Hamstrings and Marathoners

November 9, 2009 | by Dr. Jess

Hamstring Strains and Marathons Why do we get hamstring strains at the end of long runs? I’m going to cut right to the chase. Too many of us have the unfortunate combination of hamstring inflexibility and hamstring weakness that can doom us on marathon day. In this article, I’d like to review why this happens and give you one of several exercises to help prevent hamstring strains. The hamstrings have three jobs during running. One is to slow down the swinging lower leg forward during the swing phase. Their second job is to decrease too much forward lean of the trunk at the hips. In other words, the hamstrings along with the gluteus muscles hold up the trunk and prevent it falling forward at the hip. Thirdly, the hamstrings along with the glutes and with a stable lumbar spine propel the body forward by extending the hip (moving the leg backwards.) In this article, I will review job number one where the hamstring has to perform an eccentric contraction to decelerate the forward swinging lower leg (tibia.) Let’s review what concentric and eccentric contractions are. A concentric contraction is when a muscle is shortening and active at the same time. For example, in order to flex your elbow and do a biceps curl, you need to shorten the biceps and activate (or contract) them at the same time to bring the lower arm towards your upper arm. An eccentric contraction of the biceps would be you moving your lower arm AWAY from your upper arm slowly, and usually with weight, until your elbow is straight. Thus, an eccentric contraction’s primary purpose is to CONTROL a movement to reduce the likelihood of injury as well as load a muscle to recoil or spring back. A concentric contraction has the ability to produce explosive power. For example, when you jump, your quads contract and shorten to propel you upwards. When you land, your quads have to lengthen AND contract to control the impact. If they didn’t lengthen, you would land stiff legged. If they didn’t contract while lengthening, you would fall on your butt. Keeping the eccentric contractions in mind, let’s look at job number one: to slow down the swinging lower leg forward. As you push off with your right leg, it has to swing forward (known as hip flexion) to meet the ground again in front of your body. Your right knee bends as your hip flexes forward and then has to straighten so you land with an almost straight leg. The hamstring’s job is to control how fast and how much the knee straightens or extends. How can this relate to injury? If you have an imbalance between hamstring and quad strength, you can strain your hamstring because it doesn’t have the strength to control the power of the quads extending the knee while the hip flexors are propelling the entire leg forward. Also, if your hamstring is not very flexible and you have strong quads and a long stride, you can strain your hamstring in this part of the running cycle. Typically the inability of the hamstring to control the knee extension is prevalent in marathoners because the hamstrings do not have the endurance to control the leg swinging forward in longer runs. Why is this? Think of what happens on longer runs. Mile after mile, the legs fatigue. When the legs fatigue, the swinging leg actually starts to lengthen as it swings forward. In other words, the knee does not bend as much as the leg is swinging forward. What this does is create a long lever and now the hamstrings (which attach from the sit bone to the tibia below the knee) have to control the entire leg (which is now heavier) thrusting forward during the entire swinging motion. To illustrate this point, try this exercise: Stand on your left leg (feel free to hold onto the wall with your left hand for balalnce) and bring your right knee up high so your right thigh is parallel to the ground. Then while still standing on the left leg, swing the right leg backwards keeping the knee bent so your leg is behind you. Then swing the right knee back up towards your chest so your thigh is again parallel to the ground. Do this several times at a good tempo as if you are running, just swinging with the right leg. After you have done that a few times, try this: Start in the same manner by bringing your right knee up so your thigh is parallel to the ground then swing it back behind you again. This time as you swing your leg forward, extend the knee so your leg is straight and try to get the right thigh parallel to the ground again with the knee straight. Do not cheat by rounding out your back or pelvis. Everything else must stay in the same position. You will notice that it’s harder to get your thigh parallel to the ground with a straight leg. This is because the hamstring is now at it’s most lengthened position. Now the hamstring has to control the entire straight leg forward which is really much heavier than when the knee is bent- at it’s most lengthened state. And this is how you can strain your hamstring! Here’s an extra little bonus piece of information. Let’s say your hamstring is stubborn and it DOES lengthen completely during the forward swing of the leg, but it’s still inflexible and not strong enough. Where do you think the body would try to compensate? The pelvis and low back! Your body will find the path of least resistance while still trying to get you from point A to point B. Typically, if you don’t strain your hamstring in this instance, you might strain your hip, pelvic muscles and/or your low back because now they have to move too much to accommodate the lack of range of motion of the hamstring. To illustrate this point, repeat the last exercise and try swinging your leg forward as high as you can to see how high you can get your toes towards the ceiling. You will have to compensate by rounding out your pelvis and low back. Thus, marathoners will complain of hamstring tightness or strain towards the end of runs because muscles (including hamstrings) fatigue and the leg becomes straighter during the swing phase. Conversely, shorter distance runners complain of hamstring strains earlier in the run due to longer strides and decreased flexibility and an increase speed at which the knee swings forward. Dr. Jessica Greaux is a sports chiropractor and owner/founder of the sports medicine clinic, Innersport Chiropractic. Ltd. She created Innersport Chiropractic to assist athletes in doing the things they love. Dr. Greaux specializes in Active Release Techniques (ART®), Video Biomechanical Analysis, and Functional Exercise and Rehabilitation. She is starting a new business in Video Analysis called Press Play soon to launch February 2009. To contact Dr. Greaux, please email her at drjess@innersport.com or call 510-883-1126. Her website is www.innersport.com.
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