Friday, October 3, 2008

Heart Rate Zones

The low-down on HR zones (mainly from here, but I’ve made a few changes):

Zone 1
50%-60% of your individual Max HR

This is the safest, most comfortable zone, reached by walking briskly. Here you strengthen your heart and improve muscle mass while you reduce body fat, cholesterol, blood pressure, and your risk for degenerative disease. You get healthier in this zone, but not more fit—that is, it won’t increase your endurance or strength but it will increase your health.

If you are out of shape, have heart problems, or want to safeguard your heart without working too hard, this is your zone. This is also the zone for warming up and cooling down before and after more vigorous zones.

Zone 2
60% to 70% of your individual Max HR.

It’s easily reached by jogging slowly. While still a relatively low level of effort, this zone starts training your body to increase the rate of fat release from the cells to the muscles for fuel.

Some people call this the “fat burning zone” because up to 85 % of the total calories burned in this zone are fat calories.

Fit and unfit people burn fat differently. The more fit you are, the more effectively you use fat to maintain a healthy weight. On the other hand, if you’ve been exercising vigorously but not losing the weight you expected to, it could be that you’ve been working too hard and need to drop back to this zone and exercise longer. To burn more total calories, you’ll need to exercise for more time in this zone.

Zone 3
70%-80% of your individual Max HR

In this zone—reached by running easily as an example—you improve your functional capacity. The number and size of your blood vessels actually increase, you step up your lung capacity and respiratory rate, and your heart increases in size and strength so you can exercise longer before becoming fatigued. You’re still metabolizing fats and carbohydrates at about a 50-50 rate, which means both are burning at the same ratio.

Zone 4
80%-90% of your individual Max HR

This zone is reached by going hard—running faster. Here you get faster and fitter, increasing your heart rate as you cross from aerobic to anaerobic training. At this point, your heart cannot pump enough blood and oxygen to supply the exercising muscles fully, so they contract anaerobically.

This is where you “feel the burn.” You can stay in this zone for a limited amount of time, usually not more than an hour. That’s because the muscle just cannot sustain working anaerobically (this means without sufficient oxygen) without fatiguing. The working muscles protect themselves from overwork by not being able to maintain the intensity level.

Zone 5
90% to 100%
of your Max HR.

This is the equivalent of running all out and is used mostly as an “interval” training regiment—exertion done only in short- to intermediate-length bursts. Even world-class athletes can stay in this zone for only a few minutes at a time. Most people will not select this zone for exercise, since working out here hurts and there is an increased potential for injury.

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