The aim of this study is to determine the effects of the Strain-Counterstrain (SCS) technique on alleviating sudden and mechanical chronic low back pain and resolving limited lumbar flexion and extension in individuals with mechanical chronic low back pain (MCLBP), focusing on tender points in the Iliopsoas muscle. Our study is a randomized controlled trial. Based on sample size calculation, 32 voluntary patients with chronic mechanical low back pain will be recruited to the study. They will be then randomized into two groups using the Block Balanced Randomization method.

In the control group, consisting of 16 participants, 4 general exercises aimed at relieving back pain will be performed under the physical therapist's supervision. In the treatment group, also comprising 16 participants, after performing the exercises applied to the control group, the SCS technique will be applied to the tender points in the iliopsoas muscle: 90 seconds in a position of comfort, with 30-second intervals, 3 times on the more tender side and 2 times on the less tender side.

The assessment of the cases will use the visual analog scale (VAS) for pain intensity at rest and during lumbar flexion movement as primary outcome measurements TiltMeter© Application for joint range of motion (ROM), Modified Schober's Test (MST) for spinal mobility, Thomas test for iliopsoas muscle length, the Oswestry Disability Index (ODI) for stability, and 36-Item Short Form Survey (SF-36) for health-related quality of life. Assessments will be conducted before treatment, at the end of the 1st session, and at the end of the treatment (after six sessions). Significant results may reduce the burden on the healthcare system with the ease of application and low-cost advantage of the SCS technique, making treatment processes more efficient.

Low back pain is one of the leading causes of disability and has been shown to occur more frequently than other health problems. When low back pain becomes chronic, the pain may often be less intense. Chronic low back pain is defined as pain that persists for more than 12 weeks. Many professionals and individuals working in demanding jobs often experience Chronic Non-Specific Low Back Pain, which results in reduced work capacity and significant impairment in daily activities. Additionally, many patients report increased pain while sitting or transitioning from a seated to a standing position.

Despite the rising number of patients presenting to hospitals with low back pain, the exact underlying cause is often not well understood. Recent studies suggest that most cases are due to mechanical causes, potentially resulting from improper biomechanical alignment.

The spinal curves, known as lordosis and kyphosis, play a critical role in energy expenditure and mobility from a biomechanical perspective. Improper adaptations and tensions between muscles can lead to either a loss or increase in lumbar lordosis, which can alter biomechanical structure and affect muscle function and range of motion. The psoas major muscle, which attaches to the L1-L5 vertebrae, can also influence lumbar lordosis if it becomes shortened.

Low back pain is typically nonspecific or mechanical. Mechanical chronic low back pain (CLBP) arises from the spine, intervertebral discs, or surrounding soft tissues due to excessive strain or injury. The iliopsoas muscles, deep muscles rarely stretched during daily activities, can become tense and contribute to this pain. As one of the strongest hip flexors, the iliopsoas plays a significant role in pelvic movement and stabilization. Tightness in the iliopsoas is often closely linked to low back pain. A shortened iliopsoas group may result in hyperlordosis, anterior pelvic tilt, and increased pressure on the spinal muscles. If the iliopsoas muscles are excessively tight, they can pull and twist the vertebrae, leading to disc compression and dysfunction, which may manifest as low back pain and discomfort around the sacroiliac joint. Research has found that individuals who work at desks often have shortened iliopsoas muscles, which can predispose them to future low back pain.

Individuals who sit for extended periods, such as sedentary workers and students, are at increased risk of musculoskeletal problems and muscle shortening. Research has shown that sitting for more than eight consecutive hours can lead to low back pain. The iliopsoas muscle, due to its unique connection between the lumbar spine and hip joint, is an important hip flexor affected by prolonged sitting. Biomechanical and electromyography studies suggest that control of the spinal curve is primarily provided by the psoas major muscle. When other muscles become less active, the psoas major becomes more engaged, helping to maintain an upright spine; however, a shortened psoas can lead to pelvic tilt and back pain.

Given the above reasons, many studies have been conducted to address iliopsoas muscle tightness. Research comparing techniques such as Proprioceptive Neuromuscular Facilitation (PNF) and Muscle Energy Technique (MET) for stretching the iliopsoas found that PNF was more effective, emphasizing the benefits of active mobilization and autonomic inhibition. However, muscle tightness can also originate from tender points, which, when addressed, can enhance proprioceptive activity and reduce hypersensitivity once the joint returns to its normal position. Despite the biomechanical importance of the iliopsoas muscle, research specifically focusing on tender points in this muscle remains limited.

Strain-Counterstrain is an osteopathic manipulation technique and the fourth most commonly used soft tissue method after High Velocity Low Amplitude (HVLA) and Muscle Energy Techniques (MET). This technique involves passive positional mobilization designed to alleviate musculoskeletal pain. Strain-Counterstrain helps correct neuromuscular imbalances caused by prolonged muscle stimulation. It is based on the proprioceptive theory, which suggests that this technique can rectify abnormal neuromuscular activity, often caused by sympathetic nervous system responses or inflammatory reactions. Studies have shown that the Strain-Counterstrain technique effectively restores range of motion and reduces pain in the lumbar region. Additionally, it is a low-cost, non-invasive treatment method. For example, a study demonstrated that both SCS and MET were effective in reducing pain and improving functional capacity in patients with chronic low back pain. Other research has reported positive effects on lumbar range of motion, pain, and quality of life when SCS was combined with techniques such as MET or McKenzie.

Most studies have focused on the quadratus lumborum muscle or general SCS techniques, and although the iliopsoas muscle is critically important, it has been less frequently studied in conjunction with SCS. Our study aims to clearly demonstrate the immediate and long-term effects of the iliopsoas-specific SCS technique on lumbar range of motion and pain, ultimately reducing the burden on healthcare systems in terms of labor and cost.

Hypotheses:

Null Hypothesis (H0): The Strain-Counterstrain technique has no positive effect on pain and restricted lumbar flexion in patients with chronic low back pain and limited lumbar flexion.

Alternative Hypothesis (H1): The Strain-Counterstrain technique has a positive effect on pain and restricted lumbar flexion in patients with chronic low back pain and limited lumbar flexion.

Inclusion criteria:

1. Patients with chronic mechanical low back pain (CMLBP) aged between 18-60 years old;
2. Pain experience more than 12 weeks;
3. Pain intensity ≥ 3 based on Numeric pain scale;
4. Pain experience during lumbar flexion movement;
5. Positive Thomas test;
6. Having tenderness on Psoas major muscle 4 times more than palpation on ipsilateral quadratus lumborum muscle;
7. Able to understand and make communication with research team without any barrier;
8. Having consent to participate the study.

Non-inclusion criteria:

1. Pregnancy;
2. Not indicated for lumbar surgery based on diagnosis of a physical medicine and rehabilitation specialist,
3. Any type of fracture or history of trauma which makes manual therapy contraindicated for the patient,

Exclusion criteria:

1. Willing to discontinue the study progress for any reason;
2. Progressive deterioration during the study and intervention application.

We have not decided yet, but at this moment, we decided to share brief data with future researchers after requesting and submitting ethical committee permission.