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Chest monitors are very accurate, but some are subject to interference from

electromagnetic waves like those given off by some treadmills and stair-

climbers. (Better, newer models come equipped with coded signals that

prevent this interference.) Exercising next to someone else who’s wearing a

monitor may also scramble signals, a sort of electronic equivalent of getting

your braces locked with someone else’s when you’re kissing. You may need

at least 4 feet between users for monitors to function properly, although

several companies now offer models with a special device to eliminate

interference.

Less accurate than chest monitors are photo-optic models,often sold with

home equipment. These clip onto your earlobe or fingertip and detect the

heartbeat there. Your heart rate shows up on a handheld or clip-on digital

screen or special wristwatch. Those models cost only about $30, but any

movement of your wrist, hand, or fingers can cause highly erratic or false

readings. Daylight, poor circulation, and high-intensity exercise may also

skew the results.

How Much Do You Need to Do? .................................................................

Unless you’re a professional athlete or wealthier than the average Third World

dictator, you probably don’t have unlimited time to work out. So you may be

wondering: Just how much cardio exercise does it really take to get fit?

The answer depends on your goals. Exercise is not an all-or-nothing proposi-

tion. You can be fit to live a long life, fit to bicycle 30 miles, fit to run the

Mount Everest Marathon (there really is such a thing) — or anywhere in

between. In the cardio plans near the end of this chapter, we discuss how

long, how often, and how hard you need to exercise in order to achieve three

general goals: good health, fat loss, and maximum fitness. We also explain how

you can cut back on your workouts during a serious time crunch without

losing your fitness.

That said, recent research published in the Archives of Internal Medicine

attempted to answer the question of how much exercise is needed to maintain

body weight by placing subjects into four categories:

No exercise at all

Low amount of exercise (12 miles per week of walking or running) with

moderate intensity (equivalent to 4 to 5.5 in Table 8-1)

Low amount of exercise (12 miles per week of walking or running) with

vigorous intensity (also 6.5 to 8 in Table 8-1)

High amount of exercise (20 miles per week of walking or running) with

vigorous intensity (6.5 to 8 in Table 8-1)

Chapter 8: Cardio Crash Course 115