Evaluation of biomechanical sprinting parameters following the application of Lightback® in elite sprinters.

1. Conditioning and Baseline Phase Participants perform a standardized specific warm-up under the direct supervision of a qualified CAR sports scientist and sprint/strength coach, lasting between 35 to 50 minutes, which includes 5 minutes of low-intensity jogging, dynamic stretches for the upper and lower limbs, sprint drills (e.g., high knee runs, skips, and bounds), and 3 progressive sprints building up to 95% of maximum effort. This is followed by a series of resisted sprints with incremental loads using the DynaSpeed system (towing/resisted cable device) ranging from overspeed/assistance conditions (5% top-speed increase or 5 kg pulling force) to resisted loads inducing 10%, 25%, 50%, and 65% velocity loss. These sprints range from 40 to 100 meters in distance, with recovery intervals adjusted accordingly based on the specific sprint distance and the load applied by the DynaSpeed device, calculated as a minimum of 3 to 5 minutes of passive rest for shorter distances (20–30 m) and at least 5 minutes of passive recovery between repetitions for longer or heavier sprints to ensure non-fatigued states. Following this conditioning phase, a maximal effort sprint is performed to record baseline biomechanical data (Pre-intervention). Immediately following the baseline sprint, the Lightback® intervention is applied bilaterally (on both legs) in a one-on-one session directly supervised by the Principal Investigator (PI), who is a qualified physiotherapist, at the High Performance Center (Centro de Alto Rendimiento - CAR) of Madrid. This intervention uses the Lightback® device, a passive joint compression apparatus designed to perform a self-passive anterior-posterior (A-P) mobilization of the femur to induce controlled posterior femoral gliding, reduce deep gluteal muscle tension, and optimize hip joint mobility through a stretch of the posterior hip capsule and gluteal muscles. Procedure per leg: The athlete is seated on the Lightback® device, bringing the knee toward the chest until reaching 90º of hip flexion. Dosage: Once the subject reaches the maximum sensation of stretching without pain, the position is held for 10 seconds, followed by a 5-second relaxation period. This sequence is repeated 6 times for a total application time of one minute per leg. 3. Post-Intervention Assessment: 10 minutes after the Lightback® application, participants perform a second maximal effort sprint (Post-intervention). Biomechanical parameters are recorded using the same methodology as the baseline test to determine the acute effects of the intervention on sprinting performance and technique.