Biomechanics:eccentric and concentric?

[kinlover]

I know the eccen and concen. definitions but I am not able to tell the difference when its eccen or concen contractions...for example during running i cant tell at which phase its eccentric or concentric conctrations of the hip for example, I would really appreciate a full explinations of how to know when is which.

 

[MattBD]

Eccentric = muscle fibers lengthen and are activated.
Concentric = muscle fibers shorten and are activated.

Since this sounds like a HW question, I'll give you an example: If you are doing bicep curls and start in the "up" position with a weight that is too heavy for you, you will be activating the muscle fibers (trying to hold it up). However, you will not be able to keep the weight in position and will lower it. This is the eccentric condition: fibers lengthen (lowering weight) during activation (trying to hold it up).

The concentric condition is the one that people are generally more familiar with from your typical weightlifting exercise.

To answer your question, think about each phase of the stride and (a) whether or not the muscle in question is firing and (b) whether it is getting longer or shorter.

-Matt