Stop guessing: A massive 50-year study finally reveals when our bodies really start to age

A 47-year-long Swedish study set out to provide new insights into when our bodies start to age by looking at how fitness, strength, and muscle endurance change during adulthood. The results? Our bodies begin to deteriorate as early as age 35, but there’s good news — you can slow your performance loss down by moving more.

The study, which was conducted at the Karolinska Institutet and published as part of the Swedish Physical Activity and Fitness study (SPAF), followed several hundred randomly selected men and women, all of whom were born in 1958. Researchers assessed the participants’ maximal aerobic capacity, muscular endurance, muscle power, and physical performance using various athletic tests.

The scientists found that the general population showed similar changes in physical capacity to those previously demonstrated in elite athletes — peak physical performance is reached before age 35.

The good news is that researchers also found encouraging evidence that adults who became physically active improved their performance by 5-10%, demonstrating that physical activity can slow down the performance loss.

Maria Westerståhl, lecturer at the Department of Laboratory Medicine and lead author of the study, said, “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.”

The study continues, and this year the participants will turn 68 and be examined again. The researchers hope to link the changes in physical capacity to lifestyle, health, and biological mechanisms.

What are you waiting for? If this isn’t motivation to keep moving in 2026, we don’t know what is!

Follow Tom's Guide on Google News and add us as a preferred source to get our up-to-date news, analysis, and reviews in your feeds.

More from Tom's Guide

• No squats! I just tried this 8-minute chair workout, and it’s perfect for seniors, beginners, and anyone looking to build strength without impact
• Over 60? I’m a personal trainer, and these 3 floor exercises will show you how strong your core is
• I'm a personal trainer who works with seniors: This is my joint-friendly workout for clients over 50 to build strength and boost coordination