Don't Hit the Wall

When you start out with running, fueling during running is no concern. Just eat a decent amount of carbohydrates during the day, and you will be good to go. But when you start to surpass the 1-hour mark, it starts to get tricky.

In your body, there are multiple energy systems. These energy systems are categorized based on the time frames they are used and how long they can sustain energy production.

The three primary energy systems in the body are:

1. ATP-PCr System (Phosphagen System):

The ATP-PCr system utilizes adenosine triphosphate (ATP) and phosphocreatine (PCr) stored in muscles.

It is the quickest way to produce energy and is crucial for activities like a sprint, a heavy lift, or a short, intense burst of energy. This immediate energy source is for very short bursts of activity (0-10 seconds).

2. Glycolytic System (Anaerobic System):

The glycolytic system breaks down glucose or glycogen to generate ATP.

It doesn't require oxygen and is efficient at producing energy quickly, making it suitable for activities like weightlifting, high-intensity interval training, and short sprints. This system provides energy for short to medium-duration activities (10 seconds to 2 minutes). 

3. Oxidative System (Aerobic System):

The oxidative system relies on aerobic metabolism, which utilizes oxygen to break down carbohydrates, fats, and, to a lesser extent, proteins for energy.

It is the predominant energy system for activities such as long-distance running, cycling, and other endurance sports. The oxidative system can supply energy for extended periods, as it efficiently utilizes energy stores from the body's fat and glycogen reserves. Used for sustained, low to moderate-intensity activities. 

The graph below shows a clear picture of what energy systems are used at different durations of exercise.

Aerobic glycolysis is the zone where we will race the most. At race intensity, it uses the glycogen reserves in the body to produce energy. But your body has limited carbohydrates stored in the form of glycogen. Around 500 grams of glycogen in the muscles and 100 grams of glycogen in the liver.

In well-trained athletes, this can be a bit higher. These glycogen stores will last between 80 to 90 minutes roughly. This is, of course, dependent on the individual athlete.

When the glycogen stores are depleted, your body has to return to burning fat for fuel. This produces much less energy and thus forces you to slow down.

As you can see in the graph below, the harder the exercise intensity, the more carbohydrates are used.

This is where fueling during running comes into play.

When we take carbohydrates onboard during running, the body will prioritize to burn that first. This will stop the body from delving into the glycogen reserves, and you will delay the emptying of the glycogen reserves. This will make you able to run faster for longer.

So how do we fuel up during the run? Eat carbohydrates.

Maybe easier said than done, so let me explain the options:

1. Energy gels: Energy gels are the most known and commonly used in distance running. They are easy to carry around and contain somewhere between 20 and 40 grams of carbohydrates per serving. I really prefer using gels, and my favorites are the SIS beta fuel gels. They contain 40 grams of carbohydrates, which makes fueling easier.

2. Energy bars: Energy bars are solid bars that contain a high level of carbohydrates but also offer some other nutrients. Usually, there are some fats and protein in there as well. I’ve found it impossible to eat at high intensities but like it for trail running where the intensity is a bit lower. My preferred brand is Clif Bar.

3. Energy chews: Specially designed sweets that contain a high amount of carbohydrates. They are usually also easier to eat and don’t require chewing that much as you would with normal candy. I prefer the PowerBar Energy Shots Orange or Clif Bloks.

4. Carbohydrate drink mixes: If none of the above work, you could try carbohydrate drink mixes. These powders will dilute in water and give an easy-to-drink mix. Usually, this contains around 80 grams per 500 ml of water. Bonus points for also getting hydrated during your run, but a bit more difficult to carry around. My personal preference is the SIS beta fuel cherry drink mix.

5. Fruit mixes: There are some brands that offer fruity packages that have blended foods in them. It looks like baby food but usually contains the same amount of carbohydrates as energy gels and has quite a refreshing taste.

6. Solid high carb food: High carb food such as bananas can be used during running as well, but it is harder for your body to extract the carbohydrates from them. Other options are dates, dried fruits, raisins, or honey.

So, in conclusion, try to get around 40-60 grams of carbohydrates per hour if you are running longer than 1 hour. Try out different carbohydrate sources and experiment with different brands, how much you intake and at what intervals. This is an ongoing experiment, and you have to be willing to face it that way.

For me, it works best to take 1 gel if I’m running longer than 1 hour and 2 gels if I’m running longer than 1 and a half hours. When I’m running longer than 1 hour, I start to get sick of gels, so I will opt out to different energy sources like an energy drink mix or some more solid foods to alternate between them.

Thank you for reading

-Tim 👟

PS: Fueling is one part of the puzzle. The right shoes are another.
If you're serious about running longer, more comfortably, and injury-free, I can help you choose the best shoes for your stride.

Check out my 1-on-1 consults ⬇️