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Seat height and its effects on performance and injury

Mountain biking and road cycling is a past-time for a number of people around the world, and South Africa is no different. Young and old, beginner to elite and amateur to professional, thousands of cyclists take enjoyment from spending long hours in the saddle.

No matter the class of athlete or the category of cycling they fit into, two aspects remain constant: performance and injury prevention.

One of the most important aspects that is often overlooked, is seat height. Something as simple as an incorrect seat height can play a major role in performance as well as predisposing the athlete to a number of injuries.

Seat height is unique to every cyclist and thus there is no universal seat height, like most things in life it's important to find "the happy medium".  An athlete's seat height shouldn't be too low nor should it be too high, as both hamper performance and increase chance of injury.

Seat height is generally classified as being low if at the end of the push phase when pedalling, the angle of the knee joint is greater than 30-35 degrees. Seat height which is to high is as a result of the angle of the knee being less than 25 degrees during the final push stage.

Seat height that's too high is rare as it's more uncomfortable and thus is easily identified.  However having a seat height which is too low can result in a decrease in performance as well as result in the cyclist reaching his peak fatigue faster.  A study has found that a seat height which is too low can result in a cyclist reaching their peak level of fatigue up to 12% sooner, this can result in a 12% decrease in performance.

Incorrect seat height would also predispose the rider to increased risk of overuse injuries such as tendonopathy of the quadriceps muscles, as well as muscle strains and tears.  These injuries are a result of the increased force production which occurs as the knee is in a greater degree of flexion (bend).  The lower the seat, the greater the amount of muscle contraction need by the quads to overcome the increased knee flexion and maintain the desired speed or work. The increased force generated will produce more power for the athlete however he will fatigue faster, and with the nature of mountain biking and road cycling being endurance based, it won't be profitable for the cyclist as reach peak fatigue sooner and thus leaving the cyclist to pedal for a longer period of time in a fatigued state where there is an increased chance of the muscle/tendon tearing.

Prolonged riding with a seat height which is too low can result is excessive shortening of your hamstring muscle group, and this effects the force-couple relationship between the hamstrings and quadriceps allowing for poor force generation and decreased performance.

As stated earlier, seat height is unique to each rider thus there is no exact height to follow.  A general rule, however, is that at the end of the push phase the angle of knee should be in the range of 25 - 35 degrees of flexion.  Another easy method is the 109% method (saddle is positioned at 109% of your inseam leg length when measuring from the pedal axle to the top of the seat height).  All these methods generally work and allow the cyclist to set their correct seat height.

www.centreforsportsmedicine.co.za

Stuart Main
Biokineticist
Jackson and Wright Biokineticists
Centre for Sports Medicine Umhlanga
031 5605557

www.physiolink.co.za