Endurance Running

Good intentions? Marathon? In 1995, I plunged into a ¼-marathon. An experience I will never forget. Forty-six minutes of blood sweat and tears before I passed that long awaited finish line. I held onto a railing while regaining an awareness of my surroundings. This taught me an invaluable lesson: “never, never again”.

During the exercise laps, I ran like hell. I was not satisfied until I was beat. The training was no fun. I clearly needed a better approach. I found this while training for the City Pier City ½-marathon at a Road Runners club in Holland (HRR). This article discusses some of the basic theory, and presents a calculator to determine your training paces.

Heart Rate

Reliable feedback is the key to controlling your workout. An objective measure is literally at your fingertips: your heart rate (HR). Simply count the number of beats at the side of your larynx for fifteen seconds and multiply it by four. A useful tool is a heart rate monitor. hartfrequentieThe advantage of such a gadget is that it gives a reading while you are running. Reliable heart rate monitors use a strap that goes around your chest. One of the manufactures is a Finnish company called Polar.

Your heart rate is minimal in the early morning just before you jump out of bed. It gives an indication of the amount of blood that the heart can pump in one beat. Illness, fatigue, stress or extreme weather can easily raise your minimum heart rate by twenty beats per minute (bpm). The maximum heart rate mainly depends on you age although it varies widely among persons. You measure your maximum heart rate after five minutes of intensive running in which you give it all during the last 30 seconds.

Workout Intensity

Muscles need oxygen and energy to function. The lungs extract the oxygen from the air and the heart transports its via the blood to the muscles. Your body meets the requirements of a demanding workout by increasing the oxygen intake (heavy breathing) and increasing the heart rate.

We put the intensity of the workout on a scale between 0% and 100%. The minimum heart rate corresponds with 0% intensity. The heart rate during a race corresponds with an intensity of 100%. As shown in the picture above,the relation between the intensity and the heart rate is linear up to the anaerobic threshold. The anaerobic threshold is the heart rate at which the oxygen intake is just sufficient to maintain this intensity for a long period of time.


Carbohydrates are the main energy source for endurance runners. The carbohydrate reserve is stored in the muscles, liver and blood and originates from sugar, glucose and starch. The other energy source is fat. Even skinny persons have enough fat to walk an impressive number of marathons. Fat will always be there for us. Carbohydrates are what we need to think about.

The oxygen level in the blood determines if your body uses carbohydrates or fat. Burning fat requires 50% more oxygen as burning carbohydrates. At a slow pace, your breathing supplies enough oxygen to allow your muscles to utilize the fat reserves. At a higher pace (where you cannot talk anymore), the oxygen intake and blood circulation is insufficient to burn fat and the muscles “switch” to carbohydrates. A lot of people who want to lose a few pounds run fast. They probably even gain weight because they build up muscle tissue while at such a high pace their body burns carbs instead of fat. If you want to loose some pounds take one advice: run slowly for at least half an hour.


As we have seen before, the workout pace determines the “choice” between the two energy reserves. Three factors play an import role in choosing a good race pace. 1) At a high pace the blood flow can not transport enough energy to the muscles. 2) At a slightly lower pace remote carbohydrates can be burned as well. 3) Fat can only provide energy in combination with carbohydrates.

At a high pace the energy transport can not keep up with demand and your body has to rely on the carbohydrates stored locally in the muscles. This supply lasts for 1 ½ to 2 hour. When this supply runs short, the body has to switch to remote carbohydrates (from the liver and blood). The power drop associated with this is often called “the man with the hammer”. You prevent this devastating effect by not starting too fast. This way your muscles burn “remote” carbohydrates from the start.

The second part of this series is about the optimum training pace, and includes a training pace calculator.

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Passionately curious and stubbornly persistent. Enjoys to inspire and consult with others to exchange the poetry of logical ideas.

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