Woman on treadmill reading newspaper
Illustration: Sean McCabe
Extended Warm-up
There's nothing wrong with stretching, but it can eat up precious calorie-burning time if you take forever. "The best type of warm-up is one in which you emulate your exercise but to a lighter degree," says Olajide. In other words, do the same move but without the intensity. For example, if you're going on a jog, walk briskly for two minutes first, or before going full force on a stationary bike, do a couple of minutes with minimum resistance. At the end of the workout, slow down for three to five minutes before you stop and stretch.

Reading or Watching TV While on a Cardio Machine
Diverting your mind from your workout generally slows physical activity, says Alan Russell, director of the Health Sciences Institute at the National Academy of Sports Medicine. One form of entertainment, however, may actually boost your energy output: "Using music is the most efficient way to keep up intensity, especially if you can program your own," says Olijade. A fast beat motivates us to sweat off a few more calories.

Standing Around Between Exercises
Too much of a break reduces the effectiveness and intensity of your workout because you're giving your muscles a chance to rest. Jump rope while you're waiting for someone else to finishe up on the machine you want, Olijade suggests. Or prework the muscles you'll be using: "If you're on line for the treadmill or stairstepper, do calf raises and squats."

Using Weights That Are Too Light
Rushing through a lot of reps with a comfortable resistance may feel like exercise, but many fitness experts say it's a waste of time. Three sets of 10 to 12 reps per body part with a heavier weight will give you better results than will three easy sets of 20, says Russell. Choose a weight or resistance strong enough so that the last couple of repetitions are challenging but not so difficult that you can't complete them or that you lose control of the movement. You not only up your calorie burn but also build lean body mass, which helps boost your metabolism.

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