I'm wiped out. I've never been to a gym where people spend so much time wiping the machines after they used them. They wipe the mats after they stretch. They even wipe the drinking fountain after drinking -- excruciatingly polite. And if you forget to bring your towel to wipe, they've got wiping mitts at every machine, hanging next to a bottle of disinfectant.
Sure we've all wondered about sweaty machines. And that's where we stop wondering because we really don't want to know about other people's sweat. We don't want to think about that fine line between wiping and smearing, nor the possibilities of creating an explosive mixture by combining unknown sweats. The thought of sweat-carrying disease is something best not thought about at all while working out.
Until they invent the umbrella covers for humans, there is no way to contain our moisture. So we wipe.