Biomechanics is the science relative with the forces applying on the human body and the effects these forces produce. These forces play an important role in the parts of the human body that move during the performance of a skill. In a word, it is a decisive technique. Therefore when you know more about biomechanics, it can help improve cycling technique to improve performance and also avoid the risk of injury.
SADDLE HEIGHT IN CYCLING
Altering the saddle height brings many variables in cycling such as joint angles and muscle lengths, and the force output muscles could generate. Research has shown that the optimal seat height that riders sit in an upright position, can produce the power output and about 110% are from leg length. This height is believed most efficient for track sprint cyclists who would produce extremely high power outputs during the super short periods. A difference of 0.01 in saddle height in either direction with 110% of leg length can generate about 0.01less power.
THE PHYSIOLOGICAL AND BIOMECHANICAL CYCLING
As to the performance, a saddle height of 110% of leg length is usually referred to the maximum saddle height and can be used as the short-term power output, while an approximately 106% of saddle height is defined as the optimum saddle height, considered as most effective for the situation of using with the lower intensity and longer duration. The saddle height also influences the performance of the muscles in the leg. The saddle height can make the amount of muscle activity in the quadriceps decreases, and also make hamstring muscle groups increase. A greater saddle height makes cyclist much easier to pedal especially at high workloads.
SADDLE FORE-AFT POSITION
The fore-aft position means the location of the rear saddle is in the behind of a vertical line drawn to the center of the crank axle, which is the point of crank attachment. The saddle is positioned to drop a plumb-line from the patella to make the pedal axle equal when the crank is in the level forward position. This enables hip and knee fully utilize extensor and flexor muscles, minimizing strain on the knee joint. Any adjustment in the saddle’s fore-aft position will change the joint angles, too. The position of the knee over the pedal axle should be considered as the beginning point to make the minor adjustments. If the saddle is positioned forward too much, the knee angle at the zenith center will be reduced and therefore the activity of the quadriceps to extend the knee is increased, raising the risk of injuries. Conversely, a saddle positioned backward too much will decrease the efficiency of the hamstrings, gluteus maximus, and gastrocnemius muscles to work. Aiming at reducing air resistance while maximizing power output, racers would be careful to the position of the saddle, with many adopting an extreme forward posture combined with 'maximum saddle height'. Concerning the factor of safety, this kind of extreme positions of triathletes is narrowed down to time trial and track events only.