Growing up in the ‘70s, ‘80s, and ‘90s, I was all about cardio—Jane Fonda, Kathy Smith, aerobics, leotards, step aerobics, the ThighMaster, the StairMaster, Buns of Steel! Back then, the focus was always on being thin, staying slim, and doing as much high-energy cardio as possible. Strength training wasn’t even on my radar, nor was…