Most physical activities and all exercises can be put into 3 general categories based on the primary benefit that they achieve.  These categories form a "Fitness Triangle" with each exercise type forming one side of the triangle.  They are all critical to the development and maintenance of good physical health and they should all be part of any balanced fitness program.

The categories of the "Fitness Triangle" and their main goals are:

• Cardio Exercises.  This category of exercise includes any exercise or activity that strengthens your cardiovascular system, your heart, lungs, and circulatory system, by putting an increased and prolonged demand on them.  This includes exercises and activities like walking, swimming, and cycling (low impact, low to medium demand) as well as running and sprinting (high impact, high demand).

• Flexibility Exercises.  These are exercises and/or activities that are designed to improve the flexibility of your muscles, joints, and ligaments.  Examples include stretching and Yoga as well as activities as simple as swinging your arms.

• Strength Exercises.  As the name implies, these are any exercises or activities that increase muscle strength, either through lifting or through resistance.  Examples include weight lifting, resistance bands, and push-ups.

It's important to remember that ALL of the exercises and activities in ANY of these categories can be performed aerobically or anaerobically by simply increasing the intensity and/or duration.  It's also important to remember that all exercises will produce other benefits that may fit several categories.

In designing an effective cardio program, you want to choose exercises and activities that you enjoy doing and that alternate between low and high intensity. 

Other items to take into consideration include:

• Get a Check-up.  Because cardio puts an increased demand on your heart, I shouldn't have to tell you to check with your doctor first, right?  OK, good.

• Don't Overextend.  Reduce the chance of injury by staying away from high intensity, high impact activities when you are just starting out.  You need to first build your strength and endurance with low to mid level intensity workouts before you sign up for the Boston Marathon.

• Protect Your Joints.  Choose low impact activities or exercises if you have weak or bad knees or other joints.  You can always increase the intensity of any of the low impact activities if necessary.  Speed walking is an example.

• Train in Intervals.  Alternate between low intensity and high intensity activities in set intervals.  For example, walk for 15 minutes, then jog for 15, then cycle for 15, then walk for a final 15.  By doing this, your metabolism is constantly switching from aerobic to anaerobic and back again.  You'll burn both fat and carbs and gain the benefits of both.

• Cardio Warm Up.  Use low intensity cardio as a warm up or as a cool down.  Walking is great for this.

• Change up Your Routine.  This is similar in philosophy to interval training.  After a while, your body will get used to your routine.  To keep improving, you've got to occasionally change the order or the type of exercises that you do.

Why is cardio so important?  Building cardio is important because a strong cardiovascular system is the foundation of your physical fitness.  Without it, you literally don't have the stamina or endurance to work on anything else.  Cardio exercises and activities are an important part of any balanced health and fitness program.  Make sure you include them in yours.