At what age are we truly at our peak? Many imagine the twenties, when muscles are built and recovery is rapid. A large Swedish study, carried out over nearly half a century, tells a different story. She suggests that our physical abilities Global trends peak around the late thirties, before starting to erode sooner than you might think.
This longitudinal study, titled “Rise and Fall of Physical Capacity in a General Population,” followed 427 Swedes from ages 16 to 63, with five rounds of endurance, strength and power tests. Published in December 2025 in the Journal of Cachexia, Sarcopenia and Muscleit shows a peak around
35 years old and a decline which then accelerates. It remains to be understood what this means in concrete terms for our bodies.
A cohort followed for 47 years to track peak performance
In 1974, researchers randomly selected 222 16-year-old boys and 205 girls, representative of Swedish high school students. They measured their height, weight, aerobic capacity (race then Astrand cycling test), their muscular endurance via a standardized bench press and leg power thanks to a vertical jump. The same exams were repeated at ages 27, 34, 52 and then 63 to draw the performance curve over a lifetime.
Statistical models show that peak capacity is reached before age 36. Absolute aerobic capacity peaks around age 35 in women and 36 in men, as does muscular endurance in the bench press (34 for women, 36 for men). Jumping power peaks much earlier, around 19 years old for women and 27 years old for men, then gradually declines.
From the age of 35, a slow decline then increasingly rapid
According to the researchers, physical condition and strength begin to decline from the age of 35, “regardless of the training volume”. They describe “a progressive deterioration which accelerates with age”. Around the age of 40, the decline remains moderate, of the order of 0.3 to 0.6% per year. Around the age of 63, it reaches around 2 to 2.5% per year, for an average total loss of 37% between the peak age and 63 years. all tests combined.
Men and women lose capacity at the same rate, although absolute levels remain higher among men. The gap between individuals widens over the decades: some retain a lot, others decline very quickly. “Even elite athletes who continue to exercise throughout their lives lose physical function as they age“, explained the authors in the Journal of Cachexia, Sarcopenia and Muscle. The prolonged careers of LeBron James or Serena Williams, at the top at 35, fit well into this curve.
Stay active to climb higher and descend slower
In the Swedish cohort, participants who were active during leisure time had higher aerobic capacity, muscular endurance and jumping power in adulthood than those who were inactive. Switching from a sedentary to active lifestyle improved aerobic capacity by 6-7%, bench press endurance by 11%, and jumping power by 4%. “It’s never too late to start moving. Our study shows that physical activity can slow performance decline, although it cannot stop it completely. Now we will look for the mechanisms that explain why everyone reaches their peak performance level at age 35 and why physical activity can slow down the loss of performance without being able to completely stop it.“, said Maria Westerståhl, reader at the Department of Laboratory Medicine, as quoted by Karolinska Institutet.
These results remind us that physical aging begins earlier than we imagine, but also that physical activity allows us to start from higher ground and slow down the slope. If the peak is biologically programmed, the way we experience it depends largely on our habits.