The hamstring muscles are very susceptible to tears, strains and other common sporting injuries. Those athletes particularly vulnerable are competitors involved in sports which require a high degree of speed, power and agility. Sports such as Track & Field (especially the sprinting events), rugby, soccer, basketball and tennis have high rates.
How is the Hamstring Strained?
During sprinting the hamstring muscles work extremely hard to decelerate the tibia (shin bone) as it swings out. It is in this phase just before the foot strikes the ground that the hamstrings, become injured as the muscles are maximally activated and are approaching their maximum length. A pulled hamstring rarely manifests as a result of contact -if you have taken an impact to the back of the leg it should be treated as a contusion until found to be otherwise.
Dynamic Stretching. This involves gentle swings of the leg forwards and backwards gradually getting higher and higher each time. Around 10 to 15 swings on each leg should be enough. The stretches can be done early in the morning (be careful not to force it) as this will set the length of muscle spindle for the rest of the day. Do not attempt this type of stretching in the early stages of rehabilitation, or if it is painful. It works by using the properties of muscle spindles. A muscle spindle is a sensor in a muscle that senses amount of stretch and speed of stretch. By gradually taking the leg higher and higher the muscle spindle allows it to go safely and lengthen the muscle. If the muscle is forced then a stretch reflex is initiated which causes a reflex contraction (shortening) of the muscle. This is called ballistic stretching and can damage muscles. Dynamic stretching is particularly important when returning back to full fitness, especially when speed work is involved. Muscles need to be able to move throughout their full range of motion at speed - not just when stationary.