1. the obvious sweat drippings from 100people
2. few drops of blood from where some loser got a bloody nose
3. a used bandaid
4. fingernail clippings..could have been a toenail clipping of course
5. dust bunnies the size of a dime
6. dried mud from guys working out in their work boots
and now bits of these items are stuck to the bottom of your feet....nice