Blood Flow Restriction During Nordic Hamstring Exercise in Elite Adolescent Athletes

This crossover experimental study aims to compare acute hamstring muscle oxygenation responses during Nordic Hamstring Exercise (NHE) and Blood Flow Restriction Nordic Hamstring Exercise (BFR-NHE) in elite adolescent athletes. Participants will complete both exercise conditions in a randomized order separated by a 7-day washout period. Muscle oxygen saturation will be assessed using near-infrared spectroscopy (MOXY), together with total hemoglobin responses, blood lactate concentration, perceived exertion, and exercise performance variables. The findings may improve understanding of the physiological effects of blood flow restriction during eccentric hamstring exercise in adolescent athletes.

Inclusion Criteria: * Elite adolescent athletes aged 14 to 18 years. * Licensed athletes with at least 3 years of regular sports participation. * Currently participating in a regular weekly training program. * Physically able to complete the Nordic Hamstring Exercise and study testing protocol. * Willing to participate in the study. * Able to provide written informed consent. * For participants younger than 18 years, written informed consent provided by a parent or legal guardian and assent provided by the participant. Exclusion Criteria: * Hamstring injury within the previous 6 months. * Lower extremity surgery within the previous 6 months. * Current lower extremity pain or musculoskeletal injury that may interfere with exercise performance. * Cardiovascular, vascular, neurological, or other medical conditions that may contraindicate blood flow restriction exercise. * Presence of skin lesions or conditions preventing placement of the blood flow restriction cuff or MOXY sensor. * Inability to complete either exercise condition or follow the study protocol.