Aerobic training consists of doing an activity that keeps your heart rate (pulse) at its target rate for at least 30 minutes at a time. To determine your target rate, subtract your age from 220 (your maximum heart rate). Multiply that number by .70, which is 70 percent of your maximum heart rate. This is the low end of your target heart rate, and should be what you aim for when you begin cardiovascular training. As your stamina improves, increase your target rate slowly to 90 percent of your maximum heart rate. Just subtract your age from 220 and multiply the result by .90, but you knew that. You don't ever want to work so hard that you meet or exceed your maximum heart rate. Dire results follow.

You can purchase a heart-rate monitor to help you keep tabs on how your heart is doing while you're working out. Some can be worn like watches; others you slip over your finger during training. Some cardiovascular workout machines have heart-rate monitors built in. A less effective method (but still reasonably reliable if you don't have a heart rate monitor readily available) is simply to press your fingers against your wrist and count the number of heartbeats in 10 seconds and then multiply by six. Or count the number of heartbeats in six seconds and multiply by 10. This will give you a rough idea of your heart rate. Never take your pulse by pressing your fingers against the blood vessels in your neck. Although the pulse is strong there, pressing on the blood vessel can restrict blood flow to your brain, causing you to faint. Bad idea.