The goal of this randomized controlled trial is to determine the effect of a psoas major muscle intervention on non-specific and chronic lumbar pain in cleaning professionals. It is expected that this intervention will reduce the severity and frequency of symptoms. This study aims to evaluate the effect of psoas major stretching techniques. To collect data, participants will rate their pain intensity on a numeric pain scale at rest and during maximal lumbar flexion. Secondary variables include lumbar flexion range of motion (ROM), assessed by the Schöber test, and hip ROM, which will be measured before and after the intervention using a digital goniometer.