The body uses two sources for energy: carbohydrates and fats. While ingesting “gels” packed with carbs during aerobic training runs is popular, physiologically it doesn’t train your body to efficiently use its fat storage as the main energy source. Long distance running is aerobically based and aerobic exercise works best by utilizing the body’s fat reserves.
As you can see by slide number one, Fat is very effective as the core fuel for aerobic exercise. Keep in mind the half and full marathons are 98% aerobic.
The second slide shows how as one runs longer, the utilization of fat as the fuel becomes more and more important. The longer you go the more important fat utilization becomes as burning carbs is just a short-term energy pop.
So, the question becomes what is the best way to train your body to maximize utilization of its fat storage during long aerobic runs? Its simple; don’t use gels or other form of carbs during your long training runs. If your body is burning these quick hit replacement carbs you are not training your body to efficiently metabolize your own fat storage.
The final slide shows the glycogen levels in muscles while using and not using replacement drinks. When not used during aerobic training runs the glycogen levels at the cellular level are actually much higher than when replacements are used during training. You are training your body to become very efficient at burning fat as fuel for long aerobic runs. This is a science fact folks. If you are burning carbs you aren’t burning fat, its as simple as that. And fat is your primary fuel for the half and full marathon distances.
Which brings me to the question of when should you fuel? With the GO! St. Louis races only 5 weeks away, and many Lydiard Method runners moving into Phase 4; Integration, now is the time to experiment with carb gels. If you have trained properly all your long aerobic runs up to now would have been accomplished without these replacements and you have built a well-oiled fat burning machine. As you jump into a couple of races leading up to GO! try several different kinds of gels to find the one that works best for you in terms of absorption and which does not upset your stomach. Given the quick acting nature of carbs, you will feel a “boost” which will come in quite handy particularly in the last 8 miles of a full marathon. In this way you are racing on a fat burning engine you have trained well over these past few months then primed at the right times later in the race with carb packed gels.