Examining the Effects of Dynamic and Isometric Resistance Training on Knee Joint Kinetics During Unplanned Sidesteps in Elite Female Athletes.

Abstract: Kadlec, D, Jordan, MJ, Alderson, J, and Nimphius, S. Examining the effects of dynamic and isometric resistance training on knee joint kinetics during unplanned sidesteps in elite female athletes. J Strength Cond Res XX(X): 000-000, 2024-The purpose of this study was to examine the effects of a 4-week block of isometric (isometricRT) and dynamic resistance training (dynamicRT) on kinetic variables associated with anterior cruciate ligament (ACL) injury risk during unplanned sidesteps in elite female athletes. Twenty-one elite female athletes competing for a women's international rugby union team were recruited with 15 (n = 15; age: 23.4 ± 4.7 years; 170.7 ± 8.4 cm; 84.4 ± 15.4 kg) completing assessment of knee flexion moment, knee valgus moment (KVM), knee internal rotation moment (KIRM), knee joint power during unplanned sidesteps, and lower limb strength before and after a 4-week intervention. Linear mixed effects models and one-dimensional statistical parametric mapping assessed the effect of the interventions. Statistical significance was set at α = 0.05. Postintervention the isometricRT group revealed reduced peak KVM during early stance (p = 0.04) while the dynamicRT group decreased peak KIRM (p < 0.01) and KIRM over 8.8-86.6% (p < 0.01) and 96.9-98.5% (p = 0.047). An exploratory combined group analysis revealed reductions in KVM over 7.9-21.8% (p = 0.002) and in KIRM over 8.3-90.5% (p < 0.01) and 96.2-98.5% (p = 0.046). Most lower limb isometric and dynamic strength measures increased after both resistance training interventions. Overall, both groups increased lower-body maximum strength while reducing kinetic knee joint variables associated with ACL injury risk during unplanned sidesteps. These results highlight the importance of increasing single-joint and multijoint strength in female athletes to mitigate the mechanical knee joint demands during sidestepping.