The hamstrings are a group of muscles which can be injured in all types of sports, and running is no exception. In fact, many runners have hamstring problems and often do not get proper care. Here is a summary of how the hamstrings function, how they get injured, and what to do to prevent and treat hamstring injury.
The hamstrings are actually two groups of muscles which run from the pelvis to the upper leg, on the back, or posterior side of the thigh. The inner, or medial group is made of two muscles, the semimembranosus and semitendinosis, and the outer, or lateral group is made up of one muscle, the biceps femoris. The biceps femoris actually has two parts, or “heads”, a long and a short, which can be seen anatomically as two separate muscles. Except for the short head of the lateral hamstring muscle, the hamstrings all originate at the ischial tuberosity of the pelvis, or sit bone. The short head originates at the lateral femur. The semimembranosus inserts, or ends, at the medial, (posterior) back side of the upper tibia, the semitendinosis at the medial, more anterior surface of the tibia, and the two parts of the biceps femoris insert at the lateral side of the fibula. Tendons attach the muscles to the bones, and can be injured as well.
The hamstrings help us move as in running and walking. Looking at them anatomically, they create this movement because they extend the hip and thigh, and they also help bend the lower leg on the upper leg. Throughout the stride they are either contracting or lengthening according to the changing positions of the hip and knee. This function is complex, but we can identify the stride postions that create the greatest risk of injury, as described in the next paragraph. Also, the hamstrings have a function when we are just standing still- they help us remain upright against gravity by exerting a backward pull on the pelvis. This is an ‘antigravity’ function, and is important for proper posture.
Most muscle injury such as in the hamstrings can be classified according to how it occurs, as either acute (sudden) or chronic (over time). The first type, an acute hamstring injury, can occur during the rapid stretching (lengthening) of the muscle, or during the rapid contraction (shortening) of the muscle. The part of the stride when rapid stretching occurs and injury is possible is when the leg swings foward near the end of the stride. During this time, we are flexing the thigh and simultaneously extending knee, stretching the hamstring from both ends, and tearing can occur. The part of the stride when rapid contraction occurs and injury is possible is during late push off. During this time, the hamstrings rapidly change from stabilizing the knee during the support (foot on the ground) phase to extending the hip as the knee flexes. The lateral hamstring is most likely injured at this time. In either case, as the injury occurs you feel immediate pain, usually described as a “pulled muscle”. The location of the tearing is usually high in the thigh, near the where the muscle meets the tendon, or slightly below, towards the middle of the muscle. The injured area will feel sore to the touch, and the torn fibers may present themselves as a lump of tissue. The area may or may not be swollen. The tears can be graded as mild (grade 1), moderate (grade2), or severe (grade 3) depending on the amount of tearing. Fortunately for distance runners, these sudden types of injury usually occur during sprinting sports which require sudden, explosive movements, such as football, baseball and the track and field sprints. One exception, however, is when a runner finishes a distance race with a sprint, which can suddenly overload the hamstrings, which are usually tight and fatigued by that time in a race. In that case the injury will resemble more of an acute tear.
The second type of injury, the chronic one, is the more common one for runners, especially in high mileage or older runners who have been running for years. The injury usually occurs more gradually. With distance running, slight muscle tightness in the back of the knee, where the hamstrings insert, may not cause pain. But when we use a muscle often over and over for an extended period, as in distance running, the individual fibers can start to get “stuck” to each other. Upon manual examination, painful “knots” or adhesions can be felt by hand. If not treated, they then can lead to shortening of the muscle lengthwise- muscle tightness. With this tightness in place, the muscle will not lengthen properly or contract as strongly when exercised. This can eventually cause pain when enough fibers become involved. In this situation the location of the tightness is usually very high or low in the muscle, or the tendon itself can have the scar tissue. This muscle fiber tightening usually occurs either over the course of one workout or over days or weeks. Examples of immediate causes are a longer run than you are used to, or a faster speed session. It is important to note that an area of chronic tightness and/or weakness is often more susceptible to also suffering an acute tear during an end of a race sprint as described above.
Before a diagnosis of chronic hamstring injury is reached, other conditions such as sciatic nerve irritation or a pelvis stress fracture should always be ruled out. However, two injuries can exist at once, and can be related, so the hamstrings should be checked anyway if the other pain sources are found.
There are several reasons the hamstings are injured in sports. First, there is muscle imbalance, meaning one muscle is stronger than its opposite functioning muscle. In this case, the quadriceps, which extend the knee and flex the hip, are the opposing muscle group to the hamstrings, which flex the knee and extend the hip as mentioned above. If the quadriceps are overly developed in comparison to the hamstrings, the hamstrings must work harder to pull against the quadriceps, and can strain or tear if they are not strong enough. This is often the case in sprinting injury. The other common imbalance is the hip flexors being tighter than the upper hamstrings and gluteus maximus, which are the hip extensors. This is more often the case in distance running. In this case the upper hamstring will have to contract harder and can gradually tighten or become strained.
The next predisposing factor is adhesion formation, in the hamstrings and also in related muscles. As noted above, the adhesions will cause tightness and pain, with the tightness leading to more pain and so on. If untreated, then with the decreased elasticity there is even less range of motion, and the uninjured fibers will have to work harder, causing them to tighten and form new adhesions. This makes the chronic injury more likely to keep occuring. Also, muscular adhesions in the related hip muscles (gluteals, piriformis) can refer pain to the hamstrings. This can cause a feeling of hamstring strain, when none is really present, or both the hamstrings and the hip muscles can have adhesions. Also, the sciatic nerve can be “caught up” in hamstring adhesions, or further up above in the hip muscles, and either problem can further tighten the hamstring or simulate the feeling of a strain.
The third factor is pelvic alignment problems. Many people have postural distortion in the form of a lumbar spine or pelvic rotation and tilting, which causes an apparent “short leg” as one side is higher or lower than the other. Everyday activities may or may not be painful, but when subjected to the repetitive stresses of training for a marathon, the result can be muscle injury. The hamstrings can be overstretched on one side in this case, often the “long”side, and the gradual or acute type of hamstring injury then can occur.
Treatment of hamstring injury will vary depending on the both the degree of injury and which of the above predisposing factors need to be addressed.
In acute injury, self-treatment will involve ice application, with a compression wrap and elevation, at least once a day. Ceasing running for at least 2 weeks even in a mild, grade 1 tear must be done as, training through the injury will not help, and recovery must come first. Cross-training with activities that keep the range of motion to the pain-free level can be done, such as the elliptical or stair machines. In grade two tears return to running may take up to 4 or 5 weeks, and in grade three 2 or 3 months. It is important to note that the amount of healing time can vary in different people. Soft-tissue manual therapy such as active release technique must be done to minimize scar tissue formation and adhesions, and can greatly speed up healing in all three grades of tears. If the adhesions are not broken up, then the tear will heal with less flexible tissue than normal, healthy tissue and re-injury or the chronic tightness will occur. In all cases, return to running should be gradual and include an extended warm-up period, and speed training should not be done until easy and mid-paced runs are completely pain-free. Third degree tears may require surgical intervention if the tendon is fully pulled off the hip bone. This is rare, but if it occurs immediate surgery is necessary for proper healing.
In the chronic injury, the tightness must be treated by removing/reducing the adhesions in the muscle or where the muscle meets the tendon. Again, manual therapy will release the adhesions. The related muscles, such as the gluteals, piriformis, and hip flexors and also the adductors and calf muscles also should be checked. This will remove the adhesions as a pre-