What You Need to Know About the Dreaded Bonk

Recovering from Glycogen Depletion

Muscles restock glycogen at a rate of approximately 5mmol per kilogram of muscle per hour. This means it takes at least 20 hours for depleted stores to be replenished, assuming sufficient carbohydrates are consumed during that period. If glucose is given intravenously, glycogen stores can be replenished faster, perhaps in as little as eight hours.

Is it Possible to Recover and Continue Racing After a Bonk?

Most of the time, athletes do not experience complete glycogen depletion during training or racing. When athletes experience an overwhelming feeling of fatigue, scientists believe there is a central governor in the body that regulates exercise so the body does not self-destruct. The result is a decrease, or halt, in exercise pace.

Many athletes find that if they are in the situation of feeling overall fatigue, and they have not been doing a good job of fueling before or during a long training or race event, they can consume some fuel (typically carbohydrates) and fluids during the event to make a partial recovery.

For some athletes this means stopping, sitting down, and refueling. Others can significantly slow the pace, but continue to move while refueling. In both cases, the athlete can continue the event although the pace is slower than it was earlier in the exercise session.

Is it Wise to Continue After a Bonk?

If your only symptom is a low-energy feeling, and that feeling is reduced or eliminated by a reduction in pace, refueling, and re-hydrating, most of the time you are fine to continue the event.

That said, you need to use good judgment. If you can't seem to think clearly or you feel that a continuation of exercise would put you in any long-term danger, it's best to end the day. Make a call to have someone pick you up from your training session or end your race day. There are more training and race days ahead.

Active logoFuel right at your next race.

Gale Bernhardt was the USA Triathlon team coach at the 2003 Pan American Games and 2004 Athens Olympics. Her first Olympic experience was as a personal cycling coach at the 2000 Games in Sydney. She currently serves as one of the World Cup coaches for the International Triathlon Union's Sport Development Team. Thousands of athletes have had successful training and racing experiences using Gale's pre-built, easy-to-follow cycling and triathlon training plans. Let Gale and Active Trainer help you succeed.


1) Noakes, T, "The Lore of Running", Human Kinetics, 2003, pp. 106-132.
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