The effect of progressive resistance exercise on knee muscle strength and function in participants with persistent hamstring deficit following ACL reconstruction – a randomized controlled trial.

: To investigate the effect of progressive resistance exercise compared with low intensity home-based exercises on knee-muscle strength and joint function in people with anterior cruciate ligament (ACL) reconstruction and persistent hamstring strength deficits at 12-24 months after surgery. : Randomized controlled superiority trial with parallel groups, balanced randomization (1:1) and blinded outcome assessment. : We searched the databases PubMed, CINAHL, Scopus, SPORTDiscus, and the Cochrane Library from inception to January 6, 2022. : People with ACL reconstruction (hamstring autograft) and persistent hamstring muscle strength asymmetry were recruited one to two years post-surgery and randomised to either twelve weeks of supervised progressive strength training (SNG), or twelve weeks of home-based, low-intensity exercises (CON). The primary outcome was between-group difference in change in maximal isometric knee flexor muscle strength at twelve-week follow-up. : Fifty-one participants (45% women, 27 ± 6 years) were randomized to SNG (n=25) or CON (n=26), with 88% follow-up rate at twelve weeks. People in the SNG group improved their knee flexor muscle strength (0.18 Nm/kg, 95% CI 0.07 to 0.29; p = 0.002) more than the CON group, from baseline to twelve weeks. The SNG group also had superior Knee injury and Osteoarthritis Outcome Scores (KOOS) for Pain (4.6, 95% CI 0.4 to 8.7; p = 0.031) and Daily Living Function (4.7, 95% CI 1.2 to 8.2; p = 0.010) compared to the CON group. : In people with persistent hamstrings muscle strength deficits after ACL reconstruction, 12 weeks of supervised progressive strength training was superior to low intensity home based exercises for improving maximal knee flexor muscle strength and some patient reported outcomes.