is it better to lift weights in a 90 degree motion or the full range of motion?

Question

I have seen guys lifting weights only till 90 degrees and not the whole range of motion, espceially heavy weights? why is that? is it more favorable to lift weights for the whole range of the motion?

Answer 1

Conventional wisdom would suggest that you need to go to maximum contraction and squeeze as hard as you can.

There are also those who advocate doing 21's. One these you do 7 reps from full extension stopping at 90 degrees, then 7 reps from 90 degree to max contraction, then 7 reps from full extension to maximum contraction. This does create a very good pump, but it might not be the best for actual muscle gain.