Best ab exercises for a strong core

*Need a timer? Grab one from Gymboss: ***Like the music? Get the album by James Granstrom here: Here are the best ab exercises for a strong core all in one workout! This is the ultimate ab time challenge with 5 exercises, and 3 rounds. 20 seconds on, 10 seconds rest for 4 minutes then 1 minute active recovery to complete a 15 minute ab blast. #getlean 1. Plank 2. Oblique Twist 3. Sit ups with heels up 4. Table top pulse 5. Sw