Here's a trick few people talk about that I'll share with you. If you really want to have great results with cardio, then one should focus on one exercise at medium difficulty that is performed non stop for 60 mins. Take for example a 60 min medium to high level jog, will keep your heart rate up and you'll find that your body will be constantly burning fat and calories hours after you have stopped working out. Workouts shouldn't last hours. It can be effectively implimented in a hour, with no rest and higher intensities. The trick is to always have your heart rate up for the entire 60 mins with no breaks.

Will it help grow muscle? Depends on the intensity. But ine thing is for certain, you will see more tone and definition in your muscles.