Science (a 47-year-long Swedish study) now tells me I physically peaked at 35 years old. Bummer. But the bigger takeaway is not that we slow down — it’s that movement still matters, a lot, at every age. The good news is that exercise is always good news, including:
–Exercise always pays off. You may not perform as you did at 25, but your body and mind still benefit every single time you put in the work. Sure, you slow down as you age, but it is never too late to start moving.
–Exercise slows aging. Want to stay younger longer? Exercise more. Strength, energy, mobility, and even mindset all improve when exercise becomes part of your routine.
Get moving.
The Fantastic Life Rule: #5
Get a Win
Progress is always possible, no matter when you start. Even though physical performance naturally declines with age. Small steps toward better health can lead to significant gains, demonstrating that it’s never too late to achieve a win and start building momentum.
Long-term study reveals physical ability peaks at age 35
Medical XpressDecember 16, 2025
A 47-year-long Swedish study at Karolinska Institutet reveals how fitness, strength, and muscle endurance change during adulthood. The results show that physical ability starts to deteriorate as early as age 35, but it is never too late to start exercising.
In the extensive study Swedish Physical Activity and Fitness study (SPAF), researchers followed several hundred randomly selected men and women from ages 16 to 63. The study, published in the Journal of Cachexia, Sarcopenia and Muscle, provides new insights into how physical capacity changes over time.
Previously, researchers relied on cross-sectional studies to gain this knowledge. The SPAF study is one of the few that, for nearly 50 years, has regularly measured fitness and strength in the same randomly selected men and women across Sweden.
Exercise always pays off
The results show that fitness and strength begin to decline as early as age 35, regardless of training volume. After that, there is a gradual deterioration that accelerates with age. But the researchers also have positive news: individuals who started being physically active in adulthood improved their physical capacity by 5–10 percent.
“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,” says Maria Westerstahl, lecturer at the Department of Laboratory Medicine and lead author of the study.
The research continues, and next year the participants, who will then be 68 years old, will be examined again. The researchers hope to link changes in physical capacity to lifestyle, health and biological mechanisms.