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

Knee Surg Sports Traumatol Arthrosc. 2019 Jan;27(1):68-75. doi: 10.1007/s00167-018-5040-1. Epub 2018 Jun 29.


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/m2) 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 < 0.05). Strength gain was 28% and 31% in concentric and eccentric CE groups, respectively, when compared with the control group. Concentric and eccentric CE had similar effects on quadriceps strength recovery (n.s.). IKDC score, and single-leg hop distances were not significantly different among groups (n.s.).

Conclusions: Concentric and eccentric quadricep strengthening of healthy limbs in early phases of ACL rehabilitation improved post-surgical quadriceps strength recovery of the reconstructed limb. CE should be integrated into ACL reconstruction rehabilitation, especially in the early rehabilitative phases to restore quadriceps strength.

Level of evidence: Randomized controlled trial, Level I.

Keywords: Anterior cruciate ligament; Cross-over effect; Quadriceps strength; Rehabilitation.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Analysis of Variance
  • Anterior Cruciate Ligament Injuries / physiopathology
  • Anterior Cruciate Ligament Injuries / rehabilitation*
  • Anterior Cruciate Ligament Injuries / surgery
  • Anterior Cruciate Ligament Reconstruction*
  • Athletic Injuries / rehabilitation
  • Female
  • Humans
  • Knee Joint / physiology
  • Male
  • Muscle Strength / physiology*
  • Quadriceps Muscle / physiology*
  • Recovery of Function / physiology
  • Resistance Training / methods*
  • Young Adult