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## How is it possible skinny legs more powerful than muscular legs

Moderator: King Boonen

Tapeworm wrote:My analysis, whilst incorrect, is not totally baseless.

Care to map out for us Frank what the actual energy cost is then to move the cranks around (talking normal cranks here) with legs of different mass? We'll assume that there are no other forces other than gravity to consider.

Look, one can say that the pronouncement that the sun circles around the earth is wrong but not totally baseless because you observe the sun circling the earth every day. Wrong is wrong, regardless of how you got there and regardless of how right your observations seem.

It is pretty easy if one knows the configuration of the bike and rider and the masses of the various elements. All one need do is do the integral around an entire circle for each component and add them up. Now the integral is not that easy to do per se because we don't know the formula for the speed curve (and there can be both a linear and rotational energy component, depending upon the frame of reference. But, we can break the circle down into pieces and estimate the amount. The more pieces the more tedious the calculations but the more accurate the result. Anyhow, one will find that the only component worth worrying about is the thigh as it has the largest mass and is the part that deviates most from the circular, constant speed, motion. Know the mass of each thigh, the crank length, and the cadence and the energy variation is known. One could make the argument that the energy put into the leg could be transferred to the bike but that argument fails when pedaling unloaded. While it is possible to recover some of the energy put into the leg by transferring it to the bike when under load, it is not possible to transfer all of it because of the force directions involved (the thigh is moving up and down when it is slowing and at this time the pedal is moving mostly forward and aft). Anyhow, what is shown, if you do the analysis is this energy variation (and hence the cost of just making the pedal go around) varies with the square of the cadence. This means the power loss varies with the cube of the cadence.
FrankDay
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So what I get from that Frank is you don't actually know.

Give me some figures.
Tapeworm
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Tapeworm wrote:So what I get from that Frank is you don't actually know.

Give me some figures.
Well, it depends upon the masses but as I remember (it has been awhile since I did this calculation) but as one gets up to higher cadences (90-110) the power cost can be around 100 watts. An easy way to estimate the cost to you would be to put the bike on a trainer and take off the chain. Then pedal at various cadences unloaded and see where the HR stabilizes. This should give you a reasonable idea of the oxygen cost for any cadence for you. From this you can get a good estimate of the power loss to you at any given cadence and why if you lower the cadence some efficiency tends to increase and you might actually be able to get more power to the wheel. If you graph your own data I think you will find the HR vs cadence curve is an exponential.
FrankDay
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So in your example, which is very light in terms of figures and formulae, of 100 watts at 100rpm, let's increase the mass if the legs by 2kgs (1 per leg). What is the cost now?
Tapeworm
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Tapeworm wrote:So in your example, which is very light in terms of figures and formulae, of 100 watts at 100rpm, let's increase the mass if the legs by 2kgs (1 per leg). What is the cost now?
That is easy. If the original mass of the legs was 10 kg per leg and the mass is distributed equally as before then the work will increase 10%, so it will cost the rider 110 watts. The cost varies directly with the mass. But, if you didn't increase the mass and increased the RPM to 140, the cost would increase 1.4^3 or to 275 watts. If the increased mass leg increased the rpm to 140 then the cost would be over 300 watts.
FrankDay
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CoachFergie wrote:But you do not sprint at the same power at the end of a road race or criterium at the same power you would in a match sprint.

I have the power data from a World Track Champion that looks something like this....

Peak Power 1700 watts
Peak Power in a 1000m TT: 1500watts
Peak Power in a 4000m TT: 1050watts
Peak Power in a Criterium: 1010watts
Peak Power in a 100mile Road Race: 980watts

This rider has been a NZ champion in every event from 1000m TT to the road race and has won shorter stage races and ridden Professional in the US and his results indicate that in longer events he doesn't come close to using his maximal power.

If anything from 2004 when he was recording his peak powers his average power has dropped across the board but he now races smarter and went on to win a World Track Title and has placed in several more World Cups.

Which hints to one of the ways to win more sprints beyond increasing peak power is to improve technical skills, mental toughness and race tactics.

if i remember right there was a great interview with Stuart O'Grady that has stuck in my head - it's not the energy you use in a race but the energy you save.

it's why we now have 'super domestiques' who in some teams are paid more than the GC rider of rival teams.
mherm79
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Tapeworm wrote:And just to further highlight the point of how the size makes little difference to the power:-

and Brad's a "toer" (ie; rides slightly toe down) which means he uses less calf muscle and his power comes from his quads more. Toers all tend to have thin calves, yet still perform exceptionally well...
Archibald
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Archibald wrote:and Brad's a "toer" (ie; rides slightly toe down) which means he uses less calf muscle and his power comes from his quads more. Toers all tend to have thin calves, yet still perform exceptionally well...

Toe down results in contraction of the calf muscle and therefore more calf muscle use.
function
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function wrote:Toe down results in contraction of the calf muscle and therefore more calf muscle use.

really? how much are you able to use it when it's already contracted? It means more work for the quads as the driver muscle group...
Archibald
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Archibald wrote:really? how much are you able to use it when it's already contracted? It means more work for the quads as the driver muscle group...
It is an interesting problem. The leg is a chain of muscles in series and it cannot push any harder than the weakest one in the chain. And, muscles are generally stronger when in isometric (not moving) contraction than when having to actually contract. And, how hard the calf must contract also depends upon where the cleat is located because of leverage. So, we can choose to "fix" the ankle with the calf muscle (the weak link in the chain compared to the quads and glutes and the only joint that can be rigid while cycling) to make it stronger but this means the other muscles must contract further, costing more energy since they are such big muscles (I am guessing). Anyhow, from a theoretical basis I cannot see any obvious advantage one way or another to any of these techniques (toes down fixed, toes flat fixed, ankling, something in between)
FrankDay
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Archibald wrote:really? how much are you able to use it when it's already contracted? It means more work for the quads as the driver muscle group...

Archibald wrote:and Brad's a "toer" (ie; rides slightly toe down) which means he uses less calf muscle and his power comes from his quads more. Toers all tend to have thin calves, yet still perform exceptionally well...

The fact still remains that toe down means more calf muscle use. Try running on your tip toes.
function
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function wrote:The fact still remains that toe down means more calf muscle use. Try running on your tip toes.

you do know the difference between an active muscle and a static muscle, and which one is "used" most?
try developing your calf muscles by just standing on your toes as opposed to actually flexing it by raising yourself up to be on your toes from a lower heel position...
Archibald
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Archibald wrote:you do know the difference between an active muscle and a static muscle, and which one is "used" most?
try developing your calf muscles by just standing on your toes as opposed to actually flexing it by raising yourself up to be on your toes from a lower heel position...

So standing on your tip toes for prolonged periods of time would not develop them? You think they wouldn't eventually fatigue? I must say it's a strange position you're arguing, that being on your tip toes does not result in more calf utilisation than being flat on your feet.
function
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Standing on toes (static strenght) would only develop muscle at or near to to joint angle at which is exercise performed. Training at only one joint angle do not increase strenght throughout full range of motion, so standing on toes or heels would only strength that part of motion.

I was always told that spinners riding with toes down and seat height a little higher then usual, and masher pedaling with heels down for more force to pedal, of course i do not beleive in that.

Stay well!
oldborn
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### Re: How is it possible skinny legs more powerful than muscul

"Shouldn't more muscle kind of suggest that I should have more strength and perhaps power? I see the same thing in the pro ranks. How can such skinny legs generate so much power?"

I know this is a super old thread, but here goes. What I'm not seeing much of in this thread is talk of efficiency. I come from a weightlifting and automotive background, and I have legs used to squat 495 lbs max and leg press 930 lbs (18 plates) for 13 reps. I've only been cycling a short time, but my understanding is that power output on a bicycle is a matter of efficiency rather than raw power. Here's my take. I'll use the "car's engine" analogy used earlier in this thread... A larger engine is more powerful in acceleration, but will use more fuel AND create more waste. In a human body, this translates into larger muscles placing a greater load on the cardiovascular system. It makes sense to me that over time, at any given output, bigger muscles will create more lactic acid and waste products than smaller ones, and your heart and lungs have to work harder to clear it all out. It's why you don't see distance runners built like bodybuilders or sprinters built like marathoners. Having giant muscles is an unnatural state for the human body, and therefore places unnatural demands on the body's systems. I hope I make some kind of sense.
TheWrench
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You said it all wrench. Im back into lifting weights , got the bug again but I'm making sure I'm climbing as quick as ever and I am . I've put on about a stone of muscle in 2 months, strength could be better definitely struggling with the legs strength wise. But they are growing. I'm doing lots of reps on a short hill near my house. 53 x 19 for 20 reps just blasting it up . Don't take that long around 35 mins. I head over to my normal longer climbing route once a week just to check my progress and so far I've actually improved. So I'll keep getting bigger until it feels detrimental.
My riding goals are simple I like to go over to Europe,France,Spain,etc and kill it up 1 climb . I'm not into 3 /4 hour rides . I climb in my big ring . I applied my weight training theories to my climbing . I aim to ride in a harder gear I.e. Like adding more weight to bar. I have been training/ riding like that for over 10 years. It works for me ok but like I said I'm all about 1/2 hours riding not 4or 5 hours . Nice post ...
Lv426
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### Re:

CoachFergie wrote:I'm surprised it doesn't get mentioned more but look at how aero Cav is compared to the others. Word from one of the former British Track Coaches is that Cav doesn't put out a huge amount of power but is very smart with what he has got.

Since this thread is being discussed again, I'll point out - 7 years late - that sure enough Cav has said on several occasions, and written in his autobiography, that he was told by coaches he didn't have the power output to be a top sprinter.
Ruby United
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