Who hasn’t pulled a hammy?
It seems like the right thing to do—stretch that hamstring after thinking you may have pulled it. Go on-line and many resources cite hamstring inflexibility as a potential cause of hamstring strains. Beware–there is little evidence to support this theory. In fact, excessive stretching can often cause a hamstring injury versus alleviating or helping one especially during the initial days of injury.
Anatomy & Function:
The hamstring muscles run down the back of the thigh. There are three hamstring muscles:
- Biceps femoris
All three start at the bottom of the pelvis at a place called the ischial tuberosity. They cross the knee joint and end at the lower leg-past the knee. The hamstring muscle group helps you extend your leg straight back and bend your knee.
The fact that they all have different functions simply means they are injured through different biomechanical mechanisms. For example, the semimembranosus is more likely to be strained with activities that stretch the hamstring through extreme ranges of motion. (fast or slow side split/front leg split). Heed caution all of you ballerinas, gymnasts, martial artists, and yoga enthusiasts. Even a slow movement like this can overstretch and possibly tear the semimembranosus. Often the tendon is injured (tendons attach muscle to bone) which can create a longer recovery time.
The biceps femoris muscle (long head) also tends to get injured in runners because of its longer lever arm and attachment. This is most used during deceleration of knee extension and if often injured just before heel strike.
According to Askling (1), the severity of hamstring injury and rehabilitation time is directly related to how close the injury is to the pelvic attachment. (Ishial tuberosity). That is to say, if the injury lies in the tendon attachment—it is more difficult it is to treat.
Some modifiable risk factors include quadriceps-hamstring imbalance, muscle stiffness due to inadequate recovery, prior injury, warm-up, nutrition, poor lumbopelvic strength and stability, an increased lumbar curve (hyperlordotic lumbar spine) and an anteriorly presented pelvis.
As with most injuries, the single best predictor of a future injury is a prior injury. In particular according to Michaud (2), there is an extremely high rate of re-occurrence with bicep femoris strains, therefore the treatment plan should be extremely comprehensive. In a study by Askling et al which examined hamstring injuries in different in all kinds of athletes, the only running related hamstring strain that was reported occurred while the athlete was stretching before participating in the event. It was confirmed that both the semimembranosus and long head of the bicep femoris was torn.
1. Askling C, Tengvar M, Saartok T, Thorstensson. Proximal hamstring strains of stretching in different sports. Injury situations, clinical and magnetic resonance imaging characteristics, and return to sport. AM J Sports Med, 2008; 36:1799
2.Michaud, T. Conservative Management of Hamstring Strains, Part 1. Dynamic Chiropractic 2012; 11:24, 37