The Effect of Core Fatigue on Lower Extremity Kinematic Variables During Squats in Female Body Builders

Purpose: Muscle fatigue of the neuromuscular core can change the lower extremity kinematics and increase the risk of lower extremity injuries during squat movement. However, it is unclear how core muscle fatigue can change lower extremity kinematics.  Methods: Sixteen female bodybuilders were included in this one-group pre-test-post-test quasi-experimental study. Subjects performed double leg squats twice before and immediately after the core muscles fatigue protocol. Kinematic variables of lower extremity motion in sagittal and frontal planes were recorded using two 21 megapixels digital video cameras with a sampling frequency of 50 Hz. The obtained data were analyzed for kinematics variables by Quinoa Motion Analysis Software. Paired sample t-test was used to compare kinematic variables before and after the fatigue protocol. Results: The results of this study showed that core muscles fatigue can lead to significantly decreased knee flexion (P=0.001) and increased knee valgus angels during double leg squats movement, but no difference was observed in hip flexion and ankle dorsiflexion before and after the fatigue protocol (P=0.001). Conclusion: The results showed that core muscle fatigue can negatively affect the alignment of the lower extremity and increase the risk of injury in female bodybuilders.