Reverse Plank

This reverse plank is a great upper back and core isometric exercise. So much of the function of the back and core is to resist force. If you lift something heavy off the ground, most of the work is done by the lower body and the back and midsection are really just making sure your spine doesn't break in half.

Put the straps under the elbows then get into what you imagine is perfect posture (like a soldier standing at attention), then hold that position.