CYCLING is one of the fastest-growing sports in America. Like running, cycling is aerobic and primarily uses the leg muscles. But cycling is an impact-free exercise (less stress on the joints) and offers more mobility than running.

Since cyclists travel two to three times as fast as runners, they can view changing scenery and go to more distant locations. People of all shapes, sizes and ages can bike for fitness. Cycling is a skill that most people learn as children; many adults find it less stressful to begin riding than learning a new sport.

To start a cycling program you need a bicycle that fits your needs. The selection involves consideration of terrain as well as gear speeds, brakes and type of seat. The seat height should allow your legs to be slightly bent at the knees.

Always wear a helmet for safety and carry fluids (water is best) with you on longer rides. In cold weather, wear several layers of clothing so you can be warm enough without getting overheated. Peeling off the extra layers will help regulate your body temperature. Some cyclists place a few sheets of newspaper between their outer layers of clothing and take it out as they warm up.

To get a good cardiovascular workout from your cycling program, you should use a speed and distance that elevate the heart to its target rate range for 20 minutes, with a minimum of three days a week, preferably on alternate days. After the first three weeks, add five to 10 minutes each week. After a few weeks vary the route you ride in order to add a hill or two to challenge your body. Whether you're a beginner, intermediate or advanced cyclist, include the basic exercise principles of warmup and cooldown.

A good warmup increases the flow of blood and oxygen to your muscles, preparing them gradually for the extra workload. You should get the blood circulating first before you begin to stretch. Muscles are a little like rubber: Stretch a warm rubber band and it gives easily. Stretch a cold rubber band too far and it snaps.

The best way to warm up is to exercise lightly for five minutes. You can walk, jog or march in place. Once you feel warmed up or until you begin to perspire, you are ready to stretch. Cool down by slowing down. Just slow down your pace at least five minutes until your breathing returns to near normal. Then stretch again for five minutes to help reduce muscle stiffness and soreness.

Here are two stretches to add to your warmup and cooldown:

QUADRICEP STRETCH --

Lie on your stomach. Bend one leg up behind you and grasp the ankle or foot with your hand. Try to touch that heel to your buttocks. Hold for 30 seconds. Release. Switch legs and repeat.

HAMSTRING STRETCH --

Lie on your back. Bend one knee and keep that foot on the floor. Raise the other leg and grasp it with both hands. Try to straighten that leg and slowly pull it toward your chest. Keep the small of your back pressed against the floor. Hold the stretch for 30 seconds. Release. Switch and stretch the other leg.

SAFETY TIPS

Always wear a helmet.

For safety, it's best to avoid cycling at night. But if you do ride at night, be sure to place fluorescent tape or reflectors on your pedals and in the front and back of your bike. Fluorescent apparel is available. Or wear bright clothes.

Ride with the traffic.

Observe all traffic rules, stop lights, stop signs and extra caution at intersections.

Avoid riding in bad weather.

You should have a rear view mirror attached to your bicycle and be sure to use it.

Have fun cycling.

Keep it up!