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.

A smart chair that measures how fast someone stands up and sits down five times gives slightly different times than when a person uses a stopwatch — on average, it records about 2.7 seconds faster, which could matter in real medical checkups.

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.

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.

If an older person in the hospital can't stand up from a chair more than 8 times in 30 seconds, they're likely to need more help with everyday tasks like bathing, dressing, or shopping compared to those who can do it more times.