Powerful roller stretch

The best thing about the ab wheel is how it trains something called "anti-extension." Your core, as a unit, is responsible for a quintet of key actions. It helps rotate your torso (as you do during Russian twists). It resists rotation, an idea called "anti-rotation," which you fight during Pallof holds. It also braces your spine (think: planks and hollow holds), and it flexes your spine, too (as it does during classic situps.