One of the most popular abdominal exercises, the crunch primarily works the rectus abdominis muscle and the obliques, aka your abs and the side of your stomach. Building these muscles are just one part of developing your core muscles for stability and performance.

Here's how it's done:

Lie down flat on the mat, with your knees bent and feet on the ground. Alternatively, you can also lift your legs off the floor at a 90-degree angle. Afterwards, lift your hands and place them behind your head*, or keep them crossed on your chest. Inhale deeply, and as you lift your upper torso off the floor, exhale. Inhale again as you get back down, and exhale as you come up. If you're a beginner, do this exercise ten times, then repeat another two or three sets.

*If you experience neck pain from this exercise, you might be pushing your head too hard. As an alternative, try pressing your fingers against your neck instead.