Short bursts of high intensity energy output at near maximum heart rate levels followed by a recovery period has shown to help improve your performance with weight training.
The other great thing about Interval training is that it protects your muscles. Visualize yourself in an all out sprint or pedaling on your bike at your near maximum capacity and speed, which forces your muscles to work very hard. This really almost duplicates heavy weight training, giving you the same growthhormone release that you find in a resistance-training workout. Furthermore, intervals make your body produce extra levels of a chemical called Glucagon, which causes you to burn calories directly from your FAT stores.
So interval training protects your muscles and burns Fat to allow you to be able to train harder and more efficiently.Plus… My clients tell me that Interval Training keeps you motivated longer and also helps keep your mind off how much time you have left in your training: That old mind game that is played when working out.