Here’s the thing about abs: Whether you care about getting ripped or not, your core goes way beyond those six-pack muscles in both form and function. The muscles of your mid-torso — the ones on your back, sides, and underneath the more superficial rectus abdominal muscles — are the support system for your spine. Translation: They’re the foundation for almost all movement, in and out of the gym. “Strong core muscles assist in everything you do physically, in ways that would surprise you, from lifting a box over your head, to pulling a suitcase, to twisting your body while parking your car,” says Luci Gabel, an exercise physiologist and fitness coach and founder of LuciFit . Because they're so essential, when abs and back muscles are weak, it can cause all kinds of trouble: bad posture, back pain and even spinal injury, Gabel says.