This randomized controlled trial aims to evaluate the combined effects of post-isometric relaxation and myofascial release on pain, flexibility, and functional disability in individuals with low back pain associated with lower cross syndrome. Eligible participants aged 18 to 45 years will be randomly allocated into two parallel intervention groups. One group will receive post-isometric relaxation combined with myofascial release, while the comparison group will receive conventional stretching combined with Therapeutic modalities. Outcomes will be assessed at baseline and after completion of the intervention period. The results of this study are expected to contribute to evidence-based physiotherapy management of low back pain associated with postural imbalance.

Inclusion Criteria:

1. Participants aged 18-45 years old
2. having low back pain persisting for at least 4 weeks
3. with clinical diagnosis of LCS, and hamstring tightness (AKE >15°)

Exclusion Criteria:

1. Participants with the history of spinal surgery active neurological conditions
2. systemic disease affecting connective tissue (Rheumatoid arthritis, Systemic lupus erythematosus)
3. recent lower limb or spinal injury (within 6 months)
4. pregnancy or inability to lie prone for treatment.

Individual participant data will not be shared publicly due to institutional policies, ethical restrictions, and to protect participant confidentiality. Data will be used solely for academic and research purposes as approved by the institutional review board.

This study will be single-blinded. The outcome assessor will be blinded to group allocation to minimize assessment bias. Due to the nature of the interventions, participants and treating physiotherapists cannot be blinded.