TECAR Therapy in Chronic Back Pain

Brief Summary

The goal of this clinical trial is to learn whether adding high-intensity electromyostimulation (Hi-EMS) to capacitive and resistive electric transfer (TECAR) therapy improves pain and functional performance in adults with chronic nonspecific low back pain. The main questions it aims to answer are: * Does adding Hi-EMS to TECAR therapy reduce low back pain at rest? * Does adding Hi-EMS reduce pain during the Five-Times-Sit-to-Stand Test? * Does adding Hi-EMS improve pressure pain threshold and performance on the - Five-Times-Sit-to-Stand Test? Researchers will compare TECAR therapy delivered with Hi-EMS to TECAR therapy delivered without Hi-EMS. Participants will: * Receive both treatment conditions in a randomized order * Wait one week between treatment sessions * Receive 10 minutes of capacitive electrical transfer followed by 10 minutes of resistive electrical transfer during each session * Receive Hi-EMS during the 10-minute resistive electrical transfer phase in one of the sessions * Complete pain, pressure pain threshold, and functional performance assessments immediately before and after each session