What Is It About Endurance Training?

In the eighties and nineties, there was an assumption that in order to race fast, you had to practise suffering. We ran literally as many miles as we could at the highest possible level with the heart pounding as high as we could sustain. That sort of begat this whole concept of carbo loading. And all the jail packs and all the drinks were basically lated to get more and more sugar into your system so that you could burn more glucos for as long as you could. But once you realize that fat is the preferred fuel for humans in general, and that it becomes a preferred fuel for people who are competing, then training can become much less important.