1, 2, 3 – Contract

Muscle Actions
by Rhonda Jarmuth, RMT, CPT

The muscles we train and use everyday to move our bodies have three different types of contractions:

Eccentric, Isometric and Concentric

These muscle contractions enable us to manipulate gravity, react to external forces, momentum and resistance. Which all together produce efficient movement. And not one is more demanded in activities than another, eccentric is just as important as isometric and concentric and around you go.

Eccentric: You’ll hear this is a lengthening of a muscle. Yes it is, but a stretch is also a lengthening of a muscle. A better way to think of this contraction is the muscle is resisting gravity (or the weight of a dumbbell) and also decelerating or reducing forces. It’s our braking system. Walking down stairs is a good example of the quadriceps muscles (on the front of your thigh) eccentrically contracting to keep the knee bend under control. Without this you’d need pretty fast feet to remain upright.


Isometric: This contraction will keep a joint still and hold a position or guard the joint through motion. The muscle can make this type of contraction either with a resistance or against resistance. It’s our stabilizing system. When you’re down on all fours performing Superman the rotator cuff is isometrically contracting to keep the shoulder (of the hand remaining on the floor) still. While performing a dumbbell press the rotator cuff is stabilizing the shoulder joint throughout the movement of a rep.


Concentric: Now this is the muscle contraction most of us think as the cream of the crop when we’re working out. It’s that bulging bicep you see with arm curls. But remember that even though this is the exciting contraction it’s no more important than Eccentric and Isometric. If you want technical this is the shortening of a muscle that brings one bone closer to another and decreases the angle of a joint. It works against force (raising your heels off the ground), produces force (a jump squat) and creates acceleration (a golf swing). This is the engine.


This may seem like we a have a different muscle for each type of contraction or that one muscle is only capable of one type of contraction. Not so. One muscle can do each of these three contractions.

Here’s an example of what the Gastrocnemius muscle (the calf muscle) does:

calf raise

Concentrically it’s the main muscle responsible for you lifting your heels off the ground to stand on your toes. Then it’s working eccentrically to lower your heels back to the ground. And when your holding a standing position with heels on or off the floor it’s working isometrically to stabilize the foot and ankle.

Our muscular sytem is very dynamic and capable of moving our bodies in many ways. Knowing this makes it more important to ensure your training regiment works all three of these types of contractions. If you do, you’ll notice not only your every day activities are seemingly effortless, but your chosen sporting activities will be as well. Seriously. Take action, and all aspects of your active lifestyle will improve.

Till next time,

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