The aerobic system is where the powerful hybrid engines lie at the muscular level.
If you lower the pace a bit to an oxygen utilizing zone you get 36-38 ATP per molecule of glucose- this is the gas engine- somewhat efficient as we can store enough glycogen and blood glucose to give 90 minutes or so of activity.
Now if you slow down a bit more to below the aerobic threshold you can develop the mitochondrial machinery to break down fat into energy. Your efficiency jumps exponentially-460 ATP per fat molecule! This is the electric engine. (Endurance Sports Nutrition p 32). If you have ever driven a Prius, you see the subtle mixing of gas and electric which you cannot detect as the driver. Your body is doing this all the time in exercise. You want more electric! Any activity lasting more than a couple hours is largely electric.