Day 25 is a crunch card with no repeats in it. The circuit runs high crunches, folded crunches, cycling crunches and leg circles - 30 seconds each, two minutes total - and although three of the four have the word crunch in the name, no two of them curl the same way.
That is the design. High crunches curl straight up toward legs held vertical, which takes the hip flexors out of the movement and leaves the upper abs to do it alone. Folded crunches load the same curl diagonally by folding the knees across to one side before you start, which drops the work into the obliques without asking you to twist at all. Cycling crunches then add active rotation and alternating legs, so the curl, the twist and the leg extension all happen together. Leg circles remove the upper body from the equation entirely, holding the shoulders lifted while both straight legs draw slow circles and the abs fight to keep the lower back on the floor throughout. Four ways to load the same muscle, arranged so no two consecutive panels feel alike.
Keep the legs vertical and quiet in the high crunches. In folded crunches, curl straight upward out of the fold rather than adding rotation with the arms. In cycling crunches, slow down until each leg reaches full extension - this is the exercise most often ruined by speed. In leg circles, keep the legs together, the circles smooth and the lower back flat; shrink the circle rather than let the back arch.
Four crunch variations and not one of them curls the same way.
Make it Harder: Halve the speed of the cycling crunches and fully straighten each leg before it comes back in.
Make it Easier: Let your shoulders settle down between repetitions of the cycling crunches and concentrate on the legs alone.
