On my daily commute into Central London I cannot help but marvel at all the cyclists that brave the daily ‘gauntlet run’ to make their way into work. We really do take our life into our own hands! It makes it all the more fascinating that people will make the journey that much more difficult for themselves by not ensuring that something as simple as their seat height is set up correctly to reduce effort and maximise efficiency.
It is all I can do sometimes to stop myself from offering friendly advice to these cyclists who have their seat too low and can be seen brushing their chin with their knees as they cycle gleefully along wondering why it always seems like they are cycling uphill! Or at the other end of the scale you see the classic side to side rock of the pelvis of someone that has their seat up too high; it’s enough to make me feel sea sick as I follow behind them!
Making sure your seat height is correct is one of the easiest ways to ensure that you are relatively efficient on your bike. The ideal height would allow for a 25-35 degree knee bend when the pedal is at the lowest point in the pedal stroke. The increased knee flexion angle resulting from a seat that is too low requires much bigger ranges of hip and knee motion therefore requiring much higher forces to produce the same pedal stroke rotation. This results in a much higher muscular and therefore metabolic demand.
The telltale pelvic rock of someone who has their seat too high results in the creation of an ‘unstable trunk’. As the cyclist drops their pelvis to reach the bottom of the pedal stroke the trunk would also rock in the opposite direction to counter this. This would then be repeated on the other side as they reach for the opposite pedal. Apart from the potential for a sore back by the end of their cycle this ‘unstable base’ for their force producing muscles makes them inefficient as some of energy produced by these muscles is lost to trying to stabilse the pelvis.
The moral of the story, do yourself a favour and make sure you at least have your seat at the right height. It may mean you knock at least a few minutes off your personal best cycle into work 😉
Paul King, Physiotherapist, Chancery Lane
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