You've likely heard the cliché compliment, "They have a good head on their shoulders" when someone's intelligence is being praised. If you're someone who lifts, you want people to also notice the shoulders that head sits on.
Wide shoulders maximize the V-taper look everyone wants by making the waist appear smaller. So, you've got to hit the delts hard! This high-volume workout calls for 400 total reps, but it shouldn't take you longer than 40 minutes if you do it right.
This 10x10 isn't as crazy as it looks, but you will be feeling it by the time you finish the 100th rep. It's best to do this movement with a machine that has a stack so you can quickly change a pin.
If you don't have access to a shoulder press machine, go with whatever your gym has, or even dumbbells if you have to. Start with a light weight that you can easily do for 10 reps. Increase the weight, rest for 20 seconds, and do 10 more reps. Repeat until you've done 10 total sets.
The last set should feel heavy, but you should be able to complete all the reps. If you fail a rep or two short of the target, don't sweat it. Simply lower the weight a bit for your next set.
I like doing lateral raises seated so there is less opportunity to use momentum from the rest of your body. If you prefer standing, that works, too. Once again, you should be able to do the first set without trouble. Add weight each set and rest for 1 minute in between. When you reach the last set, try to control the negatives on the way down. Don't let the weight drop.
This exercise isn't about the weight, it's about contraction of the rear delts. So take your time moving the load. You should come to a dead stop when you move the weight and feel the contraction in the rear delts. Then, slowly return to start and repeat.
Yes, this is going to burn by the time you finish. But that is exactly what you need to develop these oft-neglected heads of the deltoids.
It's true the traps are considered part of the upper back, but many people train them with delts. That said, if you don't have a shrug machine, opt for the Smith machine or dumbbells. Don't be afraid of using straps here. The goal is building the traps, not your grip.
Try to get a good contraction at the top. Also, a normal speed rather than a slow tempo is fine for this amount of reps. If you need to stop a few reps short because the weight was heavier than you thought, do a 10-second rest-pause and get back to work. Rest for 45 seconds and knock out a second set.