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It is theorized that the increase in cadence when moving to a shorter crank length isn’t due to trying to make up for the lack of leverage, but to replicate the foot rate/speed an athlete is accustomed to on a longer crank and to use the extra available O 2, which is minimal. Most report that when they switch to a shorter crank their cadence increases. With the 195mm crank length, the foot speed is higher to cover the revolution at 90rpm compared to the 145mm length. This would be the same as an athlete pedaling a 145mm and 195mm crank at 90rpm. The athlete in the outside lane has a greater distance to cover and would have to run at a faster rate than the athlete in the inside lane to both complete one revolution of the track. One in the inside lane (we can call this the 145mm crank) and one in the outside lane (the 195mm crank) and both athletes had to run one lap (revolution) in 1 minute 30 seconds. Shorter Length BenefitsĪn easier way to think of this would be if you took two athletes and placed them on the track. It’s important to note that pedal rate is not cadence and is defined as the speed of the pedal along its axis. The results showed that O 2 uptake increases as pedal rate increases. 2 looked at efficiency and setup a study where cyclists used crank lengths of 145, 170, 195mm, where cyclists pedaled at 40, 60, 80, and 100rpm, at an intensity of 30, 60, and 90 percent of blood lactate. During the initial study, Martin 1 looked at max power and found there was no difference between 145 to 195mm lengths, but he did note that there was less oxygen uptake with the shorter cranks. There has been a lot of great research led by Jim Martin and John McDaniel on the topic of crank length. Most likely, crank length has just been passed down from one generation to another and over time has just become accepted even though there is no basis for the current “standard” with the current bicycles we ride today. There are some theories dating back to the origin of the first push bike, or the length that was optimal for the penny farthing bike (bike with a large front wheel and small rear wheel). When I present on the topic of crank length, I begin by asking where these lengths that we consider “standard” originated from.
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In this article, I want to discuss how you can use crank length to improve your speed on the bike. Aerodynamics are achieved by optimizing front surface area and shape to minimize resistive forces. Power is simply the ability to apply force to the pedals without restriction within a range of accepted biomechanical norms. Comfort is defined as the ability to sustain your position for the duration of your event. Remember that speed = comfort + power + aerodynamics. Your bike and its contact points must be selected and positioned in a manner that promotes comfort, power and aerodynamics. One of the biggest performance upgrades you can make is a proper bike fit.