CONTEXT: Decreased muscle strength and balance in patients with functional ankle instability (FAI) can be effectively improved by ankle strength training. Low-load blood flow restriction (LL-BFR) training increases muscle size and strength, but there is limited evidence from studies on muscle strength and balance in FAI patients. OBJECTIVE: To study the effects of LL-BFR training versus high-load training (HLT) on muscle strength and balance in FAI patients. DESIGN: Randomized controlled trial. PARTICIPANTS: Forty-six young adults with a history of FAI. Interventions: Participants in the LL-BFR and HLT groups performed 4 sets (30 x 15 x 15 x 15) of ankle training at 20% to 40% of the one-repetition maximum and 70% to 85% one-repetition maximum, respectively, twice a week for 6 weeks. MAIN OUTCOME MEASURES: Plantar flexion, dorsiflexion, inversion, and eversion muscle strength, and the Y-balance test scores were assessed at baseline and after 3 and 6 weeks; the thickness of the tibialis anterior, triceps surae, and peroneus longus muscles were assessed at baseline and after 6 weeks. RESULTS: Inversion, eversion, dorsiflexion, and plantar flexion muscle strength; tibialis anterior, triceps surae, and peroneus longus thickness; and Y-balance test scores were significantly increased in the LL-BFR group after 3 and 6 weeks compared with baseline (p < 0.05), with no significant difference between the LL-BFR and HLT groups after 6 weeks (p > 0.05). However, at the end of 3 weeks, eversion muscle strength and Y-balance test scores were significantly higher in the LL-BFR group than in the HLT group (p < 0.05). CONCLUSIONS: Over 6 weeks, LL-BFR training was as effective as HLT in improving ankle muscle strength, muscle thickness, and balance in FAI patients, but LL-BFR training improved the ankle eversion muscle strength and dynamic balance more than HLT did in the early stages of the intervention. This finding will provide a new intervention strategy for the clinical rehabilitation of FAI patients.
Copyright Human Kinetics. Reprinted with permission from Human Kinetics (Champaign, IL).

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