Britney Spears shocked fellow gym-goers in Los Angeles after wandering into the exercise room wearing nothing but a towel.

The Toxic hitmaker, who is set to appear on How I Met Your Mother again, was working out at Bally's in Culver City on Monday and after she finished her routine, headed to the changing room to shower.

But after getting undressed, the singer headed back to the gym to collect a water bottle - and was photographed walking through the crowded room bare foot with only a skimpy white towel to protect her modesty.

Does she strip off when attending vocal coaching classes too?