Therefore, lack of oxygen is crucial for exercise

If we devote ourselves to training where we are breathless, we become more enduring. We get better fitness. This year's Nobel Prize in medicine reveals what is happening in the body - and how we should train smartest.

What makes us more sustainable is the kind of protein that is activated in the body - for example, when we exercise. The proteins called HIF (hypoxia-inducible factor) become active in the body when parts of the body's tissues or organs experience oxygen deficiency.

That's also what happens when we train so that we get really breathtaking, explains one of this year's Nobel laureates in medicine, William Kaelin, for SVT when we meet him at Harvard University's training facility.

- Now that we run here, HIF is activated and in the organs and tissues in the body that have oxygen deficiency, an adaptation is created, for example in the muscles, says William Kaelin while jogging around on the racetrack and becoming very breathless.

Just being breathless is the key to training. Slower exercise has several positive effects, but when it comes to activating the important HIF protein, it is necessary to cause a little lack of oxygen when exercising, explains the Nobel laureate.

- It creates changes in blood flow, increases the amount of red blood cells, changes how cells burn energy - and how cells store energy. In addition, it affects the appearance of new fine blood vessels, capillaries, in the muscles, says William Kaelin.

It was about 20 years ago that this year's three Nobel laureates discovered the great importance of HIF proteins to our bodies. Since then, many athletes have also begun to speak the same language, emphasizing the importance of exposing the body to some lack of oxygen during certain workouts. This can be done, for example, by interval training, where you run really fast short distances and can breathe out for a while between each track.

- As an athlete, you strive to improve, whether you are an elite athlete or an amateur athlete. One way to do that is to run tough, because that's when you get a lack of oxygen in the muscles, says the marathon runner and training coach Anders Szalkai.

More about the Nobel Prize, the training and the body's oxygen system in the Science world in SVT Play from December 8 and on SVT2 on December 9 at 20.