A comprehensive Swedish study followed 427 people throughout their lives to determine when peak performance… peaks, and how dramatically it falls.
The longitudinal research followed both men and women from age 16 to 63, measuring aerobic capacity, muscular endurance, and muscular power at 5 different stages of life.
222 males and 205 females were randomly selected for the trial, a good mix for the study (women are unfortunately often underrepresented in research).
This is one of the more rigorous study designs in the field of health and fitness. The participants’ results were measured against themselves. In other words, your performance at age 16 was measured against your performance at 34, not anyone else’s. To be exact, the participants were measured at ages 16, 27, 34, 52, and 63.
This is notable because outliers can sometimes skew the results of the group as a whole.
When Does Peak Performance Occur?
The researchers used statistical modeling to make these interpretations. Remember, the participants were only measured at 5 different stages of life.
They determined that muscular power peaks earliest (age 19 in women, age 27 in men) and aerobic capacity peaks latest (mid 30s for both).
The decline afterwards is stark, with annual losses starting at just under 1% but progressing to over 2% with age.
There is a remarkable difference amongst participants as well. Inter-individual variance increased 3- to 25-fold from age 16 to 63, meaning people differ enormously in how they age physically. This underscores that aging trajectories are not fixed.
Part of this is within your control, as physical activity was determined to be the most important factor in maintaining higher capacity in all the tests administered (endurance, power, and aerobic fitness).
The old adage “if you don’t use it, you lose it” rings true.
Limitations of the Study
While this is one of the best long-term studies of physical aging available, there are some limitations.
The participants were only measured five times over 47 years, leaving substantial gaps in the data. The longest stretch — 18 years between ages 34 and 52 — covers what may be some of the most consequential years of physical transition.
This period is when people begin to feel their physical decline, athletes retire, and physical ailments emerge.
It would have been nice to see a data point at age 45, for example. Anecdotally, this seems like a tipping point for physical performance.
Physical activity was also measured with a simple yes or no question — do you exercise in your leisure time? There was no data collected on intensity, frequency, duration, or type of exercise. This makes it difficult to draw specific conclusions about what kind of activity matters most, how much is enough, or whether someone who walks occasionally is being grouped with someone who trains seriously several times a week.
This does not invalidate the data by any means, it’s hard to conduct a study like this, it’s just nitpicking certain variables.
Take-Home Advice
While it’s true that mother nature wins every time, you can still influence your own decline in physical performance as you age. Staying active and well-rounded in your training is the best way to maintain fitness.
In addition, it’s never too late to start. There are countless examples of people who found fitness at different stages of life and dramatically improved their healthspan.
It may seem simplistic and obvious, but oftentimes the most obvious answer is the correct one.
This story was originally published by Men’s Fitness on Feb 23, 2026, where it first appeared in the News section. Add Men’s Fitness as a Preferred Source by clicking here.