"Being able to brace your core and not collapse in any part of your spine demonstrates true core strength and spinal integrity," Rivera says.
- Place your forearms on the floor, and extend your legs back, so that only the balls of your feet are on the ground. You should look like a board, from the top of your head down to your heals. Hold for 45 seconds.
- To increase the challenge, Rivera says to place something unstable under your forearms or your feet.