Changes In Muscle Activation Patterns And Kinematics While Learning The Bilateral Barbell Squat

Abstract

While the barbell squat has been subjected to many biomechanical analyses, it is not known how the kinematics and muscle activation profiles will change as an individual learns how to perform the movement. Previous work using different motion patterns have noted decreased variability in movement patterns between repetitions as an individual learns a new movement pattern. PURPOSE: The goal of this work was to document changes in variability of kinematic and muscle activity patterns while individuals learn to perform a standard bilateral barbell squat. METHODS: Ten university age females with no prior barbell squatting experience were recruited. The participants attended four weekly sessions where they performed 4 sets of 10 squats at 50% of their one-repetition maximum (1RM) while receiving feedback on their squatting technique. During the squats the participants had their motion captured in the sagittal plane using a high speed video camera and electromyography (EMG) was recorded from 8 lower-limb muscles that were involved in the squatting motion from the right lower-limb. Prior to the first session and at the end of the last session a 1RM test was performed to determine the maximum capacity for the barbell squat. RESULTS: Despite using a load where a strength adaptation would not be expected, the participants demonstrated a significant increase in 1RM across the study (50.1±8.6 kg vs 57.1 ± 10.0 kg; p < 0.05). Interestingly, most changes in kinematic variability occurred at the ankle joint, where increased variability was observed across the 4 sessions (p < 0.05). It was also observed that the participants were squatting deeper as sessions progressed, as measured by the angle of the thigh segment (p < 0.05). Rectus Femoris (RF) showed decreased variability across the sessions (p < 0.05). CONCLUSIONS: Although an increase in 1RM was found, this improvement is likely due to changes in technique rather than strength. Our findings that the ankle increased in variability may be supported by the uncontrolled manifold hypothesis, which states since attentional focus was on the hips in this study (due to the nature of our feedback), that variability may increase in other areas. Changes in muscle activity of RF may indicate that the participants became more adept at coordinating the hip and knee joints during the squat.