Effects of Acupuncture on Time-Dependent Muscle Endurance in Men with Post-Anterior Cruciate Ligament Injury: A Randomized Controlled Crossover Trial

Objective: To investigate whether acupuncture enhances knee joint muscle endurance effectiveness and time-dependent effects after anterior cruciate ligament (ACL) injuries. Methods: This randomized, single-blinded crossover trial included 20 males with ACL injuries. Participants were randomly divided into real acupuncture (RA) group and sham acupuncture (SA) group. RA was stimulated at ST32, ST34, ST36, SP10, and BL57; the SA received acupuncture 1–3 cm near these specific acupoints for 15 min. Both groups underwent RA and SA with a 1-week washout in between. Primary outcomes included kinetic and blood biochemical parameters. Kinetic variables (maximum torque, peak power, maximum average torque, average work, average power, total work, and joint stiffness) were assessed at six time points: pre-intervention and 3, 13, 23, 33, and 43 min postintervention. Blood biochemical markers (glucose, creatine, lactate, ammonia, carnitine, and glutathione) were measured at three time points: pre-exercise, postacupuncture, and postexercise. Results: Significant group × time interaction on isokinetic parameters, joint stiffness, ammonia, lactate, and glutathione (all P < 0.05). Post hoc tests revealed significant increases in isokinetic parameters and stiffness at post1-post3/post4, and ammonia, lactate, and glutathione increased significantly postexercise (all P < 0.05). Compared with the SA, the isokinetic parameters, stiffness, ammonia, lactate, and glutathione were significantly different (all P < 0.05). No significantly difference between groups in glucose and creatine kinase (all P > 0.05), and both increased with time (all P < 0.05). Conclusion: Acupuncture can immediately improve knee joint endurance in ACL injury patients, with time effects lasting 23–33 min after needle removal.