After hearing the success Mark and Rob were having with short cranks, I decided to give it a go. I took the plunge and cut down a pair of cranks to 100mm in length, that's right, 10cm! First impressions were "this is kinda weird" but it also felt quite normal. Up and down the street I went and I watched how the cadence could easily climb to 150 rpm. Scott and Owen had a go and managed to peak around 240+ rpm! The weirdest part was trying a trike with "normal" 170mm cranks, jeezus, felt like I had my knees around my ears! This is in direct contrast to when I was competing at the OzHpv events with Bullseye 203mm cranks, used to love those back then but my knees certainly didn't.

After more than six months living with 100mm cranks, I have made the following conclusions -

• No knee pain if you keep the cadence up
• Better acceleration once moving, you always feel "over the top of the gear"
• Lactic build up decreases in legs because you are not mashing the cranks
• Cramping virtually disappears
• Heart and lungs manage the same as before (more below)
• Reduction in overall weight, shorter cranks and lower gears (more below)
• Climbing is better due to feeling over the top of the gear and legs don't load up

I wanted to test the theories more scientifically, so fortunately Ian had bought a Computrainer a while ago for tests such as this, cool! I modified some cranks at 175, 155,125 and 100mm so that I could change between the different lengths in a short time. I then strapped on the heart rate monitor (HRM) to analyze myself. I then tried to find a level of resistance that didn't put me into heart attack mode but high enough to stress. The test involved riding at 15, 20 and 25 mph results here. This test showed that the only thing that changes is cadence. Peak power was down slightly on the 100mm length, but peak is hard to reproduce each and every time. Like a small wheel revolves faster to achieve the same road speed, short cranks spin faster to achieve the same "foot speed" (FS) As the foot speed is the same, the body isn't taxed any more to spin them at a higher cadence. Cadence and gearing are directly proportional to the decrease in crank length, so if you reduce your crank length by say 30 percent, your cadence will increase by 30 percent and your whole range of gearing should be 30 percent lower.

I liken short cranks to engines, (yes, I'm into cars and bikes as well) a V8 has plenty of power, typically a long stroke and is a slow revver. A small capacity four cyclinder has a lot less power, typically a short stroke and usually revs freely. Japanese four cyclinder motorcycles, GP cars etc all rely on big rpms to produce power from small capacity engines. I liken "most" humans to the four cyclinder category, so it makes sense that we should be spinning to make up for a lack of big power.

I use and recommend 125mm cranks these days and we used these to good success in our Wonthaggi racer with most of the riders commenting on how good their legs felt afterwards. If you keep in your head "these are normal cranks" and you just imagine your normal rythym, you'll be right. Try and muscle them and you'll end up back where you stsrted with sore knees and also sore feet.

Why long cranks? I "assume" the crank lengths of today hark back to early days when gearing was limited, so you needed leverage to get you up those climbs. With a wide range of gearing available, leverage can now be achieved with lower gears. Leverage in your legs is also achieved as your legs get straighter, just watch a weightlifter heaving that mass in the air, he/she struggles to get the weight up from the knelt position, but as soon as the legs get past say 135 degrees they just stand up like there was no effort required.

I also found that I set my trike up shorter than is normally ideal, as I was now no longer working at the extremes of my legs eg. stretched all the way out or bent up like a pretzel on the return stroke. Having your legs stretched all the way out just wasn't quite right, so I'd recommend this setup with short cranks. I shouldn't be calling them short cranks, should be calling everything else long cranks ;-)