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Have there been done any scientific studies that proves that clipless pedals actually improve pedaling efficiency etc. over flat pedals? Clipless pedal enthusiasts are quick to say that you must use clipless pedals to improve efficiency when cycling, but I have never seen this being backed up by any scientific sources actually proving this claimed efficiency boost.

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For me, clipless pedals help with fatigue more than anything. After several hours the energy/effort required to keep your feet properly positioned on the pedals becomes significant. This causes a corresponding drop in overall performance. –  Daniel R Hicks Jan 16 '13 at 16:22
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@user1049697 There are circumstance where cyclists actually pull up on pedal strokes with massive forces, however, that is limited strictly to very brief accelerations such as for sprinters or competitors in "Match Sprint". –  Angelo Jan 16 '13 at 20:09
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And, in my experience, with toe straps the strap begins to dig into the top of your foot after several hours, encouraging you to use less efficient foot placement. –  Daniel R Hicks Jan 16 '13 at 20:34
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@DanielRHicks my experience of toestraps is that you cannot get you feet out when you absolutely need to and you fall over and look stupid. –  robthewolf Jan 17 '13 at 18:17
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@robthewolf - I don't generally need toe straps to look stupid. –  Daniel R Hicks Jan 18 '13 at 0:58

5 Answers 5

up vote 24 down vote accepted

The Pedaling Technique of Elite Endurance Cyclists: Changes With Increasing Workload at Constant Cadence was published in the International Journal of Sport Biometrics 7:29-53, 1991. However, it seems to come to the conclusion that they don't really make any difference as far as pedaling efficiency goes.

"...while torque during the upstroke did reduce the total positive work required during the downstroke, it did not contribute significantly to the external work done because 98.6% and 96.3% of the total work done at the low and high workloads, respectively, was done during the downstroke."

This is echoed in Physiological and biochemical determinants of elite endurance cycling performance published in the Medicine and Science in Sports and Exercise 23:93-107, 1991. There are numerous graphs showing that pedal force is only exerted between the top and bottom of the downstroke, represented by a very sharp parabola spiking at 90 degrees from vertical.

That said, I think it's obvious to anyone who has ever done any particularly technical riding that with and without clipless pedals that clipless pedals significantly improve the handling of a bicycle. A fact which is probably more difficult to verify through scientific studies.

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Thank you for providing some good sources on this topic! The last paragraph could however be disputed as being very subjective. Downhill racers traverse technical sections using both flat and clipless pedals, without differences in handling being discernible. –  user1049697 Jan 17 '13 at 15:54
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Downhill racers notice significant differences in handling between flat and clipless pedals. It's just that they have the overriding necessity to be free of the bike during their regular and inevitable crashes. That means that for a DH rider, a flat pedal has a benefit which clipless does not offer. And so many choose to use them. That safety choice does not mean that it would not be easier to traverse the same terrain using a clipless pedal. The difference in handling may not be discernible to the observer. I assure you it is discernible to the rider. –  zenbike Jan 20 '13 at 4:09
    
There are a number of pro teams out there who are looking for every little bit of power for their cyclists. They all use clipless systems. That's some pretty good evidence in my book –  Eric Gunnerson Apr 18 at 3:54
    
I find it hard to believe that the torque on the upstroke does little to reduce the work required on the downstroke. When I'm climbing on a fixed gear, I find the vast majority of my power comes from pulling, not pushing. Without foot retention, there are hills I simply cannot climb, but with toe clips / SPDs I can haul the bike up those same hills without hardly pushing on the pedals. And I mean long climbs, too. Just sayin'. –  headeronly Jul 18 at 13:59

I think it's worth noting that if the question is about efficiency and not power, then there is probably little difference, but I find it a little dubious that so many of these references say it makes little difference whatsoever.

If the discussion is about power, I'm sure that a proper study were done on the usage of clipless pedals would show that the gains in power are rather substantial. Additionally, a study that shows there is little benefit to a rider that's unlikely to pull on the pedal doesn't mean that there aren't significant gains for one that is. I did my daily commute on platforms a couple times recently and I felt absolutely helpless at sprinting to make traffic lights, or even to get going from a stop. I had no torque available when I needed it due to being limited to a single leg and using the quads alone.

I pay very close attention to cadence and stroke while I'm riding, and the benefits in maintaining a steady cadence and using all muscle groups is quite noticeable, perhaps the existing studies are just asking the wrong questions!

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If you read the scientific reports they basically say that pulling up on the pedal gives you more power at the cost of efficiency. I'd like to imagine that it is like standing while pedaling. More power, but you tire faster. –  user1049697 Oct 29 '13 at 8:25
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@user1049697 Hah, well that makes perfect sense. I don't think anyone expects free energy, but the consensus among questions and posts like this is that there's no advantage at all to riding clipless, which I feel is incorrect. –  Adam Robertson Oct 30 '13 at 18:05
    
@user1049697 I also feel that it's largely a matter of cardiovascular fitness versus leg strength. Your cardio will have an increased load due to additional oxygen requirements, but the load on the quads will be reduced at a particular power output since it's distributed across additional muscle groups. Again, the motto seems to be "do what fits your riding style." Clips allow additional training choices that you wouldn't have with platforms. –  Adam Robertson Oct 30 '13 at 18:09
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@AdamRobertson, I also find this "consensus" to be silly. If there truly were no advantages to clipless, you would have see some riders use platforms in races-- but I have NEVER seen that. Clipless pedals are universal in everything from pro races down to CAT-5 office park criteriums. There are some track riders that use straps, but even there, clipless is the vast majority. Perhaps there is no "scientific evidence" simply because it would be too boring to explore the obvious? –  Angelo Oct 31 '13 at 10:58

The case for/against clipless, or even straps, is sort of summed up in this piece from the Rivendell Bicycles website. They mention studies, albeit without citing the exact source, that actually pulling up on the pedal is extremely unlikely, except maybe on short uphill or sprint bursts, and so being attached to the pedal is far from being a must. And they suggest, without supporting evidence, that it may actually make you a better cyclist, because without attachment your legs have to learn to go in circles, and not simply be taken along for the ride.

There is also the issue with positioning your foot on the pedal: all that careful messing around with the cleats so that the ball of the foot is exactly over the pedal axle. But then there is that other blog from Joe Friel, who is an evidence nut, suggesting that there is no proper support for that being best, and that it may be more efficient to put your cleat under the arch.

Joe's blog, together with the (again, inadequately referenced) story of the Japanese competitor in Ironman New Zealand that forgot to put his shoes in the transition bag, and went to a bike personal best riding barefoot on clipless pedals, have really changed my outlook on the need for attachment to the pedals. I ride with clips on my fixie, but am more and more considering changing to plain pedals and see where that takes me.

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I disagree with the part about "without attachment your legs have to learn to go in circles". Without attachment, it's much harder to teach your legs to go in circles. Nothing like clipless pedals on a fixed gear to really get your legs trained to go in circles. With your feet free on the pedals, it's too easy to have really sloppy foot placement and not move in proper circles. –  Kibbee Jan 17 '13 at 14:57

Foot retention, in some form, has been around since the dawn of cycling.

There are multiple reasons for it:

  • Having a foot slip off the pedal during a hard effort is dangerous (especially on fixed gear bikes, but also during a race in close quarters). This isn't a risk at slow speeds, but at high cadences, it can be hard to stay on pedals without retention.

  • If you ride a lot, your pedal stroke will get more efficient just like a runner becomes more efficient with running. What this means on the bike is that your feet are not resisting each other on the upstrokes and wasting energy. It also means that on the upstroke your foot is applying little-to-no force on the pedal and it can easily shift position if it is not retained by clipless pedals or straps. If your foot is not in the right position, your stroke is less efficient and there is the danger of coming off the pedal during an exertion.

I think if you want scientific evidence for foot-retention, all you need to do is find evidence for having the foot placed properly on the pedal.

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There's actually no conclusive evidence that having your foot in one position or another is more or less efficient than anything else. There's actually more evidence that says it doesn't matter than anything else. Here's one example. There are others. –  jimirings Jun 4 '13 at 19:20
    
Note however, that in the study they still retained the feet (and only shifted the position of the cleat). Does the same argument still apply if the foot is NOT retained AT ALL or if the toe is on the spindle or if the cyclist slips off the pedal during a sprint? I think NOT! –  Angelo Jun 5 '13 at 10:59
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I'd have to disagree. But more importantly, this question is about the existence of scientific studies showing the effectiveness of clipless pedals. Please provide references for your claims. –  jimirings Jun 5 '13 at 12:13

It's not a study per se, but the Wattbike gym machine has a useful power output meter which shows the power being applied by each leg (explained in more detail on their website).

The basic premise is that by smoothing out the push and the pull you can see a visible effect on the power curve on the display. The real key (from personal anecdotal experience) is that clipless pedals assist in these actions because the pull isn't just employing a different set of muscles in the leg and adding more power (although it is doing that), you're also reducing the total down time in each cycle. If you're just pushing, there's going to be periods where either neither is pushing and thus the bike/revolving weight is decelerating or even where both are pushing and counteracting each other.

Clipless pedals aren't going to assist in the latter case, but they will in the former. So by pulling you're helping to compensate for the lag in the cycle until the other leg starts pushing and we all know that maintaining a speed is generally easier than accelerating to that speed. So if you've got even 5-10 degrees (or more) of arc in every cycle where neither foot is pushing (see the wattbike examples of a bad transition, the curve that looks like a figure-of-eight) then you're having to work to regain the previous power. While if you're managing the leg-to-leg transition, the effort doesn't drop off so much (resulting in a 'peanut' curve) and you're not losing as much power.

Additionally, as suggested here, the clip is allowing you to attach at a better point on the base of foot, rather than on the ball of the foot which is demanded by your not being attached.

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