I must be doing my squats wrong according to this guy

I'd like to hear more on this...and hear exactly what he meant before making comment.

Well if you view the exchanges between him and I, I was trying to explain to him the different type of muscle contractions. He believes that a muscle always shortens when contracted. He does not believe that a muscle can contract and lengthen at the same time. This would be the eccentric phase, as you know.

He also states:

quote:

Any time you straighten your arm, you are using your triceps.

Any time you raise your arm. you are using the biceps.

I can straighten my arm in the eccentric phase of a bicep curl and not use my triceps.

He then states:

quote:

Contraction does not lengthen the muscle. Never.

I never stated to him that contraction lengthens a muscle. What I stated was that there is a type of contraction "that allows lengthening of the muscle".

I wouldn't worry about it too much. Certainly the quad is in play during the eccentric portion of the squat as part of the stretch-shortening cycle. With that said, during the eccentric portion of a squat, one should focus "pulling" with the hamstrings to squat down, this creates proper motor patterns and develops speed and power that is transferrable over to the diamond.

XV,
He is probably stating the literal understanding of biomechanics. There is truly no such thing as a eccentric contraction. It is rather a controlled relaxation of the muscle. That does not mean that it does not have benefit. The muscle itself still is in a contraction phase, even though it is being relaxed in an amount to control the weight. It is still an important part of any lift and it sounds like you are doing your squats just fine. Follow Jon's advice above.

An eccentric contraction is the active relaxation of a muscle. This means that it requires energy to maintain the contraction. This is in contrast to passive relaxation in which less energy is used. It's called an eccentric contraction because the muscle fibers are still using energy to maintain muscle length (actin and myosin still interact with each other during an eccentric contraction).

A "controlled" relaxation would be the same as an eccentric contraction because in order to control the weight, energy is required as the actin and myosin remain engaged to prevent the fall of the weight with gravity.