If you participate in a sport or physical activity that requires regular sprinting, like soccer, rugby, football or, of course, sprinting (!) you, or someone you know has experienced a hamstrings strain.
A strain is a muscle or tendon tear. Tears sound scary, but remember that like all injuries strains present along a spectrum of severity. In the physiotherapy world we give these injuries ratings on a 3 point scale. Imagine that the muscle is like a rope, a collection of fibers that come together to make up the larger structure.
Using this model a grade 1 strain is like a frayed rope. It’s obviously damaged and painful but structurally largely intact. A grade 2 strain is a partial frank tear of the rope, at this point we will often see bleeding (bruising) and swelling.The tenderness and pain on loading the muscle is notably increased. A grade 3 strain is a complete tear of our rope, the injury is often associated with a “popping” sensation, a ton of bleeding and swelling and complete dysfunction of the muscle - a muscle with a complete tear cannot take load obviously!
Sprinting puts our poor hamstring at risk for this type of injury because the hamstring muscle is under a boatload of eccentric load during the flight phase of the stride. Eccentric loading occurs when a muscle is both contracting and lengthening at the same time (see the video below for an explanation I gave of this a few years back - I apologise in advance for my moustache). Any muscle, including the hamstring is at increased risk for for injury during this contraction type.
At the end of hamstrings range in a sprint, when the leading leg is completely extended in front of the body, the muscle at a mechanical disadvantage, and is asked to produce very high eccentric contraction force. This unhappy situation is one reason leading to the common incidence of sprinting strain injury.
Risk factors for a hamstring strain injury include a variety of factors. Advancing age (don’t feel bad, unless you are 18 or younger you are at increased risk for most injuries, so welcome to my club!), poor hamstrings flexibility and significantly weak hamstrings are all relevant risk factors.
Interestingly, previous hamstrings strain injury is also a major risk factor for the same injury again in the future. One proposed reason for this is that the muscle heals in a “scarred down” shortened position. This means that its optimal force producing length is reduced - which is a technical way of saying that it is even weaker in force production at the end range of that flight phase of sprint we mentioned a couple of paragraphs above and is therefore susceptible to reinjury.
So how can we manage this risk and reduce our chances of incurring a hamstrings strain injury (or reinjury)? Well, one great (and well researched) method is eccentric strength training. It seems like eccentric strength training is the “miracle drug” of exercise for muscle and tendon injuries, we’ve covered its use extensively on this blog for achilles tendinopathies, tennis elbow and patellar tendinopathy. Certainly it has its applications with hamstrings injury too.
The Nordic hamstrings exercise (or Nordic curl) is a classic hamstrings eccentric strength training exercise. To execute this exercise It’s easiest to first find a partner to help you out. Assume a high kneeling position as shown with your partner holding down your ankles from behind. Your job is to slowly lower your body to the ground by extending at the knees. Unless you are very exceptionally strong there will be a critical angle where your hamstrings will give out and your body will fall to the floor. For the sake of your face please have your hands out in front ready to catch you! You’ll look for this critical angle to increase as you get stronger over a period of weeks. Perform 3 sets of 7 repetitions, twice per week. Give yourself 12 weeks of training to build the protective effect of increased strength against hamstrings strain injury.
Also, I should note that you can do this exercise on your own if you can find a place to secure your feet - like under a heavy piece of furniture or a loaded bar at the gym. It’s fun to workout with a partner though!
Note that eccentric exercise is a heavy technique and should be performed by healthy athletes as a preventative measure! If you have sustained a hamstrings injury, you should consult with your physiotherapist for the timing of inserting this into your rehab, usually 6-8 weeks post injury.
Stretching to increase the length of the hamstrings muscle and push out its optimal force production length is also a good practice. As with all stretches holding for at least 30 seconds is a must (I prefer a couple of minutes). You can use the hamstring stretch from your chair at work or school as one techniques, of course other methods are available!
You may also remember from a recent entry on this blog that strength training through a muscles full range of motion is effective on par with stretching for lengthening a muscle. I recommend deadlifts as an exercise to achieve this effect at the hamstrings. Additional bonus is that you’ll get a heck of a hamstrings strength benefit too using this technique! I’ve pasted a video from that blog below but do read the full article linked above for more details.
If you sprint a lot for fitness or recreation, you may also want to consider having your sprint assessed professionally. Many physiotherapists or of course run/track coaches can help you by examining your form and cleaning up any mechanical issues that you have that are predisposing you toward injury.
Try the Nordic Hamstring Exercise described above. Give yourself a head start of 12 weeks ideally before your athletic season, of course if your activity is slated before then it’s always helpful to start “now”. Have fun with this exercise, It works well and will protect you against hamstring injury!
Further reading (if you really want to impress your friends)
Askling, C., Karlsson, J., & Thorstensson, A. (2003). Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload. Scandinavian journal of medicine & science in sports, 13(4), 244-250.
Brockett, C. L., Morgan, D. L., & Proske, U. W. E. (2004). Predicting hamstring strain injury in elite athletes. Medicine & Science in Sports & Exercise, 36(3), 379-387.
Hoskins, W., & Pollard, H. (2005). The management of hamstring injury—Part 1: Issues in diagnosis. Manual therapy, 10(2), 96-107.
LaStayo, P. C., Woolf, J. M., Lewek, M. D., Snyder-Mackler, L., Reich, T., & Lindstedt, S. L. (2003). Eccentric muscle contractions: their contribution to injury, prevention, rehabilitation, and sport. Journal of Orthopaedic & Sports Physical Therapy, 33(10), 557-571.
Opar, D. A., Williams, M. D., & Shield, A. J. (2012). Hamstring strain injuries. Sports Medicine, 42(3), 209-226.
van der Horst, N., Smits, D. W., Petersen, J., Goedhart, E. A., & Backx, F. J. (2015). The preventive effect of the Nordic hamstring exercise on hamstring injuries in amateur soccer players: a randomized controlled trial. The American journal of sports medicine, 43(6), 1316-1323.