September 27, 2022
If you have done long bike rides in the past, you will know that carbohydrate intake is essential during those rides. But you might sometimes wonder why a certain hourly carbohydrate intake is advised and why it is different per ride. In this blog we elaborate on the 5 factors that are crucial when it comes to calculating how many carbs you should take per hour. Plus, we’ll show how you can see and use these statistics in the EatMyRide app.
Your advised intake is usually expressed as an hourly intake. This is because this metric is easy to remember; you can for instance translate an intake of 60 grams per hour to roughly 2 energy bars per hour. Also, it is a good indicator of the type of products you will need – with an intake of 60 grams per hour you need carbohydrates that can be absorbed as quickly as 60 g / h or 1 g / min. Besides, it is an indication of how trained your gut needs to be. In general, the higher the hourly intake rate, the more critical it becomes to take the right the type of products and the more trained your gut needs to be.
Having said that, let’s dive into the 5 main factors that determine your hourly carbohydrate intake.
When we talk about your energy tank, we mean your glycogen stores. Carbohydrates are stored as glycogen in the body. If your glycogen stores are fuller, you will be able to use more carbohydrates that were already available in the body. This means that you will need to eat a bit less on the bike. During longer and more intense rides you might opt for carbohydrate loading (or carb loading) to start with a fuller energy tank. Especially during rides in which you burn far more carbohydrates than you can take in during riding, it is good practice to start carb loaded.
You may think, if I just make sure I start with full glycogen stores, I can keep riding until I am fully depleted. Unfortunately, this is not completely true. Your performance can already get impaired if glycogen stores drop below approximately 30% of your maximum glycogen storage capacity. During races you want to keep performance up, and therefore limit the amount of glycogen depletion. On the other hand, during certain trainings you might be less interested in maximum power output. In that case the energy tank may empty more during the ride.
It is obvious, but important: the duration of your ride is crucial when it comes to determining how much you should eat. In general you don’t start with empty glycogen stores, so during the first 1 to 2 hours you could still get your carbohydrates from glycogen stores and from the preparation meal you took before your ride. However, if the ride is 4 hours or even more, you are mainly dependent on the carbohydrates you consume during your ride. In practice this means that 2 bars per hour are often needed on rides of more than 4 hours.
As you become fitter, you start to increase your power output. Increasing your power output means increasing your energy expenditure. When it comes to nutrition intake during the ride we are mostly interested in carbohydrate burn. Your carbohydrate and fat burn – your metabolism – also changes when you become better trained. The best way to understand this is to distinguish between absolute and relative intensity.
A well-trained and a less-trained athlete might both be able to ride at 250 Watt for a prolonged period. They are thus riding at the same absolute intensity. For the less-trained athlete 250 Watt may approach his Functional Threshold Power (FTP), so it is a high relative intensity for him. On the other hand, for the well-trained athlete 250 Watt might be only 70% of his FTP, so for him it is a lower relative intensity.
The absolute intensity determines the total energy burn, while the relative intensity mostly determines how much energy comes from carbohydrates and how much from fat. The higher the relative intensity, the more energy comes from carbohydrates.
To summarize, the better trained you are, the more energy you will burn. But carbohydrate burn is determined not only by the total energy burnt but also by the relative intensity at which you ride. This brings us to the fifth and last important factor.
As we just said, the higher your intensity the more you burn and the higher your relative intensity the more of the energy comes from carbohydrates. Since your carbohydrate burn increases more than linearly when exercise intensity increases, the intensity has a huge effect on the required carbohydrate intake. When a ride has periods of high intensity as well as periods of low intensity, the carbohydrate burn will be higher compared to a stable ride with the same average intensity. If you are familiar with power meters and their metrics: if the normalized power is much higher than the average power, it is a sign that carbohydrate burn may be relatively high. We have dedicated a full blogpost to the relation between metabolism, intensity and carbohydrate burn.
When you create a nutrition plan for your rides, you will see an overview of your statistics. This means you will see things like:
Having these insight will make it easier for you to nail your nutrition during all your rides.
Your personal metabolism hugely impacts your carbohydrate burn during cycling and therefore also how your optimal nutrition plan should look like.
Taking enough carbohydrates during your rides is vital. With the EatMyRide Carbohydrate Burn/Intake Balancer for Garmin you can track your carbohydrate burn and intake in realtime.