Different Time Course Of Recovery In Achilles Tendon Thickness After Low-Load Resistance Training With And Without Blood Flow Restriction

Context: Blood flow restriction research has focused on muscular strength and hypertrophy. Limited data have been reported about the blood flow restriction effect on the tendon. Objective: To analyze and compare the time course of recovery in Achilles tendon thickness after a single bout of low-intensity resistance training (U-RT) and low-intensity blood flow restriction training (U-BFRT). Methods: A total of 56 healthy participants (24.60 [4.0] y; 23.65 [3.4] body mass index) were included. The dominant leg was assigned for LI-BFRT using low load (30% 1-repetition maximum) and 30% of the total occlusion pressure (52.21 [17.89] mm Hg) in plantar-flexion exercise (1 x 30+3 x 15 repetitions). The nondominant kg was assumed as a control condition. Main Outcome Measure: Sonography images were taken before the intervention, immediately post-training, and 24 hours after exercise (post-24) for the Achilles tendon thickness. Results: Changes in Achilles tendon thickness for LI-BFRT group were significant post(-14.5%; P < .05) and post-24 (-9.2%; P < .05). In contrast, LI-RT group showed a transient decrease after exercise (-9.67%; P < .05) followed by a recovery of thickness post-24 (-1.06%; P < .05). Thickness post-24 was different between LI-BFRT versus LI-RT (P < .01). Hedge effect size analysis showed a large effect (g = 0.90) in LI-BFRT pre-post condition and a medium effect (g = 0.57) in post- to post-24. The LI-RT obtained a medium effect (g = 0.53) in pre-post condition and a small effect (g = 0.49) in post- to post-24. Conclusions: This study showed a different time course of the acute response in Achilles tendon thickness between LI-BFRT and U-RT. This may be associated with intratendinous fluid movement in response to LI-BFRT.