How Old Is Your Body? Discover with a One-Leg Balance Test

According to a recent study, the time you can stand on one leg is the greatest indication of physical aging.

So I was lying in bed the other night, trying to see my phone, and I began whining to my wife about how my eyesight continues getting worse, and then how stiff I feel when I get up in the morning, and how a recent injury is taking too long to recover, and she answered, "Well, well, you’re 44. That’s when things start to go downhill.”

And I was like, “44? That seems extremely specific. I thought 50 was what people complained about." And she answered, “No—it's a thing. 44 years old and 60 years old. There’s a drop-off there.”

And you know what? She was correct.

This research, published in Nature Aging in August of 2024, studied a ton of proteins and metabolites in individuals of different ages and discovered, when you put it all together, that there are some substantial changes in body chemistry throughout time—and those changes peak around age 44 and age 60. I should know better than to distrust my clever hubby.

But deep down, I believe the cliché that age is only a number. I don’t much care about being 44, or becoming 50, or 60. I care about how my body and brain are aging. If I can be a happy, healthy, 80-year-old in full command of his faculties, I would consider it a huge success no matter what the calendar says.

So I’m constantly interested in methods to measure how my body is aging, regardless of how many birthdays I have passed. And, according to recent research, there is really a fairly straightforward method to achieve this.

Just stand on one leg.

The startling findings came from this research, published in PLOS One, that assessed 40 participants, half under 65 and half over 65, across a range of areas of strength, balance, and gait. The conceit of the study? We all know that things like strength and balance degrade with time, but what worsens fastest? What could be the finest statistic to inform us how our bodies are aging?

To that purpose, you have a range of connections between different parameters and chronological age.

For instance, here you see the association between grip strength—long a favorite of longevity researchers—and age, demonstrating a small, but nonetheless substantial negative correlation.

As age advances, grip strength goes down. Men (inexplicably in pink) have stronger grip strength overall, while women (confusingly in blue) lower. Somewhat less robust relationships were reported for knee strength.

What about balance?

To measure this, the researchers had the individuals stand on a pressure plate. In one scenario, they performed this with eyes open, and the next with eyes closed. They next measured how much the pressure fluctuated around the center of the human on the plate—basically how much the person swayed while they were standing there.

Sway increased as age rose. And sway increased a little more with eyes closed than with eyes open.

But the largest association between any of these indicators and age was simple.  How long can you stand on one leg?

Particularly for the non-dominant leg, what you see here is a really severe dropoff in balancing time around age 65, with younger individuals able to accomplish 10 seconds easily and some elderly people barely being able to make it to 2.

I, of course, had to try this for myself. And while I was standing about on one leg, it became evident to me precisely why this may be a reasonable measure. It actually incorporates balance and strength in a way that the other exams don’t. Balance, certainly, given you have to remain upright over a rather tiny foundation. But strength as well, since, well, one leg is holding up all the rest of you. You do feel it after a time.

So this statistic passes the smell test to me at least as a possible proxy for age-related physical deterioration.

But I should be sure to stress that this was a cross-sectional study—the researchers looked at numerous individuals who were all different ages, not the same people over time to monitor how these things change as they aged.

Also, the use of the correlation coefficient in graphs like this indicates a definite linear connection between age and standing-on-one-foot duration. The raw data—the dots on this graph—don't look that linear to me. As I said above, it appears like there could be a bit of a sudden drop-off somewhere around the mid-60s. That implies that we may not be able to use this as a sensitive test for aging that slowly receives changes as your body grows older. It could be that you’re able to effectively stand on one leg as long as you want until, one day, you can’t. That provides us less notice and less to act on.

And lastly, we're not sure if altering this parameter would impact your health for the better. I’m sure a smart physiatrist or physical therapist could develop some workouts to boost any of our standing-on-one-leg periods. And little doubt, with practice, you could raise your numbers well up. But it doesn’t always imply you’re healthy. It’s like “teaching to the test"—you could score higher on the standardized exam, but you didn’t actually understand the topic.

So I am not adding one-leg standing to my everyday fitness regimen. But I won’t lie and tell you that, from time to time, and particularly on my 60th birthday, you may find me standing like a flamingo with a stopwatch in my hand.