Starting Position: Start by getting into push-up position. Make sure your straight as a board from shoulders to hip. Don't let your core sag.
Movement: Do a push-up and on the up movement come into your side plank. Open up to the side, stack your feet and extend your opened arm up to the ceiling. Make sure your body is perfectly straight as shown in the picture.
Modification: If this is too difficult drop down onto your elbow (see last picture)
Time: Hold this for 10-15 seconds and then repeat opening to other side. Do as many as you can on each side, but limit to about 10-15. Then if you can do another set.
What is great about this exercise is you can go from the plank position (last weeks exercise of the week) into this position. I do this with a lot of my clients who have mastered the plank. We start with the plank and then I have them come into push-up positioning and then open up to one side, hold for 10-30 seconds, go back to the plank again and repeat on the other side. This is great for your abdominals, shoulders, chest, arms, legs, and back muscles, basically your whole core is working hard to hold your positioning.