A thirty-something is probably far from feeling like a stiff elderly person who can barely get out of a chair. Yet 30 is the age when muscle mass begins to decline, and it slowly becomes more and more difficult to stand up or climb stairs. Starting at age 30, humans lose about 1 percent per year of muscle. This increases with age. By age 70, it averages about 3 to 5 percent per year.

That's the bad news. The good news is that this is not because of the muscles, but mainly because of our behavior, says Luc van Loon, professor of physiology of exercise and nutrition at Maastricht University. 'That average muscle breakdown applies to the population as a whole and can largely be attributed to the fact that people are, on average, less and less physically active.' So you can turn the tide yourself. Van Loon: 'This is because muscle is constantly being broken down and rebuilt at a rate of 1 to 2 percent per day. So after about two months you will have renewed your muscles, regardless of your age.'

Dynamic muscles allow people to adapt well to new physical conditions. According to Van Loon, you can become a bodybuilder even after age 80. 'But the disadvantage of our dynamic muscles is that you also lose them quickly when you start using them less. Maintaining muscles is an active process. You have to keep stimulating them.'

Strength training

Many people do strength training to look better. However, even if you do not aspire to a tight body, it is important to have a healthy muscle percentage. Professor of nutrition and exercise Peter Weijs of the VU Amsterdam and HvA: 'Of course you need muscles to move properly, but a healthy muscle mass is also important for your energy consumption and a balanced blood sugar level. If the ratio of your muscle mass to fat mass is skewed, the prognosis for all kinds of diseases, such as cancer, is worse.'

The decrease in muscle mass and muscle strength with age or due to illness is called sarcopenia, and it is detrimental to human functioning. What is a healthy amount of muscle? 'Sometimes gyms, for example, quote percentages of what a good muscle percentage would be, but you can't simply state this,' Weijs said. 'A healthy muscle mass differs per person. For example: if you are heavy, you also need more muscles to lift your own weight. But exactly how much that is, we don't really know.' According to Weijs, there is no evidence that having a lot of muscle, like a bodybuilder, is healthier than a belly without a sixpack.

To maintain a 'normal', healthy muscle mass, it is important to do muscle-strengthening activities at least twice a week, says Liesbeth Preller of the Sports and Exercise Knowledge Center. 'It is often still thought that regular moderate-intensity exercise, such as vacuuming or walking, is sufficient. This is not so. If you want to build muscle, you have to do something extra for it, whether that is in the gym or in the garden. Only when you get a little muscle soreness are you working on muscle strengthening.'

Exercise Guideline

Since 2017, muscle and bone strengthening activities have been in the Health Council's exercise guideline. That guideline, incidentally, is followed by only 44 percent of adults, according to RIVM research. Preller: 'I understand that not everyone enjoys going to the gym, but there are plenty of things you can do to strengthen your muscles. This can also be done through everyday activities in and around the home, such as running up the stairs regularly and getting up from your chair several times without using your arms.'

According to a British study, what matters is that practitioners do at least 10 minutes of strenuous activity in which they feel tension in their muscles, or in which the muscles twitch or feel warm. The list of sports that strengthen muscles includes: running, cycling, dancing, swimming, weightlifting, athletics, ball sports, water sports, pilates and horseback riding. For people who don't enjoy themselves in any sport, Keller recommends getting pleasure from the social activities surrounding exercise. "Choose a sport that you do in a group, or with a buddy. This helps make exercise a habit.