How To Tighten Your Core. Start on all fours, with your hands below your shoulders and your knees below your hips. Engaging your core means bracing and tightening all of the muscles in your core —your four abdominal muscles, lats, paraspinal muscles, hip flexors, and glutes—to keep your spine safe and stable.
Your core — which includes back, side, pelvic, and buttock muscles — forms a sturdy central link between your upper and lower body. Picture everything from your rib cage to your pelvis: You move in toward or away from the anchor point to make the exercise harder or easier.