Background: Altered muscular activation pattern has been associated with musculoskeletal disorders. Some previous studies have demonstrated muscle weakness or tightness in athletes who have sustained hamstring (HAM) injuries. However, no study has clinically investigated the muscular activity pattern in subjects with HAM strain injuries.
Objective: To investigate the activity pattern of the ipsilateral erector spinae (IES), contralateral erector spinae (CES), gluteus maximus (GM), and medial and lateral HAM muscles during the prone hip extension (PHE) test in athletes with and without history of HAM strain injury.
Design: Cross-sectional non-experimental study design.
Participants: A convenience sample of 20 soccer athletes participated in the study. Subjects were categorized into two groups: those with history of HAM strain injury (n=10, mean age = 22.6 ± 3.74) and without history of HAM strain (n =10, mean age = 22.45 ± 3.77).
Methods: Three repetitions of the PHE were performed by each subject, and the electromyographic (EMG) outputs of the IES, CES, GM, and HAM muscles were recorded, processed and normalized to maximum voluntary electrical activity (MVE). Independent t-tests were used for comparing activation means of each muscle between athletes with and without history of HAM strain injury.
Results: There were significant differences in EMG activity of the GM (p= 0.04) and medial HAM (p = 0.01) between two groups. No significant difference was found in EMG signals of the IES (p= 0.26), CES (= 0.33) and lateral HAM (p= 0.58) between the two groups. Greater although non-significant normalized EMG outputes of IES, CES and lateral HAM were seen in athletes with history of HAM strain compared to those without HAM strain.
Conclusion: The findings of this study demonstrated greater normalized EMG activity of GM and medial HAM tested in athletes with history of HAM strain compared to those without HAM strain (altered activation pattern).
Level of evidence: 3a.
Keywords: Electromyography; hamstring strain; movement pattern; prone hip extension.