I am going to let you in on one of the big keys to Pilates exercise: the eccentric contraction. In Pilates we use all three kinds of muscle contractions: eccentric, concentric, and isometric where the muscle is held in a static contraction. But in Pilates, there is more emphasis on the eccentric contraction than one finds in most exercise systems. It is the eccentric contraction that accounts for the long, strong muscles Pilates is known for.
In an eccentric contraction a muscle lengthens as it resists a force. Contrast that image with what we usually think of as a muscle contraction, the concentric contraction, where a muscle shortens as it overcomes a weight or force. It is shortening muscle that gives a more contracted or bulky look to the muscles.
Pilates uses resistance to the springs on the large equipment like the reformer, chair, or tower; resistance to gravity; and resistance to the spring-like action of small equipment like the magic circle or exercise band to train the muscles in eccentric contraction.
Let's look at some examples of eccentric contractions from the Pilates mat exercises. On the mat it is mainly resistance to gravity that creates eccentric contractions. Examples would be the roll down part of the roll up or roll over, where we intentionally control the roll down, lengthening the torso against the pull of gravity. Another example from the mat work would be the challenge to the chest and biceps in the slow, controlled downward moving part of the push up.
When you resist the springs on Pilates apparatus, or use the magic circle or exercise band, the lengthening contraction often happens when you resist what you might think of as the return portion of the exercise. For example, with the magic circle, you squeeze it which is usually a concentric contraction; but then you control the release which becomes a muscle lengthening eccentric contraction. Or, think of the exercise band. If you stand on it to fix the middle, and pull the two ends up, that part is a concentric contraction for the biceps. When you resist the pull of the band as you let it down slowly, that is the eccentric contraction for the bicep.
It is the eccentric contraction that puts the strength in our length. What I mean is that eccentric contractions are very challenging for the muscles. They do a good job of stressing the muscles. Being stressed, and then rebuilding stronger, is how muscles build strength.
Eccentric contractions are the subject of a lot of study because it is thought that muscle strengthening might be greatest with exercises that include eccentric contraction . Because of the higher level of tensile stress that eccentric contractions create, eccentric contractions are associated with muscle soreness, and injuries like strains and tears. However, this is rarely an issue in Pilates where control is emphasized, and we don't overload the muscles.
Finally, no discussion of Pilates and the eccentric contraction would be complete without mentioning the role of the mind, and intention, in Pilates exercise. In Pilates, we actively intend length in our movement. Of course we set the stage for that with the right exercise instructions, alignment, and equipment. But ultimately Pilates moves are meant to be practiced with an attentive mind. When the mind is focused on length, all the subtle core moves that help create successful, and careful, eccentric contractions can take place.
Types of Contractions, Muscle Physiology, U.C.S.D.)