Hamstring Strains in Endurance Runners
Hamstring strains are some of the most common soft tissue injuries in running sports1. For years, long distance runners seemed to avoid these types of injuries. Unfortunately, the frequency of hamstring injury is on the rise even among them. This article will discuss possible reasons for this increase in hamstring strains as well as things an athlete can do to prevent them from recurring.
If we break down the running mechanics for road or treadmill running we would see a fairly consistent stride frequency (cadence) and stride length (the distance each leg travels per stride). Many long distance running styles encourage a shorter stride length with a faster cadence. Though the medical literature varies in the definition of an ideal stride length, it can be safely said that athletes performing longer runs typically have shorter stride lengths compared to athletes performing shorter/faster runs.
Why the Increase in Hamstring Strains?
With the advent and adaptation of interval training for endurance runners, we began to see an increase in hamstring strains in our clinic. Much of this training involved high speed sprinting on a track. Speed work on a track or sprinting is more likely to cause injury because of the increased stride length and aggressive swing phase compared to the shorter, less aggressive, strides during distance training. This is one reason that hamstring strains are so common among track and field competitors and now among marathon runners who perform track work.
Hamstring Strain Classifications
Hamstring strains are categorized into three different grades based upon the physiology of the injury.
Grade 1 Strains: These strains result in a sharp pulling sensation in the hamstring. There may be soreness at the site of the pull, and there may be mild swelling but no bruising.
Grade 2 Strains: These strains are more severe and take longer to recover. A partial rupture of the muscle may occur at the site of the injury. Typically, however, there is very little to no bruising present.
Grade 3 Strains: These are the most severe type of strain. There will be significant swelling, and bruising, and a long recovery period.
Regardless of the grade of injury, all three types of strains may require many weeks or months to recover completely. Athletes often report feeling fine while walking or even with light stretching, but when they start to run, the pulling tightness returns. Another common complaint is that patients find it difficult to sit for long periods of time due to reproduction of pain in the hamstring. Stretching, massage, and strength training typically have very little success in improving symptoms and allowing the runner to return to training.
My years of treating endurance runners have shown that most have one thing in common—very poor leg flexibility. With a short stride length, hamstring flexibility is not as critical. In other words, when the hamstring is tight, it prevents the leg from swinging as far forward as it might otherwise. This is not necessarily a bad thing, because the short, tight muscles create a spring effect and help to transfer the energy that is created when the foot strikes the ground into a propulsive force that pushes the limb forward. Without tension in the fascia and muscles, the spring effect is virtually non existent. Hyper-flexible athletes, some yoga practitioners for example, will waste a lot of extra energy contracting the muscles to help propel them forward.
Although the ideal stride length is ambiguous, most studies agree that there is an optimal flexibility of the lower limb for runners. Optimal flexibility is obtained if the athlete can lie on their back, and with a straight leg, raise it to 80-90 degrees without the knee bending. Without this degree of flexibility, the stride will be altered, leading to compensation and increased risk of injury.
If an athlete is not able to achieve this optimal level, foam rolling or using a stick on the calves and hamstrings can sometimes help improve leg flexibility. The ideal time to do these types of stretches is immediately after a workout. The muscles will be warmed up, engorged with blood, and will respond nicely to these forms of stretching.
New Approach to Hamstrings Therapy Yields Encouraging Results
However, the lack of a clear and consistently successful treatment for hamstring strains once they occur led us to consider other possible ways to treat these injuries. Through many hours of research and clinical application, we have developed a more successful method of dealing with these types of injuries. This treatment decreases recovery times and allows the athlete to return to a more normal training routine in a shorter time frame.
Our treatment considers a component of the injury that most practitioners fail to take into account during the rehab process. This factor is the presence of adhesions that form around the sciatic nerve. When these types of adhesions are addressed, the outcomes improve dramatically.
During the recovery from a hamstring strain, rest and immobilization is required in order to allow the muscle to heal. But immobilization in conjunction with compression (such as when sitting) is also a recipe for adhesions to develop along the path of the nerve.
The reason these adhesions play such a role is best understood when considering the function of the leg while running. During the swing phase of running, the sciatic nerve needs to slide through a tunnel of tissue called a fascial sleeve. There is an essential gliding and sliding that occurs as the nerve moves freely within the muscles and fascia. The sciatic nerve can travel close to 5cm in relation to the surrounding muscles during a straight leg raise to 90 degrees. If an adhesion develops between the nerve and the surrounding tissue, the nerve will get restricted or pulled. This causes a shortening of the surrounding hamstring muscle as the body attempts to protect the nerve. It is this phenomenon that I believe to be one of the most crucial components of hamstring strains.
After an initial period of rest these adhesions negatively impact recovery. When the athlete returns to running, the pain often returns. At foot strike, a healthy hamstring muscle is loaded up to 30% of its maximum load. But when adhesions are present, the irritated sciatic nerve will cause a reflexive contraction of the muscle which can result in an even greater load to the hamstring, aggravating the injured muscle and recreating the original pain. This can occur in even the most flexible runners.
However, by identifying and treating the adhesions that develop along the nerve bed, a skilled practitioner can quickly resolve many of the factors involved with chronic hamstring strains.
Once the adhesions have been released in our office, patients are given specific home exercises called “nerve flossing,” which will continue to help the gliding movement of the nerve within the muscle in relation to the surrounding muscles. Our experience has shown that restoring the mobility of the sciatic nerve will speed recovery and minimize the risk of future injuries.
Dr. Niklaus DelFavero is the owner of 1st Choice Sports Rehab Center in Decatur and Johns Creek, Georgia. His original research on this topic entitled, Sciatic Nerve Tension and Its Impact on Hamstrings Strain, was accepted for presentation at the 2015 FICS symposium, hosted this year by the Hellenic Chiropractic Sports Council in Athens, Greece. For more information or to schedule an evaluation by Dr. DelFavero, please call 404-377-0011.
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