Just think: If global warming were a good thing, you'd never have to run indoors on a treadmill ever again. The next time you're running bored on the belt, change your routine with one of our Women's Health programs. They'll help you burn calories, without burning you out!
Play by numbers
First, calculate your maximum heart rate (MHR) by subtracting your age from 220. The American College of Sports Medicine recommends hitting at least 70 percent of your MHR while you exercise to maximize your calorie burn and fat loss. If you don't have a heart rate monitor, count your pulse for 10 seconds, and multiply that number by 6. Keep working at 70 percent of your MHR for as long as you can. When you get tired, slow the treadmill to an easy jogging pace, and rest for a few minutes. Next, see how long you can go at 85 percent of your MHR.
Tom Holland, a triathlete and physiologist in Darien, Conn., suggests watching a 30-minute TV program, like the nightly news. Increase your speed so that you're running hard (about 80 percent of your maximum) during the commercials. When Katie Couric returns, slow your pace to an easy jog.
Take a hike
Rebecca Rusch, top adventure racer and 2003 winner of the Raid Gauloises, likes to walk or run on an incline to mimic hiking outside. Some treadmills have preprogrammed hiking trails, but if yours doesn't, Rusch recommends this: Walk at 3.5 miles per hour on a flat belt. Increase the incline every minute until it reaches 5 percent, and stay for 3 minutes. Next, lower and raise the belt every 2 minutes until you've been exercising for 25 minutes. Gradually lower the belt and decrease your speed over 5 minutes to cool down.
Weight it out
If you're short on time, do double duty with your cardio and grab a pair of 2- to 5-pound dumbbells. Perform biceps curls as you walk, raising and lowering your arms with each step. Next, perform military shoulder presses. Hold the dumbbells at shoulder height, with your palms facing forward. Press them up overhead, and return them to start. Do 10 repetitions of each exercise. If you need your hands for balance, try this on a stationary bike.