A 47-year Swedish study published in 2026 can tell us when fitness and strength begin declining — and I’m very surprised.
The study followed adults for almost five decades to uncover when physical decline truly begins. They looked at fitness, strength and muscle endurance, and how this evolves in adulthood. Here’s everything you need to know about the mammoth study and what age your physical fitness really starts to fade out (plus, how to fix it).
What is the study?
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I came across the study in Science Daily, but it was conducted at the Karolinska Institutet. Researchers followed people for almost 50 years to assess how physical performance evolves as we age, and the results were surprising — to me, at least.
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According to the Swedish study, fitness and strength often begin to decline around age 35 and continue to worsen gradually as we age. As a 35-year-old female, I find this pretty alarming.
According to the Swedish study, fitness and strength often begin to decline around age 35 and continue to worsen gradually as we age. As a 35-year-old female, I find this pretty alarming. That said, it’s not all doom and gloom, because the research suggests adults can begin exercising at any age, and even starting exercise later in life can have meaningful benefits.
In fact, it states that those who adopted exercise later still managed to improve physical capacity by up to 10%. “It’s a powerful reminder that staying active matters, even if you start late,” says the research, which is part of the Swedish Physical Activity and Fitness study (SPAF) and was also published in the Journal of Cachexia, Sarcopenia and Muscle.
Several hundred people were randomly selected between 16 and 63, including men and women. It’s rare for studies to follow people for such a long period, so this offers a unique insight into how the body changes over time.
At any age, exercise boosts physical ability and slows the inevitable decline in strength and fitness as we get older.
What does the research mean?
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Interestingly, the decline occurred regardless of how well-trained people were before 35. But, post-35, decline continues gradually, says researchers, which then speeds up with advancing age.
However, “encouraging evidence” tells us that exercise can slow this process down and help increase physical capacity by 5-10%, which also slows decline in performance, but doesn’t completely prevent it.
That means it’s never too late to start a yoga routine, take up Pilates, or even head to your local gym to lift weights. Whether you enjoy walking workouts, swimming, or cycling, any movement matters.
The research is still ongoing, according to researchers, who say participants will be re-examined when they reach 68, plus there will be a deeper look into lifestyle choices, overall health and biological processes. I can’t wait to hear about it.
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