I have read that the stretch-shortening cycle is important to squatting, but what is it exactly and how is it trained?

The stretch-shortening cycle is defined as an eccentric-concentric coupling phenomenon in which the involved muscles are rapidly and forcibly lengthened, or stretch-loaded, and immediately shortened in a reactive or spring-like manner.

It consists of three phases: (1) the eccentric phase, or the negative portion of a lift, such as the descent in a squat, (2) a short pause between phases 1 and 2 called amortization, and (3) the concentric phase, in which the muscle produces the desired movement (the upward movement in the squat.)

In layman’s terms, your muscles and tendons can act like a rubber band in certain conditions. During the eccentric phase, elastic energy is increased and stored with a rapid stretch. A very short amortization phase leading to an immediate concentric phase will release this elastic energy, increasing the amount of force produced.

An important point to remember is that the stretch-shortening cycle is only activated in quick, explosive movements. You are losing valuable force potential with a slow descent and a pause at the bottom of the squat. As an example, perform a standing vertical leap and measure the height of the jump. Next, try an approach jump in which you take a few steps before you leap or a double jump in which you jump twice in rapid succession and measure the height of the second jump. Because of the eccentric stretch loading of the approach jump and the double jump, your vertical leap height will have increased from the static jump height.

There are two effective methods to improving your force generating capabilities. Plyometric training is used in many sports to increase starting strength and power. While not often utilized by powerlifters, we still may benefit from complex training, a system in which some plyometric training is incorporated with our training routine at periodized intervals.

A second method, which has become very popular in powerlifting, is the use of bands to increase the eccentric loading of a lift. Bands have actually been used to enhance speed, power, and strength in other sports such as swimming and sprinting. A recent study in the Journal of Strength and Conditioning Research using increased eccentric loading in the bench press shows promise that this method will increase maximal strength. While the methods used in this study may not be easy to duplicate in a normal gym setting and more research is needed to develop an optimal and user friendly training program, this study is also accompanied by anecdotal claims of the efficacy of band training, which cannot be discounted.