This particular move is made much more effective by using the Core Hammer as resistance because of the distal load, grip, and stability challenge. With proper form the athlete can not only increase mobility in the shoulders and isometric core strength, but also improve Lat engagement and concentric core engagement.
Master Trainer Helya Glen from The Studio in Ventura CA describes some of the pointers for a proper shoulder mobility exercise. She also includes a number of added challenges for ROM and explosive core engagement like changing your grip position and adding a lunge.
Consult a physician before performing this or any exercise program. You as the user are responsible independently for use of any fitness programs or equipment and assume the risks of any resulting injury.