Over 50 here, I use the following as a test of someone's general balance/strength/flexibility:

Taking off your socks/shoes(tie/untie) without sitting down: hard for most in their 20/30s. Very hard with out bending over.

Pants are what gets hard when you get older, if you can't put on/off pants without sitting down I'd advise some basic training and/or doctor to help.

*assumes otherwise healthy person with no disabilities. I'm not a doctor, this is my own opinion.