Objective To determine the acute effects of blood flow restriction(BFR)running warm-up on Achilles tendon morphology and function in basketball players in order to provide a theoretical basis for optimizing warm-up protocols for military personnel and athletes susceptible to Achilles tendon injuries.Methods Twenty-seven male basketball players were subjected and asked to participate in 3 different running warm-up protocols:low-speed running(LSR),high-speed running(HSR),and BFR combined with LSR(BFR-LSR).The acute changes in Achilles tendon morphology,mechanical properties,and functional performance across the 3 testing sessions were analyzed and compared.Results Immediately after training,both HSR warm-up and BFR-LSR warm-up significantly improved Achilles tendon thickness,blood flow,stiffness,and gastrocnemius maximal voluntary isometric contraction(MVIC)when compared with LSR warm-up(P<0.05).No statistical differences were observed in above indicators between the BFR-LSR and HSR warm-ups(P>0.05).24 hours after training,compared with LSR warm-up,HSR warm-up still significantly improved Achilles tendon thickness,blood flow,stiffness,and gastrocnemius MVIC(P<0.05).Although BFR-LSR warm-up did not show statistically significant differences in these parameters compared to LSR warm-up,it still demonstrated positive trends.Immediately and 24 h after training,no obvious difference were found in jump performance among the 3 warm-up protocols(P>0.05),but,both BFR-LSR and HSR warm-ups exhibited superior performance than LSR warm-up.Conclusion Immediately after training,BFR-LSR warm-up demonstrates comparable effects to the HSR warm-up on improving Achilles tendon morphology and performance,as well as enhancing jump performance.However,its sustained and long-term effects require further investigation.