Tuesday, 20 September 2011

Have you checked your Bike set up recently?

Bicycle saddle height and knee injury risk

 

It's a well-accepted fact that the correct bike set-up is crucial, not only for cycling performance but also to prevent injuries. However, there's no universal agreement among sports scientists and coaches as to what exactly is the optimal configuration. One of the most important parameters to get right is saddle height because set incorrectly, the risk of knee injury is greatly increased. To this end, scientists from New Zealand have conducted a meta-analysis (an analysis of a large number of previous studies into this subject) on bicycle saddle height on measures of cycling performance and lower limb injury risk. To do this, 62 scientific papers published since 1960 were reviewed and their findings on 'body positioning', 'saddle',  'posture, 'cycling' and 'injury' were analysed and the data from these studies pooled. The results from this analysis included the following:

 

●● The methods for determining optimal saddle height are varied and not well established, and have been based on various relationships including saddle height and lower limb length, length from groin to floor and a reference range of knee joint flexion;

 

●● Increasing saddle height can cause increased shortening of the vastii muscle group (outer quads of the frontal thighs), but no change in hamstring (rear thigh muscle) length;

 

●● The length and velocity of contraction in the soleus muscle of the calf seems to be more affected by saddle height than in the gastrocnemius (the other main calf muscle);

 

●● The majority of evidence suggests that a small (5%) change in saddle height can affect knee joint kinematics and moments by a large amount (35% by 16% respectively);

 

●● The compressive forces around and under the kneecap (patellofemoral) seem to be inversely related to saddle height (ie increased by lower saddle height and vice-versa) but the effects on other forces between the lower leg and thigh are uncertain.

 

 The researchers concluded that: "On the basis of the conflicting evidence on the effects of saddle height changes on performance and lower limb injury risk in cycling, the saddle height that best minimises the risk of knee injuries and increases cycling performance is one that results in a knee flexion angle of 25-30° when the leg is maximally extended" (ie at the bottom of the pedal stroke). Given that 50% of cyclists can expect to experience some knee joint pain as a result of overuse at sometime in their cycling career, this '25-30o' rule might be a good starting point when setting up saddle height for maximum performance and injury-free riding!

 

Sports Med. 2011 Jun 


Grant Roberts

The Sports Specialist

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