Heart Rate

Personally, I'm not a fan of the "fat burning zone" I blame Covert Bailey for popularizing the myth that slower is better. He overemphasized the fact that you burn a higher percentage of fat (as opposed to carbs) at lower intensities... well, you do, but you burn more *total* body fat and more *total* calories when you train intensely. Both the 20 minute aerobic solution and HIIT push us way past the mythical "fat burning zone" to the limits of our capabilities... and that's GOOD. It allows us to train harder, run longer, recover faster, get leaner, and generally kick the butts of those who take a more conservative approach. :-)

Here are the various zones. They're all important. That's why the 20 minute aerobic solution takes us through all of them. We even hit "Zone 5: Redline" on our 10s.

ZONE 1: Beginners and warm-up/cooldown
Goal: 50%-60% of Max HR
Reached by brisk walking, this pace strengthens your heart and improves muscle mass while reducing body fat, cholesterol, blood pressure, and risk for degenerative disease. Health improves in this zone, but neither endurance nor strength is gained. Zone 1 is a good warm-up/cooldown for serious athletes.

ZONE 2: Getting going
Goal: 60%-70% of Max HR
Reached by jogging slowly, this pace trains your body to burn fat for fuel. Up to 85 percent of the calories burned in this zone are fat calories.

ZONE 3: Aerobic fitness
Goal: 70%-80% of Max HR
Reached by running, this zone taxes all your body's systems, forcing increases in the number and size of blood vessels; lung capacity and respiratory rate; and size and strength of heart. Bottom line: You can exercise longer before becoming fatigued.

ZONE 4: Anaerobic athlete
Goal: 80%-90% of Max HR
Reached by running faster, this zone pushes your heart rate into anaerobic ("without oxygen") territory, where your heart can't pump enough blood and oxygen to supply the exercising muscles. You "feel the burn" in your muscles, which can only handle this for a limited time (less than an hour) before they begin to shut down.

ZONE 5: Redline
Goal: 90%-100% of your Max HR.
Reached by running all out for short bursts for less that a couple of minutes at a time (known as "interval" training). It hurts. And there's an increased risk of injury. But it is essential for teaching the body to go faster.