You need two Bosu balls for the planks I did today - my last exercise of the day, so I was already fried!

First Bosu ball is flat side down, elbows on the squishy part. Second Bosu is flat side up, one foot in the middle of it, on your toes, other foot in the air. Hold as long as you can - I was doing a minute. Then switch feet and do it again. Repeat.

Veronica