A massive Swedish study that tracked people for nearly five decades has uncovered a striking reality about aging and physical performance. Researchers found that fitness, strength, and muscle endurance begin declining around age 35. But the findings also deliver an encouraging message: becoming active later in life can still significantly improve physical ability.
The research was conducted at Karolinska Institutet as part of the Swedish Physical Activity and Fitness study (SPAF). Scientists followed several hundred randomly selected men and women in Sweden from ages 16 to 63, repeatedly measuring their fitness and strength over a span of 47 years.
The study was published in the Journal of Cachexia, Sarcopenia and Muscle.
Rare Long Term Fitness Data
Most previous studies on aging and physical performance relied on cross sectional comparisons between different age groups. In contrast, the SPAF project repeatedly tested the same individuals over decades, making it one of the few long running studies of its kind.
By tracking the same participants over time, researchers were able to build a much clearer picture of how the body changes through adulthood and aging.
Physical Decline Begins Around Age 35
The results showed that physical capacity starts decreasing as early as age 35, even among people with different training backgrounds. After that point, the decline continues gradually and becomes more pronounced with advancing age.
Researchers examined changes in fitness, muscular strength, and endurance, all of which followed a similar downward trend over time.
Still, the study also found important evidence that exercise remains highly beneficial at any age. Participants who became physically active during adulthood improved their physical capacity by 5-10 percent.
Exercise Still Makes a Difference
“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 Westerståhl, lecturer at the Department of Laboratory Medicine and lead author of the study.
The researchers plan to continue following the participants as they age. Next year, the group will be tested again when participants reach 68 years old.
Scientists hope the ongoing work will help reveal how lifestyle habits, overall health, and biological processes influence the way physical performance changes across a lifetime.