why do some people not make full extension when lifting weights?

Question

I've noticed some people don't fully lift weights to a full extension when lifting. One prime example is Lou Ferrigno in "Pumping Iron". when he benches he doesn't fully extend his arms. Is there a reason for this?

Answer 1

In Lou's case, he is trying to keep resistance on his pecs and not lock out thereby making the bench into a triceps exercise.