Blood Flow Restriction with Low-Intensity Functional Training Improves Lower-Limb Strength Balance in Amateur Badminton Players: A Randomized Controlled Training Intervention

Technical Summary: Blood Flow Restriction with Low-Intensity Functional Training in Amateur Badminton Players

Problem Statement
Amateur badminton players (rated Level 3 or above) frequently exhibit asymmetric lower-limb loading and strength imbalances due to the sport's repetitive lunging, rapid acceleration/deceleration, and unilateral movement patterns. These imbalances can compromise movement control, limit sport-specific performance, and increase injury risk. While high-intensity functional training (HIFT) is effective, it imposes high mechanical loads that may be unsuitable for amateur players with varying training backgrounds or recovery capacities. Conversely, low-intensity functional training (LIFT) alone may fail to provide sufficient stimulus for comprehensive strength adaptation. There is a need for a practical training strategy that improves lower-limb strength and balance while controlling external mechanical load. This study investigates whether combining Blood Flow Restriction (BFR) with LIFT (BFR+LIFT) offers a superior or comparable alternative to HIFT and LIFT alone for this population.

Methodology

• Design: A randomized, assessor-blinded, three-arm, parallel-group controlled training intervention.
• Participants: 48 healthy amateur badminton players (China Badminton rating Level 3+) were recruited. After two withdrawals, 46 participants completed the 8-week intervention (15 in BFR+LIFT, 15 in HIFT, 16 in LIFT).
• Intervention Groups:
  • BFR+LIFT: Performed functional training at 30% of estimated 1RM with pneumatic cuffs applied to the proximal thighs (40–60% of estimated arterial occlusion pressure).
  • HIFT: Performed the same functional training protocol at 70% of estimated 1RM without BFR.
  • LIFT: Performed the same functional training protocol at 30% of estimated 1RM without BFR.
  • Protocol: All groups trained 3 times/week for 8 weeks (24 sessions). Exercises included weighted dead bugs, farmer's walks, bird-dogs, single-leg Romanian deadlifts, Bulgarian split squats, BOSU lunge jumps, and calf raises.
• Outcome Measures: Assessments were conducted pre- and post-intervention using a Biodex isokinetic dynamometer (60°·s⁻¹) and sport-specific performance tests.
  • Strength: Relative peak torque (hip, knee, ankle flexion/extension).
  • Balance: Agonist-antagonist ratios (e.g., hamstring-to-quadriceps) and bilateral strength differences.
  • Performance: T-test, badminton court lateral change-of-direction, multi-directional "Mi"-shaped movement test, and 30-m sprint.
• Analysis: Changes were analyzed using change-rate comparisons (post-pre/pre) via ANOVA or Brown-Forsythe tests, followed by post hoc pairwise comparisons.

Key Results

• Lower-Limb Strength: Both BFR+LIFT and HIFT produced broad, significant improvements in relative peak torque across hip, knee, and ankle plantarflexion muscles. These improvements were generally superior to those observed in the LIFT group. Specifically, BFR+LIFT and HIFT significantly outperformed LIFT in hip flexion/extension, right knee extension, and ankle plantarflexion.
• Muscle Strength Balance: The effects on balance were selective.
  • BFR+LIFT demonstrated specific advantages over other groups in reducing knee flexor bilateral asymmetry and increasing the left knee flexion-to-extension ratio (hamstring-to-quadriceps ratio).
  • Both BFR+LIFT and HIFT improved ankle dorsiflexion-to-plantarflexion ratios, whereas LIFT showed no significant balance improvements.
• Badminton-Related Performance:
  • The BFR+LIFT group showed significant within-group improvements in all four performance tests (T-test, lateral change-of-direction, "Mi"-shaped movement, and 30-m sprint).
  • Between-group analysis revealed a significant advantage for BFR+LIFT over LIFT only in the 30-m sprint. No significant between-group differences were found for the agility and complex footwork tests (T-test, lateral change-of-direction, "Mi"-shaped movement).

Significance and Claims
The study concludes that BFR+LIFT is an effective low-load strategy for amateur badminton players, capable of inducing lower-limb strength adaptations comparable to high-intensity training (HIFT) while using only 30% of the external load.

• Strength and Balance: The combination of low-intensity functional training with BFR appears to enhance the training stimulus sufficiently to match HIFT in strength gains. Furthermore, BFR+LIFT showed selective advantages in optimizing knee-related strength balance (specifically reducing bilateral asymmetry and improving the agonist-antagonist ratio), suggesting it may help correct the specific imbalances common in badminton players.
• Performance Transfer: While BFR+LIFT improved foundational physical qualities (strength and sprint speed) more effectively than LIFT, the transfer to complex, sport-specific agility tasks was less consistent between groups. The authors suggest that while BFR+LIFT provides a strong foundation for rapid initiation and push-off (evidenced by sprint improvements), complex footwork and agility may depend more heavily on technical proficiency and braking ability, which may not improve linearly with strength gains alone.
• Practical Application: The authors propose BFR+LIFT as a viable alternative or supplement for amateur players who cannot tolerate high external loads. It allows for the maintenance of training stimulus and improvement of strength balance during periods of high badminton-specific volume, recovery phases, or competition periods, thereby potentially reducing injury risk associated with excessive mechanical loading.

Limitations
The authors note that the sample size was limited to amateur players, the intervention was short-term (8 weeks), and the study did not include direct mechanistic measures (e.g., EMG, muscle morphology) or long-term injury tracking. Consequently, the findings regarding injury prevention are inferred from strength balance improvements rather than direct evidence.