A muscle strain, also called a pulled muscle, is an injury to the muscle or to the tendon (the fibrous tissue that connects the muscle to the bone). The injury can be a minor overstretching of either the muscle or the tendon, or both. However, in more severe cases, it can be a partial or complete tear in the muscle or tendon.
A muscle strain is different from a sprain. Whereas a muscle strain is an injury to the muscle or tendon, a sprain is an injury to the ligament (the fibrous tissue that connects bone to bone).
Muscle strains can happen to anyone, not just to athletes. While some people may think it takes exercise or sports to get a muscle strain, the nature of the activity is not really the only risk factor for getting a muscle strain. Even daily routine activities, when done with improper technique or muscle condition, can result in muscle strains.