Dr. Marc Bochner provides a comprehensive explanation on the different types of hamstring injuries and how to diagnose, treat and prevent in the first place. Hamstring injuries in runners are typically very stubborn and difficult to treat so we highly recommend reading this article.
Here he covers the common causes:
There are several reasons the hamstrings are injured in sports. First, there is muscle imbalance, meaning one muscle is stronger than its opposite functioning muscle. In this case, the quadriceps, which extend the knee and flex the hip, are the opposing muscle group to the hamstrings, which flex the knee and extend the hip as mentioned above. If the quadriceps are overly developed in comparison to the hamstrings, the hamstrings must work harder to pull against the quadriceps, and can strain or tear if they are not strong enough.
Adhesions will cause tightness and pain, with the tightness leading to more pain and so on. If untreated, then with the decreased elasticity there is even less range of motion, and the uninjured fibers will have to work harder, causing them to tighten and form new adhesions. This makes the chronic injury more likely to keep occurring.
Pelvic Alignment Problems
Many people have postural distortion in the form of a lumbar spine or pelvic rotation and tilting, which causes an apparent “short leg” as one side is higher or lower than the other. Everyday activities may or may not be painful, but when subjected to the repetitive stresses of training for a marathon, the result can be muscle injury. The hamstrings can be overstretched on one side in this case, often the “long”side, and the gradual or acute type of hamstring injury then can occur.
Read the entire article to learn more about treatment and prevention.