The Zercher squat will build your upper back and anterior core as well as isometrically taxing your biceps. You can do these with or without a box, off pins, or performed as carries.

To do the squat, the bar will sit in the crook of your elbows. It'll force you to use your anterior core and posterior chain.

Set up in squat stance and then pull the bar in close to your body. Keep everything tight and engaged and explode up. Lower it back down on the pins. You can do this as a box squat too.