There's no doubt that that adding an exercise ball to your routine will perk it up, but--depending on your sense of balance--it may also land you on the floor. Instructor Keli Roberts and her two able assistants make no such descents, but beginners are bound to wobble, which Roberts acknowledges with reassuring frequency. The three 10-minute workouts can be done individually or combined since they focus on different areas. Round 1 concentrates on the lower body with squats while holding the ball, balancing on it for a variation of the yoga bridge and squeezing it with the upper thighs. Workout 2 tones the arms and back by lifting dumbbells while sitting or leaning on the ball and using it for pushups. The final routine is specifically for the abs: sit-ups, curls, yoga's plank and downward dog, and Pilates scissors--all atop the ball. Weights are recommended for the second routine. --Kimberly Heinrichs