iCranks, the first true second generation power meter, is coming soon
What is a 2nd generation power meter and what are iCranks? A first generation cycling power meter is what we are all used to - a device that attaches to the bicycle that gives the rider their actual power while they are riding and it collects that power (and some other metrics like HR and speed) for later analysis. A few "2nd generation" power meters are now on the market that give independent right and left power, but not much, if anything more. A true second generation power meter does all this but also is able to give and collect individual pedal force information to allow the rider to analyze pedaling technique and muscle use. This can only be done when there are two power meters located in each crank, pedal, cleat, or shoe and when there is appropriate software to analyze the data. The iCranks power meter is located in the crank arm of the basic PowerCranks and will come with software that does this analysis. This gives the iCranks the ability to measure and display the riders pedaling technique and to measure actual muscle weaknesses in real time (indoors in front of the computer) or using saved data for later analysis.
Before we move on let's discuss the question: What is the ideal pedal stroke? Most people think that cycling is a simple activity and we all do it pretty much the same way. We push on the downstroke and unweight/relax on the upstroke. Such a pattern ends up giving a force application pattern that resembles a sinusoidal repeating curve. Since power is nothing more than the force (in the direction of the motion) times the velocity the power curve looks similar since the pedal speed is almost constant around the circle. The total power shown on the power meter is the average power for the entire stroke circle. Can we analyze and then modify our technique to get a higher average power? Let's see.
The major thing that confuses most people is that all of the power going to the bike comes from muscle contraction but all of the forces seen on the pedals do not come from just muscle contraction. Therefore, people look at the typical force pattern of the typical rider and conclude that all of the power comes from the pushing (downward motionof the pedal) and the upward motion is unimportant and can be ignored. Nothing is further from the truth because gravity and other non-muscular forces interfere with the analysis. This improper analysis results in inefficient muscle coordination and lost power. For instance, here is the force/torque pattern of an elite cyclist, which is the typical pattern of almost everyone.
But, when we remove the non-muscular components of these forces the pattern suddenly changes showing that this rider is actually doing work around the entire circle but it is still unbalanced, with most of the work being done on the downstroke and the weakest part of the stroke being over the top.
It would be easy to say that this is still the best way to pedal until one considers that all the rider need do to apply substantial power across the top is to start the contraction of the big quadriceps muscle about 10 o'clock instead of waiting until 1 o'clock. And, to stop the quads contraction by 3 o'clock because that "pushing down," as we normally think about it (invoving the quads), when the pedal is past three means the quads contraction is tending to push the pedal forward when the pedal is moving backwards, in other words doing negative power. Is it possible to fix this. Well, here is the actual muscle technique of an elite triathlete riding at the same power and cadence who has been training on PowerCranks for about 10 years.
Notice, with proper training, it is possible to distribute the work done around the pedaling circle evenly. This is what is meant by pedaling in circles, not the equal distribution of force around the circle, which is impossible because of the effects of gravity. Also note, that the actual measured pedal forces and muscle forces compare very well at the top and the bottom of the stroke. it is only the front and the back that are difficult to interpret.
So, how does one use this data? Here is a screen shot of two riders using completely different techniques. How can one tell a better stroke from a worse one? Well, one needs to compare the top and the bottom numbers because they are the closest to reality. 99.9% of you are weak coming across the top compared to the bottom. Then look at the circularity. Does the trace look like a circle? The more uneven (oval, egg shaped) you are the more your stroke needs help.
Let me go into more detail using some actual data. Here are several examples. Let me say that negative number per se are not necessarily bad if the rider is at a low power. Look at the shape of the curve and the evenness because we tend to pedal the same way whether at high or low power. Having said that, do these tracings make any sense to you. If you saw one of these in you would you know where you needed to concentrate your efforts to improve your technique?
bad-technique from Eric Allen on Vimeo.
And, here is an example of data from a rider the iCranks calls having good technique. While much better technique there is still room for improvement.
good-technique from Eric Allen on Vimeo.
And, now, here is an example of a rider who has been using PowerCranks for many years (me). Yes, they finally have the software (beta) that works with the prototype iCranks I have. Note that there are zero negatives anywhere in the circle and, in fact, I am doing substantial work on the backstroke (at the top of this graph because its orientation is off 90º). Further, the power is off (low) by about 40% because this was done on 125mm crank length so the calibration is off. Why 125mm? See the crank length discussion. While the software is not perfect yet at least we have something we can show and talk about.