Muscle loss is an inevitable part of getting older. But your lifestyle has a significant impact on both your muscle mass and strength. In this article I talk about ageing muscles and summarize practical recommendations on how to combat age-related muscle loss.
What are muscles?
A muscle is a tissue structure of cells in the body that can contract and relax, allowing movement. There are three types of muscles in our body:
- Skeletal muscles (striated muscles);
- Smooth muscles in the gastrointestinal tract, the walls of blood vessels and the respiratory tract;
- The cardiac muscle.
Of all the muscle mass in the body, the majority is skeletal muscle. The human body contains more than 500 skeletal muscles!
40% of the body weight of a healthy adult consists of skeletal muscle. Someone weighing 70 kg therefore has approximately 28 kg of skeletal muscle.
Skeletal muscles are important for skeletal movement. Skeletal muscles allow people to perform movements such as walking, lifting and writing. Skeletal muscles are attached to the bones by tendons. Skeletal muscles consist of different muscle bundles containing muscle fibers. These muscle fibers are made up of proteins (myosin and actin), which in turn are made up of amino acids.
Muscle mass is needed for muscle strength, physical functioning and mobility. Reduced muscle mass is not only associated with a reduced ability to perform daily activities, but also with an increased risk of hospitalization, a longer hospitalization time and an increased risk of mortality.
Muscle protein turnover
The body is constantly building muscle tissue (anabolism) and breaking it down (catabolism). Normally 1-2% of muscles are replaced every day. Amino acids are needed to build muscle tissue.
The build-up and breakdown of muscle proteins is called muscle protein turnover. The net balance between build-up and breakdown determines whether muscle mass increases or decreases. Quite simple: if there is more muscle building than muscle breakdown, muscle mass increases; if there is more muscle breakdown than building, muscle mass decreases.
Daily protein turnover is approximately 350 grams. During fasting, the body loses some of the protein and replenishes it during and after meals.
Anabolic resistance and muscle loss in the elderly
Muscle protein synthesis can be stimulated by two major anabolic stimuli: protein intake and physical activity.
With aging, muscle protein synthesis in response to an anabolic stimulus decreases. This is also called anabolic resistance. Anabolic resistance involves resistance to building up body proteins. The result: older people have less muscle protein synthesis than younger people in response to the same anabolic stimulus. So, if a young person eats a meal with 20 grams of protein, more muscle protein synthesis will take place than if an older person consumes the same amount of protein. Anabolic resistance thus contributes to muscle mass loss with aging.
The peak in muscle mass is reached approximately at the age of 30. As you get older, the balance between muscle building and muscle breakdown changes. Muscle building decreases (anabolic resistance) and muscle breakdown increases. The result is a loss of muscle mass. An excessive decrease in muscle mass leads to reduced physical functioning and ultimately to disability. When aging, it is therefore important to limit the loss of muscle mass.
In the elderly, muscle mass normally decreases by an average of 0.2 kg annually. Compared to peak muscle mass, the average percentage loss of muscle mass is:
- From 70 years: 35% loss
- From age 80: 44% loss
- From 90 years: 50% loss
Muscle mass does not only decrease due to aging. Other factors can also contribute to additional loss of muscle mass. These factors include:
- Less protein via diet
- Decrease in physical activity
- Disease
- Admission to hospital
- Bed rest
- Malnutrition
- Medication (such as corticosteroids)
Muscle mass decreases due to inactivity and bed rest. As I’ve said, normal muscle loss in the elderly is 0.2 kg per year. Compared to a loss of 0.2kg per day during a hospital admission! Loss during an admission to the ICU is even higher: 0.8 kg per day.
After such a crisis, muscle mass does not fully recover. Multiple crises can therefore significantly reduce muscle mass.
Exercise is essential for muscle strength
There is no way around it: exercise is essential for building and maintaining muscle mass. If the muscles are not used, muscle mass decreases rapidly.
The other way around also applies: if the muscles are used, muscle mass increases. And that can be achieved well into old age!
There are different forms of movement, including:
- Strength training: increases muscle strength and muscle mass. Weightlifting is an example of strength exercise. Jumping, climbing stairs and dancing also belong to this group.
- Endurance training: improves oxygen intake and fitness. Cycling and running are examples of endurance activity.
- Balance exercises. These are exercises aimed at improving balance while a person is standing or moving, such as standing on one leg or picking up an object from the ground.
Ideally, all three types of exercises should be performed weekly.
For maintenance of muscle mass, strength exercises at least twice a week are recommended. This is an addition to the general advice to have a moderate level of physical activities on a daily basis.
There are no contraindications for strength training other than that the load must be built up slowly to prevent injuries. You can start at any age! Also if you have (diganosed or not) sarcopenia, a disease of the skeletal muscles.
Dietary protein is also essential for muscle strength
Consuming sufficient protein and spreading it well throughout the day is very important for maintaining muscle mass and strength.
The Nutrition Centre of the Netherlands does not recommend a higher protein intake for the elderly population. The recommended protein intake in the Netherlands for the majority of the population is 0,83 g per kg body weight. Vegans are strongly advised to consume 30% more protein. However, some authorities and expert groups suggest protein recommendations for the elderly in the range of 0·94–1·3 g/kg/d.
The recommendation is to spread the protein intake more or less evenly over the main meals (breakfast, lunch, dinner). In practice, this means that you have to consume 25-30 g of protein per meal.
Might you be lookig for inspiration… Here are three of my original recipes with >30 g protein per portion:
It is probably good to know that protein dietary strategy works synergistically with exercising. This means that one plus one equals three in this case!