As he rounded the corner of the last 400 meters, Jim felt a sudden tightness followed by a wave of nauseating pain. He reflexively grabbed the back of his right thigh as he slowed to a contorted hobble. He could barely walk. He had been hamstrung by his hamstring.
Hamstring injuries are as common in sports as trucks are in Texas. Seems like everyone one you know has had one. And everyone you meet seems to have an opinion of what to do to heal the injury and prevent another one from happening. So, I thought I would give another perspective.
Most discussions of hamstring injuries center around the lengthening contraction that occurs as the muscle helps decelerate the lower leg during the swing phase of running and usually while running fast. The thinking is that the speed of the movement becomes too much for the poor old hamstring to keep up with so one day out of nowhere it fails. Apparently, it just can’t lengthen fast enough. We assume the hamstring fails because of its relative inflexibility and its inability to control the lower leg at high speeds. So we often stretch the hamstring, strengthen the hamstring, and train the hamstring only to find it keeps failing again and again. Researchers have even tried to correlate EMG data and time of maximum muscle activity with time of injury (Mann RA, Hagy JL: Running, jogging, and walking: a comparative electromyographic and biomechanical study, in Bateman JE, Trott AW (eds): The Foot and Ankle. New York City, Thieme-Stratton, 1980 ). The results have been conflicting and have led to the conclusion that there is probably a complex, poorly understood neuromuscular coordination pattern associated with hamstring injuries. So, that makes me wonder. Why do we focus on the movement of the lower leg? Doesn’t the hamstring connect at both the hip and the knee? Why are most injuries of the hamstring closer to the hip and not the knee? Why do we not consider the possibility that the hamstring is injured when your foot is on the ground rather than while swinging in the air? And, why do Olympic level athletes have such an injury? Are they not fit enough? Strong enough? Flexible enough? These are things rumbling around in my brain that wake me up too early in the morning.
The hamstring is one of the more schizophrenic muscles in the body. It serves four main functions during running including:
1. Flexing the knee (although not much as it doesn’t have to work very hard thanks to inertia – more on that later)
2. Slowing extension of the knee
3. Creating extension of the hip
4. Stabilizing the knee and hip upon contact with the ground.
When your foot hits the ground, the force absorbed through your leg, pelvis, and trunk is nearly four times your body weight. The hamstring slows the fall of your pelvis toward the ground and then as your body moves forward it begins to extend your hip. This
requires a shift from a lengthening to a shortening contraction in milliseconds and must be an exceptionally well timed event. This shift is referred to as coupling time. The shorter the time the greater the force. (Knowles, Denis, Training for Speed Strength
Modern Athlete & Coach Vol. 37, No. 2, pgs. 35-38, April 1999) During this shift is where I believe most hamstring injuries actually occur and it’s the swing phase when you discover them. Here’s why.
Imagine yourself standing out in your front yard and a friend is on the roof with a 50lb bag of dog food. He tells you to get ready. He is going to toss the bag to you and you are supposed to catch it. You immediately prepare yourself for the impact. You shift your body and the very thought of catching creates a motor output cascade in your brain. Your muscles begin to contract before the bag even leaves your friends’ hands. Now, imagine this same scenario but you are blindfolded. You have no idea when the bag will hit your outstretched arms. In which scenario will you more likely be injured? Most often, it is when you do not have time to prepare.
Optimal function of the hamstring requires time to prepare for impact. What gives the hamstring just the right amount of time is augmented by a primitive reflex – the Flexion Reflex. This reflex is activated by one thing: ankle dorsiflexion or lifting up of the toes and foot. When you lift your foot and toes up, you also stimulate flexion of your knee and hip. It’s just the way we are all wired. You are probably thinking so what?
Because dorsiflexion of the foot activates the Flexion Reflex, the hamstring doesn’t have to work as hard to flex the knee allowing it to spend more time preparing to control the hip and knee at impact. If the emphasis during running is placed on hip flexion, such as “lift your knees higher”, the foot tends to lag behind. Dorsiflexion is delayed causing the hamstring to be used more to assist knee flexion rather than allowing inertia to do most of the work thereby demanding energy from the hamstring and causing it to work longer than it should. Remember, we are talking about events that occur in milliseconds that generate huge amounts of force. A 2 or 3 millisecond delay can translate into a huge transference of unexpected force and the hamstring needs this recovery time.
So, how does this help runners? Remember that images and words in the brain create a motor cascade in advance of actual movement. If I want more speed and less hamstring injuries, I need my dorsiflexors to work for me. I have to think about pulling my foot up while I’m running. I may even have to say something like “lift foot” to aid the process.
The next time you see someone hamstrung with a hamstring injury just think about movement of the foot. Consider adding a word picture of lifting the foot to your regimen. Avoid getting hamstrung and give the hamstring a little more time to get ready.
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