The hamstrings are not one muscle, but actually a group of three muscles that run down the back of your leg from the pelvis to the lower leg bones making up the bulk in back of your thigh. Your hamstrings function to extend the hip and flex the knee joints. The three muscles that make up the hamstrings are the biceps femoris, semi-tendinosus and semi-membranosus.
A hamstring pull is a muscle strain where muscle fibers are torn either partially or completely. If you have a hamstring injury you are likely to know it right away. A sudden, sharp pain in the back of the thigh could be your first indicator. After which it will be hard to straighten your leg out all of the way without pain. CT scans and MRI may be used to define the more serious injuries.
Hamstring injuries happen when the muscles are stretched too far causing tearing of the muscle fibers. Sudden sprints or other fast or twisting motions with your legs (e.g. soccer, running, jumping, basketball) are the major causes of hamstring injuries. The primary risk factors for injury include:
- Age: As you age, your muscles loose flexibility, making it easier to suffer from a hamstring injury.
- Fitness Level/Flexibility: Your fitness level is based on strength, endurance and flexibility. The less flexible you are, the more likely you are to pull a muscle and depending on what activity you are participating in, the more likely that muscle will be your hamstring.
- Strength Imbalances: The muscle strength and flexibility imbalance, specifically between the quadriceps and hamstring muscle groups can lead to hamstring injuries. The hamstring muscles of one leg may be much stronger than the other leg, or the quadriceps muscles may overpower the hamstrings leading to injury.
- Fatigue: When you’ve done too much, too soon or have pushed yourself beyond your limits you lose coordination between muscle groups. This lack of coordination can easily result in a pulled muscle.
- Improper Warm Up: Muscle fatigue and not warming up properly can contribute to hamstring injuries.