Bente Klarlund answers questions from readers. This time about training.
I need to improve my fitness. What kind of training is best?
Sune: I am a 43-year-old man. I am healthy, but I weigh about 90 kg, which I think is too much. I have just participated in the Royal Run, where I ran 5 km in 31 minutes and 30 seconds. I would like to run faster next year. This means that my fitness level needs to go up. What training is the best?
Bente Klarlund Pedersen: You are right that there is a clear connection between the time you can achieve in a long-distance race and your fitness. When we use the term fitness in everyday speech, we are thinking of the circulatory fitness, i.e. a person’s training status in terms of endurance in, for example, running, cycling and swimming. Technically, fitness is the same as maximum oxygen uptake. The fitness number is calculated by dividing the maximum oxygen uptake by body weight. The individual person’s fitness number is important for how fast he or she can run. This does not mean that fitness is the only factor that determines performance, but it is an important factor.
First of all, it is important to get enough oxygen into the blood. To ensure this, you need to train your heart and circulation. The heart is a muscle, and the heart muscle can be trained. When you train, the heart grows and can pump blood out more efficiently with each beat. At rest, the trained body does not need more blood than the untrained body. Therefore, the resting heart rate decreases as your fitness improves.
Conditioning training causes the heart to fill better, beat more strongly and pump more blood to the muscles with each beat. Stroke volume is the amount of blood the heart pushes out per beat. A well-trained runner’s heart can pump twice as much blood around the body per beat as the heart of an untrained person. The amount of blood the heart can pump out per minute is called cardiac output. Cardiac output depends on the heart rate and the heart’s stroke volume. Since stroke volume increases with exercise while the heart rate decreases, cardiac output at rest is independent of the level of exercise. At rest, the heart pumps out approximately five liters of blood per minute in both trained and untrained people. During maximum work, the heart can pump out 15-20 liters per minute in untrained young men and up to 35-40 liters in very well-trained men.
Maximum oxygen uptake is best increased by high-intensity exercise, where you become breathless, have a high heart rate and cannot talk while you are active. In principle, you can also train your heart’s pumping capacity at lower intensities, but in that case you have to train for a much longer time. I suggest that you try so-called high-intensity interval (HIIT) training. For example, you can try 10-20-30 running, which is an intensive interval training form where you run: 30 seconds at a slow pace, 20 seconds at a moderate pace and 10 seconds of sprinting. Each interval takes one minute, and you repeat this three to five times. Then you take a one to four minute break. You can also run on hilly terrain and give it your all up the hill, so that you are maximally breathless.
You mention your weight yourself. By fitness number we mean the maximum oxygen uptake divided by body weight. The formula shows that you can improve your fitness number by increasing your maximum oxygen uptake. However, if you reduce your weight, your fitness number and thus your running speed will also improve.
Source:
Love running with the marathon book by Tor Rønnow & Bente Klarlund p.1-287. Bianco Luno 2011
What is the most important training?
Jesper: I only have limited time to exercise, but there is a lot of heart disease in my family, so I know it is necessary and important. But what is most important when I am busy? Is it strength training or running? I am 54 years old.
Bente Klarlund Pedersen: There are actually quite a few people who are currently asking the same question as you: which type of training gives the greatest benefit if you want to live a long life? Is it the cardio training that gets your heart rate up and your forehead sweating? Or the strength training that builds muscles?
Recently, an answer to that question has been provided. The research project, called the Østerbro Study, has followed almost 10,000 Danish men and women for 27 years, during which around 5,000 died. The study shows that both strength training and cardio training reduce the risk of cardiovascular disease and extend lifespan. But the study also shows that cardio training has a better effect than strength training. People with high fitness had a 10 percent lower risk of both early death and cardiovascular disease compared to those who trained hardest in the muscular strength group.
The vast majority of studies on health and the heart focus on getting your heart rate up and training your circulation. In strength training, your heart rate doesn’t get that high, so it’s kind of surprising that strength training has a good effect, even though it’s not as effective as cardio training.
However, the conclusion is not that you should give up strength training. It is incredibly important for maintaining balance, preventing falls and bone fractures. Therefore, a combination of cardio and strength training is the ideal form of training. If you can’t handle having to train in both ways, remember that the best training is the one you actually do.
Sources:
Schnohr P et al. Comparison of Muscle Strength and Cardiorespiratory Fitness in Relation to Cardiovascular and All-Cause Mortality: The Copenhagen City Heart Study. Mayo Clin Proc. 2025 Mar;100(3):488-498.
https://videnskab.dk/krop-sundhed/nyt-studie-saadan-skal-du-træene-hvis-du-vil-leve-sondere-og-lengere/
Bente Klarlund Pedersen
