Almost anyone who has participated in an endurance event has experienced that terrible feeling of hitting the wall or bonking. An article I read recently has shed some light on why this happens by focusing on a team of elite cyclists with diabetes (Team Type I). Diabetics must closely monitor their blood sugar in order to prevent problems associated with too much or too little sugar in the bloodstream. Sugar is stored in muscle as glycogen and is used by the muscles for fuel. Lack of fuel creates the phenomena of bonking. Information gleaned from working with these elite diabetic athletes may carry over to the rest of us struggling to figure out how much is too much or too little sugar to keep performance levels up.

Researchers associated with Team Type I concluded that approximately 0.455g of carbohydrates should be consumed per pound of body weight per hour to replenish blood sugar levels while performing intense exercise (about 1g per kilogram of body mass per hour). For my body weight of approximately 175lbs, this comes to almost 80g of carbs per hour. I quickly retrieved one of my goo packets I use while running to see what the carb content was and found it to be a mere 25g! I use these approximately every 5 miles of running or every 40-45 minutes. That means I’m just getting about a third of the glucose I need to replenish the stores I’m using. Even taking into consideration that my intensity may not be as great as these elite cyclists would conservatively put me at about ½ of the required carbs!

A second interesting observation arose out of working with these unique athletes is that there may be two glycogen recovery stages instead of just one. The researchers found that the first window falls within 1-2 hours after the exercise bout is over. Glycogen recovery is based on the depth of the glycogen loss. So the more you’ve used on your training bout, the more receptive the stores are to be replenished. As they fill, this receptivity declines. The 1-2 hour window is when they are at their optimum to be re-filled. For me this was significant because after my runs, I would immediately throw myself into the day, playing with my kids, working, or running errands and would not take sufficient care to restock my reserves.

The second window occurs a few hours later. The researchers found that if their cyclists did not consume a second round of glycogen-replenishing food, they entered an anabolic mode, during which their bodies began breaking down useful substrates in order to keep their blood sugar levels up. So, if you’ve loaded after your run or ride and think you can have a light dinner you may be missing out on another opportunity to re-stock your glycogen reserves.

So, those of you suffering from bonking, take heed and pay more attention to your fuel consumption during your training as well as the recovery process to get those glycogen stores up. To help with that, below is a recovery drink recipe from Rick Crawford, former pro cyclist and triathlete. Bottom’s Up!

RECOVERY BOMB

25 grams whey protein isolate (the kind in most high-quality protein powders)
70-100g complex carbohydrate* (1.2g per kilogram of body weight)
8 oz. grape juice or other sugary liquid
1 banana
1 cup frozen fruit (Crawford’s favorite is blueberries, but mangoes are a close second.)
8 oz. water

Process all ingredients in a blender until smooth. Makes 3 cups, or one serving.

*Look for a pure maltodextrin powder at your local health food store. It gives the best results and the best value. Use a commercial recovery drink in a pinch.