Background/Purpose: Female athletes have a higher incidence of knee injuries than males due to biomechanical differences. The purpose of this study was to determine if hip flexion angles and dynamic knee valgus movement would differ during a single leg squat before and after quadriceps and hamstring fatigue protocols on physically active females.
Method: Thirty-one active females (21+2.13 yrs, 61.02+7.33 kg, 167.34+6.08 cm) with lower extremity injury participated in this investigation. Subjects completed two single leg box squats from their dominate leg to approximately 70 degrees of knee flexion. Sagittal plane hip angle motion and valgus knee dynamic motion was measured prior to and after isokinetic concentric knee strength and an isokinetic concentric knee fatigue protocol.
Analysis/Results: Post dynamic hip flexion angles (136.48±10.98) were significantly different to pre-test hip flexion angles following the fatigue protocol (140.43±10.03), t(29)=4.05,p<.01. Significant differences (F2,30=20.17,p<0.001) existed between standing (5.12±2.56 degrees) and peak knee angle before fatigue protocol (10.43±6.15 degrees) and following fatigue protocol (9.89±5.62 degrees). There was no significant main effect (p>0.05) in peak valgus knee angle for both dependent variables.
Conclusions: Once the hamstring and quadricep muscles were fatigued, mean post fatigue hip flexion angles decreased signifying an increase in hip flexion. Significantly different mean knee valgus angles existed in the frontal plane between standing and peak knee valgus movement. Fatigue of hamstring and quadriceps musculature does not appear to significantly change knee valgus.