I'm a beginner at the gym so I always listen to what somebody has to say and see if its true, but today a man at the gym said that when doing a seated db shoulder press to have my upper arms level to the floor and no lower. After he left I watched him and everything he did he only went half way.
The weight was heavy but I don't think he would make it if he went down all the way. Also later I overheard him say he couldn't go up in weight for the past few months.
Ive heard of not extending all the way on somethings like a curl so that your muscle is always under stress but this got me wondering. The guy was good sized but I would think if you only go down about half way benching would you really be doing any good?