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Eccentric Muscle Contraction: The Rock-Solid Core of Pilates

Pilates aims to build muscle strength and definition without unnecessary bulk. Stretch your mind around Groupon's study of eccentric muscle contractions to understand one of its major tools.

Anatomists identify three types of muscle contraction: concentric, eccentric, and isometric. Isometric contraction occurs when a muscle resists a force without moving or changing its length. Concentric contraction can be exemplified by a set of rapid crunches: the ab muscles repeatedly shorten during the emphasized upward movement, and often don't revert fully to their relaxed state until the set is complete or the gym teacher looks the other way. Eccentric contraction, on the other hand, is what happens when the muscles resist a force as they lengthen—as they do in the Pilates version of a crunch, the roll down.

To build any muscle, you need to do some controlled damage to its fibers, prompting the body to generate new muscle cells to make repairs. And eccentric muscle contractions are especially good at doing this. Pilates, like almost any form of exercise, involves all three types of contractions, but in characteristic movements such as the roll down the emphasis is on the downward movement. Students carefully control their abs and resist their own body weight as they slowly relax back onto the floor, challenging the muscles in their elongated state.

Eccentric exercises force muscles to work harder than they would in a concentric state—which is why, to a Pilates instructor, 5 slow, perfectly-controlled roll-downs are more productive than a quick set of 50 crunches. This phenomenon explains why beginning Pilates students can experience muscle soreness the day after a deceptively easy workout. Besides trying to prevent addiction to IcyHot, Pilates instructors limit rep quantities because muscles tend to revert into concentric contraction as they tire, which can counteract any gains in flexibility.