The purpose of this study is to evaluate the efficacy of a cross-education rehabilitation intervention following anterior cruciate ligament reconstruction on ameliorating the acute losses to function and performance. The cross-education phenomenon describes the strength gain in the opposite, untrained (surgical) limb following unilateral resistance training of the 'trained' (non-surgical) limb.

Protocol:

44 eligible and consenting patients (allowing for 20% attrition) with unilateral anterior cruciate ligament (ACL) injury that have elected to undergo surgical reconstruction will be recruited into this study. Patients will be randomly assigned to one of two different conditions: 1) standard ACL rehabilitation plus 8-weeks of contralateral muscle resistance training, [INTERVENTION]; 2) standard ACL rehabilitation plus placebo exercises (time-matched unrelated upper limb flexibility exercises, [CONTROL].

Assessments of knee extensor and knee flexor neuromuscular performance of both limbs will be obtained prior to, at 10-weeks post- and at 6-months post- surgery. Assessments of function (1-leg hop for distance) and patient-reported outcomes (International Knee Documentation Committee [IKDC]) will also be conducted at these times. Further, all patients will be asked to wear a tri-axial accelerometer to gain an objective measure of habitual physical activity (PA) and sedentary time and pattern for one week pre-surgery (5 weekdays and 2 weekend days), during the first and final week of the INTERVENTION/CONTROL and then again at 6 months post- INTERVENTION/CONTROL.

The initial assessments at 10-weeks post-surgery will evaluate the efficacy of the contralateral training programme, specifically whether the training intervention on the non-injured leg elicited changes in the performance of the injured leg compared to the control group. The assessments at 6-months post-surgery will evaluate any carry-over effects of the contralateral training programme, specifically whether any changes in performance of the injured leg were retained at 6-months post-surgery compared to the control group. 6-months post-surgery is currently the earliest opportunity when we would permit patients to return to sports and activities.

ACL surgeries will be performed by the same three surgeons at the RJAH Orthopaedic Hospital throughout the study and according to standardised techniques and procedures.

Sample size and data analysis:

The means and standard deviations of the primary outcome measure (peak strength) and the correlation coefficient between baseline strength and 8-weeks of strength training, all needed to calculate the sample size, were based on previously accrued data from our laboratory on similar cohorts of ACL patients. Assuming the trial will be powered to detect a difference between the groups of 50N (12.5% of peak strength) with 80% at a two-sided p=0.05 significance level, the trial will require 18 patients in each group assuming analysis will be by ANCOVA (Analysis of Covariance; see formula in Borm et al., 2007). Based on a drop-out rate of 20%, the trial will require a sample size of 22 patients per trial arm (44 patients in total).

Patient recruitment Potential participants will be identified from records of patients listed for ACL surgery and during out-patient clinics. They will be approached by a member of the clinical trial team (consultants, registrars, physiotherapist, lead researcher). The study information and design will be explained to the patients meeting the inclusion criteria and who are interested. They will be given a patient information leaflet and informed consent form to take away with them. These patients will be contacted by phone by the physiotherapist or lead researcher at least 24-hours later to ascertain their verbal consent into the study and to arrange an appointment for an initial assessment. Patients will have the opportunity to ask any questions about the study at this stage also. Written informed consent will be obtained at the first appointment, prior to the initial assessment. Once consented in to the study, patients will be assigned a number. A master copy of individuals' unique identification number and all data will be held on a password-protected computer, stored in a locked cabinet, in a locked NHS research office.

Data monitoring:

Scheduled monthly meetings with the research team will enable monitoring of study progress. Quarterly meetings of the RJAH data monitoring group will provide independent monitoring of the study. No adverse advents are expected, however, ant will be recorded in the on-site file and reported immediately to the data monitoring group.

Inclusion Criteria:

• Mentally mature
• Listed for unilateral ACL reconstructive surgery following informed surgical consent
• Autologous graft tissue; either patella tendon or semitendinosus and gracilis from the ipsilateral leg

Exclusion Criteria:

• Patients under 16 or over 50 years of age
• Patients with systemic pathologies (e.g. renal failure)
• Symptomatic non-operative knee
• Additional ligament injuries, meniscal transplant and,or, articular cartilage repair to the operative knee

Individual data will not be shared