Since the force you are noticing occurs between 180 and about 270 degrees and disappears at 270 degrees, it may be due to "pushing back" rather than "pulling up".

Suit yourself.

The bottom line is, I go with objective data. You apparently reject objective data, and pour scorn on everyone who produces it. Sounds like an impasse to me.

You keep using that word, I do not think it means what you think it means.

It is an objective fact that I do not have the power I normally have when climbing a hill on flats vs. with clipless. It is an objective fact that my foot lifts off the recovering pedal forcing me to lessen the force from my descending foot least I push myself off my bike.

Now then, tell me how my objective facts fit into your model.

I've accepted your data. For what it is worth. The argument is just that: what is it worth?

If you only use "objective data" (the way you define it), I assume you have no point at all to make about cycling conditions outside the parameters of the experiments you cite, right?

I'm actually OK with that view.

However, I really can't recall a lot of people who say "I'm switching from platforms to clipless because my foot keeps sliding off the pedals!" ;)


Yes, I concur. It would be great if we could see that data. We'll have to wait until something like the Garmin Vector hits the shelves.

I was referring to the trend as power increases, not the shape of the 400W plot. Effective force at 270 degrees is effectively zero at 400W from a minimum of -50N at 100W. The trend appears more or less linear; it leads me to believe you get positive force above 400W for that particular individual rider tested.

And as far as I can tell, they are all steady-state trainer measurements

I'm guessing they don't exist because it hasnt been the subject of a study. Everything we have seen has been about pedaling techniques - which makes sense. These are the things trainers would want to study. They don't do these things just to satisfy their curiosity, they are looking for things that could get them results.

In the absence of any clear, relevant data, we have to fall back on our own, personal observations. Ask any experienced cyclists if the add power by pulling up on a hard, burst sprint effort or steep hill climb and I can assure you, they will almost all say yes. Yes, they could be all wrong, but without evidence, its the best we have. We've had a few people, including myself, report that we came unclipped on a climb or sprint. That seems to further add weight to the notion that a significant amount of force was being applied to the pedals for that to happen.

I would like to see the full context of those remarks. Its difficult to imagine they would be including sprints and steep climbs in that.


I've seen that before, and I agree that these studies prove them wrong when it comes to cruising on a bike.

I could equally ask you to clarify what would make you expect that the data would be essentially the same. This is personal experience, that in those two conditions, I apply force to the pedals in a very different way than when I am cruising along.

I don't think I have seen anyone claim a huge power advantage.

As you pointed out in one of your earlier posts, one of your references was on PubMed and you stated categorically you weren't about to hand around your password for that site.

That data you showed is an average of a number of riders. Below is the individual data from Coyle's study clearly showing that some elite cyclists pull up and obtain power during steady state cycling. This was for their preferred pedaling style with no instruction to 'pull up'. Unfortunately, there isn't enough data around to settle this argument definitively.

http://www.bikeforums.net/attachment...6&d=1373408583

I think this graphs illustrates perfectly what the proponents have been saying. That low cadence one is the real clincher for me, but it's also notable that for all the other cadences, there is uptorque evident through large chunks of the phase between 180 and 360.

Sure, the amount of uptorque is small compared with what happens on the downstroke, and may even disappear, but it does exist, based on those graphs, and exists in varying amounts depending on the cadence. Which goes to the heart of people's claims of using uptorque in conditions that seem logical -- hard climbing, for example.

Track cyclists use retention systems because of the very high cadences they require in sprints. Keeping feet on the pedals at those speeds become problematic. But I imagine they use those retention systems to very great effect when starting -- as evidenced by the number of pull-outs that have occurred in competition (on the upstroke).

Which correlates with my own observations about standing starts and other short but high torque sections like coming out of a sandtrap in a CX race.

And no one has given a biomechanical reason why all that data, collected under different conditions, that all produce the same force curves, has relevance whatsoever to sprinting.

Is it the rider position? Cadence? Levels of power output? Anaerobic or max effort?


Nope.... Bad data is bad data.

And also assume that at some point in their careers, Pruitt and/or Burke have done lab tests involving sprints, even if they haven't published the data.


http://velonews.competitor.com/2007/...-part-ii_11555
pp 132 http://books.google.com/books?id=msd...ciency&f=false


I'm glad we can agree on something. :)

Perhaps, although most of the instrumented pedals used to show left and right torque profiles are not portable so it may not be possible to get that data in the field. Sprinting on a trainer is quite different than sprinting on the road.

By the way, Ed Burke died in 2002. His research was conducted before power meters were widely available.

He is not alive for his methodology to be challenged.

Shame we don't have Rick Stern still posting here on BFs. He could have provided us with enlightening, albeit taciturn, up-to-date information on this.

#249

Data is data. There is no such thing as "bad data" (unless you are talking about falsified data). What you don't believe in is unquantified data from natural experiments. It is smart to not put too much stock in unquantified data; that said, if you restrict your worldview to only quantified data from controlled experiments, you miss out on a lot. Millions of sport cyclists through the last half century (maybe more) have chosen foot retention for some reason. A true scientist will ask why. There are clear advantages to power transfer; everyone who rides much knows this. Now then, is that advantage always present? Perhaps not; these studies suggest that retention doesn't do much for steady state power. Fair enough. On the other hand, there are modes of cycling where it is clear to the practitioner that foot retention is essential to maximum power production. What say you to this data point? Is a half century of cycling history wrong? Or perhaps is your model a little over-simplified?

And yet none at 270, which should be the peak angle for "pulling up". That suggests that the power transfer you are highlighting may be due to horizontal effort.

The graphs don't show the vector forces. The torque after 270 on the mashing cadence, does suggest some upward force. Which is still different from saying there is no upward force or torque applied to the crank.

this makes no sense.
i don't see how this is possible unless you were lifting your leg purposefully.
because otherwise physics would dictate your foot rides the pedal up as it forces your leg upward because your other foot is forcing the other pedal downward.
and i doubt you were downstroking so hard that the upward force was launching your foot off the pedal.

Whenever you are climbing stairs, you are doing the same thing. It happens whenever the force required to turn the pedals exceeds your body weight. The cure, of course, is to pull up with your recovering foot while pulling on your bars. But that never happens, as we all know from studying steady state trainer data. :rolleyes:

I thought about this thread as I rode home on my commuter bike with flat, strapless steel cage pedals, in my work loafers. I also tried to observe my normal pedal stroke and I experimented a bit with it.

Most of the time my foot stays horizontal, but I noticed that every once in a while, without really thinking about it or planning it, I would “ankle” on the first part of the upstroke, tipping my foot down about 45 degrees at the bottom of the stroke and leveling it out again halfway up. I was also aware of “pulling” the pedal back and up when I did that. It’s just a habit I seem to have, doing it for two or three cycles and then returning to keeping my foot horizontal. Probably just varying which muscles I use. Of course I’m using pressure on the pedal as I do it, so it’s really a dragging rather than lifting motion.

If I deliberately took one foot off the pedal and tried to pedal as far around the cycle as I could with the other foot, I could get the pedal to about 45 degrees past the bottom (or to 225 degrees if you wish) even with my foot flat, or actually all the way to middle of the upstroke (270) if I ankled. Again this is a dragging effect on the pedal, not “lifting it” as you might if you had foot retention. So you don’t need cleats or straps to get a little bit of upward force on the back part of the pedal circle.

I could also deliberately “pull up” up all the way through the upstroke without losing contact with the pedal, consistent with the notion that pulling up in some cases simply partially unweights the pedal and helps lift your leg, without actually providing an upward force on the pedal.

However at normal easy cruising cadence – maybe 50 rpm, I could easily lift my foot right off the pedal on every pedal upstroke stroke if I wanted to, suggesting that people who choose to pull the pedal upwards with their cleat can do so. Whether they should, or how long they want to do it for, is another matter. When I cranked up the RPMs to what I thought was about 100, I could still lift my foot right off the rising pedal if I tried, but not repetitively, since I couldn’t consistently reconnect to the pedal at that speed, so it would take a lot of coordination to actually assist the pedal in rising on every revolution at high cadences. However, presumably skilled cyclists could do it, or learn to do it at higher cadences than I can manage and up to a certain threshold. Again, whether they should do it, is another matter.

So what did I learn? At low cadences I can lift my unretained foot off the pedal on every upstroke, suggesting I would be pulling the pedal upwards if I were clicked in. You probably can only do that up to certain RPM threshold – probably well below 100 in my case, but who knows what it would be for some pros. You can also “lift” the pedal a little bit even without foot retention, by tilting your foot and dragging the pedal backwards during the first part of the upstroke.

The one thing that hasn't been discussed in the pedal retention debate is centrifugal force. I suspect that it is the reason why pedal retention becomes important at much higher cadences because the higher speed of the foot/leg mass results in a tendency for the foot to fly away from the pedal.

Anti-upstroke summary: Some studies show that moderate, steady state riders do not exert upward force. Therefore, no riders, including sprinters or climbers, ever exert upwards force on the pedals either.

Yeah, I always laugh when people say clipless pedals "teach you to pedal in a circle". More likely they make it unecessary to learn that skill, as the cleat does it for you - keeps your foot on the pedal when it otherwise it would fly off and leave the circle.

Objective, n=1 data
 

Don't know the reason but to advance the science (BS) a little bit I went out this evening and compared riding clipless with platforms. I did the same route and efforts, first with a set of platforms, followed by clipless pedals. I used an SRM to record power and zeroed the meter before each set of tests. I did this with an open mind and went all out on the sprints and steep hill. (I'm 50+ and not a sprinter so no wisecracks please)

For normal steady riding I didn't find any noticeable difference. My foot obviously moves around more with platforms and I don't find it as comfortable but I wouldn't have any issue doing a long ride with the platforms. The sprints were, on average, about 200w less with the platforms and the steep hill about 150w less.

One of the most noticeable differences was just starting out from a stop. With the platforms I couldn't go much above 400w but with the clipless I routinely start out briefly around 500-600w and it was very easy to feel the difference in pulling up. Not a big deal but I suspect this is why track sprinters need their feet firmly locked to the pedals.

Results are summarized below:

http://www.bikeforums.net/attachment...3&d=1373476108