Mark Rippetoe is an American strength training coach and author. In this video, Rippetoe focuses on a common error made by lifters while doing the back squat. Rippetoe points out that this error is performing the movement with “too vertical of a back angle.” Any attempt to maintain compressive force on the spine is mechanically incorrect. The spine needs to stay more horizontal so the muscles that control the position of the back and can increase in strength. In doing the back squat, we are intentionally trying to train the back muscles, and in doing so, the correct back position is actually slightly forward. This video shows the incorrect way that is commonly done, and the correct way to do a squat.