We can't even imagine the pressure of having cameras follow us 24/7 -- let alone during a sweaty workout session!

But celebs have to be camera-ready at all times, whether it's in the parking lot outside of Equinox or at the top of Runyon Canyon.

From adorably stylish workout brands like Lucy and Lululemon, to old standbys like Nike and New Balance, find out what Reese Witherspoon, Jessica Biel, Katy Perry, and more chose to wear during their sweat sessions: