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Bonking on the Bike

10 Jan 2004

During the Tour of Italy 1984, I usually rode a bike for a portion of each stage, preceding the start of the race by 40-50 minutes, pedaling at the greatest speed possible to get to the food supply zone ahead of the riders, then getting aboard the pusuit car to follow the rest of the race. 

The 7th stage of that Tour of Italy crossed the inland sector of the Puglie region, from Foggia to Marconia di Pisticci—a distance of about 230 km. 

That morning I felt in particularly good form, inspired by Francesco Moser’s fantastic performances in the preceding days. 

Two food supply zones were planned for that stage—the first at the 90 km mark, and the second at 150 km. My plan was to reach the first zone. 
The race rhythm that day was relatively flat, so that I was able to reach the food zone with the same 40’ lead on the racers that I had when I started. I decided to keep on going to the second zone. 

It was a magnificent day, the course mildly hilly, my legs in good shape. I didn’t have much nourishment with me—just a banana and a water bottle. 

The wind came up around noon. Around me there were only endless fields of wheat. Despite my efforts, my average speed had fallen from 36 to 33 km/h. Afraid of being caught by the racers, I pushed myself harder. 

Suddenly, after covering about 120 km, in the space of a few hundred meters, I felt completely empty. My legs and arms had no strength, my mind was scattered. My speed now fell to 20-22 km/h, and it felt like my bike was simply stuck to the asphalt. 

Despite the sunny weather, I felt cold, and my pulse, even though I was putting out maximum effort, didn’t get above 120-130. Slight grades of only 2-3% became impassable “walls”. My spine, in the lumbar region, was stiff and painful. 

Finally I was forced to stop at a lowered level-crossing. A journalist friend pulled up in a car and recognized me. 

“Have anything to eat?” I struggled to ask him. 

“Just a couple of cokes. Want them?” he replied. 

I gulped down the two cans of coke, and the 70 g of sugar turned my brain back on. Heat returned to my body, prompting me to start pedaling again, albeit at a much lower speed, as far as the food zone that I reached only a few minutes ahead of the racers.


“Bonking” have hit all bicycle racers at one time or another, and every great champion has felt their effect at least once. From Coppi to Merckx, from Anquetil to Hinault, from Ullrich to Armstrong, with more or less disastrous results. 

All these crises can be traced to a single cause: exhaustion of hepatic and muscular glycogen reserves. About 100 g of glycogen are stored in the liver to maintain a constant blood sugar level (glycemia), essential to correct brain function. 

Exhaustion of this supply can be easily countered by an intake of at least 30-50 g of sugars or quickly absorbed carbohydrates for every hour of effort. 

Running out of muscular glycogen (about 400 g) can be prevented by an adequate intake of carbohydrates in the 12-24 hours preceding the effort. 

But a proper intake of lipids in the diet, along with an appropriate training strategy, leads to better use of fats as fuel, therefore reserving the glycogen for the end of the race.

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