Bicycle abdominal exercises are the most effective abs exercise as they target the muscles of the abdominal girdle. Bicycle crunches are a great abdominal exercise to work on obliques and rectus abs. Cycling has been known for years and is believed to be good exercise in maintaining good muscle tone. Bicycle crunches are suitable ab exercises for beginners and can be taken to advanced versions to continue strengthening the rectus abdominus and oblique abdominal muscles. Abdominal exercises are easy to do and require no equipment and are the most effective types of exercises for achieving flat abs at home.One of the basic versions of the bicycle crunch is done on the floor. Lie flat on the back as if doing a crunch; lift the legs up with the upper leg being parallel to the floor. Now perform the exercise just like a normal crunch by lifting your shoulders off the floor but in a twisting motion. Perform a one shoulder at a time crunch and in a bicycle fashion bring the left knee and right shoulder off the floor towards the centre of the body. Now repeat and switch the crunch to the left shoulder and to right knee. Continue twisting the shoulders and switching the legs as if pedaling a bicycle. Don't let shoulders touch the ground until done and keep the low back pressed down the entire time.After mastering the floor bicycle crunch an individual can proceed to the ball bicycle crunch with either a stability ball which is also known as Swiss, balance or physio ball. For doing this exercise lie in the same position as for the floor bicycle crunch but with an added challenge of rolling the ball between the legs as you pedal. A side crunch is a variation of the basic crunch that is done with the side of the body resting on the floor or mat. Lie with back flat on the exercise mat and bring the knees up into normal crunch position with feet flat on the floor. Now drop the knees to one side so they remain bent and rest toward one side. Bring the hands behind the head so that the finger tips just touch each other as they rest behind the head. Inhale before performing crunch on the other side and exhale while coming up. Be sure that the head remains in line with the neck the whole time while performing the crunch to prevent neck strain.