If you only have 15 minutes to sweat, it's easy to skip out on a workout. I mean, how much can you really accomplish in 15 minutes, right? Umm, a lot, actually—if you spend them wisely. That's the ...

Circuit training involves quickly rotating through a series of exercises targeting different areas of the body. You can do it at the gym, at home, or during an exercise class. Share on Pinterest Getty ...