knee extensions
54 reps
Lay down on the back. You can place the hands under the hips to help support the lower back and core, if you like.
You’re going to do 54 repitions of this cycle: first, knees come into the chest. Then extend the legs straight out (but keep the feet off the floor). Now, raise the legs up to 90 degrees. Restart the cycle by bringing the knees back down to the chest.