All You Need Are This $12 Ball and These Videos to Strengthen and Sculpt Your Whole Body

Beachbody trainer Autumn Calabrese shares three of her favorite exercises that work not only your core, but your booty and hamstrings, too. It's "big work from such a small ball," she says.

Equipment needed: 9-inch ball

Directions: Do 15 reps per side of each move.

• Fire hydrant knee tucks
• Side plank hip drop, knee tuck
• Reverse plank alternating knee tucks