The human body is powered with fibrous material, that which we refer to as muscles. The muscles help the body in movement and are also the most affected in case of a sudden pull of any body part or a jerk of movement. We all know muscle pulls and spasms as common issues. Like those which are felt after a sudden stretch of leg or arm, etc.
The muscle fibers in the human body generate tension, when in action and movement, and during this, the muscles may contract, and here, in muscular system, it does not mean only shortening. The muscle fibers may lengthen or remain the same too.
We generally refer to any contraction of the muscle, as the muscle getting shorter, and which is true in certain cases of muscle contraction. This type of contraction is known as concentric contraction. But, when a muscle lengthens as the muscle fibers get under tension, the type or contraction produced is called eccentric contraction.
To be more specific, it occurs when an external force acts upon a muscle to lengthen it, while the muscle is contracting. So, when the muscles shorten when contracting, concentric contraction takes place, while eccentric contraction is when the muscles are stretched and elongated.
About Eccentric Contraction
Now during a normal movement, for example, walking or when carefully placing down a heavy object or also when, lowering a barbell in biceps curl, the muscles are lengthening, and they are in an active state. When the external load on the muscles goes high, it reaches a point where the force generated by the muscles is less than the external force.
Eccentric contraction of a muscle will have two main aspects. The first one being the high relativity of the absolute tensions achieved to the maximum capacity of the muscle to generate tetanic tension. The second important one is that, the absolute tension is relatively independent to the velocity or speed of the lengthening of the muscle.
A very simple one being, when you fold your hand (like when you place the palm on the shoulder), the muscles contract. Now as you open up the arm to extend it outside, (straighten the arm), the muscles will take over to eccentric contraction. This helps a smooth and slow movement of the muscles as the hand gets straightened.
And, this prevents the joint of the elbow from getting damaged. The eccentric movement helps in creating a sort of resistance to the movement, else in the absence of an eccentric contraction, the arm will just snap out, with the same velocity, causing harm to the joint.
Eccentric contractions can however, cause injuries and harm too, when in excess. Too much strain on a muscle can cause harm; for example, extreme stretching before warming up the body, or during any sports activity, especially in athletes.
Well, eccentric contraction is necessary, and in a controlled manner. After a strenuous exercise routine, or after walking down long, you know how bad the muscles hurt, at least for a day. Take care and avoid excess straining of the muscles, and by that, now you know it means, eccentric contraction!