Muscle Building - Full Range of Motion Or Not?

By this I mean contracting the working muscle completely at the top/concentric part of the movement and fully stretching it at the bottom/eccentric part of the movement.

So if you were performing bicep curls you would lift the bar all the way up till your biceps are fully contracted, letting you squeeze the muscle for a second. Then lowering the weight all the way down till your biceps are stretched and your opposing muscle (in this case the triceps) is contracted.

This is when you focus on keeping the tension on the muscle for the entire set. To avoid losing tension on the muscle you're working you must use a partial range of motion.

In the bicep curl example, lift the weight just before you start to lose tension, a few inches before full contraction, because when you get to the top gravity stops the weight from putting any stress on the biceps. On the way down bring it just shy of a full stretch, leave the elbows slightly bent. Keep the motion within this range; it should be a smooth, constant movement – keeping the stress on the muscle all the time.

The optimal way to stimulate a growth response from your muscles is to train them with high intensity. This means creating the most amount of stress possible on your muscles. You must threaten their survival in order to create the response you want.

Keeping the muscles under tension throughout the whole set will create much more stress for them. Causing the muscle to perceive a much greater threat and resulting in higher intensity workout. Your muscles don't care if you are performing the exercise in a perfect full range of motion, they don't even care about the type of exercise it is, all they know is that a high amount of stress is being placed on certain muscles and in order to survive these muscles must increase in strength.

Therefore partial range of motion is the better option for increased muscle growth. This doesn't mean performing reps in a manner which would be deemed as cheating, it means performing the exercise with good form and mostly full range, but stopping just shy of losing tension.

Using partial range of motion will ensure you place the most amount of stress upon the working muscles – creating a bigger response and more muscle growth.