Relationship Between Quadriceps Rate Of Torque Development And Knee Joint Power During Jumping Post-acl Reconstruction

Abstract

Relationship Between Quadriceps Rate Of Torque Development and Knee Joint Power During Jumping Post-ACL Reconstruction.Kelsey A. Reeves, Darren L. Johnson, Chris Fry, Brian Noehren. University of Kentucky, Lexington, KYThe inability to generate knee joint power after an anterior cruciate ligament (ACL) reconstruction limits athletic performance and contributes to low return to sports rates. However, the underlying factors contributing to a lack of knee joint power in the injured limb remain unclear. Rate of torque development (RTD) of the quadriceps may play a critical role in the development of knee joint power. To date, there is no work on the relationship between early and late stage RTD and knee joint power. Late stage RTD may be more relevant for concentric (CON) movements because of the time it takes to generate power in the knee. PURPOSE: To evaluate the relationship between RTD and knee joint power during the CON phase of a drop vertical jump (DVJ) in patients who were 6 months post ACL reconstruction. METHODS: Three DVJs were recorded for each subject (n = 20, age 20.5 ± 6, BMI 24.0 ± 3.4, 9 female) using instrumented 3D motion analysis. Knee joint power was calculated during the CON phase of the DVJ using custom computer code. RTD was obtained from the subject’s maximal voluntary isometric knee extension strength using an isokinetic dynamometer. Early and late stage RTD were defined as 0-100 ms and 100-200 ms from muscle activation onset, respectively. Relationships between variables were determined using Pearson Product Moment Correlations. RESULTS: Average peak knee joint power was 3.0 ± 1.3 W/kg. Average early and late stage RTD were 6.4 ± 3.6 Nm/kg/s and 2.9 ± 1.3 Nm/kg/s, respectively. Late stage RTD was significantly correlated with knee joint power (r = 0.75, p = 0.000) whereas early stage RTD was not (r = 0.27, p = 0.243). CONCLUSION: Late stage RTD is an important contributing factor to the development of knee joint power during athletic movements such as a jump following an ACL reconstruction. Interventions should look to target late stage RTD to help restore an athlete’s ability to generate power and safely return to sport.