Arms in a Y to light up the lower traps and shoulders.
Keep the arms at 45 degrees forming the Y, lift from the shoulder blades not the neck.
Setting the arms at 45 degrees splits the difference between an I and a T, putting the lower traps in prime position to raise the arms while keeping the lever slightly friendlier than straight overhead. The shoulders assist to keep the thumbs-up arms tracking in the Y as they lift. It is a staple of overhead prep, building the shoulder blade control that pressing and pulling overhead depend on.
The 45 degree line points your arms roughly along the pull of the lower traps, so they do the lifting instead of your neck or upper traps. Drift too wide or too narrow and you turn it into a different exercise.
You are borrowing range from your spine. Brace your core, keep your forehead near the floor, and accept a smaller arm lift that comes purely from the shoulder blades.
Slow the tempo and add a pause at the top first. After that, very light plates or dumbbells are the progression, and light means lighter than you think.
