A 47-year Swedish study set out to uncover when the human body truly starts to age by examining changes in fitness, strength, and muscle endurance throughout adulthood. The findings were eye-opening: physical decline can begin as early as age 35. However, there’s encouraging news — staying physically active can help slow this decline.
How the Study Tracked Fitness Over Decades
Conducted at the Karolinska Institutet and published as part of the Swedish Physical Activity and Fitness (SPAF) study, the research followed several hundred randomly selected men and women born in 1958. Participants underwent detailed testing to measure maximal aerobic capacity, muscular endurance, muscle power, and overall physical performance through a range of athletic assessments.
Peak Physical Performance Comes Earlier Than Expected
Researchers discovered that the general population experiences physical changes similar to those seen in elite athletes. In both groups, peak physical performance is typically reached before the age of 35, after which gradual declines become noticeable.
Physical Activity Can Slow Performance Loss
Importantly, the study also highlighted positive outcomes for those who increased their activity levels. Adults who became more physically active showed performance improvements of 5–10%, proving that regular movement can significantly slow down the loss of physical capacity.
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Expert Insight on Staying Active
Maria Westerståhl, lecturer at the Department of Laboratory Medicine and lead author of the study, emphasized the importance of movement, stating that it is never too late to start being active. The findings show that while physical activity may not completely stop decline, it can meaningfully reduce its pace. Researchers are now working to understand why peak performance occurs around age 35 and how activity helps delay deterioration.
What Comes Next in the Study
The research is ongoing, and participants will be re-evaluated as they turn 68 years old. Scientists aim to connect changes in physical capacity with lifestyle choices, health factors, and underlying biological mechanisms.
