Blood Flow Restriction During Nordic Hamstring Exercise in Elite Adolescent Athletes

Official title

Comparison of Hamstring Muscle Oxygenation Responses During Nordic Hamstring Exercise and Blood Flow Restriction Nordic Hamstring Exercise in Elite Adolescent Athletes: A Crossover Experimental Study

Overview

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.

Detailed description

Hamstring muscles play a crucial role in sprinting, jumping, change-of-direction movements, and other high-intensity athletic activities. Nordic Hamstring Exercise (NHE) is one of the most effective eccentric strengthening exercises for improving hamstring function and reducing the risk of hamstring strain injuries. Recently, blood flow restriction (BFR) training has gained increasing attention because it may enhance metabolic stress and alter muscle oxygenation responses during exercise. However, evidence regarding the acute physiological effects of combining BFR with Nordic Hamstring Exercise in elite adolescent athletes remains limited.

This study aims to compare hamstring muscle oxygenation responses during conventional Nordic Hamstring Exercise and Blood Flow Restriction Nordic Hamstring Exercise in elite adolescent athletes. A prospective crossover experimental design will be used, allowing each participant to complete both exercise conditions and serve as his or her own control. The order of the interventions will be randomized, and the two testing sessions will be separated by a 7-day washout period to minimize potential carryover effects.

Elite adolescent athletes aged 14-18 years who have participated in regular training for at least three years will be recruited. During each testing session, hamstring muscle oxygen saturation (SmO₂) and total hemoglobin (tHb) responses will be continuously monitored using wearable near-infrared spectroscopy (MOXY). Measurements will include baseline SmO₂, minimum SmO₂, delta SmO₂, recovery SmO₂, baseline total hemoglobin, peak total hemoglobin, and delta total hemoglobin. Blood lactate concentration, rating of perceived exertion using the Borg Rating of Perceived Exertion Scale, exercise performance variables, and post-exercise symptoms such as muscle soreness and fatigue will also be recorded.

Nordic Hamstring Exercise will be performed according to a standardized protocol under physiotherapist supervision. During the Blood Flow Restriction Nordic Hamstring Exercise condition, the same exercise protocol will be performed while individualized blood flow restriction is applied to the proximal lower extremity using a pneumatic cuff. The cuff pressure will be individualized based on participant tolerance and safety, and the intervention will be discontinued immediately if any adverse symptoms occur.

The primary objective is to determine whether blood flow restriction alters acute hamstring muscle oxygenation responses during Nordic Hamstring Exercise. Secondary objectives include comparing total hemoglobin responses, blood lactate concentration, perceived exertion, exercise performance, and post-exercise recovery between the two exercise conditions. The findings of this study are expected to improve understanding of the physiological mechanisms of blood flow restriction during eccentric hamstring exercise and provide evidence for its safe and effective use in adolescent athletic populations.

Interventions

• Other Nordic Hamstring Exercise
  Participants will perform a standardized Nordic Hamstring Exercise protocol under physiotherapist supervision. From a kneeling position with the ankles stabilized, participants will lower the trunk forward in a controlled manner while maintaining alignment of the trunk and hips.
• Other Blood Flow Restriction Nordic Hamstring Exercise
  Participants will perform the same standardized Nordic Hamstring Exercise protocol while individualized blood flow restriction is applied using a pneumatic cuff positioned on the proximal lower extremity.

Primary outcome measures

• Difference in Change in Hamstring Muscle Oxygen Saturation (Delta SmO₂) Between NHE and BFR-NHE [Time frame: During each exercise session, with the two sessions separated by a 7-day washout period]
• Difference in Minimum Hamstring Muscle Oxygen Saturation Between NHE and BFR-NHE [Time frame: During each exercise session, with the two sessions separated by a 7-day washout period]
• Difference in Hamstring Muscle Oxygen Saturation During Recovery Between NHE and BFR-NHE [Time frame: Immediately after each exercise session during the recovery period, with sessions separated by a 7-day washout period]
• Difference in Peak Hamstring Total Hemoglobin Between NHE and BFR-NHE [Time frame: During each exercise session, with the two sessions separated by a 7-day washout period.]
• Difference in Change in Hamstring Total Hemoglobin Between NHE and BFR-NHE [Time frame: During each exercise session, with the two sessions separated by a 7-day washout period.]
• Difference in Post-Exercise Blood Lactate Concentration Between NHE and BFR-NHE [Time frame: Immediately after each exercise session, with the two sessions separated by a 7-day washout period]

Secondary outcome measures (3)

• Difference in Rating of Perceived Exertion Between NHE and BFR-NHE [Time frame: Immediately after each exercise session, with the two sessions separated by a 7-day washout period]
• Difference in the Number of Successfully Completed Nordic Hamstring Exercise Repetitions Between Conditions [Time frame: During each exercise session, with the two sessions separated by a 7-day washout period]
• Difference in Post-Exercise Hamstring Muscle Soreness Between NHE and BFR-NHE [Time frame: 24 hours after each exercise session]

Eligibility criteria

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.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

Randomized

Model

Crossover

Masking

Open label

Primary purpose

Other

Study locations

Turkey (Türkiye) · 1 center

• Adana Olympic Preparation Center — Adana

Identifiers

NCT: NCT07715786 · 06/101-23.06.2026

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗