Anti-Aging: Preventing Bonking and Hitting the Wall, part 1 – Road Bike Rider

By Coach John Hughes

In a recent column Brian W. asked, “I have been riding on and off for about 35 years. I am 54 now. frequently ‘bonk’ after about an hour. It doesn’t matter if I am doing a moderate or higher intensity ride. I can do 20 miles flat riding at about 15 MPH, my heart rate stays above 150 the whole time, after about an hour I just run out of gas.  I drink Gatorade and eat small snacks every 30 minutes or so. Sometimes I find a second wind. Sometimes I just crawl (metaphorically) back to the car. I always recover quickly. About an hour after a ride my heart rate is 70 or so. My resting HR is about 60. What can I do to increase my endurance and be able to ride 75 plus miles without bonking? I have the right gears and my position on

Brian is asking three different questions:

  1. How to avoid bonking after about an hour?
  2. How to ride 75 miles without bonking?
  3. How to get back to where he was 20 years ago?

This column addresses the first two questions

Experiment of One

I’ll share with you what I know from the scientific literature, 40 years of coaching and 50 years of turning the cranks. However, we’re each an experiment of one. What follows may or may not work for you.

I. How to avoid bonking / hitting the wall after about an hour

Bonking and hitting the wall mean the same thing: your body is running out of glucose. 

You are always metabolizing a combination of fat and glucose even when you are sleeping.  The more active you are the higher the proportion of glucose you are burning.  Riding below your anaerobic threshold (AT), also called lactate threshold, about 50% of your energy is coming from glucose and 50% is coming from fat. The lower from your AT you ride you’re burning a higher proportion of fat; however, you continue to burn glucose. Glucose is used in the metabolism of fat. Even at a recovery pace you are burning a little glucose.

Above your AT your major fuel is glucose although you are still burning fat. The harder you ride above AT the more glucose per minute you are burning. Only about 5% of your energy comes from protein.

Glucose is stored in the body as glycogen. The average person stores about 1,800 calories of glycogen. (1,400 in the muscles, 320 in the liver and 80 in your blood) How much you store depends on your body size and your fitness. 

Your body has about 100,000 calories of energy stored as fat, an unlimited supply of fat.  Even the skinniest pro has enough body fat to fuel a long race.

When you run out of glucose you only have half as much fuel and you bonk / hit the wall with dead legs. Your brain can only burn glucose for fuel and when you run out of glucose your brain turns to mush.

To compound the problem the metabolism of fat for energy requires some glucose so even your fat stores aren’t providing 100% of the energy.

Endurance Training

Endurance training helps to defer bonking and hitting the wall in two ways.  By riding at a conversational pace over many rides your body will shift to metabolizing more fat and less glucose thereby sparing glucose. (This doesn’t mean you’ll lose weight. To do that you need to consume fewer total calories than you are burning.) Endurance training also increases your muscles’ capacity to store glycogen by 20 to 50%. If you’ve been doing endurance exercise for years both of these adaptations have taken place but if you’re a relatively new roadie you can improve your fuel mix and your storage capacity with endurance riding.

Brian’s Case

Brian rides 20 miles on flat terrain at 15 mph (1:20 of riding) with his heart rate above 150 bpm the whole time. He drinks Gatorade and eat small snacks every 30 minutes or so but after about an hour he feels like he runs out of gas.

Riding at 15 mph (24 km/h) a roadie burns approximately 4.5 calories / pound of body weight (10 cal. / kg.) This assumes riding on flat ground with no wind and not drafting. (The Cyclist’s Food Guide by Nancy Clark MS, RD and Jenny Hegmann MS, RD)

If Brian weighs 150 lbs he is burning about 675 total calories / hour. If he weighs 180 lbs the burn rate is about 810 calories / hour. About ½ of the calories come from fat and ½ from glucose. A 150 lb. rider burns about 338 an hour calories / hour of glucose and a 180 lb. cyclist burns about 405 calories / hour of glucose. These burn rates are less than 25% of the body’s capacity for storing glucose. Brian is drinking Gatorade and eating snacks during his ride so he’s at least partially replenishing his glycogen. The feeling of running out of gas probably isn’t from glycogen depletion over just one hour.


Brian rides at a heart rate above 150 bpm for the 1:20. Is this a good endurance pace? Can he still talk comfortably in full sentences? Or is he riding too hard? Maybe. The endurance conversational pace (Zone 2) is 69 – 83% of AT (LT). The slightly higher tempo pace (Zone 3) is 84 – 94% of AT.  Riding tempo a rider can still talk in complete sentences by can’t whistle. Let’s assume Brian’s 150 bpm is at the upper part of a conversational pace, 80% of his AT. This would mean his AT is 188 bpm! Given his age and volume of riding I doubt Brian’s AT is 180 bpm.  He’s probably riding toward the top of Z3, i.e., 90 to 94% his AT. This is a hard pace to sustain.

Given these assumptions, cumulative fatigue is probably one of the factors causing him to feel like he’s running out of gas. As an experiment, if he rode 20 miles at 12 miles an hour (1:40) and consumed the same amounts of Gatorade and snacks, would he run out of gas?

II. How to ride 75 miles without bonking

The American College of Sports Medicine (ACSM) recommends consuming 25 to 60 grams of carbs (1 to 2 ounces or 100 to 240 calories) per hour after the first hour of exercise. This is sufficient for several hours of exercise. If you are riding for three hours or more start eating carbs in the first hour. If you are relatively small or exercising lightly 25 grams / hour is enough. If you are larger or riding at a moderate to fast pace eat up to 60 grams / hour.

These are grams of carbs. Most sports drinks like Gatorade are 100% carbs. One 20 oz. bottle of Gatorade has 36 grams of carbs = 140 calories. A chocolate brownie clif bar has 250 calories; only 176 calories are from carbs (44 g). A chocolate performance PowerBar has 240 calories; 180 calories from carbs (45 g) The data is from CalorieKing, a terrific resource with information about food products.

Daily nutrition

What Brian consumes on the bike is only part of the solution to riding without bonking. Brian needs to start a ride with a full tank of glycogen (the way glucose is stored). Glycogen comes from carbohydrates, which include fruits and vegetables as well as grains and sugars. The US Department of Agriculture recommendations for healthy eating emphasize carbohydrates. For daily diets of:

  • 2,000 calories consume 2-1/2 cups of vegetables or equivalent, e.g., juices; 2 cups of fruit or equivalent, e.g., juices and 6 oz. of grains.
  • 2,800 calories consume 3-1/2 cups of vegetables or equivalent, e.g., juices; 2-1/2 cups of fruit or equivalent, e.g., juices and 10 oz. of grains.

The Swiss have developed a food pyramid for athletes exercising five hours a week, which recommends for daily carbs:

  • 3 servings (1 serving = 120g or 4.25 oz.) of vegetables (at least 1 of raw vegetables)
  • 2 servings of fruit (1 serving = 120g or 4.25 oz. or a handful)
  • 3 servings of whole grain products. (1 serving of bread = 75–125g or 2.5–4.5 oz. or legumes (dry weight) 60-100g or 2-3.5 oz. or potatoes 180-300g or 6.5-10.5 oz. cereal / pasta / rice / corn (dry weight) 45-75g / 1.5-2.5 oz.
    • Add 1 serving for each additional hour of exercise past five hours / week
    • When exercising more than 2 hours a day sports drinks / foods can be used. 1 serving of sport food = 60-90g or 2-3 oz. of a bar, 50-75g or 1.5-2.5 oz. of carbohydrate gel or 300-400 ml or 10-13.5 fl. oz. of sports drink

Swiss Food Pyramid

I wrote detailed columns on:

If Brian is eating fewer carbs and more protein and fat every, he may be developing chronic glycogen depletion.

Pre-ride nutrition

Brian is burning glucose 24 hours a day, although the amounts vary depending on how active he is.  Overnight he’s fasting until he eats break-fast. He’s still burning glucose even though he’s sleeping. If his glycogen stores are already low because of his daily diet and he goes for a fast ride in the morning before breakfast then he’s more likely to bonk.

High protein (Paleo) diet

I wrote an article on Anti-Aging: 7 Nutrition Myths. One of the myths is because our ancestors ate meat, so should we. The Paleo diet, relatively high in meat, is popular on the theory that if we eat more like primitive mankind, we’ll be healthier. However, no long-term studies have demonstrated positive health outcomes from a paleo diet. The paleo diet is much higher in protein and in fat than recommended in the Dietary Guidelines for Americans. As a result, riders on the paleo diet usually aren’t getting enough carbs.

High fat low carb (keto) diet

Another myth is we’ll perform better if we eat a high fat low carb diet. The American College of Sports Medicine position paper on Nutrition and Athletic Performance says, “Although there has been historical and recently revived interest in chronic adaptations to high-fat low carbohydrate diets, the present evidence suggests that enhanced rates of fat oxidation can only match exercise / performance achieved by diets or strategies promoting high carbohydrate availability at moderate intensities, while the performance at higher intensities is impaired.” I wrote this column on High Fat Low Carb Ketogenic Diets.

In addition to eating correctly, riding 75 miles without bonking depends on training effectively before the ride and pacing during the ride. I’ll address these in the next column.

Related columns

Healthy Nutrition Past 50

I address the vital role that healthy nutrition plays in helping you stay active, energetic, happy and fulfilled into your 50s, 60s, 70s and beyond. I explain in detail:

  • The key role of carbohydrates in providing the energy you need and many of the vitamins and minerals.
  • How much protein you really need, and nourishing protein choices.
  • The important role of fat in your diet, and healthy choices to get needed fat.
  • The principal vitamins and minerals you need.

I review what to consume while exercising, including the key roles of carbohydrates, fluid and electrolytes. I discuss how to eat preventively in order to reduce your risks of the most common health conditions as you age: heart disease including stroke; diabetes; being overweight, which increases your risk of heart disease and diabetes; how to reach and maintain a healthy weight; and osteoporosis. The 28-page Healthy Nutrition Past 50 is $4.99.


Eating and Drinking Like the Pros: How to Make Your Own Sports Nutrition  

I researched what the former Team Sky, Garmin-Cervélo and RadioShack riders consume before, during and after a stage and discussed the results with cycling nutrition experts. We all require energy and replenishment of lost minerals and nutrients when we ride. Eating and drinking like the pros offers us the same nutritional benefits, which we can customize to our own needs – typically at a fraction of the cost of commercial sports food and drink, if we choose to make our own. I worked with a professor of nutrition and an expert on hydration and electrolytes (both experts are cyclists) in creating recipes for both sports drinks and food. They’re easy to make, with known, unprocessed ingredients, and can be tailored to your specific taste and needs. The 15-page Eating and Drinking Like the Pros is $4.99.

Nutrition for 100K and Beyond: What to eat before, during and after a bike ride.

I combine the best of current research with 50 years of riding experience to teach you proper nutrition for cycling. Initially written for longer rides the lessons apply to all endurance riders.

If you don’t fuel properly, you won’t get very far either in training or in rides. We all know the basic point: when cycling we are using energy and we need to replace the energy. However, energy needs vary by individual and type of riding and not all fuels are equally effective. This article will teach you:

  • Personal Energy Need: how to estimate how many calories you are burning per hour at different speeds.
  • Types of Fuel: how carbohydrates, fat and protein contribute to your energy needs.
  • Training Implications: what are the training implications of your personal energy needs, your cycling goals and the types of fuel.
  • What to Eat: what you should eat including quantity per hour, types of fuel, complex vs. simple carbohydrates, sports products vs. grocery store food and sample foods.
  • Hydration: how much to drink both to avoid dehydration and to avoid hyponatremia, diluting your blood sodium.
  • Electrolytes: what you need and a comparison of sources.
  • Experiment of One: we are each an experiment of one, how to test and refine your nutrition.
  • Before and After Events: what to eat pre-event for strong performance and post-event for optimum recovery.
  • 24-Hour and Beyond: how to maintain energy over a 24-hour or longer event.
  • Myths: common popular myths about sports nutrition.

I will teach you everything you need to know to avoid hitting the wall with dead legs or bonking with a fuzzy depressed brain. The 17-page Nutrition for 100K and Beyond is $4.99.

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.

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