Hamstring muscle strains often occur when the muscle lengthens as it contracts, or shortens. This does sound confusing and contradictory, but muscle strain takes place as you extend a muscle while it is weighted, or loaded. This is called an "eccentric contraction."
A number of factors increase the risk of sustaining a muscle strain. These include:
1. Muscle tightness: tight muscles are vulnerable to strain. This is why a daily stretching routine is necessary for performance athletes.
3. Muscle imbalance: in the scenario where one muscle group is much stronger than its opposing muscle group, this imbalance can result in muscle strain. This is commonly the case with the hamstring muscles, because the quadriceps muscles (the muscle of the anterior thigh) happen to be frequently stronger. As a result, and while engaging in physical activities that require your body to move at a high velocity, the hamstring muscles may become fatigued more easily than the quadriceps. This fatigue can lead to a strain.
4. Muscle fatigue: when a muscle is fatigued, its ability to use energy decreases, rendering this muscle at a higher risk of injury.
5. Type of activity: the physical activities that are most likely to be associated with hamstring strain are:
· Running or sprinting
Most hamstring strains heal very well with conservative treatment. In your case, and I suspect the injury has occurred a while back, whatever the activity has caused and is still causing injury to your hamstring must be temporarily discontinued to allow for the muscle to heal properly. Oral non steroidal anti inflammatory drugs (NSAIDs) for a few days are also needed along with rest – they will not be beneficial if you continue to put load on your affected leg. Should these measures prove ineffective in producing improvement of symptoms, have a doctor examine your leg.