Is this a reasonable set to start with ?
1 Quadriceps Stretch
* Balance against a bike or a wall and grasp the right foot behind the back with the right hand.
* Gently pull the foot up and away without bending at the waist.
* Repeat with the other leg.
2 Hamstring Stretch
* Lean on the bike and bend over at the waist.
* Place one foot forwards and the other directly behind to form a triangle.
* Lower the body slightly with the weight on the front foot, which is where the hamstring stretch should be felt.
* Increase the stretch by lowering the body still further if comfortable.
* Repeat with the other leg.
3 Pulldowns: Lats, Trapezius and Triceps Stretch
* Balance on the bike with weight resting on the arms.
* Let the head drop deeply between the shoulder blades to create a powerful stretch in the lats and triceps.
* Pulling down with the arms increases the stretch further.
4 Squats: Lower Back Stretch
* Hold onto the bike for balance and squat down keeping heels on the floor.
* Try to lower the backside as close to the heels as possible to maximise the stretch.
5 Calf Stretch
* Lean against a wall and place the leg to be stretched backwards with the other in front taking most of the weight.
* Keep the heel of the rear foot firmly on the floor with the toe pointing in front.
* Push the hips forward as far as is comfortable to stretch the calf.
* Repeat with the other leg.
Source = http://bicycle-training.suite101.com/article.cfm/stretching_exercises_for_cyclists
