Traditional crunches are out! Why waste your time spot toning when you can work your abs in a full-body exercise? Capitalize on the instability of an exercise ball (it makes you work harder) and try the tuck crunch. This move strengthens your core while toning your low abs, arms, chest, and shoulders. Learn how to do this straightforward move by watching the video; we love it so much that we've even included a variation to work your obliques. Once you mastered the tuck crunch, be sure to try the more challenging plank to pike exercise.