This is how a Bulgarian split squat is PROPERLY performed. My shoulders are in external rotation, my core tissue is active. I am some thoracic extension and a neutral spine so when I flex the knee, I am not hinging forward. THE SPLIT SQUAT IS NOT A HINGE. YOU WILL GROW YOUR ASS MORE STANDING STRAIGHT UP. I put this in all caps because this is widely popular exercise in which I observe about 1 of of 5k people doing it correctly. Again, it’s a split squat. The goal is getting the knee flexed low like the bottom of a parallel squat. If we hinge forward, not only are we not using all of stabilizers and synergists muscles to help, but we are putting stress on the lower lumbar disks from attempting to flex the knee low while in a hinge. SO remember: squat your squats, hinge your deadlifts.