Shoulders Require Metabolic Stress to Grow
Believe it or not, the shoulders don't usually respond well to heavy weights. The deltoid is made up of mostly of slow twitch muscle fibers. That means most lifters will get results from higher rep ranges, around 12-20 reps.
Higher reps work for almost every lifter by decreasing external loads placed on the shoulder joint, thus decreasing cumulative joint stress over time. Less weight moved equals less stress on the joints. But this doesn't give you the excuse to get fluffy with your shoulder training and go light without challenging yourself.
Building strength and size in the shoulders requires placing an emphasis not only on progressively overloading staple movements, but also on eliciting a huge metabolic pump effect in the tissues.
More Reps, More Sets, Less Rest
There are a few key methods that will increase the metabolic stress of the shoulders that work extremely well for growth:
- Increase the rep ranges over 20 reps and really pump the muscle full of blood.
- Do more sets. Try 4 to 5 instead of the conventional 3.
- Reduce rest periods between sets to only 20-40 seconds.
This applies to just about any shoulder movement. Regardless of which one you choose, it'll turn your shoulder workout into a metal blood bath and get them growing again.