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Exercise and Fitness Tips to Improve Your Health

Get answers to your questions about exercise, and tips for getting the most from your workouts.

Q. What is interval training? continued...

For example, if you now run for 30 minutes at 6 mph, try this routine: Jog for five minutes to warm up. Then, increase your speed to 6.5 mph for one to two minutes (less if you can't go that long). Then, jog for a few minutes at your normal speed, then again at the faster speed, and so on until you reach your time limit. Your ratio of work to active rest would be 2:3 if you ran for two minutes at 6.5 mph, then jogged for three minutes at 6 mph.

You can also use your heart rate to set intervals. For example, if your heart rate hits 70% of your maximum when you jog at 6 mph, start at that speed. Then increase either your speed or elevation (if you're on a treadmill) to get your heart rate to 85% or 90% of maximum for one to three minutes. Then, go back to jogging at the 70% heart rate, and continue alternating.

As your fitness improves, your heart rate will be lower at the higher speeds, and then you can spend more time at those speeds. A good starting ratio of work to active rest is 1:3; you can always vary the ratios if they turn out to be too hard or too easy.

I recommend interval training just once a week to start, as it is more intense than you may be used to. Once you get a feel for it, you can do it more often.

Q. What's the difference between the fat-burning mode and the cardio mode on the machines at the gym?

There are problems with the fat burning option on the cardio machines, and it really ought to be eliminated.

The idea behind the fat burning option is this: Because fat is denser than carbohydrate, it requires more oxygen to burn. So, to maximize the percentage of fat you burn, compared to carbohydrate, the fat-burning mode would have you work out at a pace at which your body can deliver lots of oxygen to your muscles. That generally means a slow pace, to keep you from getting breathless.

The problem is that when you exercise at a slower speed, you burn fewer total calories -- from both carbohydrate and fat -- because you simply don't do as much work. Further, the way to get aerobically fit is to get your heart rate into the training range (usually 60% to 85% of your maximum heart rate), which is hard to do at slower speeds. And fitness is ultimately what you're after, whether your goals are better health, burning calories, or improving heart and lung capacity.

The bottom line is that the fat burning mode probably won't be intense enough to maximize total calorie- or fat-burning, or to help you increase or maintain optimum fitness levels. Use the cardio mode to maximize your exercise benefits.

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