Quadriceps Strength And Rate Of Torque Development Are Associated With Countermovement Jump Knee Kinetics Post-aclr

Abstract

Quadriceps neuromuscular dysfunction is ubiquitous after anterior cruciate ligament reconstruction (ACLR) and can impair knee function during athletic activities. While peak quadriceps strength is often measured, time-dependent metrics such as rate of torque development may be important to sports performance. PURPOSE: To determine the relationships between quadriceps strength, rate of torque development, time since surgery, and knee joint kinetics during jumping in collegiate athletes up to 2 years post-ACLR. METHODS: 31 Division I athletes (age 20.3±1.3, BMI 26.1±3.9 kg/m2, 17 female) performed countermovement jumps (CMJ) on force plates while whole body kinematics were recorded and completed maximal and rapid voluntary isometric knee extension (KE) contractions. Sagittal plane KE impulses were computed for concentric (CON) and landing (LAND) CMJ phases; KE peak torque (PT) and rate of torque development from 20-80% of peak torque (RTD) were extracted from isometric KE efforts. Limb symmetry indices (LSI) were computed and clinically relevant cutoffs of 90% LSI were investigated. A mixed effects model accounted for repeated measurements and assessed the relationships of PT, RTD, and time from surgery with CON and LAND. All possible pairwise interactions were tested. RESULTS: Among 31 athletes, 81 tests were completed 4-24 months post-surgery. PT and RTD were significantly correlated with CON (PT: p=.001, RTD: p=.044) and LAND (PT: p=.009, RTD: p=.008). No significant pairwise interactions between PT, RTD, and time from surgery were detected. Among 24 instances of PT LSI ≥ 90%, mean CON and LAND LSI were 87.3% and 94.2%, respectively. In comparison, among 15 occurrences of RTD LSI ≥ 90%, mean CON and LAND LSI were 93.0% and 102.2%. Among the 22 assessments completed ≥ 1 year post-surgery, mean CON and LAND LSI were 82.4%, and 83.3%, respectively. However, when CON and LAND LSI were ≥ 90%, mean PT was 94.5-94.7% and mean RTD was 85.1-85.3%. CONCLUSIONS: Both peak and rapid knee extensor torque development are strongly associated with symmetrical sagittal plane CMJ knee mechanics. CMJ knee kinetic asymmetries did not resolve over time, independent from quadriceps function. Restoring maximal and rapid quadriceps torque capacity appears to be an important step in recovering symmetrical CMJ mechanics post-ACLR.