So why are runners (especially long distance runners) plagued by hamstring injuries so often? Well, there can be many causes—going out too fast and too strong without properly warming up, not properly fueling the body, dehydration, lack of strength in the posterior chain (back, glutes, hamstrings), and being quad dominant. And then there is always the odd injury for which there is no apparent reason for the cause.
From my reading, schooling, and talking with other runners, being quad dominant and having a weak posterior chain are probably the two biggest causes of hamstring injuries. I've mentioned it in previous posts how so often runners do not include resistance training into their weekly routine. Runners often shy away from the gym because they feel they're getting enough exercise on the run. They also don't want to bulk up.
Runners need to change their perception of the gym. They also need to realize that many resistance exercises can be done using body weight or light weights at home. And no, doing resistance training will not turn you into a bulky "Arnold" and no you won't gain an Austrian accent in the process.
A December 2008 Running Times article does a great job of explaining the issue of quad dominance. In a nutshell, quad dominance happens when the "quad muscles overpower the action of the hamstrings in the movement of the leg during a running stride."
Long distance runners log a lot of miles. That constant repetitive action puts an overload on the quads causing them to become more dominant than their antagonist—the hamstrings. When your hamstrings become significantly weaker than your quads, then Running Times says one of two things may happen:
1) Your hamstrings will tear as a result of not being able to take the load developed by the contracting quadriceps and momentum from hip extension
2) You will run slower as a result of diminished power from the hip flexors and knee extensors as the hamstrings have to contract earlier to be able to break the ensuing movement.
Hamstring injuries are slow to heal and often, once you get them, they'll reoccur over and over. The recurrence, however, is usually due to the runner not addressing the real cause of the problem......weak hamstrings. That's where resistance training can play a huge role in overcoming or preventing this problem.
First of all, for everyone (not just runners) strengthening the posterior chain (the muscle groups found on the back side of the body) is most beneficial. Having a strong posterior chain can help prevent a whole host of injuries especially later down the road as we age. The posterior chain mainly consists of the erector spinae muscles (the lower back muscles), the glutes (butt muscles), and the hamstrings (upper backside of the leg).
Exercises that target the hamstrings include:
Bulgarian split squats
Stability Ball Leg Curls
Standing Leg Curl with Ankle Weights