Most men perform the inchworm as a warmup exercise. The move stretches your calves, hamstrings, and thighs, while preparing your muscles for just about any activity. But throw a towel under your feet while you do it, and suddenly the inchworm becomes a grueling core-strengthening move called the inchworm slide.
"Sliding the towel to meet your stationary hands activates your abs, hip flexors, and obliques," says David Jack, C.S.C.S., owner of ActivPrayer in Phoenix, Arizona, and the creator of The High-Intensity Body-Weight Workout. "You'll finish feeling stronger and loose." Ready to give it a shot? Watch the video below to learn how to do the inchworm slide with perfect form. Then visit our essential guide to chiseling your front, and fortifying your back.