Hamstring strain is the most frequently occurring injury in sport, particularly in those sports that involve (repeated) high-speed running such as football. However, the cause and consequences of repeated maximal sprints over time are insufficiently studied.
In this paper published in Scientific Reports, we demonstrated that both central and peripheral fatigue, assessed via surface electromyography (sEMG) and electrical stimulation, contributed to the immediate loss of muscle function in both the quadriceps and hamstring muscle groups, but that peripheral factors mainly contributed to the sustained loss of hamstring muscle function. Moreover, we established that a lower myoblast:fibroblast ratio in isolated primary human muscle stem cells correlated with improved recovery from both repeated maximal sprints and an in vitro artificial wounding assay within the first 48 hours. We also report that biceps femoris long head architecture (i.e. physiological cross-sectional area) was associated with hamstring fatigue, and that neuromuscular fatigue led to reduced knee extension during the late swing phase of steady-state running. Thus, with this interdisciplinary study, we have identified novel cellular and neuromuscular mechanisms underpinning central and peripheral fatigue following repeated sprinting, which ultimately led to kinematic changes during the running stride phase associated with hamstring strain injury.
Baumert, Philipp; Temple, S.; Stanley, J. M.; Cocks, M.; Strauss, J. A.; Shepherd, S. O.; Drust, B.; Lake, M. J.; Stewart, C. E.; Erskine, R. M.: Neuromuscular fatigue and recovery after strenuous exercise depends on skeletal muscle size and stem cell characteristics. Scientific Reports, 2021, doi:10.1038/s41598-021-87195-x