How do muscles move? Well there are three distinct way in which are muscles move within our body. Concentric, eccentric, and isometric.
Concentric- This action is one of the more known actions we know of. This is when the muscle and its fibers actually shorten. So imagine the biceps being a slinky, when the slinky becomes smallest in size that is the concentric phase. The concentric phase is when you move AGAINST resistance (gravity or weight on pulley).
Eccentric- Opposite to concentric comes eccentric, and this is when the muscle lengthens in size. So regarding the slinky example this would be when the slinky stretches out and all the metal strands separate from each other. An example would be the bicep moving from the top portion of flexion back into a straightened arm again. There has been lots of research regarding this phase of movement to have the most correlation to muscle soreness 48-72 hours after exercise, refered to as Delayed Onset Muscle Soreness (DOMS), which we will talk about later. The eccentric phases when you move WITH resistance (gravity or weight on a pulley).
Isometric- Lastly we have isometric. Isometric refers to no change in length but just held in a steady position. So if we were to use the slinky imagine this slinky being one strong slinky, strong enough to hold its shape in between steps. And for the arm curl example imagine just holding the arm ridged in a 90 degree position. Isometric contractions are when the body is held in one position for a long period of time such as doing a plank.
The next post will build on this topic by talking about agonists and antagonist muscle groups within our body!
Earle, Roger W., and Thomas R. Baechle.NSCA's essentials of personal training. Champaign, IL: Human Kinetics, 2004. Print.
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