Prone Shoulder External Rotation From 90 Degrees of Abduction: The Prone Shoulder W
The prone shoulder W is part of a group of upper body exercises known as the T-Y-I-W series. As the name indicates, it is typically performed in a prone position and is intended to activate and strengthen posterior shoulder girdle muscles.
Ronai, P. (2017). Prone shoulder external rotation from 90 degrees of abduction: The prone shoulder W. ACSM's Health and Fitness Journal, 21(6), 33-36. doi:10.1249/FIT.0000000000000345