Ok, first thing first. This set up Is Not Useful, Effective or Realistic. It won’t work if you rig it up like this. This band isn’t even at shoulder height. Its also not stretched tight.
What you can see is a band streched horizontal, with the handle also horizontal.
This next picute sucks to. The handle should be at shoulder height, and off to my side at arms length. Instead it’s down and in front. What you can see is me grabbing it, knuckles up.
From there, I straighten my arm and try to turn my thumb up. Or supinate my forearm. Also externally rotating my upper arm. While also engaging my serratus to pull my scapula into good tilt. All the details are in this discussion.
It just looks like a simple twist of the wrist. But it’s not! It’s a complex motion involving 3 joints and probably 50 muscles.
The wrist and elbow stay “straight” while the arm “turns over” or external rotates, supinates and extends. As the serratus “locks down,” and the shoulder locks into a good position. Not to mention all the posture muscles and hip muscles that turn on and lock in.
With a little imagination, you could think of the Fat Gripz handle like the handle of a dumbbell. Then you could set up that “handle” at the “top” of any dumbbell exercises. Like you could sit on a bench with the handle overhead, like the top of a seated dumbbell press. Then you could reach up, grab it, and make the same external rotation, thumbs up, posture lock down, handle twist motion with your arm. And develop perfect tightness and setup for the dumbbell press.