Research Study Objectives: To quantify changes in running kinetics and kinematics during a repeated-sprint test in football players, and explore the sensitivity and specificity with which these variables can identify previous hamstring injury.
Design: Western Australia State League footballers with previous unilateral hamstring injury and 20 players without completed a 10 × 6-s repeated-sprint test on a non motorized treadmill dynamometer.
Methods:Changes in horizontal force, vertical force, contact time and flight time were compared between previously injured and uninjured legs of participants.
Results:Mean horizontal force production of the previously injured leg in the injured group was 13% lower (p = 0.001), and this magnitude of change was used to identify the injured legs within the cohort with 77% specificity and 85% sensitivity. Furthermore, the area under the Receiver Operating Characteristics curve (0.846) demonstrated that the between-leg difference in mean horizontal force was a good instrument for identifying previous hamstring injury.
Conclusions:There is a greater fatigued-induced change in mean horizontal force during a repeated-sprint test in legs with previous hamstring injury than the non-injured legs of the injured players or the legs of uninjured players. Such asymmetry may contribute to impair performance in football players returning from a hamstring injury and also to the high rate of hamstring re-injury. Rehabilitation and return-to-play strategies should emphasize a reduction in asymmetry, particularly during repeated high-intensity efforts. Furthermore, binary regression and Receiver Operating Characteristic analyses suggest that changes in mean horizontal force could be used to assess risk of hamstring injury, re-injury and/or return to play.
Reference: Cameron Lord, Anthony J.Blazevich, Eric J. Drinkwater, Fadi Ma’ayah, and Plum X Metrics. 2018. Greater loss of horizontal force after a repeated-sprint test in footballers with a previous hamstring injury. Journal of Science and Medicine in Sport DOI: https://doi.org/10.1016/j.jsams.2018.06.008