The Sugar Bonk Demon Bites Tony

Have you ever been riding long and after a couple or three hours maintaining a good pace, say 20mph, you rather suddenly just can't go more than maybe 16 or 18mph. No matter how hard you try that seems to be all your legs are capable of . You're likely experiencing glycogen depletion, a sugar bonk. You've had to fall back to a pace, an exertion level your body can support with fat alone. If you try to go faster your body can't supply the oxygen to continue metabolizing fat for energy so you need sugar (no oxygen required) to meet the higher exertion or pace level - BUT THERE'S NONE THERE. You down a couple of gels and magically after a minute or two you are back... but not for long unless there's more sugar on the way.

Glycogen rules endurance athletics, always has and always will. Even riding, racing, training or whatever below our LT, we're still burning SOME sugar, uh glycogen (blood sugar); no one is ever completely aerobic. Our bodies can certainly handle the lactic acid downside of low to moderate level sugar burning BUT there's another problem associated with glycogen use...

... you can run out of it. Add a higher level of effort (anaerobicity) to the equation and you can run out pretty fast. Our bodies only store a couple, maybe three thousand calories of it and it's not all available in an instant. I might be leading a ride (often in front - OK, my choice), working pretty hard and burning at least 400-500 calories of just sugar an hour (maybe 1200 calories overall including the fat burning that's also going on). In three to four hours, if I'm not replenishing glycogen, I'm out.

Happened to me last Sunday pulling a group on the Silver Comet Trail for 124miles. At about mile 90 I ran out of gas. I had been feeding on sugar and simple carbs but not fast enough to match my burn. At first, because I had been consciously fueling, I thought I had simply fatigued out; it was my second day of long hard riding and maybe it was catching up with me. But then I realized I knew the feeling. My legs were just not responding, I wasn't thinking straight, I was almost dizzy when we stopped at intersections. I downed three gels (my choice for the day of sugar fuel), drank a bottle of water and within minutes I was pulling at speed again. For ten minutes at least and then BAAM! it happened again. Used the new all up...

I've been reading more and more about studies that are starting to emphasize this... not sugar before or after but sugar during... don't let Gatorade or Powerade read this... turns out there's a connection to cramping too... more later