Low-load blood flow restriction training as a viable alternative to high-load eccentric training for improving Achilles tendon properties: the superiority of a calf-specific regimen

Abstract Objective To compare the effects of 2 different blood flow restriction (BFR) rehabilitation protocols versus classic high-load eccentric resistance training on the morphology and biomechanical properties of the Achilles tendon in healthy adults, and to provide alternative training strategies for preventing Achilles tendon injuries in military training. Methods​ A randomized controlled trial was conducted. Fifty-five healthy adults from a university in Xi’an were enrolled between December 20 and 23, 2024, and randomly assigned to one of three groups using a random number table: a high-load eccentric resistance training group (HL, n=18), a low-load eccentric resistance training with calf-applied BFR group (C-BFR, n=16), and a low-load eccentric resistance training with thigh-applied BFR group (T-BFR, n=19). All groups completed an 8-week training program. Achilles tendon cross-sectional area was assessed using color Doppler ultrasonography at baseline, 6 weeks and 8 weeks. Achilles tendon stiffness and Young’s modulus were evaluated using color Doppler ultrasonography and a wireless microFET3 dynamometer. The maximal voluntary isometric contraction (MVIC) of the medial gastrocnemius was simultaneously measured using the wireless microFET3 and surface electromyography. Countermovement jump (CMJ) height and drop jump (DJ) ground contact time were measured using a three-dimensional force platform. Results After 8 weeks of intervention, color Doppler ultrasonography assessment revealed that the cross-sectional area of the Achilles tendon significantly increased in all three groups compared to baseline (P