Low back pain (LBP), which occurs below the costal border and above the buttock folds, is one of the most prevalent public health issues worldwide (Van Tulder et al., 2006). Non-specific LBP (NLBP) refers to LBP for which no clear cause has been found and accounts for approximately 80–90% of all cases of LBP (Casazza, 2012), and a significant proportion of patients (10–20%) develop chronic NLBP (CNLBP) lasting at least 12 weeks (Maher et al., 2017). LBP is a major risk factor for physical disability globally, thus affecting nearly 20–25% of the global population over the age of 65 (Vadalà et al., 2020). In the United States, the total annual fiscal effect of low back and neck pain is the third-highest proportion of health care expenditures (Dieleman et al., 2016) and it affects approximately 13.1% of adults from 20 to 69 years old (Shmagel et al., 2016). However, satisfice with treatment is low for CNLBP patients (Patrick et al., 2014). In addition, CNLBP patients usually have a high recurrence rate (Taylor et al., 2014) and were associated with an increased risk of comorbidities such as depression and anxiety (Taylor et al., 2014). Conventional drug therapy appears to provide a short-term benefit to the symptoms of patients with CNLBP; however, recent studies have questioned the effectiveness and safety of these interventions (Deyo et al., 2015b; Al-Qurain et al., 2020; Cashin et al., 2021). Meanwhile, long-term use of analgesics is associated with psychopathy-like depression (Maher et al., 2017) and may decrease bone mass and induce sexual dysfunction (Bishop and Wing, 2003). Pharmacotherapy is insufficient to resolve chronic pain symptoms and improve physical function for this population. Therefore, recently, various clinical guidelines have recommended that the treatment of CNLBP should focus on non-pharmacological interventions (Bernstein et al., 2017; Qaseem et al., 2017; Stochkendahl et al., 2018).

Over the past decades, the advantages of exercise therapy have been discovered in the literature (Miyamoto et al., 2019; Hayden et al., 2020, 2021a; Owen et al., 2020), and it has been used as a first-line option to treat CNLBP (Chiarotto and Koes, 2022). Mind-body exercise (MBE), is a mild to moderate intensity physical activity, such as tai chi (TC) (Qin et al., 2019), yoga (Zhu et al., 2020), qigong (Li et al., 2019) (e.g., Baduanjin and Wuqinxi), and Pilates (Miyamoto et al., 2013), has attracted researchers' wide attention (Zou et al., 2019; Wen et al., 2022). MBE underlines mind-body integration and has the advantages of both mind-body therapy and exercise therapy. It involves various slow body movements synchronized with musculoskeletal relaxation, breathing control, and a meditative state of mind (Bower and Irwin, 2016; Zou et al., 2018). In recent years, it has been successfully used worldwide for the treatment of CNLBP (Teut et al., 2016; Cruz-Díaz et al., 2018; Liu et al., 2019; Yao et al., 2020) and is recommended as a complementary and alternative medicine therapeutic intervention based on the guidelines of the American College of Physicians (Qaseem et al., 2017). Moreover, some meta-analyses indicated that MBE is beneficial for pain intensity and back-specific disability of patients with CNLBP (Li et al., 2019; Qin et al., 2019; Zou et al., 2019; Anheyer et al., 2022). Evidence for these results was also supplied in our previous study (Wen et al., 2022).

Although there is some evidence that MBE intervention is effective in treating the symptoms of patients with CNLBP, there are varying modes. The low efficacy of MBE intervention not only delays the CNLBP patients' condition but also increases unnecessary medical costs. It has become a critical task to further rank the efficacy of different forms of MBE to obtain more comprehensive evidence in terms of MBE for improving symptoms of CNLBP. However, there has been little effort to compare the curative effect of different MBE modes to obtain a deeper awareness. Most randomized controlled trials (RCTs) compare MBE interventions with no treatment or usual care groups, and direct comparisons between different MBE modes were very few. Based on our search results, only one RCT direct compared yoga with qigong in the treatment of patients with CNLBP (Teut et al., 2016). It is because, a head-to-head comparative study would be very expensive, and it would be impractical to use an RCT to examine the relative effects of all MBE modes. Meta-analyses provide a summary estimate of treatment effects by combining data from various studies. However, an important drawback is that standard meta-analyses can only compare two interventions at a time. Meanwhile, network meta-analysis (NMA) can indirectly compare multiple treatments by a common comparator to synthesize evidence across a network of RCTs. Therefore, researchers will be able to rank the effectiveness of multiple MBE modes by the use of NMA.

To date, limited reviews and NMA were done on exercise for patients with CNLBP (Owen et al., 2020; Hayden et al., 2021b; Fernández-Rodríguez et al., 2022). Owen et al. (2020) accomplished a sequential analysis and NMA to evaluate whether or not there was ample evidence to support the application of physical exercise for CNLBP patients and whether one exercise mode was better than another. But TC was included in “Other exercise” intervention group and Qigong-related studies were not included in their NMA. Similar classification appears in the studies of Hayden et al. (2021b) and Fernández-Rodríguez et al. (2022). We cannot find out which MBE mode is the most optimal for improving pain intensity and physical function of patients with CNLBP through current studies. Moreover, most NMA does not include Chinese RCTs because of language barriers and limited retrieval resources. Therefore, it is necessary to identify and assess the best MBE modes for CNLBP treatment by a new systematic review and NMA.

This review aimed to conduct a systematic review and NMA of current evidence from RCTs to compare the therapeutic effects of four common MBE modes (TC, yoga, qigong, and Pilates) in improving pain intensity and physical function for adults with CNLBP. The results of this review may help clinicians choose the ideal MBE modes for the treatment of CNLBP and enrich the theoretical basis for MBE selection. Meanwhile, for patients, the results of this study are assumed to provide evidence-based advice for treatment planning for them and to use optimal MBE intervention as the ideal form of self-care to relieve their symptoms and improve physical function.

In our study, we tried to compare the curative effect of the four most popular MBE modes in improving pain intensity and physical function to identify optimal MBE interventions for patients with CNLBP. Pilates might be the best MBE mode for decreasing pain intensity, followed by TC, yoga, and qigong. However, the differences were minor for yoga and qigong. Pilates continued to be the best performer in improving physical function, with little difference in the remaining three modes. Interestingly, TC performed well in managing the pain but significantly less well than Pilates in improving physical function. Overall, Pilates is perhaps the most appropriate MBE intervention for treating patients with CNLBP.

Our NMA found that Pilates was the most effective mode in decreasing pain intensity, consistent with prior reviews on other exercise therapies (Owen et al., 2020). There was a close correlation between CNLBP and core muscles, particularly deep multifidus and transversus abdominis (Ferreira et al., 2010). In CNLBP patients, activation of multifidus psoas and transverse abdominis is delayed or reduced, and physiologic tonic activation of transverse abdominis is lost during gait and extremity movement. In addition, dysfunction of these muscles might lead to the loss of lumbar support and increase the stress and load on the joints and ligaments of the spine (Ferreira et al., 2010; Hides et al., 2011). This may cause pain and functional abnormalities in CNLBP patients, thus, improving core functions is the key to treating CNLBP (Tang et al., 2016). Developed by Joseph H. Pilates, Pilates exercise therapy is used to improve an individual's “flexibility, strength, and body awareness” and it is referred to as a technique that focuses on core stability, posture, breathing, flexibility, strength, and muscle control (Wells et al., 2012). Moreover, the Pilates approach focuses on strengthening the lumbar region with the active involvement of the core muscles (Rydeard et al., 2006). Previous studies comparing core muscle activation in three different postures between Pilates practitioners and the general population have found that the core muscle activation in Pilates practitioners is significantly higher than that in the general population (Lee, 2021). Therefore, Pilates may decrease pain intensity by enhancing the core muscle. Although current evidence shows the analgesic effect of Pilates in patients with CNLBP, objective neurophysiological studies to elucidate the analgesic mechanism are lacking. Widespread oscillatory abnormalities in chronic pain patients and enhanced alpha activity by therapeutic means are associated with pain relief (Arendsen et al., 2018; Ahn et al., 2019). Bian et al. (2013) found that peak alpha power increased for healthy participants during Pilates training, which indicates that Pilates practice may relieve pain by modulating peak alpha frequency in chronic pain patients. Future studies may consider exploring the effect of Pilates training on peak alpha frequency in patients with CNLBP to further clarify the neurophysiological mechanism of Pilates analgesia. Apart from that, Pilates has the advantage that the exercises can be performed in various settings, with or without equipment, thereby keeping the spine in a neutral position and avoiding excessive impact or stress on muscles, joints, and tissues as compared with other MBE modes. As the exercises progress and an individual wishes to increase the difficulty of the activities performed, one can incorporate the use of various types of equipment, including the reformer, cadillac, ladder barrel, and step chair.

A novel finding from this NMA is that TC (SUCRA = 77.2%) may be the intervention that came closest to the effect of Pilates (SUCRA = 86.6%) in reducing pain intensity among the other three MBE modes. Meanwhile, TC originating in China is an established form of gentle MBE mode and incorporates physical, psychosocial, spiritual, and behavioral elements to improve physical and mental health (Wang et al., 2018). Although the underlying mechanism of TC remains unclear, the effect of TC may be attributable to the potential of these exercises to influence altered central elements. Furthermore, when practicing TC, the body's center of gravity constantly changes with the movements, the spine is in an unstable state, and the central nervous system recruits more muscle fibers to maintain stability, which strengthens the core muscles to some extent. Respiratory exercise therapy does have a therapeutic effect on patients with low back pain (Mehling et al., 2005). Herein, TC emphasizes reverse abdominal breathing, which strengthens the core muscles during the breathing process. Notably, CNLBP is often accompanied by structural and functional connectivity abnormalities in brain regions (Ji and Neugebauer, 2011; Neugebauer et al., 2020). Regular TC practice can bring about regional structural changes in the precentral gyrus, insular sulcus, and middle frontal sulcus (Wei et al., 2013). A previous RCT also found moderate to high correlations between TC-associated pre-post differences in the functional connectivity of the amygdala-medial prefrontal cortex (Shen et al., 2021). Therefore, TC may directly affect the cerebral cortex to regulate pain through regular practice. Considering that it is not too difficult, cost-effective, and safe, TC and qigong are often chosen by elderly people to practice (Li et al., 2020; Siu et al., 2021). Pilates and yoga are more difficult than TC and qigong to practice and usually require the guidance of a professional instructor to ensure safety during practice (Achilefu et al., 2017; Zou et al., 2019). Therefore, TC and qigong seem to be worthy of promotion in the elderly population with CNLBP.

Guidelines about CNLBP suggest that treatment should pay more attention to improving pain intensity and its associated dysfunction (Oliveira et al., 2018). Our study suggested that Pilates (SUCRA = 98.4%) had the highest probability of improving physical function. Interestingly, TC was effective in reducing pain intensity, however, lagged far behind Pilates in improving physical function. Age is an essential factor affecting physical function (Maher et al., 2017). We compared the groups included in this study, and found that the average age of the Pilates group was younger than that of the TC group. It may be the reason why the function improvement effect of the Pilates group was better than that of the TC group. Therefore, it would be interesting to see if Pilates outperforms other MBE modes under strict age restrictions. There are various schools of TC in China, such as Yang-style TC and Chen-style TC. Although they are all based on the basic theories of the balance of Yin and Yang, the balance of the five elements, and the interaction between man and nature (Peng, 2012; Zhang et al., 2019), there are still great differences in movement characteristics and the degree of difficulty. Among the included studies, there are three that used Chen-style TC, one article designed an improved TC movement for CNLBP, and the other two did not tell, which may be partly responsible for the poor effect of TC in improving function. Similar to TC, there are various kinds of qigong, such as Neiyanggong (Blödt et al., 2015) and Wuqinxi (Yao et al., 2020). Different kinds of qigong have different effects on the physical function of CNLBP patients. A meta-analysis (Bai et al., 2015) involving 10 RCTs indicated that only internal qigong could improve chronic pain in adults. Therefore, it is a meaningful research direction to explore which style of TC or qigong movements are most suitable for enhancing physical function for patients with CNLBP.

Our NMA shows that Pilates might be the best MBE therapy for the non-pharmacologic treatment of CNLBP in pain intensity and physical function. It has a reasonable benefit, which would be a powerful option for patients who don't profit from existing pharmacological medicines. Our study provides richer options for CNLBP management and more evidence for MBE treatment of CNLBP. However, more high-quality, large-sample, multicenter, long-term follow-up RCTs directly compare the efficacy of two or more MBE modes in patients with CNLBP to further confirm our findings.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author/s.

JS and Z-YH wrote the manuscript. Y-FW, Z-YH, JS, and Y-LW contributed to the conception. Z-YH and H-ZZ searched the literature. JS and Y-RW were involved in the data analysis. Y-YL, JS, Z-YH, Y-TL, and Y-LW contributed to the acquisition of data. All authors contributed to the article and approved the submitted version.

This research was funded by the Guangdong Hopson-Pearl River Education Development Foundation, grant number H20190116202012724.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.