by Steven T. Gaines, M.D.

Athletes of all levels train to varying degrees of intensity according to their respective aspirations and athletic goals. Each has the ability to reach and reveal the potential their bodies hold. But despite preparation for participation in sports, athletes are faced with the unwanted generation of injury. The hamstring strain is one injury that can be quite dramatic in its adverse effects to the athlete.

Anatomy of the Hamstring

Anatomically, the hamstring muscle group consists of three muscles: the biceps femoris, the semimembranosus, and the semitendinosus. All three originate from the lower part of the pelvis, or the ischial tuberosity, traverse the back of the thigh, and attach around the knee on the proximal tibia and fibula. Their complex attachments around the knee help provide stability to the knee while providing the power to both flex the knee and resist extension of the knee (as in swing through phase of gait).

The hamstring muscles are composed of a preponderance of Type II (or fast twitch) muscle fibers that provide power as opposed to Type I fibers which are slow-twitch and provide more endurance. This is important for the hamstring muscles since they provide the strength and speed necessary to function adequately in running (especially sprinting), cutting and kicking sports.

Development of Hamstring Injury

The hamstring injury is simply an overload on an over-stretched muscle. The hamstrings contract during the mid-swing phase of gait to control momentum as the leg swings forward in the stride. In a runner, this provides the "perfect storm" for the hamstring injury as they are being lengthened maximally while suddenly, eccentrically contracting to slow the forward momentum of the leg down for heel strike. The injury occurs in both early stages (secondary to inadequate warm-up and stretching) and late stages (secondary to fatigue) of participation. Not only is this injury seen in athletes participating in running, jumping or kicking sports, but is also seen in water skiing, weight lifting, dancing and ice-skating.

Hamstring injuries are classified as Grades I, II or III with the simplest and least damaging being the Grade I in which the muscle is overstretched leading to less than 5 percent of the muscle being injured. A Grade II injury is moderate in severity and results in a partial tear of the musculotendinous unit. The Grade III injury is a complete tear of the muscle and is the least common, and includes the complete avulsions both proximally and distally.

Treatment Options

Treatment is generally non-operative, with surgery being required only on rare occasions. The injury requires prompt evaluation by a physician. Acute injuries are typically addressed initially with rest, ice, compression and elevation (RICE). Other adjuncts to treatment include NSAID's, crutches and physical therapy. The expertise of an athletic trainer or physical therapist can be vital to the successful rehabilitation of the hamstring injury. Extreme care must be taken to avoid further injury to the muscles during the healing process to minimize risk of chronic problems. Therapeutic modalities include electrical stimulation, massage, isometric exercises, isotonic exercises and isokinetic exercises, with early avoidance of eccentric exercises that produce too much tension on the injured muscle fibers.

As full recovery can take as much as one year or more before return to full participation, prevention becomes extremely important for the athlete. Factors that predispose one to this injury include previous hamstring injury, poor flexibility and muscle imbalance. An imbalance of strength between the quadriceps and hamstrings must be avoided as this can predispose the athlete to future injury (the hamstring muscles are roughly 60 percent as strong as the quadriceps muscles). Differences in strength of greater than 10 percent between the hamstring muscles of the two legs can likewise predispose to injury. Furthermore, the older athlete is more prone to muscle strain. The fatigued athlete, regardless of age, is likewise more susceptible to this injury. Therefore, prevention is directed at improving flexibility, maintaining appropriate strength and balance of quads and hamstring strength, and good overall conditioning (endurance).

Summary

In summary, hamstring injuries occur in both young and old athletes who participate in running, jumping or kicking sports. The injury can be quite damaging in its severest form necessitating considerable efforts at rehabilitation over many months. Any degree of injury requires appropriate attention for early "damage control" with RICE modalities, followed by gradual therapeutic efforts at improving flexibility, strength and endurance. Sport specific rehabilitation facilitates the athlete's return to play while minimizing their risk of re-injury. Professional guidance during one's rehabilitation from a hamstring injury provides the safest and quickest means to get the athlete back in action in his or her preferred sport.

Signs and Symptoms
* Pain
* Swelling
* Bruising
* A pop or tear during injury
* Difficulty bending knee
* Loss of strength in hamstring muscles, making it difficult or impossible to move leg

Signs or symptoms of a hamstring injury may or may not show up immediately following the injury. Signs of a mild hamstring injury may be felt only when you are resting after an activity. It is important to promptly schedule an appointment with your physician following injury.