Flexibility and Agility Help Prevent Hamstring Injuries in Sprinters
When running, the hamstring cycles through transitions between eccentric contractions immediately followed by a concentric contraction. During the swing phase of sprinting at maximum speed, the hamstring is maximally stretched as it simultaneously creates tension to slow knee extension. Upon contact, the hamstring instantly contracts as the body is propelled forward. It is believed that the majority of hamstring injuries occur during the eccentric contraction during the swing phase.
Sugiaru et al. investigated the impact of flexibility and agility training on hamstring injuries. Two probable methods of hamstring injury included a lack of synchronization between the hamstring and the quadricep, and a lack of flexibility in the hamstring. If the hamstring and quadriceps do not function in rhythm, the hamstring has the possibility of overstretching. In addition, if the hamstring is too tight, the high velocity of the swing phase may lengthen the hamstring further than it can handle causing injury. They found that adding flexibility and agility training to an existing strength program decreased the prevalence of injury.
It is well known that strengthening the hamstring will decrease hamstring injuries. One common method that the researchers confirmed is the Nordic hamstring curl. The emphasis on the eccentric portion of the exercise correlates to the action of the hamstring during the swing phase of the stride. They also found that dynamic and static stretching as a means of increasing flexibility was successful in reducing the rate of injury. However, stretching immediately before exercise had no correlation to a decrease in injury. Agility training such as mini hurdle jumps and step overs assisted in developing greater synchronization of the hamstring and quadriceps, contributing to a decrease in injury risk. In order to reduce the risk of a hamstring injury, incorporating a mix of strength, agility, and flexibility exercises is preferred.
You can find the article here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5298567/