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January 6, 2015 11:56 AM EST

As you get older, your body reliably falls apart. Right? Not even close, finds a new study published in the Journal of Physiology. Age really is nothing but a number—but if your number happens to be high, that only applies if your exercise levels are, too.

The study from King’s College London and the University of Birmingham in the U.K. looked at older adults all between ages 55-79 who were very active cyclists. The researchers collected extensive physiological information of every person, including heart stats, respiratory and metabolic levels, endocrine functions, hormones, brain power and bone strength. Many of these measures showed a significant association with age—but they varied so much from person to person that no single measure was able to reliably predict a person’s age.

That’s probably because exercise levels have such a strong influence over many of those numbers, the study authors note, and being sedentary arguably plays the biggest role. Said Norman Lazarus, study co-author and professor at King’s College London, in a press release, “Inevitably, our bodies will experience some decline with age, but staying physically active can buy you extra years of function compared to sedentary people.”

Write to Mandy Oaklander at mandy.oaklander@time.com.

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