Peaks Challenge Series – Power to Weight Ratio and Tuning Your Metabolic Efficiency

In this article, I go into more details on improving your power to weight ratio and your metabolic efficiency. Two important things to consider when training for the Peaks Challenge events.  

The Importance of Power to Weight

While cyclists get fanatical about getting the lightest wheel and bike, the real savings can be made much cheaper and result in a far greater gain in performance. All you have to do is focus on losing a few of those extra kilograms of body weight that you are caring around.

It’s all about the power to weight ratio. So we work on roughly 3 to 5 Watts per kilogram when you’re going uphill. If you weigh 10 kilograms more than somebody else, then you need to put around 30 to 50 more watts into the bike just to stay with them. That’s big, especially when you’re riding at threshold or on a ride that has as many vertical meters of climbing as in the Peaks Challenge Cradle Mountain. One of the big things that we did with our athletes last year in the preparation for the Peaks Challenge Series was to work on reducing their body weight down to a real athletic level so that they could climb at their maximum.

By losing those few extra kilograms of body weight that you are caring around you will shave time off your Peaks Challenge Cradle Mountain ride. I recommend that you only lose 1 kilogram per week. And the myth about losing strength when dropping your weight is unfounded. I’ve never seen it in the athletes that I’ve coached as long as they are losing fat, not muscle.

Optimal percentage of body fat ranges from 5% to 13% for men and 12% to 22% for women.

To do this just watch your consumption of calories. Reduce your meal sizes and cut out any unnecessary treats and snacks.

Don’t go crazy with it though. You’ll still want to be eating while out riding. If you get back from a training ride feeling starved then take a little more food with you on your next ride.

Metabolic Efficiency – The ability to burn more fat at higher intensities

Also, you can improve your metabolic efficiency. This is the ability to burn more of your fat reserves at high exercise intensities.

The way that you burn them is very important. The blend ratio of fat to carbohydrate that you use varies depending on the intensity that you ride at. In this case, we’ll measure intensity in watts. When you ride at an easy pace (low power outputs), you burn a higher percentage of fat to carbohydrate. As you increase your intensity and ride faster, you produce more power on the bike. When you do this, the ratio of fat to carbohydrate changes and you start burning a higher percentage of carbohydrate to fat. Please see figure one.

Figure 1 General percentage of fat to carbohydrate burn rates based on cycling intensity (in watts)

A seasoned cyclist will have enough carbohydrate stored in their bodies to provide them with around one to two hours of high-intensity cycling. Once the carbohydrate stores are depleted the cyclist then bonks or hits the wall.

The onset of bonking comes on very fast. It only takes around 2 to 3 minutes to go from riding very well at high intensities to not being able to ride faster than around 12 km/h. The reason for this is that fat is not able to be metabolised fast enough to provide the muscles with enough energy to drive them back up at to ride at these high intensities.

No amount of willpower will enable a cyclist to push through the laws of metabolising energy. When you run out of carbohydrate, you can only ride slowly, nothing more.

Many cyclists misinterpret the gradual drop off of performance during a long endurance ride as bonking. This gradual decrease in performance is more likely caused by general fatigue due to poor preparation and fitness leading up to the event rather than running out of carbohydrate and bonking. It’s important to understand the distinctions between bonking and general fatigue when understanding your nutritional requirements.

In the 1980s when the marathon craze hit the world, many people suffered from hitting the wall in the closing km of their run. To deal with it many people adopted a very poor form of carbohydrate loading. They would consume a large amount of carbohydrate in the final days before their race to store as much carbohydrate in their bodies as they could before the event. This form of carbohydrate loading is fundamentally flawed and will only provide a very minimal form of performance improvement on the day of their event. Unfortunately, many people continue to pursue this practice today.

A better way to deal with reducing the chance of bonking is to work on improving the efficiency of burn ratio between carbohydrate and fat. It’s called improving metabolic efficiency and is a far more successful protocol to adopt.

Cyclists that live on a diet rich in high Glycogen Index (GI) carbohydrate tend to exhibit a poor metabolic efficiency. Figure two provides an example of the burn ratios of carbohydrate and fat in these cyclists. As you can see this cyclist has a very poor ability to use fat as a primary energy source and relies heavily on carbohydrate as an energy source for much of their cycling at most intensities. This cyclist has a very high chance of bonking and will need to consume large amounts of carbohydrate during their endurance rides to ensure that they maintain their carbohydrate levels.

Figure 2 Example of poor metabolic efficiency in a cyclist

Cyclists that train their metabolic efficiency can change their burn ratios of carbohydrate and fat. The process of doing so can provide an adaption in around six to eight weeks. The result is a curve similar to the one shown in figure three. In this case, the cyclist has lifted their ability to burn more fat at higher intensities that enable them to become less reliant on consuming a large amount of carbohydrate during their long endurance rides. As you can see this provides a curve closer to the figure 1.

Figure 3 Example of good metabolic efficiency in a cyclist

How to Improve Your Metabolic Efficiency.

You can do this by reducing or eliminating the amount of high GI carbohydrates like sugary foods and snacks that you eat. See this table for more information:

Food GI Score (1-100)
Soft Drinks ~63
White Bread / Rice ~70
Potatoes (Excluding Sweet Potatoes) ~80
Beer ~66
Cake ~40-80
Commercial Cereals ~80


Here is a good article on GI index:

Increasing the glycogen storage through carbohydrate loading is one way to increase the time it takes to bonk or hit the wall. But its effect is limited in increasing storage for the average cycling event of 100km or more.

In recent times we have been using a technique called metabolic efficiency. In this method, we train the body to burn more fat at higher intensities thus extending out the time it takes to deplete our glycogen store.

Here are two options that I recommend specifically for recreational riders (the protocols are different for racing cyclists):

Protocol One

  • Wake first thing in the morning but don’t eat.
  • Do a 1-hour interval session that includes at least 30 minutes of intervals at around E3 (85-91% of max heart rate or 91-105% of 60-minute threshold power).
  • Then do a one hour ride at around E1 (65-74% of max heart rate or 56-75 % of 60-minute threshold power)
  • Drink straight water (not a sports drink) if required.
  • Eat your typical low GI carbohydrate breakfast as soon as the ride ends.

Protocol Two

  • Wake first thing in the morning but don’t eat.
  • Drink 2-3 cups of coffee (with no sugar), up to 45 minutes before cycling.
  • Do a 1-hour high-intensity interval session that includes at least 30 minutes of intervals at around E3 (85-91% of max heart rate or 91-105% of 60-minute threshold power).
  • Drink straight water (not a sports drink) if required.
  • Then do a one hour ride at around E1 (65-74% of max heart rate or 56-75 % of 60-minute threshold power)
  • Eat your typical low GI carbohydrate breakfast as soon as the ride ends.

***IMPORTANT*** If at any time that you are riding using these protocols and feel faint, your vision becomes blurry, have a dramatic loss of energy or a sudden onset of fatigue then you must stop riding and consume a High GI Carbohydrate immediately!

***IMPORTANT*** In this case more is not better. Do not use these protocols for rides longer than two hours. If you do, you’ll most certainly bonk or hit that wall, and that is not the outcome that you want. If you are riding for more than two hours then always consume around 30-60 grams of carbohydrate an hour.

***IMPORTANT*** Do not do this type of training for your long weekend rides. I recommend that for these rides you consume a low GI carbohydrate before the ride and then consume low GI food during the ride. Stay away from sports drinks and gels. If the weather is hot, then use a sports or electrolyte drink to avoid muscle cramp and dehydration.

The important thing is to train your body to burn fat in a glycogen depleted state. When you wake up in the morning your glycogen stores are relatively low so by training first thing in the morning you take advantage of this. Later on in the day you would have eaten and still providing a supply of carbohydrate that your body can supply to your glycogen stores.

In the next article, I’ll be discuss tapering for the Peaks Challenge Cradle Mountain and final tips for the event as well as getting started with your Peaks Challenge Falls Creek Training.

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