Differences In Lean Mass And Strength In Adolescent ACLR Female Athletes

Abstract

PURPOSE: To compare differences in total and segmental lean mass (LM), muscle strength and lower leg force production between adolescent female athletes with and without anterior cruciate ligament repair (ACLR). METHODS: Twenty-four females, 12 ACLR and 12 healthy controls (CON), were matched by age (16.4±0.9 vs 16.4±1.0 yrs), body mass index (23.2±2.1 vs 23.2±2.7 kg/m2), and sport. Total, segmental, and regional body composition were measured by 3 DXA scans (1 total body, 2 lateral leg). Muscle peak torque for knee extension/flexion (60, 120°/sec) was measured using isokinetic dynamometry. Lower limb force, power and jump height were measured using a squat jump on dual force plates. Paired t-tests assessed total, regional and segmental lean mass, peak torque and lower limb force production differences within (Involved/Non-involved) and between groups (ACLR/CON). Linear regression assessed the total-leg LM vs peak force relation of each leg and of ACLR vs CON. RESULTS: No body composition differences were observed between ACLR and CON groups (p=0.07-0.90). However, ACLR INV legs had significantly lower total LM (7.1±0.8 vs 7.4±1.0 kg, p=0.004), anterior upper leg LM (1.5±0.3 vs 1.62±0.2 kg, p=0.007), and posterior upper leg LM (1.9±0.2 vs 2.0±0.2 kg, p=0.036). Peak torque was significantly lower in ACLR INV vs NINV legs (p<0.003) and vs CON (p=0.010-0.019) for extension at 60 and 120°/sec and flexion at 60°/sec (p=0.011), with no differences between ACLR NINV vs CON (p=0.23-0.90). Peak force was significantly lower in ACLR INV vs NINV legs (296±45 vs 375±55 N, p<0.001) and between ACLR INV legs vs CON (296±45 vs 372±88 N, p<0.015), but no significant (p=0.736) difference between ACLR NINV leg vs CON. The slope between total LM and peak force was smaller for ACLR participants (INV: m=0.02 r=0.36, p=0.25; NINV: m=0.03, r=0.50, p=0.10) compared to CON (INV: m=0.06, r=0.63, p=0.03; NINV: m=0.06, r=0.62, p=0.03). CONCLUSION: One year post-ACLR female athletes have significant differences in the quantity and quality of leg muscle, compared to matched CON athletes, for both involved and non-involved legs. Importantly, muscle function (strength and force production) is limited in both ACLR legs relative to the amount of lean mass, which may provide evidence for increased risk of ACL tear in the involved and non-involved legs.