Comparison of Squat Strength and Muscle Activity Between Female Athletes With Varus Versus Valgus Knee Angles During Jumping

This investigation examined squat strength and muscle activation during jump landings between female athletes who landed with a varus knee position versus a valgus knee position. Twenty-one female athletes were recruited from Appalachian State University. Subjects had at least two years of resistance training experience, and played basketball or volleyball at least 4 hours per week. All subjects performed a one repetition maximum (1RM) in the back squat and performed three of each of the following jumps: countermovement jump, 20 cm, 40 cm, and 60 cm drop jumps. Knee position was calculated using 3D videography at the moment of peak knee flexion. EMG activity was collected on the Vastus Lateralis (VL), Vastus Medialis (VM), Biceps Femoris (BF), and Gluteus Maximus (GM) using wireless electrodes. Average muscle activity for 100 ms prior to peak knee flexion was averaged for the left and right leg and EMG activity of the VL and VM were averaged together to represent quadriceps activity. Activation of quadriceps, BF, GM, absolute 1 RM and relative 1RM were not significantly different between the valgus versus varus knee angle groups. Significant differences were observed in knee angles between the valgus and varus groups in all jump conditions (p =0.05).