It's okay to stay inside when it's cold outside; we won't judge. "But don't just hop on a treadmill, press a few buttons, and slog through a monotonous, boring routine," says Joe Dowdell, C.S.C.S., owner of peak performance in Manhattan. He has seen his share of wasted gym time. Instead, Dowdell advises you to use the following interval workout and expert tips to build your endurance and burn more fat on your favorite machine. (Plus, read up on the extreme science behind fat loss-you may be guilty of the wrong exercises!)
Warm up on any of the machines below for 5 minutes, and then use the speed control and built-in heart-rate monitor to do the following workout: start with 1 minute at 85 to 90 percent of your maximum heart rate. (Multiply your age by 0.7 and subtract that number from 207 to estimate it.) Recover for 2 minutes at 55 to 65 percent of your max. That's 1 interval. Do 8, using the tips on this page to accelerate your gains. Too difficult? Do 6 intervals of 2 minutes at 70 to 80 percent of your max followed by 2 minutes of recovery.
PLUS: Learn how to transform your body forever with the NEW Spartacus Workout!