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How is it possible skinny legs more powerful than muscular legs

Moderator: Tonton

12 Nov 2010 12:24

Tapeworm wrote:Incorrect. Given that cranks are fixed to each other (unless you are using powercranks or the like) the weight of the leg on one side balances the other leg. Almost the prefect counterweight*, ie: all the power driving the crank is driving the crank unless you are actively pushing on the upstroke (which usually does not happen). There is no "lifting" of the opposite leg.

* Not the PERFECT counterweight as everyone is asymmetrical.


I think that the other poster may be onto something, albeight I don`t think that it`s a huge difference, splitting hairsénegligible sort of thing.

It`s been proven in labs that no one, unless you`re on power cranks, actually produces a positive energy contribution to propelling the bicycle on the upstroke. The crank is basically lifting the foot. As the cranks are attached, that means the downstroke leg is lifting the upstroke leg. So if you have bigger legs, that means more energy on the downstroke is used to lift the upstroke leg than someone with thinner legs.

I don`t know if this really is true, but there is logic to the idea.
twothirds
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12 Nov 2010 17:11

I'm surprised at how much talk there is about aerobic/anaerobic power etc. look at olympic champions in weightlifting and then look at bodybuilders. muscle SIZE does not truly correlate to power. a large muscle is not necessarily stronger, even in a test of pure power.
ridingtorowfaster
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12 Nov 2010 18:29

Big difference between weightlifting and body building and what a body builder will do on comp day to achieve a certain look and what a weightlifter will do to achieve maximum strength on comp day.
User avatar CoachFergie
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12 Nov 2010 20:17

ridingtorowfaster wrote:I'm surprised at how much talk there is about aerobic/anaerobic power etc. look at olympic champions in weightlifting and then look at bodybuilders. muscle SIZE does not truly correlate to power. a large muscle is not necessarily stronger, even in a test of pure power.


So true, however both would have to be much stronger than the guy that works out with lighter weights to tone up a little. Then if you look at the Olympics, each weight class in weightlifting seems to be able to lift more weight than the weight class below. Never see a small lightweight powerlifting more than the heavyweights. I know it's only 1 lift. But it seems the bigger you are the stronger you should be.

I know in cycling there are many other factors involved, so it may not correlate.
User avatar Indurain
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13 Nov 2010 06:01

However if you look at power to weight it is the middle class's where you see the best results. But then these guys will be purpose built for weightlifting and naturally excel just as Contador climbs hills and Cancellara does flat time trials. Doing gymnastics my short arms and torso meant I performed some levers very well but was a major disadvantage in other areas.
User avatar CoachFergie
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13 Nov 2010 14:55

Tapeworm wrote:Incorrect. Given that cranks are fixed to each other (unless you are using powercranks or the like) the weight of the leg on one side balances the other leg. Almost the prefect counterweight*, ie: all the power driving the crank is driving the crank unless you are actively pushing on the upstroke (which usually does not happen). There is no "lifting" of the opposite leg.

You're kidding right?

The mass of the legs must be moved no matter the counterweight. I'm not going to give you a physics lesson but you even fail to take gravity into account. The weight of the legs make as much difference to the equation as the weight of the wheels and every other moving part. The most basic rules of physics dictate that the energy required to move an .... you know what, I'm not even going to bother giving you the math, I suspect you're an art student with a comment like that. Sheesh.
Hangdog98
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13 Nov 2010 20:23

Hangdog98 wrote:You're kidding right?

The mass of the legs must be moved no matter the counterweight. I'm not going to give you a physics lesson but you even fail to take gravity into account. The weight of the legs make as much difference to the equation as the weight of the wheels and every other moving part. The most basic rules of physics dictate that the energy required to move an .... you know what, I'm not even going to bother giving you the math, I suspect you're an art student with a comment like that. Sheesh.


No, no please give us the math, I'd really want to see the massive differences in force between, say a cyclist with legs weighing 10kgs each and a cyclist legs weighing 20kgs each. Assume a cadence of 80rpm and a crank of 175mm.


(This has been done with the whole "weight of the wheels" thing.)

EDIT: And to be clear I am not talking about the entire mass of the complete system (ie: rider, frame, wheels etc). Total mass is total mass.
Tapeworm
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13 Nov 2010 20:41

The whole principle of a counterweight is that work done in lifting a mass is done by the descending mass. Ordinarily I can't lift a ton of concrete but if I connect it to another ton of concrete and suspend it over a good quality pulley I will find I can lift it quite easily. So I think it's fair enough to say that the crank connects the two legs together and that the descending leg is lifting the ascending leg, (provided the ascending leg allows itself to be lifted). As such the weight of the legs would be immaterial as they cancel each out.

However, I don't believe this would apply to the situation where an uplifting force is also applied to the ascending pedal (ie pedals pulled up and pushed down simultaneously) as might be done more in sprints, accelerations and hills or by virtue of technique.

So perhaps as someone else suggested it's not a complete counterweight situation and the weight of the legs might become a factor over the course of a race?

Edit: But probably minor.
[color="DarkGreen"][SIZE="2"]"I thought of that while riding my bicycle." ~ Albert Einstein on the Theory of Relativity[/SIZE][/color]
User avatar Polyarmour
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16 Dec 2010 18:22

I think it's a combination of things. The likes of Mark Cavendish at around 69kg is that he has a lot of power in those legs and with that power and so little weight, the power to weight ratio must be trough the roof. But look at him in the mountains, and he can't climb with the real climbers who don't have such large legs. That's most likely down to the fact that he's built like a sprinter... big legs. The big muscles in our legs require alot of blood to get pumped through them to keep them fuelled. So your cardiovascular system has to work harder. Anyone that goes to the gym and tries to squat heavy weights will tell you that you are out of breath alot more after a leg workout than an upper body workout since the legs require more work from the heart and lungs to pump blood around them.

So in conclusion, weight training to build strength and lose body fat to keep the power to weight ratio in your favour.
lalorm
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16 Dec 2010 22:08

Tapeworm wrote:Incorrect. Given that cranks are fixed to each other (unless you are using powercranks or the like) the weight of the leg on one side balances the other leg. Almost the prefect counterweight*, ie: all the power driving the crank is driving the crank unless you are actively pushing on the upstroke (which usually does not happen). There is no "lifting" of the opposite leg.

* Not the PERFECT counterweight as everyone is asymmetrical.


The counterweight argument is more than a little flawed as its not just asymetry that applies here.

As has been said below, studies have shown that almost nobody produces POSITIVE power on the upstroke - fair enough - however what you are ignoring in your comment above is that the majority of trained cyclists (ie people who have spent time under coaching and/or devoting time to their cadence) the amount of NEGATIVE power applied to the pedal in the upstroke is less than that caused by the weight of the leg alone (poor wording - don't care).

The point being is that most riders do in fact at least try to get their foot out of the way on the upstroke. This not only means that the downwards leg has to do less work to produce positive power - the upward leg is working too.

How any of this applies to differnces in leg mass when there is generally a much bigger issue related to differences in overall body size is a moot point.
User avatar Martin318is
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17 Dec 2010 08:30

I can't speak scientifically, in terms of the physiological mechanisms at work, however, after 25 years on the bike it has always seemed to me that there is no real relationship between leg size and being strong and fast on the bike.

It has more to do with how the heart, lungs and leg muscles simultaneously work efficiently in generating sustained power to push the pedals. Often the guys with huge, muscular legs, while they may look intimidating, don't have the efficiency between these diverse elements to matter much in the long run.

There are always exceptions, of course, but, more than anything, they would seem to confirm the rule.
User avatar rhubroma
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17 Dec 2010 18:25

The main determinant in endurance cycling is your threshold power which is a long long way away from your strength in the gym, peak speed or peak power in a Wingate test. Having conducted a fair number of Wingate tests it seems clear that even for sprinters the higher you take the peak the lower the 30sec average power becomes.

I don't see the relevance in muscle size to fat loss when muscle is far less metabolically active at rest than other major organs in the body. All hypertrophy does is lower your power to weight and increase your frontal surface area.

The focus of training for any event over 1000m should be raising ones threshold power.
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18 Dec 2010 19:58

CoachFergie wrote:The main determinant in endurance cycling is your threshold power which is a long long way away from your strength in the gym, peak speed or peak power in a Wingate test. Having conducted a fair number of Wingate tests it seems clear that even for sprinters the higher you take the peak the lower the 30sec average power becomes.

I don't see the relevance in muscle size to fat loss when muscle is far less metabolically active at rest than other major organs in the body. All hypertrophy does is lower your power to weight and increase your frontal surface area.

The focus of training for any event over 1000m should be raising ones threshold power.


Yet so many races are won in a sprint. If you don't have a sprint you have a hard time winning no matter how much endurance you have. How do you improve your sprint without diminishing your threshold power?
[color="DarkGreen"][SIZE="2"]"I thought of that while riding my bicycle." ~ Albert Einstein on the Theory of Relativity[/SIZE][/color]
User avatar Polyarmour
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19 Dec 2010 02:10

Not to sound pithy but... you practice sprinting more. On the road you can do all sorts of drills (starting starts, flying sprints) or practice in "race simulations".

You can have a good (road) sprint power and keep your threshold power. But you will never maximise sprint power whilst being a roadie. Specificity.
Tapeworm
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19 Dec 2010 04:09

Polyarmour wrote:Yet so many races are won in a sprint. If you don't have a sprint you have a hard time winning no matter how much endurance you have. How do you improve your sprint without diminishing your threshold power?


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.
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19 Dec 2010 08:05

Polyarmour wrote:Yet so many races are won in a sprint. If you don't have a sprint you have a hard time winning no matter how much endurance you have. How do you improve your sprint without diminishing your threshold power?



and if you dont have the endurance, you won't be there at the sprint anyway.

The winner of an endurance sprint is generally the rider with the best ability to produce high end watts at the end of a long day in the saddle. Part of the way they do that is to be as efficient as possible all day and if possible to protect themselves from spending any energy.

Skinny riders are able to do this and hit the required 900W or whatever. Being able to hit 2000W does nothing for you if you cant sustain the 300-400 needed to get there.
User avatar Martin318is
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07 Apr 2011 10:42

Hangdog98 wrote:You're kidding right?

The mass of the legs must be moved no matter the counterweight. I'm not going to give you a physics lesson but you even fail to take gravity into account. The weight of the legs make as much difference to the equation as the weight of the wheels and every other moving part. The most basic rules of physics dictate that the energy required to move an .... you know what, I'm not even going to bother giving you the math, I suspect you're an art student with a comment like that. Sheesh.

You are completely right, of course. The error that those that think that pedaling costs no energy is they think that because the legs are connected by the connected cranks that energy is transferred back and forth and there is no net energy cost to making the pedals go around. This is only true for the feet because they are the only part of the leg actually moving in a perfect circle so the cranks/feet behave as a spinning disk. But, the lower leg moves in an oval and the upper leg moves in a recriprocating motion. So, while the total energy of the feet is constant (meaning it takes no external energy to keep them going), the total energy of the lower legs and, especially, the thighs, is constantly changing. This requires energy input when the energy is increasing and energy loss when it is decreasing. Since the legs are not springs that can store and release this energy variation, it is an inefficiency. The amount of this energy cost depends upon the geometry (crank length, leg lengths, mass distribution, etc.) involved and the cadence. As you pointed out, the energy cost varies with the square of the cadence.

What is most amazing to me is that some of the more well respected and vocal members of these cycling forums will use as their "proof" that pedaling doesn't cost energy a model that prohibits energy loss (the rigid man model).

Anyhow, it is nice to see someone else around here who actually understands some of this stuff.
FrankDay
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07 Apr 2011 13:15

Uh huh.

You're all over it frank. Had to troll the forum for a while to find that post eh?
Tapeworm
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07 Apr 2011 16:56

Tapeworm wrote:Uh huh.

You're all over it frank. Had to troll the forum for a while to find that post eh?

Well, I can understand your concern since you were one to call his analysis incorrect. You correctly mention that the weight of the two legs almost balance each other, but this only accounts for the potential energy part of the equation. But, your analysis completely forgets the kinetic energy part of the equation. Since energy is a scalar quantity (not directional) and both thighs are accelerating and/or decelerating at the same time it is not possible for the kinetic energy in each thigh be transferred through the fixed cranks to balance each other. It is a simple, albeit tedious, analysis
FrankDay
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07 Apr 2011 21:03

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.
Tapeworm
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