The crank length thread

[coapman]

Cycling is not limited by application of force. While we may race around 200-400 watts most of us can easily deliver 800+ watts to the pedals. Delivery of power is not the question, sustainability of that power is!

When you switch to a higher gear, it is more difficult to pedal, what percentage of this difficulty is caused by the loss of leverage in the smaller rear sprocket? e.g. 14 to a 12.

 

[deboat]

How long should the cranks be on a clowns unicycle at the circus?

a clown bike,, maybe one very long crank and one very short crank....

 

[deboat]

It is not all about power. I like to ride or race my bikes around corners too. I use 175 cranks for many reasons. On my road bike it helps me fit into not ontop of my bike. When I corner the outside foot is at BDC, this helps lower my centre of gravity. I have a lower seat height and this in return means my bars are a little lower. This also means I am more comfortable on a smaller frame. I am now using a 56 road frame and if I use 170 cranks I need a 58 frame size.

 

[FrankDay]

It is not all about power. I like to ride or race my bikes around corners too. I use 175 cranks for many reasons. On my road bike it helps me fit into not ontop of my bike. When I corner the outside foot is at BDC, this helps lower my centre of gravity. I have a lower seat height and this in return means my bars are a little lower. This also means I am more comfortable on a smaller frame. I am now using a 56 road frame and if I use 170 cranks I need a 58 frame size.

???.
1. When cornering, while your outside foot may be at BDC, lowering that aspect of your CG, your inside leg is at TDC, raising the CG of that leg. The overall effect is probably to raise your CG since your thigh is more massive than your foot.
2, Shortening your crank opens your hip angle at TDC and should allow you to lower your HB's a bit, lowering the head and lowering CG.
3. You have to increase your frame size 20 mm when you decrease your crank size 5 mm?

 

[deboat]

1. ??? Ok,, So you think I should have my inside foot at BDC when cornering. MMMMMMmmmmm,,,, NO!!!!
2. I still have to be able to see where I am going!! Why do I need to open my hip angle? I do not ride TT bikes in a straight line.
3. Using a 56 frame I use a 120 stem, with a 58 I have to use a 100 stem. And the seat is at a differant spot too.
The fact is that there is more to riding fast than just how long or short your ,,, THINGY is.
Real world use of your theory does not work.
I have to go ride my MTB now!!
Happy Trails!!

 

[FrankDay]

1. ??? Ok,, So you think I should have my inside foot at BDC when cornering. MMMMMMmmmmm,,,, NO!!!!

No, your inside foot is at TDC when cornering. Longer cranks raises both the foot and the entire leg, including the thigh such that the CG of the inside leg will go up more than it lowers in the outside leg as crank length gets longer.

2. I still have to be able to see where I am going!! Why do I need to open my hip angle? I do not ride TT bikes in a straight line.

If you don't care to improve your aerodynimcs then that is your choice. We all have to make trade-offs when doing bike positioning.

3. Using a 56 frame I use a 120 stem, with a 58 I have to use a 100 stem. And the seat is at a differant spot too.
The fact is that there is more to riding fast than just how long or short your ,,, THINGY is.
Real world use of your theory does not work.
I have to go ride my MTB now!!
Happy Trails!!

If you say so.

 

[FrankDay]

OK, so here is a new (to me) paper related directly to power and crank length. While looking at recumbent cycling there is no reason to believe this doesn't apply to upright cycling also.

http://www.academia.edu/852595/Determination_of_the_crank-arm_length_to_maximize_power_production_in_recumbent-cycle_ergometry

From the paper:

2. Peak power is greatest with the 145mm crank-arm length and least with the 265 mm crank-arm length.
...(3) mean power is greatest with the 145-mm and 180-mm crank-arm length and least with the 265 mm crank arm-length; (4) minimum power is greatest with the 230 mm crank-arm length and least with the 110 mm crank arm length; (5) maximum and minimum pedaling rates occur with the 110 mm crank-arm length.

So much for the longer crank arms give you more leverage for more power argument. The two highest powers occurred with the 110 and 145mm crank-arm lengths. My guess is that if they also calculated average power for the 30second test that the 110 and 145 crank lengths would test best.

This data does suggest to me that longer crank arms might be less fatiguing but the minimum numbers for all crank lengths is essentially the same so it is not clear this would be seen in the real world race performance.

 

[sciguy]

OK, so here is a new (to me) paper related directly to power and crank length. While looking at recumbent cycling there is no reason to believe this doesn't apply to upright cycling also.

http://www.academia.edu/852595/Determination_of_the_crank-arm_length_to_maximize_power_production_in_recumbent-cycle_ergometry

From the paper:
So much for the longer crank arms give you more leverage for more power argument. The two highest powers occurred with the 110 and 145mm crank-arm lengths. My guess is that if they also calculated average power for the 30second test that the 110 and 145 crank lengths would test best.

Frank they did calculate the average (mean) power for all the crank lengths

[quote

[/QUOTE]

and concluded that:

[quote

[/QUOTE]

The greatest mean power would be generated with a set of 175mm cranks.

Are we reading different documents?

Hugh

 

[FrankDay]

Frank they did calculate the average (mean) power for all the crank lengths

and concluded that:

The greatest mean power would be generated with a set of 175mm cranks.

Are we reading different documents?

Hugh

I see what you are saying and you are probably correct. I think I was confusing mean and median.

It simply isn't clear to me what the data showed if one looked at the rate of decline of the RPM. I think one would anticipate that the decline in ability would be either linear or follow the same path for the various crank lengths. Why does the rider decline faster at the shorter crank length? Is it because he was able to achieve a higher effort, compared to his capability, so was closer to VO2max compared to the other lengths. Is he using more fast twitch fibers due to the slower pedal speed at the shorter crank length and they fatigue faster?

This data, I think, clearly confirms the Martin Data (although it doesn't drop off below 145). But, it raises new questions regarding fatigue (I don't think this is a central phenomenon). I would love to see oxygen uptake data correlated to this data or see if the results changed if users were trained on shorter cranks.

 

[sciguy]

and concluded that:

[quote

The greatest mean power would be generated with a set of 175mm cranks.

Are we reading different documents?

Hugh[/QUOTE]I see what you are saying and you are probably correct. I think I was confusing mean and median.

It simply isn't clear to me what the data showed if one looked at the rate of decline of the RPM. I think one would anticipate that the decline in ability would be either linear or follow the same path for the various crank lengths. Why does the rider decline faster at the shorter crank length? Is it because he was able to achieve a higher effort, compared to his capability, so was closer to VO2max compared to the other lengths. Is he using more fast twitch fibers due to the slower pedal speed at the shorter crank length and they fatigue faster?

This data, I think, clearly confirms the Martin Data (although it doesn't drop off below 145). But, it raises new questions regarding fatigue (I don't think this is a central phenomenon). I would love to see oxygen uptake data correlated to this data or see if the results changed if users were trained on shorter cranks.[/QUOTE]


To be honest, I wonder if these studies that use the Wingate Anaerobic Test are all that useful for those of us more interested in events with durations a good deal more than 30 seconds. Would oxygen uptake data even be useful during such an all out anerobic event?

Hugh

 

[FrankDay]

To be honest, I wonder if these studies that use the Wingate Anaerobic Test are all that useful for those of us more interested in events with durations a good deal more than 30 seconds. Would oxygen uptake data even be useful during such an all out anerobic event?

Hugh

Well, I agree but you can only work with what you have. From a researcher point of view a 30 second test (one one revolution in the case of Martin) is a lot more doable than a 5 hour testing protocol.

The reason to get the oxygen data would be to help me to better understand and explain the bigger fatigue factor seen with shorter cranks. Would this be the case if the testing were purely aerobic? Or, if the researcher controlled for pedal speed? And, what would the data look like if the riders had a more closed hip angle at "TDC" as in an aerodynamic time-trial position (my guess the curves would be shifted left).

Anyhow, this is just one study out of many that need to be done to help us get an answer to these questions.

 

[FrankDay]

A little more analysis of this Too data is helping me a bit to understand what we might be seeing.

First, these could not have been well trained cyclists. The max unloaded RPM (the condition at the start of the wingate test) achieved by this group at 180 crank length was 167.5 and at 110 crank length was 174.1. Well trained cyclists should be able to achieve a max, unloaded RPM, on 175-180 cranks of 200. Elites can achieve about 250. This group had a neurological or technique deficiency (probably from not a lot of training) that prevented them from getting above 175 even with very short cranks. This meant pedal speed dropped with each drop in crank length. At 180 the max pedal speed was 95 m/s whereas at 145 mm the pedal speed was only 78 m/s. To just maintain the same power required an almost 20% greater pedal force and with a 5% greater power at the shorter length required even greater pedal forces. This most surely meant involvement of more fast twitch fibers which would account for the increased fatiguability seen, I think. If this group had the ability to increase the cadence closer to what is required to keep pedal speed "ideal" then, perhaps, I think, the mean and minimum curves may not have dropped so fast. Or, with additional training, more FT fibers would be converted into ST fibers and fatigue would occur more slowly.

Anyhow, just trying to explain the data.

 

[CoachFergie]

Covered rather nicely by...

http://www.plan2peak.com/files/32_article_JMartinCrankLengthPedalingTechnique.pdf

Of the remaining 2% variability, crank
length and pedaling rate each accounted for
1% or 0.02% of total (in metabolic cost)

 

[FrankDay]

More anecdotal stuff. Courtney Ogden won the Metaman Bintan triathlon on the 31st of August using 145mm cranks.

 

[CoachFergie]

More anecdotal stuff. Brad Wiggins won the Olympic TT using 177.5mm cranks.

 

[Oldman]

OK, so here is a new (to me) paper related directly to power and crank length. While looking at recumbent cycling there is no reason to believe this doesn't apply to upright cycling also.

This data does suggest to me that longer crank arms might be less fatiguing but the minimum numbers for all crank lengths is essentially the same so it is not clear this would be seen in the real world race performance.

Love the conclusion you leap to right at the beginning.

 

[FrankDay]

Love the conclusion you leap to right at the beginning.

Are you jumping to the conclusion that there is a reason to believe that data shouldn't apply to upright cycling? If so, could you give me the reason.

 

[CoachFergie]

Are you jumping to the conclusion that there is a reason to believe that data shouldn't apply to upright cycling? If so, could you give me the reason.

Specificity would be the main reason.

 

[Oldman]

Specificity would be the main reason.

I thought if I waited long enough it would occur to him...

 

[CoachFergie]

No, you now have to wait 10,000 hours for an "expert" response.

In the meanwhile you may care to peruse the work of Martin and others who have more than adequately shown how insignificant this issue is.

 

[Captain Serious]

Does anyone know what's happened to Andrew Bradley's crank length site?
It's been "under construction" for years.
http://cranklength.info/

Has he given up?

It was an extensive discussion, looking at pretty much every theory and associated conundrum.

I've got a whole hunk of it printed out, and was just having a browse

 

[FrankDay]

Another anecdotal report for those of you who care about anecdotal reports. Just received a phone call from a long-time user who had upgraded his PowerCranks to allow him to experiment with crank length. His usual crank length is 172.5 and he normally rides at 250 watts. This was his first ride on shorter cranks and he decided to try 160. He was amazed that he was able to ride at 290 watts at the same HR/effort as before on 172.5 - a 40 watt (16%) improvement from this simple change. I told him to try 150.

This is more than I would expect most to see but until you try you can't know what will happen.

 

[elapid]

Another anecdotal report for those of you who care about anecdotal reports.

No, don't care for them. Don't think many of us here care about them either. Conduct a well-designed study, publish the results, and then let us know. Anything else is just cherry-picking, car salesmen-like advertising with no scientific merit.

 

[Oldman]

What...wait! Is he selling cars? I might want one. Shorter ones can go faster and use less gas and (wait for it) there's scientific evidence.

 

[Captain Serious]

Another anecdotal report for those of you who care about anecdotal reports. Just received a phone call from a long-time user who had upgraded his PowerCranks to allow him to experiment with crank length. His usual crank length is 172.5 and he normally rides at 250 watts. This was his first ride on shorter cranks and he decided to try 160. He was amazed that he was able to ride at 290 watts at the same HR/effort as before on 172.5 - a 40 watt (16%) improvement from this simple change. I told him to try 150.

This is more than I would expect most to see but until you try you can't know what will happen.

Hmm, interesting. Does he have an injury or other biomechanical issue that prevented him pounding the longer cranks properly with the extra knee and hip flexion?