During a sprinting motion, the hamstrings can be affected and injured. There seem to be two types of hamstring injuries that can occur during a sprint, one of a sprinting-type injury that affects the bicep femoris, and one of a stretching-type injury that affects the semimembranosus (Danielsson et al., 2020). During the stance phase of a sprint, injury to the hamstring can occur due to an increased anterior trunk lean, which places the hamstring at an increased stretch. In addition, supporters of early stance phase as the primary mechanism of injury for the hamstrings also supports the fact that muscle injury occurs primarily due to increase muscle force rather than muscle strain. In addition, early stance phase is when the joint experiences high ground reaction force. Many authors believe that musculotendinous injuries come from closed-chain activities, and rarely do open-chain activities can create high enough forces to induce muscle damage (Kenneally-Dabrowski et al., 2019). Early stance during sprint also creates a high knee flexion and hip extension moment due to the increased torque produced during foot strike, these forces seem to be comparable to the forces experienced during late swing phase.
That being said, majority of the studies seem to support late swing of the sprint as the primary mechanism of injury for hamstring muscle due to its “high muscle excitation, negative work, and peak musculotendon length” (Kenneally-Dabrowski et al., 2019). The kinetics of the hip during late swing produces a large extension moment primarily as a result of muscle torques and motion-dependent torque. It is important however, to note that whether or not the hamstrings undergo eccentric action during late swing is still a topic of debate (even though it seems to be quite intuitive). In addition, the idea that late swing contributes highly to hamstring injuries is from a supportive theory where it is suggested that a muscle under high excitation can decrease the threshold of muscle strain (Kenneally-Dabrowski et al., 2019), which was extrapolated from animal studies.
There are two incidences where injury to the bicep femoris long head occurred during sprint studies, and although conclusion was not clear, most authors believe it being the late swing phase as the moment when the injury occurred (Danielsson et al., 2020). Personally, I believe that both phases are contributors to hamstring injuries. Individuals with poor running mechanics may place higher than studied knee flexion and hip extension moment due to the ground reaction force if foot strike is anterior to the centre of mass, this case can be further exacerbated if the technique of the sprint is poor (such as if they strike with their heels). I also highly believe that during the late swing phase, the hamstrings undergo eccentric contraction to control the knee (even though studies have demonstrated an isometric contraction of the bicep femoris during late swing phase). Both phases should be considered when discussing about hamstring injuries in sprinters.
With regards to prevention strategies, it seems like the Nordic hamstring curl is the golden standard. With good compliance, the Nordic hamstring is capable of being more effective than neuromuscular training for prevention of ACL (Goode et al., 2014). Hence, when designing programs for sprinters or athletes who are at risk of hamstring injuries due to high-speed runs and change of directions, it is crucial to include Nordic hamstrings as part of the program, and ensure athlete compliance.
Danielsson, A., Horvath, A., Senorski, C., Alentorn-Geli, E., Garrett, W. E., Ramon, C., Samuelsson, K., & Senorski, E. H. (2020). The mechanism of hamstring injuries – A systematic review. BMC Musculoskeletal Disorders, 21, 641.
Goode, A. P., Reiman, M. P., Harris, L., DeLisa, L., Kauffman, A., Beltramo, D., Poole, C., Ledbetter, L., & Taylor, A. D. (2014). Eccentric training for prevention of hamstring injuries may depend on intervention compliance: A systematic review and meta-analysis. BJSM, 49(6), 1-9. doi:10.1136/bjsports-2014-093466
Kenneally-Dabrowski, C., Brown, N., Lai, A., Perriman, D., Spratford, W., & Serpell, B. G. (2019). Late swing or early stance? A narrative review of hamstring injury mechanisms during high-speed running. Scanadavian Journal of Medicine and Science in Sports, 29(8). DOI: 10.1111/sms.13437