Low back pain (LBP) is a common health problem that affects people all over the world and is a leading cause of disability, affecting work performance and overall health. Chronic LBP (CLBP) is defined as a problem that develops due to mechanical or non-mechanical causes and is characterized by pain, movement, and antalgic posture in the gluteal region and spine, limiting physical activity. In patients with low back pain, spinal movements are restricted, endurance decreases, flexor, and extensor muscle strength weaken, and aerobic capacity is impaired. It has been found that in patients with CLBP, pain creates fear of movement and avoidance belief, leading to inadequacy in physical functionality and a decrease in quality of life. Exercise is an essential component in the therapy of many musculoskeletal issues and chronic disorders. Exercise therapy addresses aims such as pain relief, relaxing, strengthening weak muscles, extending shortened muscles, minimizing mechanical stress on spinal structures, correcting posture, enhancing endurance, and quickly returning to work.

The Pilates Method is a mind-body approach to therapeutic exercises that promotes movement stability and control. Pilates focuses on body posture alignment, which includes proper head, shoulder, and pelvic girdle adjustment in a neutral position while preserving spine curvatures, as well as the axial position of the lower limbs and symmetrical weight-bearing of the feet in standing position. Back pain inhibits various motions of the lumbar spine and pelvis, and this condition weakens the stabilizer muscles, which can lead to CLBP. In the rehabilitation of patients with back pain, the stabilizer muscles are emphasized in order to decrease pain and improve muscular endurance and strength. The Pilates method utilizes principles of various accepted rehabilitation methods that have scientific support for LBP, including core strengthening. This is important since core weakness has been increasingly recognized as a biomechanical deficit in patients with LBP. The systematic review study by Wells et al (2014) indicates that Pilates exercise results in statistically significant improvements in pain and functional ability in the short term compared to usual care and physical activity in people with CLBP. Another recent systematic review by Barros et al. (2020), on the other hand, shows that the Pilates exercise program in moderate-to-high quality RCTs for the treatment of lower back pain is still insufficient.

Proprioceptive neuromuscular facilitation (PNF) is based on facilitating the responses of neuromuscular mechanisms by stimulating proprioceptors which aim to increase muscle strength, improve active movement ability, increase muscle endurance, and improve stabilization at the point where the technique is applied within the movement pattern. A systematic review and meta-analysis by Tong et al. (2014), identified that compared to controls, patients with low back pain have poorer lumbar proprioception. Furthermore, Meier et al. (2019) stated that back pain-induced disturbed or diminished proprioceptive signaling likely plays a key role in causing long-term alterations in the top-down regulation of the motor system via motor and sensory cortex remodeling. Individuals with chronic LBP showed lower acuity for detecting changes in trunk position and demonstrated significantly higher trunk repositioning errors during flexion of the back compared with pain-free individuals. Nijs et al. (2012), suggested that the presence of increased proprioceptive prediction errors might originate from reduced/disrupted proprioceptive input, probably triggered by nociceptive input. Therefore, the underlying physiological mechanisms of the PNF techniques such as autogenic inhibition, reciprocal inhibition, stress relaxation, and the gate control theory may influence the competition between the proprioceptive and nociceptive inputs, resulting in pain reduction and improved joint control. Furthermore, it has been found that PNF training can increase trunk muscular flexibility, strength, and endurance, providing support for the application of PNF training in functional improvement. Pourahmadi et al. (2020) stated in their systematic review and meta-analysis study that there was a low quality of evidence and a weak level of recommendation that PNF training had good benefits on back pain and disability in LBP patients and suggested further high-quality randomized clinical trials regarding long-term effects of PNF training.

In the literature, studies using Pilates exercises and PNF exercises in patients with CLBP have demonstrated that both treatments have some beneficial effects in terms of reducing pain and disability, as well as improving the functional level and quality of life. Studies in the literature showed that both methods are among the treatment methods frequently used in the clinic, but it is difficult to provide sufficient information about which method is more effective. Therefore, the aim of this study is to examine the effects of PNF and Pilates exercises on pain, body image, fear-avoidance beliefs, core stability, disability, and balance functions in individuals with CLBP.