If you ask us, resistance bands are underrated. The stretchy plastic may seem like a been-there-done-that fitness prop, but it can actually be integrated into tons of total-body exercises.

Not convinced? Just ask Melissa Paris, a certified personal trainer and the co-founder of BYOBfit, which offers fitness classes for new moms and dads and their little ones. A longtime fan of resistance bands, Paris knows the best ways to use the get-slim tool for full-body results. 

Resistance bands can be used to upgrade all kinds of exercises. Take the standing oblique crunch, for example. By placing the band beneath your feet and holding onto the ends of it so it stays taut while you alternate lifting each knee toward your waistline, you work the arms at the same time as the side body and quads. 

Another way to spice up some of your go-to moves? Replace free weights with a resistance band for a different take on a pec fly. Here’s how: Place the middle of the band beneath your feet while in a standing position, holding the ends of the band in each hand. Then place each end of the band in the opposite hand so it creates an ‘X’ shape in front of the body. Holding the band and keeping the elbows bent at a 90-degree angle, begin to move your arms inward toward the center of your chest and then return them out to a goal post position (as you would with a normal, weighted fly). The addition of the band will help you feel more engaged in your lower body and tighter in your core, too. 

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Want more? In this video, Paris also shows you how to add a resistance band to moves like the running man and squats, so you can sculpt your entire body—from the upper arms and abs to calves—even faster.