By NRG Coach Sylvie Dansereau
Now that I have covered crank size, we should discuss crank arm length since this can significantly impact your position by improving your comfort on the bike when riding in the aeroposition and therefore can positively impact your performance.
Comfort will play a big part in determining your ability to sustain your position for the duration of your event. Shorter crank arm effectively shorten the distance between the bottom of the pedal stroke (6 o’clock) and the top of the pedal stroke (12 o’clock). In years past a typical crank arm length was around 172.5 to 175 mm. Now many good aero set ups will see athletes using a crank arm shorter than 170 mm (167.5, 165 mm being quite common nowadays). Using a shorter crank arm allows the athlete to maintain a more aerodynamic position while retaining a more open hip angle (angle between the thigh and torso). In essence, when using a shorter crank arm, your knees will not come up as close to your trunk at the top of your pedal stroke (12 o’clock), which will result in more comfort and/or efficiency while keeping you faster with better aerodynamics and this is achieved without negatively affecting your power output. All this means that it will leave you in a better place coming off the bike for your run.
Here are very good, albeit a bit more technical, discussions of this topic by the Cervelo team: http://www.cervelo.com/en/engineering/ask-the-engineers/crank-length.html
And another one on Training Peaks: http://home.trainingpeaks.com/blog/article/the-benefits-of-reducing-your-crank-length?feed=70c86158-aad7-4b07-8cc3-7c383b9bd61b&utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+trainingpeaks%2FXAlX+%28TrainingPeaks+Blog%2
There is not one single bike position that will be optimal for everyone but remember that speed and performance will be the result of power, aerodynamics and comfort and a shorter crank arm could provide you with a little added comfort and better aerodynamics without compromising your ability to produce power.
Sylvie
