Effects of breathing exercises on chronic low back pain: A systematic review and meta-analysis of randomized controlled trials

1.Introduction

Low back pain (LBP) is clinically defined as pain, muscle tension, or stiffness localized below the costal margin and above the inferior gluteal folds, with or without leg pain [1]. Chronic low back pain (CLBP) is characterized as experiencing LBP for more than 12 weeks [2]. It causes pain and functional impairment and has in recent years, been the leading cause of disability across the globe [3, 4]. The lifetime prevalence of LBP is approximately 80% while the prevalence of CLBP is in the region of 23% [5] with more than half a billion people suffering from CLBP globally [6]. As global incidents of CLBP have escalated, it has impacted its sufferers physically and psychologically; additionally, it has placed overwhelming financial strain on economies around the world, due to the expense of medical treatment and widespread absenteeism from work in all socio-economic areas [7, 8].

Currently, there is no well-defined, established paradigm for the treatment and management of CLBP. Although patients with CLBP are frequently managed with pharmacological therapy, a lack of efficacy combined with adverse events can result in unresolved complications [9]. Nonpharmacologic therapies, including exercise and psychosocial management, are the preferred approach for the majority of patients and may be supplemented with adjunctive drug therapies [10, 11, 12]. According to clinical practice guidelines, the implementation of exercise therapy is advocated as a primary treatment as it performs a fundamental role in pain reduction and developing improved levels of mobility and function [13, 14]. Clinical observations have noted that breathing exercises are crucial to the treatment and prevention of CLBP [15, 16, 17]. Breathing exercises support muscle activation which strengthens core muscles; greatly improves spinal stabilization via the co-contracting of deep muscles such as the internal oblique abdominals, multifidus, and pelvic floor muscles; and significantly increases muscle thickness (in contraction); and improves contraction rates [18, 19]. Additionally, breathing exercises modify the patient’s pulmonary function by improving their forced vital capacity alongside other oxygenation and blood volume indicators, allowing for the development of enhanced breathing patterns and improving lumbar pain and function [20]. A combination of these physical factors creates a scenario whereby a patient will experience reduced levels of anxiety concerning their motor performance and improvements in their mental well-being [21].

While some studies have demonstrated the potential benefits of breathing exercises for the treatment of CLBP, it remains whether breathing exercises are more effective than the current rehabilitation therapy paradigm [22]. Therefore, this systematic review and meta-analysis intend to quantitatively analyze clinical studies concerning the implementation of breathing exercises for the treatment of CLBP as it relates to the symptoms (pain, lumbar function, and pulmonary function) and to conduct a direct comparison between breathing exercises and the current routine rehabilitation exercises.

2.Methods

This systematic review was performed in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) and was registered in the PROSPERO database under identification number CRD42022380578.

2.2Inclusion and exclusion criteria

Figure 1.

Flowchart of search strategy and study selection.

Studies were eligible if they met the following criteria: (1) used the randomized controlled trial (RCT) design; (2) included participants diagnosed with CLBP (18 years of age or older), regardless of gender, social factors, or the clinical setting; (3) compared breathing exercises with the placebo (sham tape) or routine rehabilitation intervention (e.g., physical therapy, exercise therapy, spinal stabilization); (4) the study included at least one of the following outcome assessments: pain, pulmonary function, or lumbar function; and (5) where chronic pain was defined as lasting more than 12 weeks.

Studies were excluded if any of the following criteria were met: (1) studies were crossover trials, quasi-RCTs, case reports, animal experiments, conference abstracts, and review articles; (2) studies with unavailable data or low-quality; (3) included patients with LBP caused by pathological changes such as tumours, spinal infections, ankylosing spondylitis, spondylolisthesis, or any extensive neurological disorder.

3.Results

3.2Characteristics of included literature

The main features of the included studies are recorded in Table 1. Sixteen studies (from China, the USA, Iran, and Korea) were included in this summary. All of the results were published between 2005 and 2022 and contained the details of a total of 807 participants. The baseline data of the included studies demonstrated no significant difference. Ten studies [20, 21, 28] chose VAS assessment as the primary method of pain assessment for CLBP patients. Eight studies [20, 21, 28] elected to use the ODI for lumbar function assessment. Four studies [23, 24, 25, 27, 29, 30, 33, 35] assessed pulmonary function by FEV1; four studies [22, 23, 24, 25, 32, 33, 35] assessed pulmonary function using FVC; three studies assessed pulmonary function by FEV/FVC, and two studies reported pulmonary function with MVV.

Figure 2.

Plot of the risk of bias of the included studies.

3.3Quality assessment

Figure 3.

Forest plot of pain. Abbreviation. VAS, Visual Analog Scale.

Figure 4.

Forest plot of lumbar function. Abbreviation. ODI, Oswestry Disability Index.

The quality assessment results for the included articles are shown in Fig. 2. Randomization was performed in all the studies, and eight of them detailed the randomization methods [16, 19, 21, 23, 26, 27, 28, 30]. The blinding of participants and personnel was mentioned in two articles [16, 19]; two studies reported the blinding of participants and personnel [16, 21], and four studies recorded the blinding of outcome assessment [18, 19, 27, 30]. Only one study [26] contained incomplete data as it should have reported dropout reasons and was, therefore, considered to demonstrate high-risk detection bias. The overall risk of bias was assessed as low when considering incomplete outcome data, selective reporting, and other forms of bias.

3.4Results of meta-analysis

3.4.1VAS

Ten studies [16, 18, 19, 23, 25, 26, 27, 28, 29, 30] reported that VAS was employed to evaluate lumbar pain. The meta-analysis indicated that breathing exercises could significantly improve lumbar pain when compared with the control group (SMD =-0.84, 95% CI = [-1.24, -0.45], P< 0.0001). The result indicated a lack of significant heterogeneity (χ2 = 0.30, P< 0.00001, I2= 77%) and the random effects model was applied (Fig. 3).

3.4.2ODI

Eight studies [16, 21, 24, 26, 27, 28, 29, 30] reported that ODI was used to evaluate lumbar function. The meta-analysis indicated that breathing exercise could significantly improve lumbar function when compared with the control group (SMD =-0.74, 95% CI = [-0.95, -0.54], P< 0.00001). The result indicated no significant heterogeneity (χ2 = 8.59, P= 0.28, I=2 18%) and a fixed-effect model was applied (Fig. 4).

Figure 5.

Forest plot of lung function. Abbreviation. FEV1, Forced Expiratory Volume in the first second.

3.4.3FEV1

Four studies [16, 19, 20, 21] reported that FEV1 was used to evaluate pulmonary function. The meta-analysis indicated that breathing exercises could not significantly improve pulmonary function when compared with the control group (MD = 0.22, 95% CI = [0.00, 0.43], P= 0.05). The result indicated no significant heterogeneity (χ2 = 3.72, P= 0.29, I=2 19%) and a fixed-effect model was applied (Fig. 5).

Figure 6.

Forest plot of lung function. Abbreviation. FVC, Forced Vital Capacity.

3.4.4FVC

Four studies [16, 19, 20, 21] reported that FVC was used to evaluate pulmonary function. The meta-analysis indicated that breathing exercises could significantly improve pulmonary function when compared with the control group (MD = 0.24, 95% CI = [0.10, 0.37], P= 0.0006). The result revealed no significant heterogeneity (χ2 = 5.16, P= 0.16, I2= 42%) and a fixed-effect model was applied (Fig. 6).

3.4.5FEV/FVC

Three studies [16, 19, 21] reported that FVC/FEV1 was used to evaluate pulmonary function. The meta-analysis indicated that breathing exercises could significantly improve pulmonary function compared with the control group (MD = 1.90, 95% CI = [0.73, 3.07], P= 0.001). The result revealed no significant heterogeneity (χ2 = 0.55, P= 0.76, I=2 0%) and a fixed-effect model was applied (Fig. 7).

Figure 7.

Forest plot of lung function. Abbreviation. FEV1/FVC, Forced Expiratory Volume in 1 second /Forced Vital Capacity.

Figure 8.

Forest plot of lung function. Abbreviation. MVV, Maximal Voluntary Ventilation.

3.4.6MVV

Two studies [16, 21] reported that the MVV was used to evaluate pulmonary function. The meta-analysis indicated that breathing exercises could not significantly improve pulmonary function when compared with the control group (MD = 8.22, 95% CI = [-4.02, 20.45], P= 0.19). The result indicated no significant heterogeneity (χ2 = 0.50, P= 0.48, I=2 0%) and a fixed effects model was applied (Fig. 8).

4.Discussion

CLBP is a complex musculoskeletal disorder characterized by pain, reduced muscle strength, imbalance and motor dysfunction [29]. The primary cause of LBP is lumbar instability and muscle imbalances [3, 30]. Additionally, many studies have demonstrated that CLBP patients are susceptible to respiratory diseases and respiratory muscle atrophy, and there may be an association between respiratory function, breathing patterns, core stability, and CLBP [12, 31]. Clinical studies have revealed that breathing exercises can enhance respiratory function, reduce pain, and improve low back function in patients experiencing CLBP [27, 28]. This study was the first meta-analysis to evaluate the effectiveness and safety of breathing exercises for treating CLBP. Following a comprehensive search of the major academic databases, thirteen studies with 677 participants were involved in this meta-analysis. The results of the meta-analysis conclude that breathing exercises were effective for the treatment of CLBP: in cases involving the use of VAS and ODI, breathing exercises provided improved pain relief and enhanced lumbar function in comparison with the control group. In addition, when examining the indicators of pulmonary function outcomes such as FVC and FEV/FVC, the implementation of breathing exercises improved pulmonary function more effectively than the control group. However, no statistical significance was demonstrated in FEV1 and MVV: these results should be interpreted with care due to the low number of studies available for FEV1 and MVV pulmonary function outcomes (⩽ 4), and this area requires further research to confirm these findings.

The meta-analysis revealed that breathing exercises significantly improved VAS and ODI scores compared to the control group, indicating that breathing exercises are effective for relieving and enhancing low back function in CLBP patients. The underlying mechanisms of breathing exercises for the treatment of CLBP were unclear; however, chronic pain can occur when the muscles of the low back experience instability caused by dysfunction and motor control damage [31]. Studies have revealed that postural control and respiratory function are mechanically and neuromuscularly co-dependent [32]. Respiration and spinal stabilization involve the diaphragm, the transverse abdominal muscle, the pelvic floor muscle, and the intercostal and internal oblique muscles [33, 34]. The pain experienced by CLBP patients can be effectively managed and reduced via increased local muscle activity. Co-contraction of the muscles, instigated by breathing exercises, combined with sustained muscle activity, proper muscle length and muscle strength, promotes the development of the deep abdominal muscles [32, 35]. As a result, the distribution of stimuli on pain receptor tissues surrounding the spine, articular capsules, and ligaments will decrease [33]. As well as being vital to respiration, the respiratory muscles play a fundamental role in controlling posture, acting as core stabilizing muscles. Therefore, breathing exercises are likely to impact postural control by affecting the core stabilisers and altering posture, increasing co-contraction of the core muscles that determine trunk stabilisation, improving the intervertebral joints and increasing motor control, which may lead to an increase in a patient’s spinal stability and balance ability [36, 37].

Many studies have demonstrated that respiratory muscle function and back proprioception control are mechanically and physiologically dependent on each other [38]. The intense contraction of the abdominal muscles caused by breathing exercises increases intra-abdominal pressure, which may lower the lumbar curve and significantly reduce the pressure exerted vertically, helping to improve balance and proprioception [16, 39]. Breathing patterns have been demonstrated through improvement following the introduction of various forms of breathing exercises which activate the deep stabilizing muscles of the trunk to maintain spinal stability and control [35]. When focusing on diaphragmatic breathing, it is essential to re-establish correct breathing patterns and ensure lumbar spine stabilization by increasing intraabdominal pressure and activating core structures to transfer force from the centre of the body to the lower extremities [40]. Following the action of the diaphragm, intra-abdominal pressure increases and activates the pelvic floor muscle causing it to contract, which enables the transversus abdominis to be easily activated during breathing due to strong abdominal contractions [24]. Furthermore, the nerves of the associated muscles are stimulated by the movement, such as the thoracoabdominal nerve, are stimulated by the movement, which results in increased local muscle activity [19, 41]. Respiratory interventions can enhance the diaphragm’s trunk stabilizing function, enabling individuals to use lumbar proprioception and reduce postural sway during balance control [35].

The findings of this review have partially clarified that breathing exercises can improve the respiratory function of CLBP patients, as demonstrated by FVV and FEV/FVC. CLBP is closely correlated with respiratory disorders [42]. Patients with CLBP are reported to be susceptible to diaphragmatic and muscular fatigue, lung capacity deviations, and diaphragm biomechanics [35, 43]. Respiratory function is often overlooked when examining patients with CLBP, although it can contribute to the instability of the lumbar spine and injuries in this region [30]. Meanwhile, a bi-directional interconnection exists between pain and respiration: respiratory fluctuations can occur in response to pain. As established by previous theories, long-term respiratory exercise has the potential to influence core muscle activity and improve respiratory and lumbar function [19, 44]. The respiratory muscles may promote lung ventilation, improve lung function parameters, deliver oxygen to the blood, and relieve pain [45]. Local muscle activity may also alter lung function parameters [46, 47]. Enhancing the stability of the trunk muscle through appropriate breathing pattern training, has been demonstrated to be a vital factor in reducing CLBP and preventing recurrence [38]. When considering reports detailing the adverse effects of respiratory training included in the literature, it was found that only one patient, in a study conducted by Mehling et al. [19], chose to withdraw due to the resurfacing of old memories, which resulted in the participant experiencing uncomfortable emotions. Subsequent other studies found no other adverse events.

Breathing exercises appear to be a promising and practical approach to treating CLBP and may enhance performance, prevent injury, encourage rehabilitation, and improve breathing capacity, trunk stability and balance [34]. Currently, control intervention (passive physiotherapy) is not recommended by the National Institute for Health and Care Excellence (NICE) [48]. The current consensus is that any active component of the intervention is more likely to demonstrate improved long-term outcomes for pain than passive physiotherapy [48, 49]. Breathing exercises are aerobic exercises that focus on motor control and reinforcing proper breathing patterns, which can increase the strength of respiratory muscles, improve spinal stability, and can be easily incorporated into daily activities to prevent CLBP and its related conditions [19, 35]. A recent study also reported reduced diaphragm thickness and lower respiratory function in athletes who suffered from LBP compared to healthy athletes [50]. For sports people undergoing CLBP rehabilitation or sports training, it is essential to incorporate breathing exercises to effectively activate the deeper trunk muscles and nerves associated with the low back, improve muscle blood flow and muscle oxygenation to the low back, and enhance athletic physical performance [51]. For medical workers with CLBP, such as nurses, breathing exercises effectively lower the parasympathetic nerves, inhibit pain gate control, improve stress management, and relieve CLBP symptoms, preventing occurrences of LBP or accelerating recovery [49, 52, 53]. Therefore, it is recommended that athletes and workers employ breathing exercises in training or daily activities to strengthen the health management of CLBP.

5.Conclusion

In this study, the evidence indicated that breathing exercises may be an effective treatment for CLBP. However, further studies with rigorous methodological quality are needed to support the conclusions of this research. Future studies should investigate different varieties, frequencies and intensities of breathing exercises to discover the most clinically effective breathing exercises.

Ethical approval

Not applicable.

Funding

The authors report no funding.

Informed consent

Not applicable.

Author contributions

X.J. and H.B. made substantial contributions to the conception and design of the work; Q.C. and Q.X. researched and selected materials and extracted data; X.J. wrote this manuscript; X.J., Q.C., G.C. and H.B. revised the paper carefully and contributed to the statistical analyses. All authors read and approved the final manuscript.

Supplementary data

The supplementary files are available to download from http://dx.doi.org/10.3233/BMR-230054.