47-Year Study Reveals The Age We Hit Our Physical Peak

Physical capability tends to slip as the years pass, yet many people assume that loss of fitness and strength is something to worry about only much later in life.

A new study challenges that expectation, indicating that markers of fitness and strength start to decline from around age 35, irrespective of how much people exercise. After that point, the drop is typically steady at first and then becomes more pronounced as age increases.

Age-related physical decline: what happens to skeletal muscle over time

Ageing is accompanied by a gradual reduction in skeletal muscle, and for some individuals this becomes particularly noticeable in their 60s, when it can begin to restrict mobility.

Work in elite athletes has long suggested that even with ongoing training, physical performance usually reaches its high point at roughly age 30. That pattern implies that the underlying processes driving age-related muscle loss may be operating for decades before they are obvious in clinical settings.

Studying athletes has clear benefits, including abundant performance data and fewer confounding effects from sedentary behaviour. However, the authors point out an “obvious disadvantage”: elite athletes are unlikely to represent the general population.

The Swedish Physical Activity and Fitness (SPAF) cohort and a 50-year view

To better capture what happens in everyday life, the researchers carried out a population-based longitudinal study designed to track physical capacity from adolescence through older age.

Much of the earlier evidence in this area comes from cross-sectional studies, which compare different people at one moment in time. By contrast, longitudinal research follows the same individuals over many years, making it better suited to showing how physical capacity shifts across the life course.

The team drew on the Swedish Physical Activity and Fitness (SPAF) cohort study, which has tracked several hundred participants in Sweden since 1974, beginning when they were 16.

SPAF includes repeated measures of strength and fitness in the same participants at five time points over the past five decades-at ages 16, 27, 34, 52, and 63-creating a rare opportunity to quantify change in physical abilities over roughly 50 years.

When do aerobic capacity, muscular endurance and muscle power peak?

The researchers report that cross-sectional studies appear to have underestimated the age-related reduction in physical capacity, while their results align with existing evidence that the overall pattern is similar in men and women.

For both sexes, muscular endurance and estimated maximal aerobic capacity reached their peak between ages 26 and 36. After that, performance declined gradually at first-by around 0.3% to 0.6% per year-before later accelerating to as much as 2.5% per year. The rate of decline did not differ between women and men.

Muscle power showed a different timing of peak performance: men peaked at age 27, while women peaked at age 19. Even so, the subsequent fall in muscle power occurred at comparable rates for both sexes, initially dropping by about 0.2% to 0.5% per year, then later steepening to an annual decrease of 2% or more. By age 63, the total reduction from peak physical capacity ranged from 30% to 48%.

Physical activity can slow the decline-even if it cannot prevent it

The findings also include a more encouraging message. Although the study suggests we may not be able to avoid-or even delay-the point at which we reach peak performance, regular physical activity can still influence how quickly abilities worsen over time.

The authors write that people who were active in their leisure time at age 16 sustained higher aerobic capacity, muscular endurance, and muscle power throughout the entire observation period.

That reinforces the value of encouraging physical activity in teenagers and young adults. At the same time, the study suggests the message applies at any age: participants who became more active during adulthood still improved their physical capacity by approximately 10%.

Maria Westerståhl, a lecturer in the Department of Laboratory Medicine at the Karolinska Institute and the study’s lead author, summarised the takeaway: “It is never too late to start moving. Our study shows that physical activity can slow the decline in performance, even if it cannot completely stop it.”

Westerståhl added: “Now we will look for the mechanisms behind why everyone reaches their peak performance at age 35, and why physical activity can slow performance loss but not completely halt it.”

Putting the findings into practice

If the goal is to slow age-related losses, it can be helpful to combine different types of training. Alongside activities that raise the heart rate (such as brisk walking, cycling or swimming), strength training is particularly relevant for preserving skeletal muscle and supporting day-to-day function, including stair climbing, carrying shopping and getting up from a chair.

It is also worth remembering that exercise is only one part of the picture. Adequate protein intake, good sleep, and limiting prolonged sitting can all support training efforts and help maintain physical capacity as you age-especially when paired with consistent, realistic routines that you can sustain over years rather than weeks.

The study was published in the Journal of Cachexia, Sarcopenia and Muscle.