Sprinter Sit Ups
To do the Sprinter Sit Up, lie on your back with your legs out straight and your arms down by your sides. Then raise both legs just slightly off the ground. Beginners may keep one leg on the ground.
Then, sit up, moving to balance on your butt as you bend one knee and bring it in toward your chest. Reach your arms out toward your feet as you come to balance on your butt with one knee drawn in.
Lie back down and straighten both legs back out, but try to keep them up off the ground. Also, do not fully relax your shoulders back on to the ground as you lie back down. Keep your abs engaged.
Then sit back up and bring the other knee in toward your chest. Keep alternating, trying to keep both legs up off the ground when you straighten back out. Make sure you feel your abs and not your low back working.