Anatomy
The hamstring is made up of four muscles that are in the posterior part of the thigh: long and short heads of the bicep femoris, semimembranosus and semitendinosus. Because all the muscles (except the short head of the bicep femoris) attach to the ischial tuberosity (origin) and the tibia and fibula of the lower leg (insertion), they affect all movement patterns above and below their attachments.
Functions
Muscle contraction works in three ways: concentric, eccentric and isometric. Concentric contraction is where the muscles generate force to shorten the muscle fibers. This type of work goes against gravity or the direction of resistance. In an eccentric contraction, muscle fibers elongate under tension to decelerate the opposite force, controlling the direction of the pull (gravity or resistance). Isometric contraction is simply no movement being made while the muscles are under tension.
The hamstring helps to concentrically flex the knee joint and to eccentrically extend the knee. An example of the latter movement is lunging, where your body is decelerating as you go toward the ground. Also, the hamstring assists in hip extension, commonly used during running, walking, stair climbing and gymnastics.
Training Misconception
Isolated exercises to train the hamstring, like the hamstring curl machine, are a common sight at the gym. Unless your goal is to increase the size of the muscle group, this is not the best way to train the hamstring―or any body part. In fact, consider your hamstring as a part of a movement system, like a cello player in an orchestra. Exercises like squats, lunges, jumps and kicks train the entire lower body, which includes the hamstrings. A holistic training approach will improve your performance, save time and reduce the risk of injury.
Application
1. Lunge matrix: Lunging in different directions is a useful exercise to train your body to decelerate and accelerate back to an upright position. The hamstrings and other lower-body parts are trained to move in different directions and at different stress levels and speeds.
2. Box jumps: This drill requires dynamic stability and balance of the entire body, particularly in the pelvis, spine and legs. When you land, every muscle in your lower body (including hamstrings) is working to decelerate your momentum and absorb the shock of the landing.
3. Leg curls on ball: This exercise works both concentric and eccentric strength of the hamstrings and stability of the pelvis. Because this method requires your whole body to work together, this is a better choice than the leg curl machine―especially for those who want to reduce size, not gain.
References
- Athletic Development: The Art & Science of Functional Sports Conditioning; Vern Gambetta; 2006
- National Academy of Sports Medicine; Integrated Flexibility Specialist; Michael Clark; 2003
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