What Causes Hamstring Injury?
Surprisingly little is known for certain about the prevention, causes and best methods of rehabilitation of hamstring injuries. Poor quality studies and absence of randomized trials, which are the most valuable, don’t help either. Firm conclusions are in a minority and theoretical approaches in the absence of strong experimental studies are the norm. Here is a sample of the possible causes of hamstring injuries discussed in sports medicine:
Less than ideal lower back and core muscle strength and mobility
Hamstring muscle inflexibility
Greater quadriceps versus hamstring strength
Less than ideal running mechanics
Age — older equals more susceptible
Previous hamstring, knee or pubis injury
It’s quite a list. Being older and having a previous hamstring injury seem to be consistent with injury but not much else, even hamstring inflexibility or quadriceps/hamstring strength imbalance, factors consistently touted as causes of hamstring injury.
How hamstrings fail. In running at least, it seems hamstrings are most susceptible to injury in the ‘eccentric’ transition phase of movement when the muscle is lengthening and being ‘pulled up’ for ground contact. Consider your leading leg when you are running at a fast pace. It stretches out before impacting the ground to push off and facilitate the other leg’s movement forward. At a point before the leading leg hits the ground, called ‘swing phase’, the hamstrings pull that leg up under control so that it does not overextend the knee joint, which would be inefficient (and dangerous). It is at this point of muscle lengthening and sudden control that the hamstrings are most vulnerable to injury. Stretching injuries are slightly different.
Stretching hamstrings. Now this may seem like heresy to anyone who has been told to stretch their hamstrings to prevent hamstring injury, but there is no consistent evidence that a stretching program prevents hamstring injury or even that ‘tight’ hamstrings predispose to injury. Stretching may even make things worse in some circumstances and in any case stretching probably only works to lengthen muscle if you keep doing it consistently. Stretching may have a role in hamstring rehabilitation but there is only limited evidence for this as well.
Quadriceps imbalance. If the quadricep muscles at the front of your thigh are much stronger than the hamstrings at the rear of the thigh then you may be at increased risk of hamstring injury. A hamstring less than 60 percent as strong as the quad supposedly predisposes to hamstring injury. Some studies show this muscle imbalance to be associated with hamstring injuries and others do not. It is a favorite tenet of exercise scientists based on theoretical considerations but lacks really solid evidence in my view. At the same time, getting those hammies up over that 60 percent threshold seems to make sense and it may prevent anterior cruciate ligament injury (ACL) of the knee. One way or another you need strong hamstrings for running and similar physical activity.
Some of the best exercises for strengthening the hamstrings are with weights in the gym. Eccentric exercises that simulate the ‘catch’ of the swing phase of running may be particularly useful. Eccentric muscle training is notorious for causing muscle soreness, so go easy on the amount of weight or effort until you get used to these. Always warm up before weight training. Hamstring warm ups could include leg swings forward and rear, the standing bicycle action exercise and light weights.
Standing leg curls with catch
Start with a light weight on the standing leg curl machine. Lift the leg with weight back in the concentric phase, pause, then as you start to lower the leg, let the weight free fall and catch it near the bottom of this eccentric phase. Your leg does not actually have to lose contact with the weight, only allow a sudden ‘drop and catch’. This simulates to some extent the eccentric swing phase during running.
(Remember, concentric contraction is when the muscle is shortening as you lift your heel up to your butt, and eccentric phase is the lengthening phase when you lower the leg down again.)
Try 2 sets of 12 repetitions for each leg working up to 4 sets over several weeks with a weight light enough so that you are not struggling to do the last one in each set.
Rest for 30 seconds between sets.
Muscle endurance and performance under fatigue may be a factor in hamstring injury so this is as much an exercise for muscle endurance as it is for strength. Do all sets on one leg first; don’t alternate legs for sets. Stop if you feel any pain or twinges other than normal effort stress.
Eccentric exercise is known to cause muscle soreness, so go easy to start with. Don’t say I didn’t warn you.
Nordic reverse curl or glute-ham curl
Kneel on the floor with feet extended flat to the rear and the trunk upright at 90 degrees, preferably with some soft support under the knees.
Support the feet under a low bench or get a partner to hold the feet down.
Bend forward until your body is at an angle to the ground under eccentric hamstring control, then snap backward to the starting position with the help of the hands.
Use the hands to stabilize this part if necessary so you don’t fall on your face! Don’t try too hard to straighten up under hamstring control because the eccentric strength on the down movement is the main target, not the concentric movement when you straighten up.
Do 2 sets of 10 exercises with 2 minutes rest in between but not on the same day as the leg curls to begin with. Stand up and loosen off between sets.
Deadlifts – Romanian, straight-legged, stiff-legged
The deadlift is the exercise where you lift the barbell from the floor to a standing position. If you perform this with the legs somewhat straighter, rather than squatting right down with knees bent for the lift and replace, you will feel the hamstrings tense up. However, keeping the legs straight while bending the back in a curve is danger territory for injury for inexperienced lifters, even if the weight is light. Here is what I do. This is usually called a Romanian deadlift or RDL.
Choose a suitable bar and plate or barbell weight that you can lift comfortably to the upright deadlift position at the thighs — but not too light.
Keeping the legs straight or only slightly bent, lower the bar until it reaches a position where you can feel the hamstrings at the back of the legs start to work.
Stop somewhere around the shins — don’t go to the floor — then return to the upright position.
Don’t overdo this to the point of pain or discomfort in the lower back and try to keep that back straight rather than curved over if possible. Bend the knees slightly if necessary.
You can do repetitions of the RDL without setting the weight on the floor if you keep the weight light enough.
Be aware that the standard deadlift from the floor is also an excellent all-round strengthening exercise for the posterior chain of muscles of the lower back, butt and hamstrings, and also the abdominals, all of which may have a role in maintaining hamstring viability.
Do 2 sets of 10 exercises with 1-2 minutes rest in between sets. Move up to three sets when you get stronger — and less sore!
Barbell good mornings
This is another excellent all-round exercise for the posterior chain including the hamstrings.
Take a barbell and place it behind the neck on the shoulders in similar position as for the back squat.
While keeping the legs stiff, bend forward at the hips with the barbell still resting on the shoulders and the back straight but not bent over at the upper spine. Keep the head steady.
You will feel the dynamic stretch in the hamstrings. Don’t overdo the weight to begin with.
Do 2 sets of 10 moving up to 3 sets over time. Don’t do them the same day as the Romanian deadlifts. Take 1-2 minutes between sets.
Note. You could do several of these similar hamstring exercises on the same day and perhaps you should after a solid period of conditioning. At the start you need to go easy to prevent excessive soreness, particularly with eccentric training.
Three sessions per week is probably optimal. Do only two sessions if soreness is a problem. Modify the number of sets if necessary. A gradual increase in volume is the key to success.
Rehabilitation from hamstring injury, particularly grades 2 and 3, the more severe injuries, requires the supervision of a sports doctor, physical therapist or trainer with expertise in sports injury rehabilitation. The exercises listed above are useful in strengthening the hamstrings for injury prevention purposes and may be used in rehabilitation, but you need to progress according to a plan under supervision.
Warm up before activity. Leg swings front to back and alternate-leg bicycle action are two exercises to use. I don’t recommend heavy stretching.
Strengthen hamstring muscles with a weights program including some eccentric exercise such as the Nordic reverse curl or glute-ham exercise, and standing leg curl catches.
Try to avoid intense running training while hamstrings are sore from weights work.
Development of the quads with weight training exercises like the squat or leg extension should be balanced with suitable hamstring strengthening exercises.
Fatigue over time may be a factor. Ensure an adequate intake of fuel in the form of carbohydrate in sports drinks during longer events or team sports.
Stretch lightly, and preferably dynamically, with exercises similar to warm up at the end of an exercise training session or at intervals in a prolonged competitive session.
Don’t even think about returning to active competition until you are advised by a competent medical authority that you are fit to do so.
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