The etiology of hamstring injury fall into two categories. The sprinting type injury and the stretching type injury. Hamstring injuries affect a wide variety of sports from track & field to soccer, rugby, GAA, gymnasts, and martial arts. Despite recent research into rehabilitation, recurrence and time to return to play, injury recurrence is high.
It is thought that the injury mechanism resulting from sprinting is caused by overload of the biceps femoris and semitendonis intramuscular tendon while decelerating, during the terminal swing phase of the gait cycle. Injuries affecting dancers and gymnasts, result in the proximal free tendon(semimembranous) being put in a position of extreme stretch. This can occur at fast or slow movements that involve simulatenous hip flexion and knee extension.
Risk factors for injury identified in the research relate to age, previous hamstring injury, hamstring weakness, fatigue, lack of flexibility, strength imbalance between hamstrings and quadriceps. Sherry & Best, (2004), found strength and coordination deficits of the pelvic and trunk muscles to be another possible risk factor for injury.
From current research, Heiderscheit et al, (2010), found that the type of injury and proximity of point of maximum pain to ischial tuberosity (sit bone), are predictive of time to return to play. Therefore someone with a stretching type injury typically disrupts the semimembranous proximal tendon and the injury is relativly closer to the ischial tuberosity, than a sprinting type injury, which disrupts the biceps femoris and semitendinous intramuscular tendon.
Regardless of the type of injury, current Physical Therapy rehabilitation protocols manage hamstring injury in the same manner. This is despite the difference in tissue damage, site of injury and mechanism of injury.
In a recent randomised controlled trial with 75 swedish football players, Carl Askling compared two rehabilitation protocols, L-protocol and C-protocol. The L-protocol was specifically aimed at loading the hamstrings during lengthening/eccentric actions. The C-protocol used conventional hamstring exercises with less emphasis on lenthening. Each rehabilitation protocol consisted of three exercises. 1) based on increasing flexability, 2) based on strength and trunk/pelvis stabilisation and 3) a more specific strength exercise. The results showed time to return to sport was significantly shorter for the L-protocol with a mean of 28 days compared to a mean of 51 days in the C-protocol. It was also noted that stretching type hamstring injuries showed longer recovery times than sprinting type hamstring injuries. The L-protocol was significantly more effective than the C-protocol irrespective of injury type.
The L-protoc0l Exercises
Exercise 1):The Extender
From a lying position, hold and stabilise thigh of injured leg with hip flexed to 90 degrees. Perform slow knee extensions to just before the point of pain. Recommendation; twice a day, three sets with twelve repetitions.
Exercise 2):The Diver
Performed from an upright position standing on injured leg, arms stretch out infront simulating a dive while uninjured leg extends behind the body. Knee flexion should be kept at 20 degrees for injured leg and 90 degrees for uninjured leg. Exercise should be performed slowly in the beginning. Recommendation; every second day, three sets with six repetitions.
Exercise 3):The Glider
The Physical Therapy exercise started with an upright trunk, legs slightly split, weight on heel of injured leg (front leg) and 10-20 degrees of knee flexion. Glide back with the other leg to just before point of pain. Reset position by using both arms, not injured leg. Recommendation; every third day, three sets with four repetitions.
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Askling C, Tengvar M, Saartok T et al. (2008). Proximal Hamstring Strains of Stretching type in different sports. Injury situations, clinical and magnetic resonance characteristics and return to sport. American Journal of Sports Medicine, 36: 1799-1804.
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Heiderscheidt BC, Sherry MA, Slider A, et al. (2010). Hamstring StrainInjuries: Recommendations for Diagnosis, rehabilitation, and Injury Prevention. Journal of Ortopaedic Sports Physical Therapy, 40: 67-81
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