Starting Position - Keep your legs straight but don’t lock your knees. Stand on a step (it could be a step or a step on the stairs) so that your heels are off of the step but the rest of your foot is still on the step so you can stand there.

The move - Go up on your toes. Move back down so your heels are slightly lower than the step. Go back to the staring position. Do 50 reps. (Yes, your vision is fine - it read 50 reps.)

• The version given to you is the full range of motion version, but if you do not have access to a step this movement can easily be modified to a move with a slightly limited range of motion: repeat the movement as you would normally do so except stand on the floor and go up on your toes and down again. This move limits you to the concentric contraction and it does not allow you the full down - eccentric contraction of the exercise.
• Doing calf raises on one foot is fine, a tad challenging for some but hey. Do whichever move you feel more comfortable doing, just as long you as get up and get moving that is what we ask. The variation? Hold the foot, of whichever leg you are not working, up so it is "hooked" onto the back of the calf you are working. (You may want to hold on to a chair or railing for balance here.) Repeat the movement by going up on your foot then down again. By the way: 50 reps still applies here.