Muscle Excitation During Single Leg Rotational Squat In Individuals With And Without Previous Hamstrings Injury

Abstract

PURPOSE: To compare lower extremity muscle excitation patterns between individuals with and without a previous hamstrings injury when performing a single leg rotational squat (SLRS). METHODS: Eight recreationally active individuals with a history of hamstrings injury within 5 years (4 males, 4 females; age=21.25±1.58 years; height=1.76±0.07m; mass=78.21±12.96kg; Hamstring Outcome Score=88.28±7.5%), were matched to 8 individuals with no history of hamstrings injury (4 males, 4 females; age=22.12±1.55 years; height=1.76±0.08m; mass=76.29±13.62kg; Hamstring Outcome Score=97.19±2.81%). Wireless EMG surface electrodes were placed bilaterally on the rectus femoris, vastus medialis oblique, biceps femoris, medial hamstrings, and gluteus medius. EMG data was sampled at 2000Hz. Participants completed five trials of a SLRS moving to four counts of a 72bpm metronome. Four phases were defined: 1) down phase from standing to squat, 2) rotating towards maximum excursion marker, 3) rotating away from maximum excursion back to straight-ahead squat, and 4) standing up from squat. EMG signals were passed through a 4th order, zero lag, Butterworth high-pass filter with cut-off at 10Hz, low-pass filter with cut-off at 350Hz, and full wave rectified. Mean EMG of each muscle during each phase was normalized to the maximum EMG of the entire task, and analyzed as %EMG. Between group differences were assessed using separate one-way ANOVAs for each muscle and phase. Alpha level was set at p<0.05. RESULTS: %EMG of the medial hamstrings during phase two was significantly higher in the healthy group as compared to the hamstring group (Healthy: 8.66 + 2.83%, Hamstring: 5.943 + 1.74%; p = 0.037, effect size = 1.15). No other significant differences were observed (P>0.05). CONCLUSION: Muscle excitation patterns of the rectus femoris, vastus medialis oblique, biceps femoris, and gluteus medius of individuals with a previous hamstrings injury appear similar to those with no history of hamstrings injury when performing a SLRS. Differences in excitation of the medial hamstrings during the rotation to maximum excursion could indicate a difference in movement strategy between the groups when performing the phase that requires the highest demand of dynamic stability.