Wait a second, who is the trainer here?

There's no slacking while working out with J Lo, as celebrity personal trainer Tracy Anderson found out the hard way the other day. The two switched roles the other day when Lopez laid down the hammer on a slacking Anderson, who took a break from their workout to read another page of Lena Dunham's Not That Kind of Girl. Yeah, yeah, we know it was staged, but lets not take away from the real news here: J Lo is ripped. Alright, maybe its not really news, after all this is the woman who brought us the video that is "Booty." However, here we get a rare look inside the fitness regimen of a popstar who is killing it well into her forties.

Watch J Lo and Anderson's video below and keep it with Sneaker Report for all your celebrity fitness news.

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I'm gonna lose my job over this brilliant book @lenadunham @jlo #jlotookmybook #backtowork #notthatkindofgirl

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