Hi, I'm Denise Druce for LIVESTRONG.com. Let's take a look at whether crunches can replace cardio for weight loss. Crunches and cardio are two entirely different activities. Crunches are designed to strengthen the muscles around the core and cardio is designed to burn calories off to melt the fat away from your core, so you really need to do both. But let's look at a great way to do a safe and proper crunch. So start by rolling down onto your back, bring your fingertips to the back of your head and push your head back into your hands. Then, pull your navel into your spine and lift up and exhale and just lift up until your shoulder blades are coming up off the floor. You can think of sliding your ribs closer to your hips. So instead of pushing muscles out, you are thinking about pulling muscles in. Exhale every time you lift. So that's a great way to do a safe and proper crunch. That was a look at the difference between crunches and cardio. I'm Denise Druce for LIVESTRONG.com.