For more of a challenge try: All Fours with Weighted Balls
Begin by lying on your back on top of a exercise ball with your knees bent and your feet flat on the floor. Extend your arms toward the ceiling and bring your hands together. Keep your arms straight as you twist from side.
For more of a challenge try: Russian Twist with Weights
Test your speed and sign up for a race.
Dena Stern is a certified personal trainer and the Content & Community Manager for Exercise.com. She works with a highly trained group of nutritionists, trainers, yoga and Pilates instructors and athletes to provide the best information, tools and motivation related to exercise and fitness.