Doing the 30-second chair stand test—standing up and sitting down as many times as you can in half a minute—can accurately show how strong your legs are and how well they work as you get older.

A lot of older patients in the hospital can't do even one sit-to-stand in 30 seconds, so this test isn't great at tracking whether they're getting worse or better when they start off very weak.

For older adults just admitted to the hospital, how well they can stand up from a chair 30 times in 30 seconds is linked to their walking and balance, but the link isn’t strong enough to use the test as a reliable measure on its own.

A smart chair that counts how many times you stand up and sit down in 30 seconds gives almost the same number as when a doctor counts it by hand — the difference is less than one rep on average.