The workout includes a dynamic warm-up to get your blood flowing and prep your body for the rest of the work ahead, and a cool-down to help you slow back down and wrap it all up. If you want to make the workout more challenging—maybe you've done it a handful of times and are ready to turn things up a notch—add weights to the lunge and squat movements. You can also, like Sims said, add another round of the main strength circuit.
Whether we’re fully conscious of it or not, we’re always looking for how to be happy. And exercise is one of the most obvious steps to take, as it’s not a coincidence that you feel better after a good workout: It’s science. A Penn State University study found that people who exercised, whether it was a mild, moderate or vigorous workout, had more pleasant feelings than those who didn’t. (1)