- Top of page
- MATERIALS AND METHODS
- AUTHOR CONTRIBUTIONS
Over the last 2 decades, musculoskeletal pain, including back pain and osteoarthritis (OA), has been consistently reported as an international health priority among industrialized countries (1, 2). Of the various treatments for these conditions, exercise has been shown to be effective for both OA and chronic back pain (3, 4). There are, however, many ways to implement exercise therapy, and because most reviews (3, 5–7) combine all forms of exercise into a single category, the effects of specific exercise programs and doses are unknown. Thus, we have chosen a specific exercise form, Tai Chi, which incorporates supervision, stretching, and strengthening components, all of which have been associated with an optimal outcome (8).
Tai chi, which originated in China, is a form of exercise that focuses on controlled movements combined with deep diaphragmatic breathing (9). There are 5 major styles, Chen, Yang, Wu, Hao, and Sun, each with its own unique characteristics but all based on the same essential principles (10). Yang and Sun styles have recently become widely used to improve balance and decrease the risk of falls among the elderly population (11), and a specific Sun-style form of Tai Chi is currently endorsed by The Arthritis Foundation in the US as a means of managing OA pain (12). Considering the increased popularity of this exercise in both North America and Australia, a growing body of research aimed at investigating the health benefits of Tai Chi has emerged. Many of the individual trials have reported Tai Chi to have positive effects on pain, physical function, and quality of life in populations with chronic conditions (13–19), and these findings have been supported by a number of review papers (20–22). However, none of these reviews have provided a quantitative estimate of the magnitude of the effect of Tai Chi for chronic musculoskeletal conditions.
The aim of this systematic review was to determine the effectiveness of Tai Chi in decreasing pain and disability and improving physical function and quality of life in people with chronic musculoskeletal pain. In contrast to previous reviews, this review used a meta-analytical approach to provide an effect size for Tai Chi on musculoskeletal pain symptoms. Because there are a wide variety of musculoskeletal conditions that could potentially be affected differently with the practice of Tai Chi, this review pooled trials with sufficient homogeneity on the origin of the musculoskeletal pain, and separately analyzed trials with heterogeneous musculoskeletal conditions.
- Top of page
- MATERIALS AND METHODS
- AUTHOR CONTRIBUTIONS
Previous reviews have reported that Tai Chi is beneficial for reducing pain and improving physical function (22, 36, 37) in painful musculoskeletal conditions, but, to our knowledge, until now the size of the effect has not been quantified. We conducted the first meta-analysis of trials investigating Tai Chi interventions for musculoskeletal pain and have provided pooled estimates of the size of effects on pain and disability. Data were extracted from 7 RCTs (13, 14, 24, 26–29) with a total of 321 participants with musculoskeletal pain. The pooled results of our meta-analysis suggest that Tai Chi has small positive effects on self-assessed pain and disability. It is important to note that these are short-term effects, seen directly after the course of treatment; data regarding long-term effects were not available. It is possible that these effects may decrease over time for individuals who do not continue to regularly practice Tai Chi.
Pooled effect sizes for pain and disability outcomes were fairly similar: both were an ∼10-point improvement on a 0–100-point scale. Narrow 95% CIs suggest adequate precision of these estimates, and in both cases P values were <0.05. Of importance is consideration of whether these calculated effects are clinically worthwhile. Researchers have attempted to quantify clinically worthwhile effect sizes for some outcomes (38, 39), but there remains no firm consensus on the size of a worthwhile effect. This is due in part to the fact that estimates provided in the literature are concerned with within-group differences, and when interpreting the results of meta-analyses we are actually interested in between-group differences.
Although the effects reported in our analysis are slightly below the worthwhile threshold reported by some researchers (39), the clinically worthwhile effect has generally been estimated with respect to treatments provided in a clinic where a patient pays for an individual session with a therapist. Tai Chi is not typically provided in a clinic, but rather is usually performed as a group exercise activity practiced at one's leisure. This difference in the style of treatment may impact a person's expectations of what is a worthwhile effect. The fact that Tai Chi is inexpensive, convenient, enjoyable, and conveys other psychological and social benefits (16) supports the idea that a smaller effect size may be considered worthwhile for this type of intervention.
In addition to pain and decreased function, people with chronic pain also experience psychological distress (40). Because Tai Chi has been said to improve mood and sleep patterns (17, 41), we decided to include quality of life outcomes in this review. Three of 7 RCTs reported quality of life outcomes, but heterogeneity of assessment tools prevented a meta-analysis and we were therefore unable to calculate a pooled estimate of the effect of Tai Chi on quality of life. In general, Tai Chi showed a trend toward small positive effects for overall physical health, tension level, and satisfaction with general health for people with OA, and improved overall mental health for people with tension headaches. Improvements in mood were not found to be statistically significant in the one trial that measured it. The effect of Tai Chi on quality of life in people with musculoskeletal pain remains unclear. The authors recommend that future RCTs use reliable and valid outcome measures such as the SF-36 to measure quality of life (42).
Difficulty with performing physical activities such as walking, lifting, and bending is common in patients with chronic back pain (43). Previous trials have attempted to incorporate performance measures as treatment outcomes, but to date there is no consensus among authors regarding how best to measure these variables. Although reviews have suggested that regular Tai Chi practice can improve physical performance, our analysis found Tai Chi to have very small positive effects that could be due to chance. Also, only 3 of the 7 RCTs reported on physical performance, meaning that conclusions were drawn from a reasonably small sample. In addition, the performance tests used in the trials, including the 50-foot walk test and the Get Up and Go test, have been shown to have small, insignificant correlations with concurrent measures of physical function such as the WOMAC, and unfortunately to have low sensitivity to change in patients with knee OA (44, 45). Future research could include outcome measures that have been shown to be reliable and responsive to change, such as the 6-minute walk test (46), or a comprehensive battery of physical performance tests such as those recommended by the American College of Sports Medicine guidelines, which include assessment of physical strength, endurance, and flexibility (47).
The I2 values for pain, disability, and physical performance outcomes were 30%, 0%, and 55%, respectively. These values indicate that statistical heterogeneity ranges from “might not be important” (0–40%) to “may represent moderate heterogeneity” (30–60%) (23). There are several potential sources of clinical heterogeneity to be considered when interpreting the results. These include population, treatment implementation, and adherence.
All studies included in the meta-analysis investigated participants with a diagnosis of chronic arthritis; however, the type of arthritis varied among trials. Of the 6 included trials, 5 investigated lower extremity OA (14, 24, 26, 27, 29), and 1 investigated RA (28). In addition, there are various factors associated with the implementation of the intervention, such as Tai Chi style and treatment dose, that may influence effect size. There were 3 different styles of Tai Chi used among the included trials: Yang, Sun, and Wu. Treatment dose, including duration and frequency, may also affect treatment outcome. The duration was fairly consistent among the trials, with 4 of the 6 trials using Tai Chi programs with 12-week durations (26–29), 1 trial using 10-week programs (24), and 1 trial using 6-week programs (14). The frequency had a greater variation among trials, ranging from 10–24 sessions. However, based on visual inspection of the forest plot, the differences in study population, Tai Chi style, and dose did not appear to explain the differences in effect size between trials.
There are other potential sources of clinical heterogeneity that were not reported but which are recommended by the CONSORT guidelines. These include standardization of intervention, eligibility criteria for treatment providers, and adherence to treatment. The trials in this review did not provide any summary data on these factors and thus they should still be considered as potential contributing factors to the variability of the effect sizes.
All RCTs included reported pain and disability as outcome measures, but the assessment tools to measure pain outcomes were inconsistent, which limits the generalizability of the pooled results. Inclusion of a simple NRS of average pain over the last week in RCTs, in addition to any specific condition-based pain measures, would help to resolve this issue. The reporting quality of the included trials was inconsistent. This could be improved by adhering to the CONSORT recommendations (48, 49). Future research should also focus on designing higher-quality trials with larger sample sizes in order to provide more precise estimates of the effects of treatment.
Meta-analysis necessarily involves assumptions of homogeneity with respect to outcomes, treatment, sample, and data. We recognize that some heterogeneity in all these areas exists but believe that the included trials are sufficiently similar to support our choice of methodology. Further, descriptive information is reported for each trial (Table 1) and individual effect sizes are presented in the forest plots (Figures 2, 3, and 4). The authors also recognize that there is some controversy about whether or not to confine a systematic review to trials published in peer-reviewed journals. We excluded this type of literature because it is difficult to access the data required for a meta-analysis. Although some authors have shown that the exclusion of unpublished work may lead to an overestimation of the effect of Tai Chi, others have shown that the inclusion of unpublished results may introduce bias if favorable results are provided more readily (23, 50).
From the available data, Tai Chi appears to have a small positive effect for reducing pain and improving disability in people with arthritis. The extent to which Tai Chi reduces other types of musculoskeletal pain, however, requires further high-quality studies with larger sample sizes considering a wider range of musculoskeletal conditions. The data also showed a positive trend toward improving physical performance, reducing tension, and improving quality of life. However, due to the questionable quality of performance measures and the heterogeneity of quality of life measures, an accurate estimate of effect for these outcomes was not possible. It is of importance to note that the results reported in this systematic review are indicative of the effect of Tai Chi versus minimal intervention (usual care or health education) or wait list control. To establish the specific effects of Tai Chi, a placebo-controlled trial would be necessary; however, no such trial has yet been conducted.