First, cycling enables you to cover much more ground and see many more sights during a given period of time than other types of exercise. For example, an average runner may complete five miles in 45 minutes, but the same individual may cycle over 10 miles during this time period. The change in scenery alone tends to make the exercise session pass more quickly.

Second, because you cycle at a faster speed than you run or walk, there is a significant cooling effect from the greater air currents encountered when riding a bike. This is especially appreciated on hot and humid days when no breezes are blowing. While it is just as important to replenish fluids regularly, cycling is one of the most comfortable warm weather activities.

Third, riding a cycle is an ideal exercise for individuals who experience overuse injuries from the landing forces encountered when running, stepping or doing other weight bearing activities. Because the seat suppoorts your body weight, cycling provides an excellent workout for the leg muscles without producing repetitive impact on the feet, ankles, knees, hips and back. The body support function of cycling is also advantageous for overweight individuals whose size hinders their performance in ambulatory activities.

Fourth, when positioned properly on a bicycle, the consistent mid-range movement pattern of the legs is a relatively safe, simple and easy to perform exercise action. Although any activity can be overdone and cause overuse injuries, recreational cyclists typically have a low risk for these problems.

Fifth, for those who prefer a variety of physical activities, cycling is ideal for cross-training purposes. For example, walking and jogging emphasize the hamstring muscles in the rear thigh. Cycling, on the other hand, places more stress on the quadriceps muscles in the front thigh. Therefore, a combination program of running and cycling tends to enhance muscle balance and reduce the risk of imbalance injuries so common in single activity exercisers.

Sixth, cycles offer storage space for water containers, snacks, and windbreakers. Extra fluid and fuel are important considerations for longer exercise session, as is a place to store outer layers of clothing after your body temperature has increased.

Seventh, cycles are interesting to use due to the different gear ratios that can be selected for best traversing various terrains. Whether cycling on the roads or trails, it is challenging to choose the most effective gear ratio for every riding situation. Generally speaking, it is advisable to use the highest gear ratio that enables you to maintain your desired pedal cadence (such as 75 to 80 revolutions per minute).

Eighth, bicycles are an excellent investment, costing relatively little on a long term basis. For example, a $300.00 bicycle averages only $30.00 per year over a decade of use. Even with an annual tune-up and a couple tube replacements for flat tires, the yearly cost is on par with a good pair of running shoes. No doubt about it, bicycling is a bargain even with the additional cost of a helmet, which is absolutely essential and represents money well spent.

Ninth, cycling is an ideal activity to do with a friend or a small group of riders. This is partly because of the drafting benefit, by which all but the lead cyclist experience a pulling-along effect related to reduced wind resistance. By frequently changing lead cyclists, everyone enjoys an easier and faster ride than cycling solo.

Tenth, contrary to popular misconception, cycling is an excellent exercise for the muscles of the upper body as well as for the legs. Consider that the low back, chest, shoulder, upper arm, and forearm muscles work throughout the ride to support your torso, and that the upper back and neck muscles are active most of the time to maintain a head-up cycling position.

While there are at least 10 good reasons to do some cycling this summer, there are also a few precautions that should be taken for safe and satisfying bicycle experiences. As one who has been hit by a car, let me assure you that automobiles must be taken seriously when cycling. Unfortunately, many drivers are in a hurry to get where they're going, and they do not give much consideration to cyclists. Always anticipate possible problems at intersections, and always stop at red lights and stop signs, especially since some drivers do not. Be on the lookout for people backing out of driveways, and avoid roadways with narrow shoulders.

Never sit on your bicycle without first securing your helmet, and tucking your shoestrings inside your shoes so they won't hook your pedal or front gear sprocket. It is a good idea to carry a full water bottle on all your rides, as well as a few supplies such as a spare tube, air pump, and plastic tire tools.

Although not essential, most riders enjoy using the detachable mini-computer that displays your cycling speed, distance, time and other interesting calculations. Some riders also prefer to wear cycling shoes, shorts and gloves designed to enhance both your performance and comfort.

Of course, there is an entirely different option for those who prefer a more challenging ride off the roads. Mountain bikes offer exciting opportunities to explore wooded trails and a variety of other cycling environments away from traffic and the hustle of civilization. Although cars pose no problem in the woods, the uneven terrain requires both a high level of attentiveness and a high level of physical fitness. Upper body strength is particularly important for safe and successful off-road cycling. I recommend starting off with a friend who can teach you the essential techniques for riding in the rough. Once you learn the strategies and get the feel of mountain biking you are likely to make it a major component of your fitness program.

My final recommendation is to spend a little time at your local bicycle shop to better understand the facts about cycling and equipment. Most shop personnel are devoted cyclists who love this superb physical activity and enjoy sharing their knowledge and enthusiasm with others.

Wayne L. Westcott, Ph.D. is fitness research director at the South Shore YMCA and author of the new book Strength Training Past 50.