The lower limb muscle activity and lumbo-pelvic movement control in soccer players: a matched case control study
Background Soccer is a sport that is gaining in popularity in the elite and non-elite populations worldwide. As a result, the number of injuries in soccer is increasing. Hamstring injuries in particular, with a reported incidence rate as high as 63%, are of significant concern. Most hamstring injuries tend to occur during the swing phase of sprinting when hamstring activity is at its highest. As the speed of sprinting increases, greater mobility in the lumbo-pelvic area is required to maximise sprinting efficiency. Any abnormal or dysfunctional lumbo-pelvic movement during this phase could induce pain and hamstring injury. Lumbo-pelvic movement control dysfunction may therefore indirectly link abnormal lumbar spine movement to lumbo-pelvic pain and hamstring injury. The first aim of this study was to compare the performance of the erector spinae, gluteus maximus, hamstrings (biceps femoris) and quadriceps (rectus femoris) muscles in soccer players, with and without recent hamstring injuries, while performing isometric contractions, a functional squat and sprinting. The study’s second aim was to compare lumbo-pelvic movement control in soccer players with and without recent hamstring injuries. Method Thirty soccer players were selected to participate in this study. Fifteen were assigned to the injured group and 15 to an uninjured group. The injured group comprised players who had sustained a hamstring injury six months prior to the research and who had partially returned to training, and the uninjured group comprised players with no recent hamstring injuries and who were actively involved in full training. Players were matched in respect of age, height, weight and playing position. All players gave informed written consent, completed the physical activity, training and injury questionnaire, and the Oslo hamstring injury questionnaire. Physical tests, which included isometric contraction of the erector spinae, gluteus maximus, hamstrings (biceps femoris) and quadriceps (rectus femoris) muscles, a functional squat and a thirty-metre sprint were done. Muscle activity during these tests was recorded via electromyography (EMG). To determine the lumbo-pelvic movement control of the players, the dorsal pelvic tilt, waiter’s bow, one leg stand and prone knee bend tests were used. Cohen's d (parametric) and Spearman’s correlation coefficient (nonparametric) were used to calculate the effect size, and the Chi-square test and Fisher’s exact to analyse the lumbopelvic movement control data. To establish a statistical significance, the p-value of the study was set at p<0.05. Results EMG muscle activity during isometric contractions was lower in the erector spinae muscles (p=0.04) and biceps femoris muscle (p=0.02) of the injured group. Both these findings were statistically significant. There was no statistically significant difference in muscle activity during the functional squat between the study and uninjured groups. The results of the EMG activity in the thirty-metre sprint were determined to be significant as they demonstrated that the hamstring muscle (p=0.01) activation in the injured group was decreased in comparison with the uninjured group. During the performance of the lumbo-pelvic test, no association was found between the two groups in the dorsal pelvic tilt and one leg stand. The performance of the waiter’s bow (p=0.01) and prone knee bend (p=0.004) revealed statistically significant differences between the study and uninjured groups. The majority of the players in the injured group performed both of these functional tests incorrectly (WB n=10; PKB n=14). Conclusion The study found that the hamstring muscle is at great risk of injury during eccentric contraction of the hamstring muscles. This can be associated with poor lumbo-pelvic movement control, as the load on the hamstring muscle is increased to provide intersegmental stability around the neutral zone, the area of high spinal flexibility.
A Research Report submitted to the Faculty of Health Sciences, University of the Witwatersrand Gauteng, 2017