A 47-year-long study has finally shared its results; finding the exact age that people reach peak physical fitness levels, as well as when this starts to decline. In an encouraging twist, the researchers also discovered that it is not all over at this age, with adults who start exercising later in life still able to improve their physical capacity by up to 10%.

The research found physical fitness starts to decline at 35, much earlier than some people believe. The Karolinska Institutet study found that physical capacity and muscle endurance peaked between the ages of 26 and 36 for both men and women.

But, after the age of 35, fitness and strength started declining regardless of how much a person exercised. The study warned that people with sedentary lifestyles may experience a significant decline in physical function after reaching their physical fitness peak.

Being physically active, whether that started in a person’s teen years or in adulthood, was associated with better outcomes. Between the ages of 35 and 63, physical capacity declined by up to 48%. This deterioration started gradually, but started speeding up with age.

Despite this finding, the researchers discovered an encouraging surprise. People who only started exercising during these years were able to increase their physical capacity by around five to 10%. This emphasises that exercise is still a vital component for healthy living at every age.

Maria Westerståhl, lecturer at the Department of Laboratory Medicine and lead author of the study, said: “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.

“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.”

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Published in the Journal of Cachexia, Sarcopenia and Muscle, the study hopes to provide a rare long-term insight into how the body’s physical capacity changes over decades. The study also discovered that having a university degree was positively associated with aerobic capacity and muscular endurance.

The researchers initially set out to see if the musculoskeletal decline that most people start experiencing symptoms of in their 60s might actually be triggered by underlying tissue processes decades earlier. In other words, uncovering the age when people’s physical fitness starts to decline.

This had previously been proven in elite athletes, showing they reached peak physical performance before the age of 35, but the scientists wanted to confirm if this would also apply to the general population.

The Swedish study started in the 1970s and followed 427 randomly selected people born in 1958 in the Swedish population. Participants were monitored from the ages of 16 to 63.

It repeatedly measured fitness and strength in the participants throughout the decades, making it one of the most comprehensive efforts in the field, and the research is still ongoing.

Next year, the participants will be examined again as they reach the age of 68. The researchers hope this latest set of results will explain how physical performance is connected to lifestyle choices, overall health and underlying biological processes.