STUDY DESIGN: Randomized, matched design. BACKGROUND: Optimal rehabilitation following anterior cruciate ligament reconstruction (ACLR) requires safe and effective interventions. Negative work exercise (via eccentric muscle activity) has the potential to be highly effective at producing large quadriceps size and strength gains early after ACL-R. The purpose of this investigation was to evaluate the short-term safety and efficacy of adding a progressive negative work exercise program via eccentric (ECC) ergometry early after ACL-R. METHODS AND MEASURES: Beginning 3 weeks after ACL-R, 32 participants were randomly assigned into either a 12-week traditional (TRAD) or ECC exercise program. Safety was assessed by measuring knee pain, thigh pain, knee effusion, and knee stability prior to surgery and at 3, 15, and 26 weeks after surgery. Efficacy was assessed by measuring negative work output during the 12-week training program and by measuring functional ability (ie, quadriceps peak torque, hopping distance, self-reported functional ability and activity level scales) prior to surgery and 26 weeks after ACL-R. RESULTS: There were no significant differences between groups in measures of knee and thigh pain, effusion, or stability at any period after surgery. Negative work output increased systematically throughout training, while knee and thigh pain remained at relatively low levels. A significant group-by-time interaction was observed for quadriceps peak torque, hopping distance, and activity level (P≤.02). Quadriceps strength and hopping distance of the involved limb improved by a significantly greater amount in the ECC group compared to the TRAD group (P<.01). Activity level decreasedto a lesser extent in the ECC group compared to the TRAD group (P = .02). CONCLUSIONS: Negative work via an ECC intervention was implemented safely after ACLR. The addition of negative work exercise also induced superior short-term results in strength, performance, and activity level after surgery. 

J Orthop Sports Phys Ther. 2007;37(1):10-18. doi:10.2519/jospt.2007.2362 

KEY WORDS: ACL, knee, rehabilitation