Whilst cycling has many healthy benefits there are potential drawbacks to this form of exercise that can be overcome with an effective regime of stretching. Stretching is a form of preventive medicine.
Cycling is described as a "mid-range" activity, involving a limited and repeated motion. During each revolution of the pedals, the leg is never fully straightened or bent to its fullest, so the muscles are never fully contracted or extended. Therefore the muscles used to pedal the bike strengthen but also become tighter and therefore shorter. This tightness can contribute to any number of overuse injuries including pain in the lower back, hamstrings and knees. 
Cyclists who put in many hours on their bike are prone to what is known as "muscular rigormortis." One of the curses of hard riding, especially in big gears, is a gradual loss of muscle elasticity and an overall decrease in joint flexibility. Stretching helps cyclists to make their muscles and joints more adaptable to the rigors of cycling. Stretching also reduces muscle soreness and stiffness during periods of intense workouts.
Since stretching improves flexibility and increases the range of motion, well-exercised muscles and joints will undergo less severe stress in a competitive situation. Muscles can also last longer during activity before tightening up if pre-stretched correctly.
The stiffness and tightness that are frequently felt after a workout can be brought under control, and even eliminated, with proper stretching. Stretching keeps the body fine-tuned and hastens recovery.
Correct techniques
Stetching for cyclists
Stretching for Tri-athletes
