The Myth of the Upstroke
Before and during the development of the Bythlon safety performance pedal system's technology, we comprehensively researched cycling science, especially the biomechanics of the pedal stroke, the technology, and the benefits of the existing clipless pedal systems.
We could confirm from the widely publicized benefits that cleats indeed secure the shoe in place on the pedal to prevent slipping and that the purposely developed road bike shoes with extremely stiff soles improve pedal power and most likely reduce the risk of injury.
However, the main argument for cleats dates back to the days where cyclists tied their shoes to their pedals with shoe clips and straps. The idea behind that is to generate a 'perfect' stroke, pedaling with one leg pushing down while the other is pulling up.
Most cyclists accept this as a foregone conclusion. There is probably no cyclist who has not heard the advice to aim for a 'round' pedal stroke. The cleat pedal is probably perceived as the essential bike component that separates the casual or novice from the ambitious and experienced rider, even more so than carbon frames or wheels.
So we were in a big surprise when we came across several articles and a video that was describing 'The Myth of The Upstroke.'
We learned that the presenter of this video, a sport biomechanist and advisor to the United States Olympic Committee, Dr. Jeff Broker, had tested more than a hundred cyclists' pedal strokes from the 1980s onwards. None of these elite and professional cyclists he tested over ten years produced a meaningful upstroke.
He developed an early power force model and called it 'cycling clock diagram.' It is still in use today and frequently cited in publications. It clearly shows that there is no 'pull' in the recovery phase (upstroke).
He first published his findings with his colleagues Robert Gregor and M. Ryan in 1991 (The biomechanics of cycling). It appeared to them that there is no 'pull' and that the entire aspect of pulling through the upstroke is a myth. That opened an entirely new element to our research. Since we found several comprehensive studies and publications citing and confirming his results, including studies researching if these results would change with uphill cycling, we dived deeper into this.
While these studies are apparently confirming Dr. Broker's findings, they are highly scientific, often limited to a handful of participants, decades-old, and therefore the sensors used custom builds. The interpretation of the laboratory data is often difficult.
Today there are many different power meters and software applications readily available that allow us to approach our research not only from the laboratory but from the field.
We took a closer look at how the results modern power meters deliver and how they are displayed. Power meters from Garmin, Pioneer, and Favero are some of the meters popular with cyclists, and all come with mobile and website apps showing the results.
We first searched online and found thousands of results posted by individuals. For data privacy reasons, we leave it to anybody interested to browse these results and post here result diagram examples from the companies' websites.
Garmin's Vector 3 power meter pedal comes with the Garmin Connect mobile and website app. Their 'Cycling Dynamics' analysis delivers a whole range of results and visualizes these in a way easy to understand and interpret. The Power Phase diagram shows how the power is produced and wherein the cycle the most power, The Power Phase, is produced. Undeniable is the absence of any power in the upstroke as it has been marked with 'No Power'.
Pioneer produces crank-based Pedaling Monitor Sensors that work with their Cyclo-Sphere data analysis web service, which displays the pedaling power similar to Garmin but using vectors displaying force and direction. Interestingly this is very similar to Dr. Broker's tests almost forty years ago. The graphic shows no power in the upstroke, and the lack of thereof is apparent as well in the pedaling graph next to it. (Update: Pioneer sold its related technology to Shimano and cased selling at the end of March 2020.)
Favero's Assioma power meter pedal uses the IAV Cycling Dynamics for analytics. The Power Phase and Peak Phase graphic symbolized by the red arc segment on the power cycle indicates where the power begins and ends. The green arc shows the Power Phase Peak, which is the segment where 50% of the total power is produced. The upstroke is marked with the words 'No Power.'
At this point, we believe it is fair to say that The Myth of the Upstroke has been debunked by scientists and field data from many thousands' individual cyclists as a popular misconception.
We are certainly not the only ones that took notice. Andy Pruitt writes in his Complete Medical Guide for Cyclists about the biomechanics of pedaling: 'The Best Cyclists Don't Produce Power When They Pull Up on the Backstroke.'
Martin Blair, a bike fitter and former road cycling champion, writes in bikeradar: 'Some power meters will show you where in your pedal stroke the power is. Even when trying, very little power is produced in the upstroke.'
Kevin Curry, the founder of Gear & Grit, published a well-written article about the myth on his website summarizing 'Pedaling circles is a myth, and one that can do real harm to you.'
Phil Cavell from Cyclefit UK has more than thirty years of experience with bike fitting and concludes: 'That is to say that even they don't produce enough force at the pedal to offset the effect of gravity on their uphill-moving leg! '
Phils's statement had been already confirmed in 1986 by Mats Ericson and his colleagues, who found: 'The active limb supplied the passive limb with some of the energy to lift it between approximately 195° and 360° crank angle '(p. 234).
Finally, the always entertaining Global Cycling Network (GCN) hosts experimented so far three times flat pedals versus clipless pedals in 2014, 2017, and 2019 and found each time that flat pedals more or less same efficient as clipless pedals.
So before our conclusion, let us look into Eriscon's and later finding regarding the muscle groups involved. The pedal stroke generates force by hip and knee extension and flexion. An extension is used pushing down during the power phase, and flexion is used to recover the pedal back to the top of the cycle for the next downstroke.
Glutes, Quads, and Calfs work together, pushing down and Hip Flexor and Hamstring pulling up. Just by looking at the size of these muscle groups, we realize that the extensor muscles are much larger than than the flexors.
That makes sense since the legs functional movements, the daily life's moves are all related to pushing: Walking, running, squatting, and lifting all require the legs to push. The only pulling movement in daily life is to lift the leg up for another step. It never has to raise more than its weight, if you disregard the weight of shoes.
Mike Schultz from Highland Training wrote this 2015 article on the TrainingPeaks Coach Blog and included a graphic with a much more detailed breakdown of the muscle groups involved based on the findings of Hug, and Dorel in 2009, and several earlier studies.