It's a bandanna, I just got done with cardio for the night and I refuse to do cardio without a bandanna because I'm one of those "HYPER-SWEATERS-THAT-LEAVES-A-POOL-OF-SWEAT-ON-THE-FLOOR-WHEN-HE'S-DONE" guys.
You won't see me anywhere else with one on except while doing cardio or in that picture