RBR Reader Kevin wrote, “I have raced tandem bikes for 14 years. I have reached a point I don’t race; I participate in long endurance rides. Last Wednesday was the Bone ride from Madison to Milwaukee Wisconsin and back (158 miles). My pilot and I weren’t able to go for any rides this year, which would have been good for us and to check out the tandem. We decided not to do it. That didn’t stop me. I rode indoors on my single bike with a Saris H3 trainer.
“I started off good. My goal was to hold 220-230 watts. I was good through the 4th hour. I then took a 1-hour break as this is normal on the Bone ride. I started up again and felt good through the 5th hour. Then I started to fade. My watts were holding around 220 and no more. The 6th hour was even tougher. My watts dropped down to about 210. I was really struggling and had to take a 15-minute break and refill my fluids. I got back on and it was still getting tougher. My watts were now down to 190-200. I was at about 147 miles and at about 7 hours and 35 minutes. I don’t know how I did it and was able to bring my watts up to 230-240 with some fluctuation. I just did a 10 min easy spin for the last 10-15 minutes which allowed me to reach the 158 miles. Was I starting to bonk?
“During the ride I was consuming peanut butter rolls that have peanut butter, oat meal, ground flax seed, honey and dark chocolate. I ate one at hour 1, 3, 5 and 7. In between I also ate 4 Clif bars and consumed 8 ounces of Hammer Gels. Is this enough? I started at 172.6 pounds and ended at 164.5 pounds.
“For fluids I used a powder mixed with water. It had a lot of sodium and a moderate amount of carbs, sugar and various other nutrients. When I got down to about 10 ounces of the 95 ounces of this fluid, I could tell there was a lot of salt. I also consumed 96 ounces of water.
“Was this enough?”
Coach Hughes
Kevin, I admire your discipline to do an almost eight hour ride on the trainer! I know how tough that was. When I was training for the solo Race Across AMerica in the 1990s, I suffered through long rides like that.
Let’s look at the factors:
Calories Burned
Riding at a recreational endurance pace about half of your energy comes from glucose from carbs and half from fat. The harder you ride, the greater the proportion of carbs for fuel. Only about 5% of your energy comes from protein. Everybody – even the skinniest racer — has enough body fat for a long ride.
Your body metabolizes carbs into glycogen, which is stored in your muscles and liver and then the glycogen is metabolized as glucose to fuel your legs. Your glycogen stores are limited to about 450 grams (1,800 calories). [Dan Benardot, PhD, RD, FACSM, Advanced Sports Nutrition, 2nd ed. pp 2-3]
If a rider weighs 120 lbs and rides (non-drafting, flat) at 18 mph then the cyclist is burning approximately 650 calories / hour. If a cyclists weighs 180 lbs and rides at 18 mph the cyclist is burning about 1000 calories / hour. Nancy Clark doesn’t have the burn rate at 20 mph. [Nancy Clark, MS, RD, and Jenny Hegmann, MS, RD, The Cyclist’s Food Guide, 2nd ed., p. 145]
You weighed 172 lbs, not 180 lbs, but you were riding an estimated 20 mph, not 18 mph. You were probably burning 900 – 1100 total calories every hour, of which 450 – 550 were calories of glucose every hour. Don’t get hung up on the exact burn rate per hour. The only way to determine it is with an expensive test in a sports lab. These estimates are close enough for our purposes.
Calories Consumed
Because glycogen stores are limited, eating sufficient carbs is the key to not bonking. Here’s the nutritional breakdown of what you consumed:
1 peanut butter roll has:
- 679 total calories
- 200 calories of carbs (50g)
- 479 calories of protein and fat
1 CLIF bar has 250 total calories
- 172 calories of carbs (43g)
- 78 calories of protein and fat
- 130 mg sodium
1 Hammer Gel has 90 total calories:
- 90 calories of carbs (22g)
- 0g protein; 0g fat;
- 25 mg sodium
95 fl. oz. drink mixture:
- 500 calories of carbs (125g)
- 2000 mg sodium
Total Calories of Carbs Consumed
| Calories from Carbs | Sodium | |
| 4 Peanut Butter rolls | 800 calories | n/a |
| 4 CLIF Bars | 690 calories | 520 mg |
| 8 Hammer Gels | 720 calories | 200 mg |
| Sports drink | 500 calories | 2,000 mg |
| PB&J (approx.) | 190 calories | 350 mg |
| 1 banana | 110 calories | 1 mg |
| Total consumed | 3,000 calories of carbs | 3,071 mg |
Assuming you started with a full load of muscle glycogen you had about 1,800 calories of glycogen on board when you got on the bike, which your body metabolized to glucose as needed. Your body metabolized carbs you ate during the ride to provide 3,000 of glucose. So you had available a total of approximately 4,800 calories of glucose.
You rode for about eight hours burning approximately 450 – 550 calories of carbs every hour. You burned a total of 3,600 to 4,400 calories of glucose during your ride.
It’s unlikely you bonked unless you didn’t start with a full load of muscle glycogen or if you were burning more calories per hour than I estimated.
To be sure your glycogen stores are full, three days before the ride start eating a higher proportion of carbs. You can read more in this column:
Hydration
“I consumed 22 ounces of water after half of the 95 ounces was consumed. After the 95 ounces was gone, I consumed another 75 ounces of water. (This totaled about 24 fl. oz. / hr.)
“I sweated a lot even though had a fan. I urinated at 1 and 4 hours. After that it was hard to go and it had some burning.
“I started at 172.6 pounds and ended at 164.5 pounds.”
You lost 8.1 lbs, which was 4.7% of your starting weight. (8.1 lbs / 172.6 lbs) You were seriously dehydrated and this certainly was a factor. The American College of Sports Medicine recommends no more than a 2% weight gain or loss during a ride. By the 6th hour you were getting significantly dehydrated.
You consumed 191 fl. oz., which is 6 quarts (12 pints), which you sweated out. Each pound you lost was another pint of fluid you sweated out, a total of 8 pints. In total you sweated out about 20 pints of fluid (12 pints you consumed + 8 pints of weight lost).
It’s possible you were a little dehydrated when you started the ride. As we age our sense of thirst diminishes. You can read more in this column:
Sodium
You sweated out about 10 quarts (20 pints) of fluid. On average a liter (quart) of sweat contains about 600 – 800 mg of sodium. You sweated out about 6,000 to 8,000 mg of sodium and consumed about 3,000 mg of sodium. The recommended daily intake of sodium for athletes is 1,500 mg to 10g. If you normally eat a low sodium diet (about 1,500 mg. / day), then you may have been a low on sodium and this may also have contributed to your fatigue. If your sodium consumption is typical of Americans (3,400 mg. / day), then sodium depletion probably wasn’t a factor. I am not encouraging anyone regularly to eat more salt — follow your health professionals advice. You can read more in this column:
Summary
This column discusses three nutritional factors as possible contributing factors to why you struggled for the last couple of hours of your long ride:
- Hydration: you were significantly dehydrated.
- Sodium: depending on your normal diet, you might have been a low.
- Carbs: you had plenty of glucose from carbs unless you started the ride with low glycogen stores.
In the next column I’ll discuss your training and how you approached the ride.
Related columns:
- The Important Role of Carbohydrates
- Anti-Aging: Preventing Bonking and Hitting the Wall, part 1
- Anti-Aging: Preventing Bonking, part 2, with Daily Nutrition
- 12 Myths About Hydration and Cycling
My eBooks
Nutrition for 100K and Beyond. If you don’t fuel properly you won’t get very far either in training or in rides. I combine scientific research and 40 years of experience to teach you what to eat before, during and after rides. The 17-page Nutrition for 100K and Beyond is $4.99.
Eating and Drinking like the Pros explains in detail what they eat before, during and after a race. I give you a dozen recipes to make your own sports drinks, gels and solid food, which are just as effective as the more expensive commercial products. And mine taste better! I evaluate a dozen choices when you’re at the minimart to resupply. The 15-page Eating and Drinking like the Pros is $4.99.
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- Cycling in the Heat, Part 2: Hydration Management is 21 pages and covers how to determine how much you should drink depending on your physiology and sweat rate, how best to replace your fluids and electrolytes, the contents of different sports drinks, how to make your own electrolyte replacement drinks, how to rehydrate after a ride, and how to deal with hydration-related problems.
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Coach John Hughes earned coaching certifications from USA Cycling and the National Strength and Conditioning Association. John’s cycling career includes course records in the Boston-Montreal-Boston 1200-km randonnée and the Furnace Creek 508, a Race Across AMerica (RAAM) qualifier. He has ridden solo RAAM twice and is a 5-time finisher of the 1200-km Paris-Brest-Paris. He has written over 40 eBooks and eArticles on cycling training and nutrition, available in RBR’s eBookstore at Coach John Hughes. Click to read John’s full bio.
Regards total calorie need, don’t forget that he probably got another 1,600 or so calories from fat metabolism. Unlikely that he bonked.
Hi Kerry,
Your brain can only burn glucose from carbs for fuel, not fat.
John