Long story short, car accident 12 mths ago, 4 weeks on hospital, 3 mths in wheel chair, 2 mths crutches. walking by myself now but i cant do that exercise.. really bad injuries to feet (skin grafts, nerve and tendon damage) any exercises where you dont have to rely on your feet?
You can do the same thing on your knees, it just doesn't give you quite the same intensity. When I first tried doing planks at the gym as part of my personal training group they give you the option to start on our knees. So pretty much in the same way you would learn push ups on your knees before progressing to toes.