Cross-education improves quadriceps strength recovery after ACL reconstruction: a randomized controlled trial

Purpose The aim of this study was to investigate the effects of concentric and eccentric cross-education (CE) on quadriceps strength and knee function recoveries after anterior cruciate ligament (ACL) reconstruction. Methods Forty-eight patients (age: 29.5 ± 6.8 years, body mass index: 26.1 ± 3.2 kg/m 2 ) who had undergone ACL reconstruction with hamstring tendon autograft were included in the study. The patients were randomly divided into three groups when they reached four weeks post surgery: (1) concentric CE ( n = 16); (2) eccentric CE ( n = 16); and (3) control ( n = 16). All groups followed the same post-surgical rehabilitation program for their reconstructed limb. Additionally, the two experimental groups followed eight weeks of isokinetic training for the uninjured knee at 60°/s for 3 days per week. Quadriceps maximum voluntary isometric strength (MVIC) was measured during the 4th week (pre-training), 12th week (post training), and 24th week post surgery. The single-leg hop distance and International Knee Documentary Committee (IKDC) scores were also evaluated during the 24th week post surgery. Analysis of variance was used for statistical analysis. Results Group-by-time interaction was significant for quadriceps MVICs for reconstructed and healthy limbs ( p = 0.02). Quadriceps strength of both knees was greater in concentric and eccentric CE groups compared to control group during the 12th- and 24th weeks post surgery ( p