Unlike many names given to the parts of the anatomy whose origins are rooted in Latin or Greek, the term "hamstring" derived from the old English word hamm, meaning the thigh. The hamstrings are frequently injured while an athlete executes a sudden, explosive movement, sometimes accompanied by a change of direction. When the hamstring is injured in this fashion, the athlete will feel an immediate sensation of pain, often accompanied by a "popping" sensation. In a more severe case, bruising will appear in the vicinity of the injury. In these circumstances, the hamstring structure cannot withstand the forces applied to it and an immediate and often debilitating injury is sustained.
The hamstrings are two separate tissues, commonly regarded as a single connected structure. The hamstrings are the prominent tendons located behind each knee; they attach to the second portion, the powerful hamstring muscles, technically known as the posterior thigh muscles. The hamstring muscles have three components: the semimembranosis, the semitendonosis, and the biceps femoris. The hamstring tendons connect these large muscles, which begin at the buttocks, to the bones of the lower leg, the tibia, and the fibula.
Functioning as a unit, the hamstrings are responsible for both the flexing and extending of the knee joint, as well as the extending of the hip through the movement of the thigh in a reverse direction. The hamstrings are of supreme importance in sports that require a powerful thrust, such as sprinting and jumping. Elite and recreational athletes alike will spend considerable effort in training to develop hamstring strength, through training devices such as plyometrics drills and interval sprints.
Hamstring injuries result from direct stresses applied to the tendon; the hamstring may also contribute to serious injuries that occur in related mus-culoskeletal components. Injuries to the hamstring muscles can be grouped into the following categories: hamstring pulls, bruises, structural imbalance injuries, and illio-tibial band injuries.
Hamstring pulls include all types of muscle tears and strains. Pulls or strains are a form of muscle or tendon damage that results from the overstretching of the tissue fibers; the stretching often results in tears of varying sizes and disabling effect. These injuries are classed by severity from Grade 1 strains, as a slight strain that might not necessarily prevent an athlete from continuing in an event, to Grade 3
Bruising is a common hamstring injury. The large hamstring muscles are vulnerable to bruising as a result of a direct blow, as may be sustained in sports such as rugby, American football, or ice hockey. Given the size of these muscles, bruising can significantly interfere with the contraction of the muscle fibers. Hamstring bruises will frequently impair muscle function and cause significant discomfort to the subject.
Structural imbalances are an often subtle but profound cause of hamstring injury. Where there is an imbalance in the relative strength of the hamstring structure and the quadriceps, located at the front of the thigh, this circumstance may cause misalignment resulting from the position of the knee in relation to both sets of thigh muscles. It is believed that this imbalance is a contributing factor in the cause of anterior cruciate ligament (ACL) injuries, especially where the ACL tear arises without external force being applied to the knee.
The illio-tibial (IT) band is the strong connective tissue that runs from the knee joint to the hip, providing support and stability to both the quadriceps and the hamstrings, which can become overly rigid if it is not properly stretched, creating further leg alignment problems. The IT band will be made correspondingly tighter when the hamstring or the quadriceps becomes highly developed.
In the event of a hamstring injury, the first medical attention to be directed to the injury should be a variation of the RICE (rest/ice/compression/elevation) principle. The greater speed with which such steps are taken with respect to the injured hamstring, the less likelihood the athlete will experience a buildup of scar tissue in the muscle or the tendon, a significant factor in the reduction of an athlete's ability to fully stretch the hamstring in the future. Most hamstring pulls and tears will heal with rest and appropriate treatment, including the use of an anti-inflammatory. Only in the most severe circumstances, a complete rupture of the tissue, will surgical intervention be required.
An important preventative measure in the reduction of hamstring injuries are concerted stretching programs. Careful attention to joint flexibility is of prime importance in the prevention of hamstring injuries. Focused warm-up and cool-down stretches assist in protecting the hamstring. Research into the cause of imbalance-related hamstring injuries suggest that the hamstring tendons and muscles should be approximately 50-60% as strong as the quadriceps muscles. Sports such as sprinting will naturally lead to an imbalance between these two components. In such circumstances the athlete will utilize different forms of weight training, including plyometrics, to improve hamstring strength relative to the quadriceps.