The importance of crank length to the cyclist.

[sciguy]

check out the postion of Raynard Tissink. He is a PowerCranker and finished in the top 10 overall and look at the potential for aero improvement here. Most were much better than him but I consider this position to be just awful. He looks to me like he is trying to mimic a parachute, trying to scoop as much air as possible.

I get the feeling that using shorter cranks might very well help solve a problem specific to the use of Powercrank style pedaling. If one searches Powercrank + aero position you will find several similar discussion threads.
Many athletes find the cranks very difficult to ride in an aero position.

Riding in aero position with PowerCranks
I'm having a really hard time doing this for extended periods of time, e.g., > 1 hour on the trainer or > 30 minutes on the road. I imagine that it's because the angles of being low and in the aero bars make it tougher for the hip flexors to lift the pedals up. Have others of you encountered this problem? At what point does it typically become as easy to ride aero as sitting up with PCs? Any tips?

"As background, I've been using PCs a little less than 3 months. My long rides have increased to 80 miles, although my hip flexors always wear out before I reach full distance. I spend most of the time in my 3x week, 1 hour trainer rides in the aero position, but on the long rides, I spend most of my time sitting up, either because I'm riding with others or because I just tire out riding aero. I'm a bit worried that, by not riding long in the aero position now, I'll not be ready to do so come my ironman in about 3 months. Thanks for any insights."

a couple of responses to the above:

"I never did master this for any length of time."

Tom Demerly

"Interesting thought Ben. I started using PC's this year and feel like my pedal stroke has improved considerably in my roadie position, but I was horrified to see I lost 25 Watts at 2 mMol lactate (Ironman pace) in the aero position compared to a road position. This was the first time I've been tested in the aero position and I was also on my new bike in a very aggressive aero position. As you can imagine, I've been tweaking my position ever since then...breaking a cardinal rule, since I race IMNZ in 10 days. My pedal stroke analysis with the SRM was also horrid in the aero position. My take home message was that I need to spend more time training in the aero position (right now I train about 75% of the time on a road bike) and I need to get some aerobars on my PC bike for some hip flexor torture sessions."
TriDi

Frank's response to the OP:

"It just takes time. 3 months is not enough time. I would put you above average though to be able to do it this long at this point in your training. If you raise your stem a bit you will be able to do it longer then when you can do it as long as you need to, then you can start lowering it."

Frank

Another very scientific response:

"My buddy rides his P3 in the aero position with PC with no problems. Heck, I watched him out sprint a pit bull this weekend with his PCs."

Now that's some excellent data

YMMV,

Hugh

 

[FrankDay]

Post #576
Going lower doesn't always improve aero. And it can end up reducing the power to drag ratio. That's why we measure these things, so we can be sure and not make WAGs and/or rely on folklore.

Thank you Alex.

Unless, Frank, you have a new interpretation of what power to drag ratio is?

Power to drag ratio can be reduced without reducing power. Sorry, that statement is open to multiple interpretations and doesn't satisfy my criteria that someone has actually acknowledged that position affects power. In fact, Alex Simmons himself, in post 770, contradicts your interpretation as to what he meant in that earlier when he posts

I will say that his highest 20 minute power is attained in that position and that includes all road and TT racing and training

. I simply refuse to accept this unless shown the actual data that the efforts and conditions are similar. Such a result certainly goes against my experience and the experience of everyone I have talked too. If it is true, then one needs to sit down and try to explain why such would be the case physiologically just as I have tried to explain my experience that aero position is usually less powerful which lead to this thread. Until the fact that position affects power (and in which way) is acknowledged by the other side we cannot discuss why this occurs. And, until we all understand why this occurs we cannot agree on the basis for this thread.

 

[blutto]

Quality over quantity:
http://www.plan2peak.com/files/32_article_JMartinCrankLengthPedalingTechnique.pdf

...very interesting way to present a study....

...my favourite part was the following...

Learning to produce maximum power
requires only 3 days (36 sec total) practice.

...36 sec of training and off to the pub to recover...now that is a very cool training schedule....CoachWhatEver is so right science is wonderful, I only wish I had read this study decades ago...

...kidding aside, is this study available in anything other than this powerpoint type presentation?...

Cheers

blutto

 

[FrankDay]

Well I am switching from 175 road bike to 172 new TTbike, and must said that I hope to see some sort of relief. I will post my experience for sure.

How should I knew that potential improvement may come from shorter crancks?

For average Joe with some experience that should be easy, with pretty much same traning stress and well known course I should be at least faster, and more confortable on run leg when doing tri. Off course those kind of thing can happens from better adaptations to brick set training, but I can live with that

Well, 2.5 mm is such a small difference (especially in power) that the changes you will be seeing due to crank length are likely to be so small that it may be difficult to discern. So, you will find that you either notice the difference or you don't. My guess is if you notice a difference with this small change it would be one mostly in comfort.

 

[FrankDay]

I get the feeling that using shorter cranks might very well help solve a problem specific to the use of Powercrank style pedaling.

Well, this certainly opens up an area or two for further discussion.

1. Is loss of power in the aero position only occur when one is doing the "PowerCranks style" of pedaling?

2. If so, what could possibly account for this difference? I mean, all the PowerCranks do is make the rider use a couple of muscles a little more than they normally do and they may change the timing of the use of the muscles slightly different. So, again, if what you hypothesize is true, how can it be explained physiologically.

 

[blutto]

Well, 2.5 mm is such a small difference (especially in power) that the changes you will be seeing due to crank length are likely to be so small that it may be difficult to discern. So, you will find that you either notice the difference or you don't. My guess is if you notice a difference with this small change it would be one mostly in comfort.

...but wouldn't comfort be one of the key benefits of moving the TDC of the pedal circle down...as in reducing the effects of you called scrunching...and that in and of itself is good, yes?...

...the other thing that I would like to bring up is the following (and yes it is anecdotal but since this has been experienced by a number of riders in my circle who have changed crankarm size it could be considered to be more than a coincidence )...going to a longer crankarm, from, say 170 mm cranks to 175mm, which was a typical change in my day, seemed to negativelly affect your ability to quickly close gaps in a race...has anyone considered or studied how different crankarm lengths could possibly affect your ability to spool up speed, which as we all know is a very critical part of racing...

Cheers

blutto

 

[FrankDay]

...but wouldn't comfort be one of the key benefits of moving the TDC of the pedal circle down...as in reducing the effects of you called scrunching...and that in and of itself is good, yes?...

Yes. It is just one of those things that is hard to quantify for some of the people here. How can you "prove" your improved comfort is due to this change? And, if you are so out of whack that 2.5 mm improves your comfort noticeably, you probably need an even bigger change.

 

[FrankDay]

BTW, just had a back and forth with one of the top sprinters in the pro-peloton. He contacted us wanting to get on the independent cranks for this off-season. I spent quite a bit of time encouraging him to also experiment with crank length and he seemed open to the idea. We will see. If he does give us some good data along these lines I will pass it on.

 

[Alex Simmons/RST]

Power to drag ratio can be reduced without reducing power. Sorry, that statement is open to multiple interpretations and doesn't satisfy my criteria that someone has actually acknowledged that position affects power. In fact, Alex Simmons himself, in post 770, contradicts your interpretation as to what he meant in that earlier when he posts . I simply refuse to accept this unless shown the actual data that the efforts and conditions are similar. Such a result certainly goes against my experience and the experience of everyone I have talked too. If it is true, then one needs to sit down and try to explain why such would be the case physiologically just as I have tried to explain my experience that aero position is usually less powerful which lead to this thread. Until the fact that position affects power (and in which way) is acknowledged by the other side we cannot discuss why this occurs. And, until we all understand why this occurs we cannot agree on the basis for this thread.

Still carry that bucket of logical fallacies around with you huh?

I have said repeatedly that I actually measure both the power and the aero.

Here's another example, even though I'm not positioned quite as radically as the rider in that earlier posted photo, my own all time highest ever 20-min W/kg is from racing performed on my TT bike (at the UCI World Cup earlier this year). I'm pretty proud of that all things considered.

And it is also commonly reported by those that TT regularly, like over at the TT forum.

Of course there are those that do lose power when in TT position, and those that don't.

That's why we measure these things. Those pesky power meters are kind of handy for that.

 

[blutto]

OK. I see each of the following related to crank length possibly modifying power and aero positioning potential.
1. Depending upon rider flexibility, how high the knee is forced up by the crank arm will determine how low the rider can physically go, affecting frontal area and aerodynamic potential.
2. If the rider cannot actively raise the foot as far as the crank length requires then energy must be diverted from the wheel to get the foot over the top. The greater the discrepancy the more the energy cost, affecting efficiency and lowering power.
3. The higher the foot at TDC the more the knee is bent, causing the knee joint to lose efficiency, making the quads to contract harder for any given pedal force, affecting efficiency and, potentially, lowering power.
4. The higher the foot at TDC, the more the hip angle, causing the hip to lose pushing efficiency, making the glutes to contract harder for any given pedal force, affecting efficiency and, potentially, lowering power.
5. The greater the pedaling circle the higher the pedal speed at any given cadence. Higher pedal speeds make it more difficult to apply force to the pedal. Pedal speed and tangential force are the components that actually determine power. For any given power, there will be an optimum pedal speed for optimum power production, both too high and too low are less efficient.
6. If one's pedal is moving at the optimum pedal speed the crank length will affect cadence. I believe as cadence increases above 90 or so efficiency will drop because of the fixed time it takes for a muscle to relax, affecting blood flow potential during recovery (this explains why we can't just keep going shorter and shorter).
7. The higher the pedal speed the more difficult it is to get the foot out of the way on the recovery portion (increasing back pressure on the upstroke and increasing efficiency)
8. At the extreme levels at TDC, the hip flexors may be outside of their most efficient contraction range, further reducing efficiency.

Now, before anyone comments that I don't have proof of any of this, I admit I don't have proof of any of this (even though much of this is nothing more than well known physiological principles). These are all theoretical considerations that I believe can help explain the improvements being reported by those trying these extremely short and unconventional crank lengths.

Comments are welcome. This should get this thread to over a thousand replies soon.

...thanks, that was most helpful...though I wish I had a bit more knowledge of physiology to tease out the full import of the ideas you listed...as in primarily, do these gains mean loses elsewhere in the power producing system...oh well more interesting food for thought...

...but the most interesting part of the thread discussion is still the fact that despite what seems to a radical change with how we have perceived the relationship between power production and crank-arm length ( where longer was perceived as the path to more power because of the use of a longer lever ) the shorter cranks produce similar levels of power...now some see that as a negative against the use of shorter cranks but given that the shorter crank allows one to potentially rotate the trunk forward to achieve a better aero position that no-gain study can be more usefully perceived as a half empty/half full glass scenario...yeah no power change but it opens up other important options in the applied world....which may explain the positive anecdotal comments we have seen...

...just wish I still had my wife's old 165 mm cranks kicking around...

Cheers

blutto

 

[FrankDay]

Of course there are those that do lose power when in TT position, and those that don't.

Let's just consider those who do lose power when they get into the TT position. Why does it happen?

 

[FrankDay]

...thanks, that was most helpful...though I wish I had a bit more knowledge of physiology to tease out the full import of the ideas you listed...

...the most interesting part is that despite what seems to a radical change with how we have perceived the relationship between power production and crank-arm length ( where longer was perceived as the path to more power because of the use of a longer lever ) the shorter cranks produce similar levels of power...now some see that as a negative against the use of shorter cranks but given that the shorter crank allows one to potentially rotate the trunk forward to achieve a better aero position that no-gain study can be more usefully perceived as a half empty/half full glass scenario...yeah no power change but it opens up other important options in the applied world....

...just wish I still had my wife's old 165 mm cranks kicking around...

Cheers

blutto

I think he has it, I think he has it, the rain in Spain stays mainly in the plain, I think he has it …

 

[Oldman]

Let's just consider those who do lose power when they get into the TT position. Why does it happen?

Mostly because the position varies greatly from the position they train in. The best TT'ers lose the least because a)they train their TT position b)that position isn't radically different in terms of overall posture than their training position. I'm not talking about moving your elbows in; it's about maintaining relationships between back, hips and upper body.

 

[FrankDay]

Mostly because the position varies greatly from the position they train in. The best TT'ers lose the least because a)they train their TT position b)that position isn't radically different in terms of overall posture than their training position. I'm not talking about moving your elbows in; it's about maintaining relationships between back, hips and upper body.

But, why? The exact same legs and the exact same muscles are moving in the exact same circles. Why do they lose power just because they lower their torso?

 

[acoggan]

...very interesting way to present a study....

...my favourite part was the following...

Learning to produce maximum power
requires only 3 days (36 sec total) practice.

...36 sec of training and off to the pub to recover...now that is a very cool training schedule....CoachWhatEver is so right science is wonderful, I only wish I had read this study decades ago...

...kidding aside, is this study available in anything other than this powerpoint type presentation?...

Cheers

blutto

1. You're confusing learning effects with training effects.

2. You can find all of Jim's crank length studies by searching PubMed, and download at least those published in J Appl Physiol for free.

 

[acoggan]

But, why? The exact same legs and the exact same muscles are moving in the exact same circles. Why do they lose power just because they lower their torso?

Because the exact same muscles are NOT acting in the exact same manner.

 

[onetrack]

...but wouldn't comfort be one of the key benefits of moving the TDC of the pedal circle down...as in reducing the effects of you called scrunching...and that in and of itself is good, yes?...

...the other thing that I would like to bring up is the following (and yes it is anecdotal but since this has been experienced by a number of riders in my circle who have changed crankarm size it could be considered to be more than a coincidence )...going to a longer crankarm, from, say 170 mm cranks to 175mm, which was a typical change in my day, seemed to negativelly affect your ability to quickly close gaps in a race...has anyone considered or studied how different crankarm lengths could possibly affect your ability to spool up speed, which as we all know is a very critical part of racing...

Cheers

blutto

One thing I expected before trying shorter cranks was that I would be trading some acceleration and climbing ability for more top end speed on the flats. My first ride out, I found that both improved. I have no data to prove I accelerate better, but I found I could "muscle" the cadence higher giving the feeling that I have a motor on the bike. This is both from a stop and while riding. After 5 months, I am used to the motor feeling, so now it is just how I am able to ride.

Of the 4 cyclocross races I started on the front line, I got the hole shot every time.

 

[FrankDay]

Because the exact same muscles are NOT acting in the exact same manner.

Why not? Explain this phenomenon using a physiological basis.

 

[Martin318is]

Why not? Explain this phenomenon using a physiological basis.

The lowering of the torso is highly likely (note I am not using an absolute) to involve some form of difference in pelvic tilt and that would then result in a change to the angles of leverage with respect to the muscle attachment points.

Assuming I am correct about this (and once again I use language that will hopefully stop WW3), it would mean that SOME people would have a drop in power but it is also possible that SOME would get an improvement. What is likely though is that not many would produce identical power in two different positions

 

[FrankDay]

The lowering of the torso is highly likely (note I am not using an absolute) to involve some form of difference in pelvic tilt and that would then result in a change to the angles of leverage with respect to the muscle attachment points.

Assuming I am correct about this (and once again I use language that will hopefully stop WW3), it would mean that SOME people would have a drop in power but it is also possible that SOME would get an improvement. What is likely though is that not many would produce identical power in two different positions

I would accept that as a partial explanation although I have a problem with the "some would improve and others would not" since we are all built pretty much the same and all fit pretty much the same on a bicycle such that I would not expect such a small change from this basic position to improve some and worsen others. Part of my objection to this goes to the fact that no one has submitted any evidence that power actually increases in some with this change beyond the "trust me, I have seen it" argument.

I guess anything is possible but I would like to see some evidence, let alone proof, that some riders can actually increase their power by lowering their torso to TT position. Even though we all "know" that many lose power when they lower their torso, I would also like to see some evidence documenting that also, not so much to prove to me that the phenomenon exists (although proof is always nice to see) but, rather, to document how large the drop in power is on average.

 

[onetrack]

Assuming I am correct about this (and once again I use language that will hopefully stop WW3), it would mean that SOME people would have a drop in power but it is also possible that SOME would get an improvement. What is likely though is that not many would produce identical power in two different positions

Absolutely. The lucky ones can get very aero and still churn out a ton of watts. Those of us who can't will probably benefit from dropping 3-4cm on the cranks. now we know that there doesn't seem to be any disadvantage to going as short as 110mm, I can't see how anyone wouldn't consider this issue worth a closer look. Even if you only have a handfull of watts to save, and gain only a handfull of watts, you will ride faster at your given fitness level. And in some situations, that makes all the difference in a race outcome.

 

[CoachFergie]

Absolutely. The lucky ones can get very aero and still churn out a ton of watts. Those of us who can't will probably benefit from dropping 3-4cm on the cranks. now we know that there doesn't seem to be any disadvantage to going as short as 110mm, I can't see how anyone wouldn't consider this issue worth a closer look. Even if you only have a handfull of watts to save, and gain only a handfull of watts, you will ride faster at your given fitness level. And in some situations, that makes all the difference in a race outcome.

Martin (2001) found a significant drop in ability to produce power as crank length went from 145 to 120mm.

That's hard data rather than personal observations or input from someone who markets adjustable length cranks.

 

[sciguy]

Well, this certainly opens up an area or two for further discussion.

1. Is loss of power in the aero position only occur when one is doing the "PowerCranks style" of pedaling?

2. If so, what could possibly account for this difference? I mean, all the PowerCranks do is make the rider use a couple of muscles a little more than they normally do and they may change the timing of the use of the muscles slightly different. So, again, if what you hypothesize is true, how can it be explained physiologically.

1. Neither my wife nor I find a measurable loss of power in the aero position with normal cranks. We do train in that position a good bit.

2. Since those using Powercranks must rely on their hip flexors to raise the rear pedal the "scrunched" position puts the hip flexors are into a very poor bio-mechanical orientation to exert sufficient force to raise the pedal. The action of the quads on the other hand is unhindered by being scrunched.

 

[Martin318is]

I would accept that as a partial explanation although I have a problem with the "some would improve and others would not" since we are all built pretty much the same and all fit pretty much the same on a bicycle such that I would not expect such a small change from this basic position to improve some and worsen others.

the part in bold leaves me dumbfounded...

Brad Wiggans and Tommy Voeckler are nothing alike physically, nor are their bikes set up the same way. Brad and Fabian are closer physically and they still don't have the same position.

If we were to accept the idea that we are all pretty much the same then nobody would need to be positioned professionally, we could just buy offf the rack and go racing. If we were all the same then there would be a higher quantity of conclusive research published because of the removal of variation

 

[Oldman]

Why not? Explain this phenomenon using a physiological basis.

Now you're just being purposely obtuse. Try doing a free weight squat, using a rack in the standard positon. Next try it with your back straight up and down.