Here's how to get in shape in 2018

As the music swells in the early notes of Bruno Mars’ “24K Magic,” 20 men and women in sweats and spandex are in a small South Side gym, poised with fire in their eyes, ready to attack the weights and machines in front of them. The song hits an early crescendo, and Adam Cross yells “GO!” and they are off: a flurry of legs pumping and arms flailing — and within 15 minutes that collective glint has given way to a bunch of thousand-yard stares as they fight throu