The hamstring is the large group of three muscles that run down the back of the leg from the ischium (the part of the pelvis you sit on) to the lower leg bones (tibia and fibula). Injury to the hamstrings can range from minor strains to total rupture of the muscle.

Signs and Symptoms

Hamstring injuries usually occur at the end of the swing phase of the runner's gait as the leg swings forward and the shin extends. The hamstring acts to stop the forward motion of the thigh and to bring the leg down. A sudden, sharp pain in the back of the thigh that stops you in mid-stride, is probably a hamstring injury. At the time of injury, it may feel as if it snapped. Sharp pain and swelling can be accompanied by severe bruising. The knee of the injured leg may not extend more than 30 to 40 degrees short of straight without intense pain.

Causes

Flexibility: To test your hamstring flexibility, lie down with your back on the floor and your legs extending up a wall. Push your buttocks as close to the wall as possible while keeping your legs straight. If you cannot bring your buttocks closer than eight inches from the wall, you need to improve your hamstring flexibility.

Strength: A weak hamstring can have insufficient strength to control the force of the swing and foot plant. Eccentric strength or the lengthening force of the muscle is very important in preventing injury. This is the power needed to stop the forward motion of the thigh in a running stride. Often injury occurs in the transition between concentric and eccentric forces. Include concentric strengthening as well. The "good morning exercise" or modified deadlift works the hamstring muscles both eccentrically and concentrically and is also an excellent stretch for the hamstrings.

Muscle Imbalance: If the quadriceps dominates the hamstring, as they do for almost all athletes, then the hamstrings can be prone to injury. Normally, quadriceps and hamstrings power is related three to two. In sprinters the quadriceps can be even more dominant-three or four to one.

Biomechanical problems: Sometimes subtle biomechanical flaws can predispose the hamstrings to injury.

Fatigue: An exhausted muscle from over-training or over- exertion is easily damaged.

Posture: Excessive lordosis (arched back) tilts the pelvis forward and can add stress to the hamstrings. Hypolordosis (flattened back) excessively shortens the hamstrings.

Leg Length Differences: The shorter leg can develop overly tight hamstrings that can be overtaxed by the 25% lengthening that occur during the swing phase.

Warm-up: Insufficient warm up and stretching before intense exertion can result in injury to this muscle.

Previous Hamstring Injury: A previous hamstring injury can seriously predispose the muscle to re-injury. This can be a very frustrating injury to rehabilitate because of how vulnerable the hamstring is to re-injury.

RX Measures

During the acute phase of injury rest your hamstrings, usually for at least two to three weeks. Severe injuries may require a longer rest and crutches in order to prevent muscle stress.

RICE--Rest, apply Ice and Compression. Elevate the leg if possible.

Aspirin or anti-inflammatory medications can help relieve pain and swelling but may repress clotting of torn and bleeding tissues and vessels. Therefore, avoid NSAID's (non-steroidal anti-inflammatory drugs, like ibuprofen) during the first 24 to 48 hours after the injury. There is also evidence that NSAID's can delay the return of muscle strength.

A stretching program should be started as soon as the initial, severe pain and swelling subsides.

A strengthening program should be used to rebuild the strength of the injured muscle in order to prevent re-injury. Strengthening should focus on both the eccentric forces (lengthening of the muscle), and the concentric forces (shortening of the muscle).

Ultrasound therapy is sometimes helpful.

A thigh wrap can be applied to provide support as the muscle heals.

Alternative therapies include Arnica Montana to reduce inflammation.

To Avoid Future Problems

Hamstring pulls are probably the most common muscle injury to runners. Hamstring muscles are extremely prone to re-injury. To prevent pulls, maintain flexibility and strength in the hamstring. It is essential that strength and flexibility be developed. This is probably the most important muscle for runners to warm-up and stretch before a workout. Stretching after the workout should not be neglected. The key is to analyze the possible training error and to correct it. Possibilities include too much too soon, too much competition, hills, underlying illness or fluid intake error.

Related Conditions: Sciatica, piriformis syndrome, spinal disk compression, stress fracture.

Cross Training: Swimming or stationary bicycling, if they can be done without pain.

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