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Monday, May 23, 2011

Clipless versus platform pedals

I have had a few clients asking about whether platform pedals will make them faster on their mountain bike.  I think it's important to carefully consider equipment choice when it comes to your bike, since that can severely affect how enjoyable the sport is.

I'm not here to tell you that flats or platform pedals are bad, and clipless pedals are good.  In fact, I think there are situations that warrant either.

Normally, I wouldn't mention anything, but some of the advice and "facts" I have read of late have convinced me that the "No Harm, No Foul" rule has been violated.  If someone who coaches cyclists is telling them, "You know, you might ride better and more confidently on flats"  I don't take issue.  It very well may be true, and in the best interest of that client.

But when I read about claims that clipless pedals cause injury, "mask dysfunction", "feed into dysfunction", "artificially strengthening the weak link of the feet", they can "increase your risk of overuse injury"  with no explanation of what dysfunction they're feeding into, I think some balance regarding the science is needed.

I do a lot of bike fits.  As a practicing physical therapist for 14+ years, I have seen and assessed thousands of riders using some of the most sophisticated infrared motion capture equipment on the planet.  I assess clients who ride with flats and with clipless pedals, and each group has consistent numbers of knee pain.  There never has been any research that proves the claim that clipless pedals cause more injuries because of their inherent "dysfunctional movement".  There is no research whatever that shows platforms to be better that clipless.

So let's get to the research cited.  I have seen two main articles cited as evidence that platforms are superior to clipless.

KORFF, T., L. M. ROMER, I. MAYHEW, and J. C. MARTIN. Effect of Pedaling Technique on Mechanical Effectiveness and Efficiency in Cyclists. Med. Sci. Sports Exerc., Vol. 39, No. 6, pp. 991–995, 2007.

The Korff et al article in a nutshell took 8 cyclists (with a minimum 2 years experience experience cycling)and had them perform 4 different pedaling trials at 90 rpm and at 200 watts.  The four trials of different pedaling where referred to as:
  1. Preferred: they used their preferred pedaling technique
  2. Circling:  pedal in circles and to concentrate on the transition phases through top dead center
    and bottom dead center of the crank cycle
  3. Pulling:  emphasize an active pull during the upstroke of the crank cycle
  4. Pushing:  emphasize the pushing action during the downstroke of the crank cycle
Each pedaling test was 6 minutes long followed by 6 minutes of passive rest.

The long and short of the results is that the cyclists had the lowest metabolic cost (or the highest metabolic efficiency = least energy expended) during the "Preferred" and the "Pushing" tests.  But the "Pulling" and the "Circling" had significantly higher mechanical effectiveness (you might say it was the most even or balanced distribution of power throughout the entire pedal stroke).

Some issues to consider:

Just because the cyclists "Preferred" pedaling style and the "Pushing" closely mirrored each other is not proof that "we already know how to pedal", and instructions to change this (cueing riders to pull up to even their distribution of force) just screws up our stronger natural instinct on how to pedal.  The authors of the study even think that this lends support to the idea that other pedaling styles (other than just "Pushing") may be better in the long run because:

"...multiple physiological systems are likely to adapt in response to training with a specific pedaling technique. Our data support this speculation by demonstrating that in all participants, the preferred pedaling style was accompanied by the greatest gross efficiency."

Another thing to consider is that these cyclists were tested on an ergometer (power meter) at a low wattage of 200 watts -- really just easy spinning for most riders, especially the male cyclists employed in this study.  No significant effort was required so it's not surprising that the "pushing down" was emphasized during their "preferred" pedaling style.  If you are trying to determine efficiency (metabolic) and effectiveness (mechanical), a range of wattages would provide for better data -- a more difficult study, for sure, but it would shed more light on the differences and benefits of the pedaling styles.

Pedaling in a circle decreased torque?  It did, but only "peak Torque", or the very high of the high end, and, again, at a very sub-maximal 200 watts -- severely limiting what conclusion you can draw about torque and force profiles.  I.E. drawing "Peak" or "Maximal" torque conclusions from sub-maximal testing  (actually not even close to their threshold level) is not very effective.

Metabolic efficiency was highest for the "pushing down only" pedaling style?  True, again, but only at 200 watts, but "mechanical effectiveness" increased significantly.

One thing to reiterate is that this study only tested eight (yes 8) cyclists.  In research, that's referred to as a study with N = 8.  Not very in depth, and certainly in need of more subjects of varying abilities to draw better conclusions from.

Another problem:  We don't know a lot of things -- like if these cyclists were ever trained in circular or a balanced pedaling style.  They were just prompted into this technique briefly before the study began.  We don't know how much they actually ride  -- only how many years they have participated in the sport.

Mornieux G, Stapelfeldt B, Gollhofer A, Belli A. Effects of pedal type and pull-up action during cycling.Int J Sports Med. 2008 Oct;29(10):817-22. Epub 2008 Apr 17.

On the other study, Mornieux et al., 8 elite cyclists and 7 non-cyclists were tested at 60% of their maximal aerobic power (MAP) in three different pedaling situations:
  1. With platform pedals
  2. With clipless pedals
  3. With clipless pedals and instruction to pull up on the upstroke

Despite claims I have read online to the contrary, the pedaling forces of the trained versus the untrained cyclists are different through the pedaling styles.  The untrained cyclists have much greater negative pedaling forces no matter how they were pedaling, than the trained cyclists.  This actually lends support to the idea that more practice with a balanced pedaling technique (some pulling up on the back-stroke with clipless pedals) may lead to better effectiveness in your pedal stroke. 

Of course, you see I'll say it MAY lead to better effectiveness.  This, again, is a very small study with barely over a dozen of participants, so we have to be careful of the conclusions we draw.  It was also conducted with low power output -- 60% of MAP is a very steady, easy pace (it's not 60% of their "maximum" but of their aerobic max -- much different).  But all  the same, it actually makes it worthwhile to consider testing a "pulling" pedal stroke further to see what benefits can or should be gleaned from this.

In fact the authors of this study in a more recent article called Muscle coordination while pulling up during cycling from 2010 concluded:

" training the pull up action could be of interest to optimize this muscle coordination associated with better pedalling effectiveness by additionally relieving hip or knee extensors during the downstroke."

Scientific research is great, but at least three rules should be adhered to:
  1. Read the whole article
  2. Learn how to dissect a research study to find it's strengths and weaknesses.
  3. Be careful with the conclusions you draw -- the good research authors usually are.  they understand that research can almost never pronounce anything with 100% certainty.  For example, in the full text of the Korff et al article the authors say in the Discussion:
"Although our results suggest that actively pulling on the pedal reduces gross efficiency during steady-state cycling, there may be situations during which an active pull is beneficial in terms of adding power to the crank.....A limitation of our that it does not rule out the possibility that there may be a more efficient
pedaling style if participants are given enough time to adapt to it. Longitudinal studies are needed to explore this possibility."

Again, my purpose is not to do a flame-job on anyone, or tell you that clipless pedals are better for everyone in all situations, but reading these articles and drawing conclusions like,

"...clipless pedals literally offer no help....and will decrease pedaling force and screw up their (riders) pedaling patterns."

is not prudent or helpful for readers looking for good advice.

You can't take one idea about movement and apply it to all things -- this is why the study of human movement is difficult and takes years of schooling and clinical work to best understand.  

Can you generate a lot of peak power with platforms?  Yes, definitely.  Nathan Rennie is a super strong pro mountain biker.  He tested at 1800 watts on platforms.  But, there are also a few dozen track cyclists that test between 2300-2400 watts all with clipless pedals (and some with pedals that are molded into their shoes -- you don't unclip at all, you have to take the shoes off to get off your bike).

Again, I'm not hear to tell anyone they have to do anything one way or the other.  But the discussion went from "Flats are good on technical terrain, and for gravity racers" to "Clipless pedals are bad for you and don't help anyway, so no matter how you ride you should use flats".

Many cyclists on the dirt find clipless pedals more useful because of the fact that they do allow you to smooth out the peaks and valleys of power generation, and decrease the likelihood of spinning your rear wheel on a steep, loose climb.  Some of us still ride on hardtails, which makes this even more important, but even on the best full-suspension machine, there are times when smooth, not maximal, power generation will get you up a climb.

I can see flats being better when you're on terrain you're really not comfortable tackling yet, if you are more into the gravity end of the sport, or if you're riding very leisurely.  But road riding/racing on flats? -- sorry nope, and I think you'd be hard-pressed to convince any roadies to give up their clips.  If you mountain bike, and you sometimes ride easy, you sometimes ride harder racing your buddies, sometimes you go downhill fast, sometimes you flat-track fast, sometimes you climb, sometimes you single speed, sometimes you ride the White Rim liesurely, then like many of us, you may ride better with clipless pedals.  Maybe not.

So try them both,and decide for yourself.  Research doesn't prove anything one way or the other (as is usually the case).  I'm here to tell you that just because you ride with clipless or platforms you don't have a "dysfunction".

That's all for now.



  1. Clipples pedals do not only offer pull pedaling possibilities. Far more importantly they help you cycling more securely.

  2. This comment has been removed by a blog administrator.

  3. Have you got a source for Rennie's power figure? I've been trying to find one for a while, without success.