I used to be what I’ve heard guys in the weight room call, always with a teensy bit of derision, a “cardio queen.” For 15 years, I’d been taking spin classes, running on treadmills, and on my low-energy days, hopping on an elliptical machine for 40 minutes at a pace easy enough to watch a rerun of 30 Rock without bouncing too much. Exercise to me meant cardio. Jacking up my heart rate.

This is not to say I’d never touched a dumbbell. I went through a brief Tracy Anderson phase, dancing around with tiny little arm weights for 15 minutes. I took the occasional Pilates class, sometimes even a hybrid cardio/lifting class. Better, I carried my 40-pound toddler around when she got too tired to walk at Santa Monica Pier. But I’d never dedicated any real time to strength training. I treated strength as something that would happen along the way—like, say, at the end of a boxing class when you hit the floor for three minutes of abs.