4 Important Exercise Tips from the American Podiatric Medical Association.
Target Heart Rate: “As you work out, monitor your heart rate to stay near the target heart range (start with 220, subtract your age, then multiply by 0.8 to find target heart range). You should be within five of the target range. Monitor pulse at peak and after final cool-off and compare. The difference is known as your cardiac reserve.”
Hydration: “Drink adequate water to avoid dehydration during workouts which can cause nausea, dizziness, muscle fatigue, and cramping.”
Cool Down: “Don’t under estimate the importance of the cool-off period. It burns off lactic acid (which makes muscles feel tired) and adrenalin, while keeping blood from pooling in the extremities.”
Pace Yourself: “While fitness professionals exercise vigorously six times a week, it’s best to start slower. Although it varies by the individual, it’s safe to start exercising twice a week for several weeks, then gradually increase to a maximum of five times a week. Remember to pace yourself, and listen to your body. If you feel pain, stop. Don’t attempt to exercise through pain, or you may aggravate an acute injury into a chronic or even permanent one. If you continue to be bothered by pain more than 24 hours after exercising, see a physician.”
The above is taken directly from http://www.aapsm.org/aerobics.html.