC with other forms of exercise need equivalence testing in terms of intensity, volume, and length of training.

To date, only three studies have used blind outcome assessment to prevent performance and detection, including two from the Atlanta FICSIT trial bias [33, 35, 38]. However, blinding was not mentioned as a method to prevent bias, so it is not clear whether or not the authors tried to keep the patients, caregivers, or the outcome assessors unaware of the intervention procedures.

The conditions in which TC learning is conducted need further examination, as a number of studies relied on grossly different styles and forms of TC. When a sequence of movements has to be learned by heart, focusing on the exact movement form may be a disadvantage for people with learning disabilities, spatial perception problems, or cognitive impairments. As no information was given with regard to older adults’ learning difficulties, it is not possible to draw any firm conclusions about the cognitive benefits of TC practice. In addition, the mind–body effects of TC exercise could be an adjustment between cognition and action during TC practice. This may be enhanced via qualitative components from the instructor’s experience and personality and are quasi-absent in Western rehabilitation programs [4, 42, 43]. The procedure and the guidance used by the TC expert could account for most of the results [26, 30–32]. As TC intervention relies on qualitative components (imagery, philosophy, TC principles, etc.), it is likely that the expert’s guidance and his personality are mediators of adhesion [26, 31, 32]. Both the improvement and perception of control of our own health also mediate participation and adhesion to exercise prescription [3, 31, 37]. For these reasons, more studies are needed to assess the qualitative components of expert guidance on mood improvement.

Finally, there is no formal evidence that TC is more beneficial than other forms of exercise of the same intensity. At the psychological level and in terms of quality of life, practice through its philosophical and aesthetic aspects would seem to have some beneficial effects, which in turn might be more marked in populations educated to high school level and beyond [33, 35, 37]. Moreover, no gender effects on mood, self-efficacy, outcome expectations, and well-being have been reported to date, yet some data [37] suggest that gender might be a moderator.

These conclusions should be taken with caution, as the literature searches were in English and French, so most of the Chinese studies were not reviewed here. However, a large systematic review of Chinese studies has been performed by others [17].

Conclusion

TC is a form of risk-free exercise suitable for people unsuited to high intensity physical activity. The movements of TC might therefore be the thrust of future interventions in populations with a sedentary lifestyle or the elderly. Our conclusions confirm those of Sandlund and Norlander [14]. They stated that the beneficial effects reported in TC practice need further investigations about the time needed to learn the techniques, the learning procedures, and the perception of the activity from the subject’s point of view. Moreover, as the intervention procedure and the expert guidance are mediators, more extensive studies are required on this issue.