Effectiveness of an IVR-based Therapeutic Exercise Program With Altered Visual Feedback in Fibromyalgia Patients

Participants will wear an HTC Vive Pro head-mounted display with waist, hand and foot trackers during 60-min sessions, 2 times/week for 6 weeks (12 sessions). A gender- and skin-tone-matched first-person avatar will be calibrated to the user's anthropometrics and will mirror all real-time movements. Standardised audio instructions will be played through the headset; a virtual mirror will provide visual feedback. To facilitate lumbar mobility, two sensorimotor illusions will be applied: (1) Flexion illusion: Avatar upper-limb length will be reduced by ≈20%, encouraging greater trunk flexion; (2) Extension illusion: A virtual bar will rise with lumbar extension but will under-represent real movement by ≈10%. Both manipulations will update continuously throughout each repetition. A physiotherapist will supervise every session and will record adverse events.

Participants will undertake a 6-week therapeutic exercise program, consisting of two sessions per week (12 sessions total), with a primary objective of reducing fibromyalgia's impact on daily life. Each session will involve ten exercises performed in one or two sets each, depending on the week of the protocol. Exercise repetitions and intensity will be individualized using the Borg Rating of Perceived Exertion (RPE) scale (6-20), maintaining an intensity range of RPE 13-17. Specifically, intensity will start at RPE 14 (moderate) in Weeks 1-2, increase to RPE 15 (moderate-high) in Weeks 3-4, and peak at RPE 16 (high) in Weeks 5-6. No external load will be applied during the first three weeks to allow participants to adapt to the program, while progressive resistance will be introduced during the final three weeks according to individual capacity, ensuring a safe and gradual overload.