Plenty of old people practice tai chi just for balance. Falling is a major death Factor... I do not understand the numbers I use for unipedal stance duration t

Plenty of old people practice tai chi just for balance. Falling is a major death Factor... I do not understand the numbers I use for unipedal stance duration though. I had a 60 year old relative stand on hens non-dominant leg and hen gave up after a minute--so I'm not sure what 10s/s actually measures...