Pedaling "efficiency"- clarification?

Triathlon Forum
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Been trying to keep up with the eternal PC-related war of words. (Yaquicarbo, gotta say you’ve done a good job standing in for Frank the past coupla days. You get an “A” for effort, at least!)

My question concerns what we mean when we talk about “efficient” pedaling.

If we say someone is an efficient swimmer, we mean that most of the effort they expend is used to move them forward through the water. An inefficient swimmer wastes a lot of energy- the power they produce isn’t used to move them forward.

You can’t say that about cyclists. Pretty much all the energy a cyclist produces is used to move the bike forward. Their isn’t much “wasted” energy, no matter what the cyclist’s cadence is.

The question, if I’m getting this right, isn’t what’s most “efficient,” but what is “optimal” for the rider’s physiology. Sort of like a runner trying to cover 10 miles. Is it more efficient to run one mile at a time as fast as he can, or run all 10 miles at once at an even pace? Neither- it takes the same amount of energy either way. One method is probably optimal for a particular runner, though.

Am I understanding this correctly?

2

I think you’re on the right track. Efficient and Optimal are different things in bike riding. In my mind, Optimal is a much more useful term than Efficient. If a cyclist is operating Optimally, he can be at least relatively efficient compared to operating sub-optimally in many cases, but you don’t have to be anywhere near Optimal to be very Efficient…at least for a while…then the energy system/muscular contraction limits rear their ugly heads and performance plumments…not Optimal at all!

4

Pretty much three-fourths of all the energy a cyclist liberates goes to heat.
We know you’re the expert in liberating energy to heat.

5

Pretty much three-fourths of all the energy a cyclist liberates goes to heat. Dang. This is what I get for poking the sleeping dog with a stick.

7

Just pointing out what you seem to have overlooked. And you’re right, of course. I think you know what I mean, though- can you help me formulate the question more precisely, and give me your answer?

8

Some definitions that can make these discussions more informative:

“Efficiency” is a measure of how much of the body’s total energy production is turned into physical work, or power. Rip’s post reflects this. About 60% (not 75%) goes to heat, and this is the same in almost all humans. Another 17-20% goes to the processes of keeping the body alive (producing other fuel; building protein; moving the gut; feeding the brain; etc). Only 20-23% is turned into work. More if you’re lucky, less if you’re not. Efficiency is “a” part of endurance sport success, but is not the primary driver (raising LT ever-closer to VO2max is the biggest driver, and that reflects many things, of which Efficiency is only one). Efficiency tends to improve with training, but only adds a little to LT power/pace.

“Economy” on the other hand is a measure of how much of that work (or power) is turned into movement along the ground. For example, one can use up a lot of energy, and produce a lot of power, by running with great big vertical hops. This is bad “economy” because so much of the power is wasted in vertical motion, rather than transformed into movement along the running lane. A highly Efficient runner running with bad Economy will run slow.

Bikes are wildly economical, the simple evidence being that we go so fast on them compared to running. Swimming is wildly UNeconomical.

Now, the big question(s) are:

(1) Can we increase Efficiency through technique? Perhaps, by a tiny bit. Spreading a given workload around to more muscles has been shown to improve Efficiency. Cadences that are too high or too low have been shown to hurt Efficiency. Frank Day would argue that PowerCranks help to improve Efficiency by training the hip flexors to contribute to the total workload (or something like that). Real-world evidence (and careful study) tends to show that trained athletes naturally find the most Efficient way to do any given thing.

(2) Can we increase Economy? On the bike itself, yes. Disc wheels, a lubricated chain, a more aerodynamic position – these all help to turn a given amount of rider power into more speed. Can “pedaling technique” improve economy? Well, if the rider is pedaling in some absurd manner (akin to the bouncing runner), then yes. But, in the case of a reasonably experienced cyclist, no. Although, Gary would argue that Rotor Cranks improve Economy by eliminating a glitch in the standard bike design. Runners get more Economical with training, and drills like strides are said to help improve Economy. Swimmers are the biggest beneficiaries of Economy gains. Swim technique is entirely about Economy. Huge gains in speed can be had by improving swim technique.

So, Vitus’ post raises good questions, but I thought it would help the discussion stay on track if we use “Efficiency” and “Economy” as two separate things.

9

I was once a full time swimmer and am now novice cyclist so keep that in mind with this answer. I think that there is you can judge how efficiently and optimally you are either swimming or cycling.

In swimming, your stroke technique can make you swim more or less efficiently. This can also vary with conditions. Whether you are swimming optimally depends upon things like how far you are swimming and water conditions. Some people can swim butterfly faster than freestyle for a short distance. Not breathing as much makes you faster in the short term for freestyle or butterfly, but slower in the long term. You might also be able swim faster for a shorter distance by increasing your turnover even if you take an extra stroke or two per lap. A stronger kick helps you in waves or in pools with no or poor lane lines.

Taking what I know about swimming and speculating about cycling, it seems that not pedaling as smoothly as you can, moving around too much or not being positioned as well as Tom Demerly says that you should be would make you less efficient. Optimal cycling would depend upon what gearing and cadence makes sense for you in given circumstances just like your stroke, how often you breath and how fast a turnover you use.

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Ashburn, big thanks. That answer is most helpful.

“Economy” on the other hand is a measure of how much of that work (or power) is turned into movement along the ground. OK, this is what I’m asking. I don’t think it’s possible to be a more economical cyclist by varying pedaling technique. Moving

11

Wow, you hit all the hot button topics- efficiency, Frank, economy, Rip, PCs, Gary- this is going to be better than a six pack and a bug zapper! I predict a minimum of 100 replies. Sit back and watch the show!

Ken

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CTL wrote: it seems that not pedaling as smoothly as you can, moving around too much or not being positioned as well as Tom Demerly says that you should be would make you less efficient.

Just be careful about the pedalling smoothly thing. I used to have a very nice SMOOTH pedal stroke, as pointed out to me by Jim O’Brian, one of the Southeastern bike Gurus that has worked with George Hincapie, Chris Harkey, Pat McCallion, and their ilk. I told you that not to drop names, but to give credence to the idea that a knowledgeable person commented that I had a smoother stroke than 95% of all the people he’s ever seen pedal a bike. Well, I found out (we won’t go into how I found out) that my smooth stroke was a result of me resisting on the upstroke…I had in fact taught myself to be smooth at the expense of being more powerful. I quickly learned that smooth for the sake of smooth wasn’t a good idea in itself…not when it screws up your pedal stroke like mine was screwed up.

Now, if by smooth, you mean straight tracking on the bike without unnecessary body movement, etc., by all means…smooth for smoothness sake is good!

13

Ashburn, great post.

vitus979, i disagree. Not sure if you finished your post, but I feel/think improving technique on the bike or in running form or swimming for is the basis of becoming more economical and more efficient. I say this b/c my thinking is that let say in the TT posistion you are pedaling w/ your knees flared out. This, I am paralling to running in big leaps. With the knees out, you will need to work that much harder to overcome teh drag- making you less efficient. Concurrently, I feel you would be less econimical b/c the movement is a bigger range as compared to cycling with the knees more toward the top tube. Still trying to get my mind around it, but hopefully this sparks a thought for someone to continue.

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Thanks for the information, and I’ll it in mind.

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I say this b/c my thinking is that let say in the TT posistion you are pedaling w/ your knees flared out. This, I am paralling to running in big leaps. With the knees out, you will need to work that much harder to overcome teh drag- making you less efficient.

Lurker, we don’t disagree about that. I agree that being more aero is more economical. I’m confining this strictly to the manner in which work/effort/power/etc is applied to the pedals- mashing big gears, spinning small ones, round strokes, up and down strokes, etc.

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This kind of says it all.

http://jap.physiology.org/cgi/content/full/93/3/823

Seems that the metabolic cost of cycling has little to do with technique. Metabolic cost is simply proportional to (1) how much power you’re putting to the pedals (big surprise) and (2) how fast you’re turning the pedals. Greatest overall efficiency is attained at lower cadences when you’re putting out low power, higher cadences are most efficient as power output increases. If cadence and power account for 99% of metabolic cost as this article claims, PC’s or RC’s or one legged drills or whatever you do for your pedal stroke aint gonna do much.

To quote the article:

"Because both the cost of unloaded cycling and delta efficiency contribute to metabolic cost, gross efficiency (power output/metabolic cost) is a function of power output (7). At low power output, metabolic cost is strongly influenced by the cost of unloaded cycling, and lower pedal speeds provide greater gross efficiency. For example, at a power output of 50 W, our subjects’ gross efficiency was greatest (16.7%) at the lowest pedal speed (0.61 m/s). As power output is increased, delta efficiency becomes increasingly deterministic of metabolic cost. If our subjects were able to produce 400 W aerobically (e.g., elite cyclists), their gross efficiency would have been greatest, 23.5%, at a pedal speed of 1.4 m/s. "

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Cool. My thought process then leads me to the questions: What effect pedaling economy/efficiency? Does bike position? Cleat position? I guess I am having a tough time seperating/narrowing down to what effects efficiency/economy. I think the two are tied and that position on the bike and essentially how you move through the pedal stroke would effect both as well.

19

You can’t say that about cyclists. Pretty much all the energy a cyclist produces is used to move the bike forward.
As an offshoot to what YQ said, you can end up wasting the power generated by one leg on pushing around the other leg. It’s said by Romanov our legs produce the most power between 1 & 4 'o clock. If one leg is in that position, the other (between 7 & 11) has a good chance resisting its motion.

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Spreading a given workload around to more muscles has been shown to improve Efficiency. Not true, at least during cycling.

I agree. Not in cycling. I was thinking about rowers, who refine their technique over many years and get better and better Efficiency. Cycling is a fixed mechanical system, and there is not a lot we can do to move the workload around.

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you can end up wasting the power generated by one leg on pushing around the other leg. It’s said by Romanov our legs produce the most power between 1 & 4 'o clock. If one leg is in that position, the other (between 7 & 11) has a good chance resisting its motion.

True, but I think this only applies if you’re actively resisting with one leg. I don’t think there’s any difference in absolute work between unweighting one pedal versus letting the leg on the downstroke push the other leg up.

23

But, let us never forget that “Efficiency” is but one piece of the performance equation. Performance is determined (on the bike) by whomever puts out the most power (assuming equal aerodynamics) over the race duration. This is NOT determined by Efficiency. Low efficiency and high power trumps high efficiency and low power every single time. Power is a function of many, many things (stroke volume, capillary density, fiber type ratios, mitochondria density, etc., etc.). Efficiency is one of those things, but it is far from being at the top of the list. Your efficiency can remain fixed at a given level for years at a time, while you get more and more powerful.

To put it another way: 23% of 1000 is 230. 20% of 1200 is 240. Which athlete just produced more power? The less efficient one. This is not always the case, of course. But – it goes to show that we should focus our training on how much power we produce, and at what pace we run/swim, not on how efficient we are or are not.

I tested an (allegedly) efficiency-improving cycling device once. I might have gotten more efficient, but I couldn’t improve my power so I went back to hard interval training and my power improved.

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I was thinking about rowers, who refine their technique over many years and get better and better Efficiency.
Is there evidence linking changes in technique to improvements in rowing efficiency?

“However, even on a stationary ergometer, elite rowers are more efficient than well trained but non-elite oarsman. This is not due to a difference in fiber compostion. So, it appears that subtle changes in rowing technique can continue to contribute to improved rowing efficiency and performance with additional years of training.”

From: http://home.hia.no/~stephens/effiperf.htm

An excellent website with lots of good layperson-compatible physio stuff.