Bicycles are commonly used by people seeking to improve their fitness and cardiovascular health. In this regard, bicycling is especially helpful for those with arthritis of the lower limbs and who are unable to pursue sports such as running that involve more impact to joints such as the knees. Furthermore, since cycling can be used as a form of transportation, there can be less demand for self-discipline to maintain the exercise because of the practical purpose of the activity.

Cycling while seated is a relatively non-weight bearing exercise that, like swimming , does little to promote bone density [2] . Cycling up and out of the saddle, on the other hand, does a better job by transferring more of the rider's body weight to the legs. However, excessive cycling while standing can cause knee damage. It used to be thought that cycling while standing was less energy efficient, but recent research has proven this not to be true. There is no wasted energy from cycling while standing. [3]

Endurance cycling is an aerobic exercise , Sprint Cycling is an anaerobic exercise , however both types involve both forms of exercise to some degree and can improve cardiovascular health. One measure of cardiovascular health is Vo2 max .

Cycling makes use of the largest muscles in the body (the Gluteus Maximus and Quadriceps ) so it is good for people who are trying to lose body fat. Exercising at low intensity is better for people who want to lose weight as the body doesn't have the chance to burn fat at high work rates and will burn glycogen instead (although the body will replace the burnt glycogen by metabolising body fat as soon as it can - see Krebs cycle ).

It has been estimated that, on average, approximately 20 life-years are gained from the health benefits of road bicycling for every life-year lost through injury [4] .

Injuries can be divided into two types:

• Physical trauma (extrinsic)
• Overuse (intrinsic).

Acute physical trauma includes injuries to the head and extremities resulting from falls and collisions. Since a large percentage of the collisions between motor and pedal vehicles occur at night, bicycle lighting is required for safety when bicycling at night.

The most common cycling overuse injury occurs in the knees, affecting cyclists at all levels. These are caused by many factors: [5]

• Incorrect bicyle fit or adjustment, particularly the saddle.
• Too many hills, or too many miles, too early in the training season.
• Poor training preparation for long touring rides.
• Selecting too high a gear. A lower gear for uphill climb protects the knees, even though your muscles are well able to handle a higher gear.

Overuse injuries, including chronic nerve damage at weight bearing locations, can occur as a result of repeatedly riding a bicycle for extended periods of time. Damage to the ulnar nerve in the palm, carpal tunnel in the wrist, the genitourinary tract [6] or bicycle seat neuropathy [7] may result from overuse.

In extreme cases, Pudendal Nerve Entrapment can be a source of intractable perineal pain [8] . Some bicyclists with induced pudendal nerve pressure neuropathy gained relief from improvements in saddle position and riding techniques [9] .

Note that overuse is a relative term, and capacity varies greatly between individuals. Someone starting out in cycling must be careful to increase length and frequency of cycling sessions slowly. Muscular pain is a normal byproduct of the training process, but joint pain and numbness are early signs of overuse injury.