Let's talk about your core for a moment: it likely needs to be stronger. You need a strong core for just about every activity, from running to dancing, from yoga to heavy lifting. This simple workout is a great way to start building strength — it's great for beginners, too. And let's review: your core is more than your abs. That's right — it's your back muscles, too, along with your glutes (both the glute max on the back of your pelvis and your glute meds on the sides of your pelvis).