Can you stand on one leg for 10 seconds?

You're pulling on a sock while standing up, and halfway through you put a hand on the wardrobe door. Or the bus moves off before you've sat down, and you grab the rail harder than you meant to.

Most of us laugh it off. Balance feels like something to worry about in your 80s, after a fall.

But balance starts to slip in midlife, faster than strength does, and you won't notice it until you test it.

Most falls happen later in life, but the balance that prevents them is built in your 40s, 50s and 60s. A 30-second test at home shows where yours is now.

The full set of balance and strength tests, with benchmarks, is in the Functional Strength Guide, p.13 to 15.

Monday's rule 6 was to train your balance. Here's what the research says about when it starts to go.

Balance drops off faster than strength. Mayo Clinic researchers tested 40 healthy men and women over 50 (PLOS ONE, 2024). Of everything they measured, time standing on one leg dropped the most with age, faster than grip or knee strength. The non-dominant leg declined fastest, and the rate was the same for men and women.

It starts dropping in your 40s and 50s. In normal values from 549 adults, average time on one leg with eyes closed fell from about 13 seconds in people's 40s to 8 in their 50s and 4 in their 60s. With eyes open, most people hold steady until their 60s, which is why it's easy to miss.

Balance in your 50s predicted how long people lived. A British study in the BMJ tested 2,766 men and women at age 53, then followed them for 13 years. Those with the weakest eyes-closed balance had about 3.4 times the death rate of those with the best. The link was stronger in men, but it held for women too.

In the BJSM study from Monday, about 5% of people aged 51 to 55 couldn't stand on one leg for 10 seconds. That share roughly doubled every 5 years, to about half of people aged 71 to 75.

Falls are common, and serious. More than 1 in 4 adults over 65 fall each year (CDC), and falls are the leading cause of injury death in that age group (CDC MMWR). Women report slightly more falls, 29% against 26% for men, but men are more likely to die from one.

Balance can be trained, even later in life. In a Dutch trial in Physical Therapy, 70 older adults at risk of falling did 4 weeks of treadmill walking with sudden slips and trips built in. Over the next 6 months, their falls dropped by 64%, against 19% in a group that walked without the surprises. It was a small study, and one author works for the company that makes the treadmill, but it shows balance can still improve in your 70s.

A fall at 80 often has its roots decades earlier. The balance that would have caught it is built or lost through your 40s, 50s and 60s, a little at a time. It's a lot like saving for retirement, where the small, regular amounts you put in during midlife are what you draw on later.

First, find out where you are. It only takes 30 seconds.

Retest in 4 weeks. Notice whether stairs and getting dressed feel steadier, and check whether your times have gone up.

One honest caveat. Most of this research follows people over time, so a weak one-leg time is a warning sign rather than a diagnosis. If you're not confident, do the eyes-closed version with someone nearby.

A daily reminder makes it easier to stick with. Set it for when you usually brush your teeth.

On Friday we show you what an ordinary week looks like for longevity, with a day-by-day plan you can stick on the fridge.

Until Friday.

Longevity Daily / The Building Decades