Author(s): OSTERLOH, J.1, KNAACK, F.1, MAU-MÖLLER, A.2, HOLL, N.1, LAPPE, C.1, WEBER, M.A.1, BIELITZKI, R.3, BEHRENDT, T.4, LUTTER, C.1, BADER, R.1, BEHRENS, M.1,5, Institution: ROSTOCK UNIVERSITY MEDICAL CENTER, Country: GERMANY, Abstract-ID: 335

INTRODUCTION:
Anterior cruciate ligament (ACL) rupture is a common injury associated with pain, functional impairments, and increased osteoarthritis risk [1]. As smaller ligament size is a risk factor for ACL injuries [2], increasing ACL volume may represent a potential prevention strategy. A recent study found a positive correlation between ACL volume and quadriceps femoris muscle (QF) volume [3], suggesting that training targeting QF hypertrophy might also increase ACL volume. Therefore, the present study investigated the effect of high-load resistance training (HLRT) and blood flow restricted low-load resistance training (BFR-LLRT) on ACL and QF volume.
METHODS:
In a three-arm, prospective, randomized, controlled trial, 60 healthy adults (33 females, age: 24.4±4.0 yrs; body mass index: 23.6±3.0 kg/m2) were allocated to one of two strength training groups (HLRT or BFR-LLRT, 16 weeks, 3 sessions per week) or a passive control group (CG) using sex-stratified block randomization (1:1:1). ACL and QF volume were assessed with 3T magnetic resonance imaging before and after the interventions. Statistical analyses included per-protocol (PP, n=47) and intention-to-treat (ITT, n=60) approaches using analyses of covariance with baseline adjustment and sex as additional factor, followed by Tukey post-hoc tests and effect size calculation (ηp2, Cohens d). Significance was set at p<0.05.
RESULTS:
PP analysis revealed a group effect for ACL volume (F2,40=3.393, p=0.044, ηp2=0.2). Post-hoc tests indicated that the BFR-LLRT group exhibited a significantly higher ACL volume (2.75±0.20 cm3) compared to the HLRT group (2.56±0.20 cm3, p=0.041, d=1.0) and a non-significantly higher ACL volume, with a large effect size, compared to the CG (2.61±0.20 cm3, p=0.142, d=0.8). Interestingly, this effect was predominantly observed in male participants (BFR-LLRT: 2.87±0.20 cm3, HLRT: 2.55±0.20 cm3, CG: 2.57±0.23 cm3, p≤0.094, d≥1.6). Furthermore, PP analysis revealed a group effect for QF volume (F2,40=24.536, p<0.001, ηp2=0.6). Both training groups showed significant increases in QF volume compared to CG (BFR-LLRT: 2081±73 cm3, HLRT: 2102±74 cm3, CG: 1939±73 cm3, p<0.001, d≥2.0). PP findings were consistent with the ITT analyses.
CONCLUSION:
Baseline-adjusted post-intervention data indicate that ACL volume in the BFR-LLRT group was higher compared to the HLRT group and showed a positive trend compared to CG with a more pronounced adaptive response in males. BFR-induced local hypoxia might have led to enhanced collagen synthesis [4], promoting morphological changes of the ACL. Consistent with previous studies [5], both HLRT and BFR-LLRT led to comparable increases in QF volume. The findings suggest that BFR-LLRT exerts equivalent effects on muscle but greater effects on ligamentous hypertrophy in comparison to HLRT.
REFERENCES:
[1] Spahn et al. Orthopade 2016.
[2] Whitney et al. Am J Sports Med 2014.
[3] Shultz et al. J Orthop Res 2022.
[4] Centner et al. J Appl Physiol 2019.
[5] Lixandrão et al. Sports Med 2018.