That's right quality is the key to success. Most trainers recommend low intensity (running) followed by high intensity (weights, bag work, sprints) ,but recent studies have shown that high intensity exercise followed by low intensity works best for maintaining good body composition. This has a lot to do with working your muscles up to an optimum level i.e. conditioning the phosphogen and lactic acid systems first, then using your aerobic system once all the nerves to the muscles are fired up.