The standard band external rotation exercise has a few drawbacks. It's easy to compensate by using the lumbar spine. Not good. It's also hard to tell if you're getting full range of motion.
These problems can be solved by doing this supine variation. It's impossible to compensate with the lower back and you'll know when you're reaching full ROM when your wrist bones touch the floor.
related posts
Reactive Strength
How a bony white boy from Buffalo increased his strength by a whopping 60 pounds in 56 days!
Tip: Do the Pizza Plate Press
Test your shoulder mechanics and get stronger overhead with this diagnostic exercise. Check it out.
Tip: Upgrade Your Hip Thrust
Strong glutes make your whole body stronger. Also, having a nice butt is, well, nice. Try this twist on the now-classic hip thrust.
Bottoms Up Training
It seems that in every family there's always a black sheep, someone who just doesn't quite fit in with the rest. It might be your crazy Aunt Sally who's run off and joined a cult, or maybe your family has its own cousin Eddie of National Lampoon "Vacation" fame.