Study on the Effects of Unilateral Resistance Training on Lower Limb Muscle Strength and Symmetry After Anterior Cruciate Ligament Reconstruction Surgery

Peking University

Status: Completed

Conditions: Anterior Cruciate Ligament Reconstruction Rehabilitation

Treatments: Behavioral: resistance training

Study type: Interventional

Funder types: Other

Identifiers

NCT07271173

M2025001

Details and patient eligibility

About

Brief Summary Study type: Randomized controlled trial (interventional). Purpose: To find out whether six weeks of unilateral resistance training (URT) improves lower-limb strength and inter-limb symmetry more than traditional bilateral resistance training (BRT) after anterior cruciate ligament reconstruction (ACLR).

Main questions:

Does URT produce better limb-symmetry in knee flexor/extensor peak torque than BRT? Does URT lead to larger gains in feed-forward motor control, Lysholm knee score and International Knee Documentation Committee 2000 (IKDC 2000) subjective rating? Comparison: Participants will be randomly assigned to URT (each exercise done one leg at a time) or BRT (both legs work together). Training volume, frequency, session length and progression rules are identical in both groups.

What participants will do: After giving consent, complete baseline tests of strength, motor control and knee questionnaires. Attend 3 supervised sessions per week for 6 weeks. Each session lasts ~70 min:

5 min warm-up on cycle ergometer 5 min core-stability work 50 min strength circuit (6 exercises, 2 min between sets, 3 min between exercises) 10 min stretching/cool-down One-repetition maximum (1RM) re-tested at week 3 to adjust load. Final assessment within 3 days after the last training session (same tests as baseline).

Full description

Detailed Description This single-center, prospective, randomized controlled trial will enroll 48 patients who have undergone primary anterior cruciate ligament reconstruction (ACLR) at Chongli Campus, Peking University Third Hospital. After providing written informed consent, participants will be randomly allocated in a 1:1 ratio to either the unilateral resistance training (URT) group or the bilateral resistance training (BRT) group (24 per group).

URT: Each exercise is performed independently with one limb at a time, isolating the target limb while contralateral stabilizers are simultaneously activated to maintain balance.

BRT: Both limbs simultaneously move against a shared resistance, keeping the center of gravity stable and the movement symmetrical.

Baseline assessments will be completed within one week before the first training session; post-intervention testing will occur within three days after the final session. The program lasts six weeks, with three supervised sessions per week. Every session comprises:

5-min warm-up on a cycle ergometer 5-min core-stability work 50-min strength training (the only component that differs between groups) 10-min stretching and cool-down Six exercises are prescribed in identical order for both groups: towel-squeeze press, seated leg press, knee-extension against resistance, long-lever glute bridge, prone hamstring curl, and Romanian dead-lift. Two minutes of rest are given between sets; three minutes separate exercises. Load is set at 60 % of the relevant one-repetition maximum (1RM), re-tested at baseline and week 3 to allow progression.

URT protocol: Each exercise is executed first by the involved leg, then immediately by the uninvolved leg; completion of both sides constitutes one set. The time needed for the uninvolved leg is counted as part of the inter-set interval.

BRT protocol: Both legs work simultaneously; 1RM is determined bilaterally. Training volume, frequency, session duration, and progression criteria are therefore identical; only the resistance modality (unilateral vs bilateral) differs.

Primary outcomes are limb-symmetry indices for peak torque of knee extensors and flexors (isokinetic dynamometry). Secondary endpoints include feed-forward motor control scores, Lysholm knee scale, and IKDC 2000 subjective evaluation. All measurements are obtained pre-intervention and at week 6. The study will determine whether six weeks of URT confers superior strength recovery and inter-limb symmetry compared with conventional BRT after ACLR.

Enrollment: 48 patients

Sex: All

Ages: 30 to 55 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• Age 30-55 years
• ACLR performed with hamstring-tendon autograft ≥ 3 months ago
• Full extension (no loss) and ≤ 5° difference in knee-flexion range between limbs, with flexion ≥ 120°
• Able to recruit quadriceps adequately (no lag during 10 consecutive straight-leg raises on the involved side)
• Can stand pain-free on the involved leg for ≥ 5 s without support
• Has signed informed consent and can complete all study procedures

Exclusion criteria

• Previous lower-limb surgery on either leg, including revision ACLR
• Any prior knee surgery on the contralateral limb
• Associated ligament ruptures or fractures
• Severe patellar chondral damage
• Post-operative arthrofibrosis
• Professional athletes
• Cardiac disease
• Pregnant or lactating women

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

---

48 participants in 2 patient groups

Control group: Bilateral resistance training group

Active Comparator group

Description:

Control group: Bilateral resistance training (BRT, referring to the training method where both limbs (both hands or both legs) simultaneously resist the same resistance. The force is transmitted synchronously on both sides, the center of gravity is stable, and the movements are symmetrical). The movements in the BRT group were similar to those in the URT group. Each movement was completed simultaneously by both legs. The resistance setting was based on measuring the 1RM of both lower limbs (60% of 1RM).

Treatment:

Behavioral: resistance training

Experimental group: Unilateral resistance training group

Experimental group

Description:

Experimental group: Unilateral Resistance Training (URT, referring to the training method where one limb (either one hand or one leg) performs resistance movements independently, emphasizing the application of load to the target limb while activating the stabilizing muscle groups on the opposite side to maintain balance). In the URT group, each movement is performed first by the affected leg and then by the healthy leg. A set is completed when both legs have finished. After the training of the affected leg, the timing begins. The training time of the healthy leg also counts as the interval time. The resistance setting is measured separately for each side of the lower body's single side (1RM) at 60% of 1RM.

Treatment:

Behavioral: resistance training