Well, being a self confessed couch potato, I wouldn't have thought that sports attire would be at the top of your list when going clothes shopping anyway, lol.
It won't be long before you'll be using the term regularly whilst talking with work colleagues or regaling friends at social events and such, lol.
Well, while I admittedly don't spend my spare time whizzing madly about through traffic on a bicycle, dressed in black stretchy "undercrackers", I do spend a lot of time on my feet, both on the job and off. A typical workday sees me walking 10-15km according to the nosy little app on my phone, and while at home I walk more than that each day with the dog...so while it's true that "sports attire", to me, refers to hunting clothes, I do pay attention to footwear in general. Good to be able to scratch a few supposedly Name Brands off my list.
As for using the term "undercrackers" in the lunchroom, or at parties...I suspect that we will have been subjected to a killer asteroid strike...and a supernova...and an alien invasion...and probably a zombie apocalypse or two, before that slips into my normal day-to-day banter.
But just for gits'n'shiggles, I may stand up in the lunchroom tomorrow, dance around a bit to shake my parts loose and announce that I am just adjusting my undercrackers; should be good for a laugh.