These are a great full-body exercise, with an option for some cardio as well. You alternate between push-ups and back extensions, with a challenging transition between the two. Here is a video demonstrating the move, with a modification on the knees shown as well. Scroll down for a tutorial video and a cardio challenge! Also, I don't know why these videos are showing up so bright on here, but hopefully you can still see well enough to follow along!
Take these slowly and really focus on your form and alignment, and feel free to come down to your knees if needed.
Whether you are on your knees or toes for the push-up, be sure to keep your core engaged and think of making one long line from your head to your feet or knees so your spine is in line. You can modify the superhuman fly back strengthening part by lifting just your upper or lower body, instead of both. You can also bend your arms out in a “goal post” 90 degree position to the side, rather than straight in front of you.
For a bit of cardio, try adding in a burpee-style jump once you reach the top of your push-up!