This is an excerpt from Stronger Legs & Lower Body by Tim Bishop.
The hamstring muscles—the semitendinosus, the semimembranosus, and the biceps femoris—are located on the posterior thigh. They are responsible for bending and flexing the knee, and they also assist with hip extension. The hamstring group is often overlooked and undertrained. When people think about developing bigger and stronger legs, they usually think about the quads first. The hamstrings are hard to see, which leads to an “out of sight, out of mind” effect. But the quads are naturally stronger than the hamstrings because of their size and weight-bearing responsibility, so it is important to train the hamstrings as much or even more than the quads. A lack of strength in the hamstrings compared with the strength in the quads not only can create a cosmetic and functional imbalance, but it can also result in an unstable knee joint and assorted lower-body injuries.
The term posterior chain refers to the series of muscles that include the low back, the glutes, the hamstrings, and even the calf muscles. Posterior chain exercises involve most, if not all, of these muscles in a chainlike manner. Athletes in sports that involve swinging, throwing, and lifting know that generating power in one area is not enough; the muscles must be strong enough to transfer it along the chain.
Posterior chain exercises also contribute to a strong core. A common assumption is that the term core applies only to the abdominal muscles, but the low back, glutes, and even the top of the hamstrings are all part of the core as well. This back side of the core must also be developed and maintained.
Strong and flexible hamstrings and posterior chain muscles are an important part of an injury-prevention strategy. The low back is one of the most commonly injured areas, often leading to lost work hours and high medical expenses. And in the world of sports, athletes are routinely sidelined by hamstring injuries. Performing hamstring and posterior chain exercises can help you avoid becoming one of these statistics.
As with the quads and glutes, you can train the hamstring group and the posterior chain muscles by using compound movements such as deadlifts or isolation movements such as leg curls. You will see the best strength gains in this region of the body from using a combination of compound and isolation exercises.
Read more from Stronger Legs & Lower Body by Tim Bishop.