Recently, a team of experts combed through the research to find the scientific answer to the age-old question. The exercises they looked at fell into a few broad categories: traditional core exercises (situps), core stability exercises (planks), exercises involving a stability ball (like a crunch on a ball), free weight exercises (squats), and upper-body exercises (bicep curl). The studies they looked at—17 in total—used measures of the electrical activity in muscles to determine how hard different core muscles were working. The conclusions, which were published in the Journal of Strength and Conditioning Research: Free weight exercises like squats and deadlifts are the best at activating the core muscle that stabilizes your spine, the lumbar multifidus—a group of deep muscles that run along your spine. (Research on other core muscles was either mixed, weak, or nonexistent.)  While it won’t help you create a visible six-pack, this muscle is important for another reason: protecting your spine from injury, says senior investigator John Mayer, DC, PhD, of the University of South Florida.  Although you might feel a bigger “burn” from crunches, you’d be surprised at just how well exercises like squats can work your core. That’s because those muscles are supporting and stabilizing your upper body during the entire exercise so that you don’t topple over. “Whole body exercises such as squats not only train the core muscles, but also may have numerous other potential benefits—improving body composition, bone density, overall strength, and balance,” Mayer says. “In comparison to isolated core exercise, whole body exercise is more versatile and efficient, and offers more potential benefits.” Instead of doing crunches during commercials, try a round of squats, lunges, or even pushups—all full-body exercises that activate your core. Or try this complete No-Crunch Ab Workout that will boost your metabolism, strengthen your bones, and prevent low back pain—without a single situp!