What is the difference between concentric and eccentric isotonic contractions?

Answer 1

Under loading, concentric muscle action is contraction, while eccentric muscle action is extension. For example, while holding a barbell with elbows at the side, hands out, lifting them would be concentric, while letting it down slowly would be eccentric. "Isotonic" being relatively immobile and in tension, slight contraction would be concentric, while slight extension would eccentric.

It's been shown that both actions are necessary for muscle development and health, so, for example, hiking downhill can be just as important as hiking uphill.

Answer 2

Concentric Isotonic Contraction

Answer 3

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What is the difference between concentric and eccentric isotonic contractions?

Answer 4

Concentric contraction is easily understood- the muscle contracts and shortens to generate force- eg biceps in bicep curl. The opposite to that is relaxing.

Eccentric contraction occurs in cases where the muscle contracts but is still extended. It may be sound weird, but think about what happen to your hamstrings when you walk down a pretty steep hill. You bend your knees as you walk, making them contract, but at the same time using your hamstrings as brakes so they extend. Basically anytime a muscle acts as a brake (eg tricep when lowering the bicep curl slowly it can classify as an eccentric contraction.

There's some evidence eccentric contractions are the most effective in building muscle, hence the theory that when doing weights it's better to let the weight come down slowly and in a controlled motion each rep to force the muscle to go into eccentric contraction. You'll see some guys at the gym do many reps very quickly- that won't work as well because they're 'cheating', using stored energy in tendons to do work rather than muscles.

Answer 5

Concentric contraction is what to you looks like the normal action of a muscle. For example, doing a leg extension (unbending the knee), is a CONCENTRIC contraction of your quadriceps muscles. Now, a leg CURL (bending at the knee), is a concentric contraction of the HAMSTRING muscles. As for an eccentric contraction, when you are extending the leg (unbending your knee), that is an eccentric contraction of your hamstring muscles, and bending of the knee is an eccentric contraction of your quadriceps muscles. In summary, an eccentric contraction of one muscle works in conjunction with the concentric contraction of an opposing muscle.

What does this mean clinically? The hamstring muscles are commonly injured in athletes. This is typically because they overtrain their quadriceps muscles, and undertrain their hamstring muscles. So when they extend a leg, the conctentric contraction of the quadriceps is much stronger than the ECCENTRIC contraction of the hamstrings, and because they are working together, the quadriceps tears the hamstring muscles. In conclusion, injuries to muscles in athletes and weight lifters are normally incurred during eccentric contractions, not concentric.