Justin Kirk, PT, is a physical therapist at UAB Medicine. Below, he answers some questions about hamstring strains.
Are hamstring strains or quadriceps strains more common? Who is most likely to get a hamstring injury?
Hamstring strains are much more common, and some estimates show that the rate of hamstring injuries has almost doubled in the past few years. The quadriceps (quads) are typically 33-67% stronger than the hamstrings, even in well-developed athletes. Typically, as the strength imbalance between the quads and hamstrings increases, the chances of a hamstring strain increases. Hamstring injuries are most common in sports that involve sprinting, quick stopping, cutting, jumping, and/or quick lunges.
What causes hamstring strains and tears?
The muscle activity in the hamstrings increases exponentially the faster we’re moving. As your leg pushes off the ground, swings forward, and reaches for the next step, the hamstrings are rapidly absorbing force. The hamstring is also doing this at a long muscle length, meaning the hamstring is already mechanically stretched in this position.
When you add large forces – along with a high rate of force development, long muscle lengths, and a strength imbalance between the quads and hamstrings – it really sets the stage for why hamstring strains are so common. Also, strains are associated with two-joint muscles more often than with one-joint muscles. Three of the four hamstring muscles are two-joint muscles, because they cross both the hip and the knee joint. In contrast, only one of the four quadriceps muscles crosses both the hip and knee joint.
Can hamstring strains be prevented? Does stretching your hamstrings prevent hamstring strains?
Unfortunately, stretching alone does not prevent hamstring injuries, but I do think hamstring strains can be prevented because they are non-contact injuries. At the very least, we can reduce the risk for a hamstring strain by using proper training methods. Warming up before practice and competition is highly important, because it gets the hamstrings warm and ready for the demands of sport. Warming up is often neglected or given half effort, but it should be a priority if you’re interested in preventing hamstring injuries.
Next, we have to train the hamstrings to be long and strong, using resistance exercises that focus on the eccentric portion (controlled lengthening) of the lift like hamstring slides, Romanian deadlifts (RDLs), hamstring ball curls, single-leg RDLs, and Nordic hamstring curls. Lastly, we have to train the hamstrings to move quickly to match the demands of sports with exercises like sprints, bounding, decelerations, backward running, lunges, skipping, and jumping. Things take time to adapt, but the hamstrings can get stronger and more resilient with enough consistency.
What is the average return-to-sport timeline for the three grades of hamstring tears?
Return-to-sport timelines vary because each injury is different, even within the same injury grade. As redundant as it might sound, people are different, and we all heal at different speeds. The return-to-play discussion is usually highly nuanced, and it can end up involving the athlete, the physical therapist, the athletic trainers, coaches, parents, and more.
That said, it usually takes 7-28 days for grade I injuries. Grade II injuries can take anywhere from two weeks to 12-plus weeks. Grade III hamstring injuries are typically season-ending injuries that can take 3-6 months to heal. These are broad estimates and not patient-specific. We can usually get a better estimate by comparing the degree of injury with the physical exam. I once got a referral for a high-level football athlete with six weeks left in the regular season that was noted as a grade III hamstring tear. Much to my surprise, he was able to rehab and get back on the field by the playoffs.