Two people can celebrate the same birthday while their bodies have aged very differently.
One may have more physiological reserve to draw on. Scientists call this hidden reserve vitality capacity.
A new study suggests that a familiar habit is associated with having more of it: continuing aerobic exercise across decades.
Researchers at Université Côte d'Azur in France found that healthy adults over 55 who had exercised regularly for 30 years had higher vitality capacity than inactive peers.
The clearest difference was not muscle strength, but the timing between heartbeats and blood-oxygen levels, measured at rest and grouped by the researchers under immune and stress response.
That does not show that exercise caused the difference.
Discussions of healthy aging often focus on disease. Vitality capacity asks something different: how much reserve remains in the systems that keep the body functioning under pressure?
The World Health Organization treats this reserve as part of a person's physical and mental ability. Vitality capacity spans immune and stress response, energy and metabolism, and nerve and muscle function.
To explore the connection, the researchers studied 39 adults from the Nice area, averaging about 64 years old. None had a chronic illness or used medication.
Nineteen had performed aerobic activity at least three times a week for 30 years. They completed at least 2.5 hours of moderate exercise each week, or half that amount of vigorous exercise.
The other 20 did no regular sport or exercise and reported no more than 75 minutes of weekly activity during leisure or getting around. Questionnaires and a wearable sensor confirmed the difference in current activity.
The team combined 12 measures – ranging from blood markers and heart rhythm to muscle strength and lung function – into a single vitality score.
When the researchers combined those measures, lifelong exercisers came out ahead. Older participants also tended to have lower scores. Because the researchers measured everyone only once, however, they cannot say that vitality capacity declined over time within the same people.
The clearest difference appeared in two measures taken at rest.
Active participants had an average blood-oxygen saturation of 96.8 percent, compared with 94.8 percent in the inactive group. Their heart-rate variability was 49.9 versus 27.2 milliseconds.
Heart-rate variability does not mean that the heart is beating erratically. It describes the small variations in timing between beats.
Yet the active group did not outperform the inactive group in every measure.
Inflammation markers showed no clear difference, nor did participants' ratings of their immune health. Grip strength, knee strength, and lung function also showed no clear difference, and no clear overall gap emerged in energy and metabolism or nerve and muscle function.
The association was concentrated in particular aspects of physiological reserve, rather than showing that lifelong exercisers were better on every measure.
Exploratory comparisons by sex found that active women had more lean mass and less body fat than inactive women, but similar differences were not detected among men.
Vitality capacity was also not associated with reported quality of life. Scores leaned toward the high end, which may have made a relationship harder to detect.
This was a small, exploratory study, and people who stay active throughout their lives may differ from inactive people in their genes, social and economic circumstances, or other habits.
The inactive group was also unusually healthy despite doing little exercise, which may have made the groups appear more similar. All participants were healthy, older, and White, so the results may not extend to other populations.
The vitality score itself is new and has not been validated as a clinical test. Two blood markers were chosen from four candidates using the same dataset, which could make the score appear stronger than it is, although repeating the analysis with alternative markers produced largely similar results.
The study also cannot identify the best type or amount of exercise, or show whether becoming active later in life would produce the same pattern. Studies that follow people over time, along with trials that assign people to exercise, will be needed.
Related: Study Reveals a Turning Point When Your Body's Aging Accelerates
For now, the conclusion is narrower: among this small group of healthy older adults, decades of aerobic activity were associated with greater overall physiological reserve, with the clearest signal in heart-rate variability and blood-oxygen levels.
The study was published in GeroScience.
This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.