My promised pedaling technique analysis. I will break this post into two posts as the forum has a limit of 4 images per post and my analysis includes 6 images.
There are two different ways most cyclists currently know how to increase power: 1) push harder, and 2) pedal faster. Both of these methods are effective.
Rarely does the cyclist think about improving technique, probably because there is no easy way to measure technique and it has never been shown that there even is an "optimum" technique. But that is about to change because second generation power meters will soon be available that will completely change how the cyclist looks at power generation.
Here is a rider's actual data from a second generation power meter system that we will analyze. For this analysis I am going to assume that the rider cannot push any harder nor pedal any faster (which is easy as the rider being analyzed is at a cadence of 133 for this shot).
First, there are two displays, one for the left and one for the right crank. On each display the actual crank torque at each point around the circle is shown in red and the zero torque line is shown in yellow and the average power that torque generated in 30º increments is shown. But, we can’t learn anything useful if we don’t know what we should be looking for or what we should be doing?
In the above graph, the total power for each leg is the sum of these 12 wedge power numbers divided by 12, the average for the circle. The total power for the rider is the sum of the right and left crank This power variation and how it is averaged is easier to “see” when it is expressed in graphical terms.
What can we see immediately? We can see that the right leg is substantially better than the left leg, having both a higher peak down force and less negative force such that it is averaging 305 watts around the circle while the left is only averaging 266 watts, a 39 watt difference between the legs. Add them together and we find the rider is generating 571 watts, the number he would see on his power meter. The imbalance information, by itself, is important to know as athletes with substantial leg imbalances are more prone to future injury. Working on strengthening the weak leg will not only give this rider more power but will reduce risk of future injury.
Before I move on I want to discuss the “ideal” pedaling stroke.
Most people think that cycling is a simple activity and we all do it pretty much the same way. And, they are right. 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 and that is what we see above.
Since the total power is the average power for the entire stroke, the ideal pedal stroke should be some variation in this sinusoidal pattern that results in the highest average power. We've already made the assumption that this rider has maxed out how hard he can push. What other changes can this rider make to improve his average power? One obvious thing he could do would be to just to eliminate the negative forces from his current pattern.
Just eliminating the negative forces from the pedaling circle, improved the right crank power from 305 to 324 watts and the left crank power from 266 to 296 watts. Making this simple change alone he would improve his power from 571 to 620 watts, a 49 watt improvement. If he could make the weak leg the same as the strong leg he would gain another 28 watts, giving him a total improvement of 77 watts!
Not bad, but can more be done? Remember how I said the curve resembled a sinusoidal curve. Let’s broaden the force pattern to be a true sinusoidal curve, assuming the rider can do this, and see what it might change in the power numbers were he able to change force pattern to resemble this curve, without changing his peak force.
By broadening the curve, suddenly much more work is being done around much more of the circle and, without pushing one ounce harder, this results in an improvement in power to over 500 watts for each leg or over 1000 watts for the rider. By simply using more of the circle to generate power (and eliminating all the negatives) we could theoretically improve this rider’s power from the 571 watts he was doing to 1002 Watts! This is almost a doubling of power from a simple technique change, again without him pushing any harder. The pedaling form issues limiting the power this rider was seeing were two, he was losing about 50 watts from the negative forces on the pedals during the upstroke. But, more importantly, he was losing almost 400 watts because he was doing essentially no work across the top and decreasing a little too quickly across the bottom.
If possibly losing 400 watts by concentrating on the push and ignoring other aspects of the stroke doesn’t get your attention, nothing will.
continued in part two
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