Rotate in, build a stable, bulletproof shoulder.
Keep that elbow glued to your ribs. The motion is all rotation, not a pull from the arm.
Standing side-on with your near hand on the handle, rotating the forearm in across your belly trains the internal rotators at the front of the shoulder against the stack's smooth resistance, one arm at a time. It pairs with external rotation work the way rows pair with presses, train one direction alone for long enough and the joint feels it. It earns a place in shoulder maintenance for keeping the cuff balanced front to back, cheap sets with a long payoff.
If you're doing external rotation work, matching it keeps the cuff balanced rather than trained on one side only. It costs one light set or two per arm, that's cheap for a joint you use in every upper body lift.
The elbow never leaves your side. Pinned at 90 degrees, only the forearm sweeps in across your stomach, the moment the elbow drifts or your torso turns, the cuff stops being the thing doing the work.
Light enough for slow, clean reps of 12 to 15 per side with zero lean. Internal rotation gets help from big muscles if you let it cheat, so strictness matters more than the number on the pin.
