The crank length thread

[sciguy]

Re:

Today I received a report of a trial comparing 145 and 175 mm cranks. The trial tried to make the crank length the only variable. The ride was done on the Expresso bike system which allows a rider to ride repeated courses against "ghosts" that represent previous rides. Here is the result of two rides over the same course using a "fixed" gear following the same ghost. The rides lasted about 25 minutes and were within 0.2 seconds of each other so it seems they would be pretty comparable from a power output perspective. Note the the ride on the 145 cranks the average and maximum heart rate was 10 bpm lower than when done on 175 cranks. Since HR corresponds reasonably well to oxygen consumption this would suggest that in this instance the 145 cranks improved rider efficiency about 7-8%. Such that if his efficiency on 175 cranks was 20% his efficiency on 145 cranks would be about 21.5%. Needless to say the rider was pretty excited. I believe another rider did the same thing with a similar result Here is the graph of this one effort. Discuss.

Frank,

The "cursor heart rate" listed on the data table was 7 BPM higher for the trial where the rider used the longer cranks. It appears the cursor heart rate may be the athlete's heart rate just before the start of the trial. That alone leads me to believe there was some difference between trials beyond just the crank length. Hmmmmmmmmmm maybe the athlete just completed a trial with shorter cranks and in now doing a second trial with longer ones with some level of residual heat accumulation and or fatigue. Come to think of it, the heart rate graph of my first and second intervals of a 2 X 20 minute workout would look exactly like his two plots. My average pulse is always ~ 10 BPM higher for the second interval. Gosh someone must be sneaking in and changing my cranks between intervals

Let's repeat the experiment but do the longer crank trial first before we get too excited.

Hugh

 

[elapid]

Re:

You're baiting and then provoking people is rather lame. If it isn't of interest, such is life.

+1. Oh goodie, let's discuss another n=1.

 

[FrankDay]

Re: Re:

You're baiting and then provoking people is rather lame. If it isn't of interest, such is life.

+1. Oh goodie, let's discuss another n=1.

Isn't that the way of internet forums, mostly discussing people personal experiences and opinions? So, the thread that preceeded this had 1893 posts before it was cut off and this one started that now has over 350 replies. So, it seems there is some interest in this topic even though most of the discussion has revolved around anecdotal evidence and opinions. If you are no longer interested in this thread then it seems nothing is forcing you to click on it nor to put in your 2 cents. Anyhow, perhaps you have never seen the old saying, the plural of anecdote is data.

BTW, I believe the person in question repeated this little test (or a similar one) with 2 different people with similar results. He just forwarded me his results as he found them exciting and interesting. I did also so I thought others might be interested in seeing them also.

 

[sciguy]

Frank,

There seems to be a huge disconnect between your contention that "it takes a huge amount of time and effort to change one's pedaling technique" with the athlete made a huge change in crank length and he is instantly way more efficient with no adaptation period needed. These two don't seem to square up with each other. Any reason you didn't reply to my last post?

Hugh.

 

[FrankDay]

Re: Re:

Today I received a report of a trial comparing 145 and 175 mm cranks. The trial tried to make the crank length the only variable. The ride was done on the Expresso bike system which allows a rider to ride repeated courses against "ghosts" that represent previous rides. Here is the result of two rides over the same course using a "fixed" gear following the same ghost. The rides lasted about 25 minutes and were within 0.2 seconds of each other so it seems they would be pretty comparable from a power output perspective. Note the the ride on the 145 cranks the average and maximum heart rate was 10 bpm lower than when done on 175 cranks. Since HR corresponds reasonably well to oxygen consumption this would suggest that in this instance the 145 cranks improved rider efficiency about 7-8%. Such that if his efficiency on 175 cranks was 20% his efficiency on 145 cranks would be about 21.5%. Needless to say the rider was pretty excited. I believe another rider did the same thing with a similar result Here is the graph of this one effort. Discuss.

Frank,

The "cursor heart rate" listed on the data table was 7 BPM higher for the trial where the rider used the longer cranks. It appears the cursor heart rate may be the athlete's heart rate just before the start of the trial. That alone leads me to believe there was some difference between trials beyond just the crank length. Hmmmmmmmmmm maybe the athlete just completed a trial with shorter cranks and in now doing a second trial with longer ones with some level of residual heat accumulation and or fatigue. Come to think of it, the heart rate graph of my first and second intervals of a 2 X 20 minute workout would look exactly like his two plots. My average pulse is always ~ 10 BPM higher for the second interval. Gosh someone must be sneaking in and changing my cranks between intervals

Let's repeat the experiment but do the longer crank trial first before we get too excited.

Hugh

I am not sure how I missed your post. Anyhow, I believe the "cursor HR" is the HR at where the cursor is on the plot. I think it has little relevance to the overall data. If you look at the first couple of minutes the HR climbs "identically" except the shorter cranks HR levels off at a lower level. Further, I am quite certain the first trial was with the longer crank length. That having been said, it is obvious to me that it would be better if there were more trials done in a random order showing a similar pattern. I believe he intends to do more of this but right now his bike is down getting some modifications.

The other thing is I don't believe the difference seen is entirely due to crank length. I have suggested some other trials for him to test if there might be another mechanism in play here.

 

[FrankDay]

Re:

Frank,

There seems to be a huge disconnect between your contention that "it takes a huge amount of time and effort to change one's pedaling technique" with the athlete made a huge change in crank length and he is instantly way more efficient with no adaptation period needed. These two don't seem to square up with each other. Any reason you didn't reply to my last post?

Hugh.

When we consider pedaling technique I tend to think more about the muscle coordination involved rather than some of the other aspects that could also be considered part of technique. There is no evidence that changing crank length (or saddle height, etc.) affects the basic pedaling muscle coordination in any way. Therefore, changing these "technique" items might result in an immediate improvement (or worsening). What takes a long time to change is the basic unconscious pedaling muscle coordination.

I didn't reply to your last post because I didn't see it. Not sure why. I have replied now.

 

[sciguy]

Re: Re:

Today I received a report of a trial comparing 145 and 175 mm cranks. The trial tried to make the crank length the only variable. The ride was done on the Expresso bike system which allows a rider to ride repeated courses against "ghosts" that represent previous rides. Here is the result of two rides over the same course using a "fixed" gear following the same ghost. The rides lasted about 25 minutes and were within 0.2 seconds of each other so it seems they would be pretty comparable from a power output perspective. Note the the ride on the 145 cranks the average and maximum heart rate was 10 bpm lower than when done on 175 cranks. Since HR corresponds reasonably well to oxygen consumption this would suggest that in this instance the 145 cranks improved rider efficiency about 7-8%. Such that if his efficiency on 175 cranks was 20% his efficiency on 145 cranks would be about 21.5%. Needless to say the rider was pretty excited. I believe another rider did the same thing with a similar result Here is the graph of this one effort. Discuss.

Frank,

The "cursor heart rate" listed on the data table was 7 BPM higher for the trial where the rider used the longer cranks. It appears the cursor heart rate may be the athlete's heart rate just before the start of the trial. That alone leads me to believe there was some difference between trials beyond just the crank length. Hmmmmmmmmmm maybe the athlete just completed a trial with shorter cranks and in now doing a second trial with longer ones with some level of residual heat accumulation and or fatigue. Come to think of it, the heart rate graph of my first and second intervals of a 2 X 20 minute workout would look exactly like his two plots. My average pulse is always ~ 10 BPM higher for the second interval. Gosh someone must be sneaking in and changing my cranks between intervals

Let's repeat the experiment but do the longer crank trial first before we get too excited.

Hugh

I am not sure how I missed your post. Anyhow, I believe the "cursor HR" is the HR at where the cursor is on the plot. I think it has little relevance to the overall data. If you look at the first couple of minutes the HR climbs "identically" except the shorter cranks HR levels off at a lower level. Further, I am quite certain the first trial was with the longer crank length. .

So why is it listed second? Seems like one would list them in the order tested. If you check the initial pulse rate the trial with the 175s was nearly 10bpm higher to begin with. Perhaps there was a coffee break in between trials. That's always good for a multi-beat bump.

Hugh

 

[FrankDay]

Re: Re:

So why is it listed second? Seems like one would list them in the order tested. If you check the initial pulse rate the trial with the 175s was nearly 10bpm higher to begin with. Perhaps there was a coffee break in between trials. That's always good for a multi-beat bump.

Hugh

I don't know but in the "note" column the first line (the 145 line) says "ride #2" and that was the order I was told. Either way, this should be done many times (N>1) in a random order to confirm the difference is real. Right now all this data does is suggest something real going on.

Edit: I was also told another rider did the same test with a similar result but we don't have that data.

 

[sciguy]

Re: Re:

Frank,

There seems to be a huge disconnect between your contention that "it takes a huge amount of time and effort to change one's pedaling technique" with the athlete made a huge change in crank length and he is instantly way more efficient with no adaptation period needed. These two don't seem to square up with each other. Any reason you didn't reply to my last post?

Hugh.

There is no evidence that changing crank length (or saddle height, etc.) affects the basic pedaling muscle coordination in any way.

Boloney, try climbing or descending a set of stairs where the riser height is just 1" greater or less than normal and report back to me. If the treads are an inch higher you'll be stubbing you toes if you don't take great care. If they're an inch less you'll be nearly falling over without substantial conscious care exerted. The general direction of force application may well be the same but the timing will be totally different.

Hugh

 

[FrankDay]

Re: Re:

Frank,

There seems to be a huge disconnect between your contention that "it takes a huge amount of time and effort to change one's pedaling technique" with the athlete made a huge change in crank length and he is instantly way more efficient with no adaptation period needed. These two don't seem to square up with each other. Any reason you didn't reply to my last post?

Hugh.

There is no evidence that changing crank length (or saddle height, etc.) affects the basic pedaling muscle coordination in any way.

Boloney, try climbing or descending a set of stairs where the riser height is just 1" greater or less than normal and report back to me. If the treads are an inch higher you'll be stubbing you toes if you don't take great care. If they're an inch less you'll be nearly falling over without substantial conscious care exerted. The general direction of force application may well be the same but the timing will be totally different.

Hugh

What on earth are you talking about? First, you hold me to task for putting out anecdotes to support a view and then you counter my claim with less than an anecdote; a thought experiment that has almost nothing to do with pedaling a bike (force is applied in a straight line - down - and involves full weight bearing plus the foot is unconstrained for more than half of the movement). Then, you say,

The general direction of force application may well be the same but the timing will be totally different.

Now, this is just silly. The general direction of the force application is determined by the timing of the various muscle contractions. How on earth is is possible for the general force application to be similar but the timing to be totally different?

Anyhow, my point remains intact. The reason for the sudden improvement in efficiency from simply changing crank length can easily be explained without needing to invoke any change in pedaling coordination.

 

[CoachFergie]

Thanks for spamming the group yet again Frank.

I suggest people consult an actual sport scientist or a cycling coach who uses science based practice for real information that benefits their cycling.

 

[CoachFergie]

Quit watching after 10min of that infomercial. What a load of horse waste! No new information provided, same old cherry picking of poorly performed or outdated research. Same old made up charts. Same old reinvention of the laws of physics to suit your marketing claims. Pathetic!

 

[FrankDay]

Re:

Quit watching after 10min of that infomercial. What a load of horse waste! No new information provided, same old cherry picking of poorly performed or outdated research. Same old made up charts. Same old reinvention of the laws of physics to suit your marketing claims. Pathetic!

Since this is the crank length thread and the crank length portion of the video started about 15 minutes in it seems your stopping watching the video 10 minutes in makes your post a little off topic, or so it would seem to me. LOL.

 

[CoachFergie]

Seeing the first 10 minute was marketing drivel had no reason to expect the rest to be any different. Go SPAM elsewhere!

 

[sciguy]

Re: Re:

Quit watching after 10min of that infomercial. What a load of horse waste! No new information provided, same old cherry picking of poorly performed or outdated research. Same old made up charts. Same old reinvention of the laws of physics to suit your marketing claims. Pathetic!

Since this is the crank length thread and the crank length portion of the video started about 15 minutes in it seems your stopping watching the video 10 minutes in makes your post a little off topic, or so it would seem to me. LOL.

Frank,

Isn't it interesting that both Sam Glyde and Dave Campbell have gone back to longer cranks after you convinced them to give shorter cranks a try? Dave spent 18 months on 175 cranks but now has gone back to his 200s. Sam was singing the praises of 140s a few months ago but is now back on 175s. How do you explain that?

http://forum.slowtwitch.com/gforum.cgi?do=post_view_flat;post=5510288;page=1;sb=post_latest_reply;so=ASC;mh=28;

Hugh

 

[sciguy]

Re:

Today I received a report of a trial comparing 145 and 175 mm cranks. The trial tried to make the crank length the only variable. The ride was done on the Expresso bike system which allows a rider to ride repeated courses against "ghosts" that represent previous rides. Here is the result of two rides over the same course using a "fixed" gear following the same ghost. The rides lasted about 25 minutes and were within 0.2 seconds of each other so it seems they would be pretty comparable from a power output perspective. Note the the ride on the 145 cranks the average and maximum heart rate was 10 bpm lower than when done on 175 cranks. Since HR corresponds reasonably well to oxygen consumption this would suggest that in this instance the 145 cranks improved rider efficiency about 7-8%. Such that if his efficiency on 175 cranks was 20% his efficiency on 145 cranks would be about 21.5%. Needless to say the rider was pretty excited. I believe another rider did the same thing with a similar result Here is the graph of this one effort. Discuss.

Well I just swapped in a set of 170mm cranks for the ancient 177.5mm cranks that were on my old mountain bike turned gravel grinder. Interestingly enough my max 20 minute power and heart rate at that power are still exactly the same. Go figure????????

Hugh

 

[FrankDay]

Re: Re:

Quit watching after 10min of that infomercial. What a load of horse waste! No new information provided, same old cherry picking of poorly performed or outdated research. Same old made up charts. Same old reinvention of the laws of physics to suit your marketing claims. Pathetic!

Since this is the crank length thread and the crank length portion of the video started about 15 minutes in it seems your stopping watching the video 10 minutes in makes your post a little off topic, or so it would seem to me. LOL.

Frank,

Isn't it interesting that both Sam Glyde and Dave Campbell have gone back to longer cranks after you convinced them to give shorter cranks a try? Dave spent 18 months on 175 cranks but now has gone back to his 200s. Sam was singing the praises of 140s a few months ago but is now back on 175s. How do you explain that?

http://forum.slowtwitch.com/gforum.cgi?do=post_view_flat;post=5510288;page=1;sb=post_latest_reply;so=ASC;mh=28;

Hugh

At least they were willing to try. My current recommendation is that people ride the longest cranks they can that allow them to get into a great aero position and not lose power. Sam doesn't lose power going shorter but doesn't gain any either. Check out Sam's position.

He is low enough that the increase in drag seen from shorter cranks balances any decrease he might see in getting lower. Anyhow, hard to argue with his results, at least he has experimented and I think because there isn't a noticeable difference he likes staying with his SRM and the crank length he has.
Compare his position to that of some of the women. Mirinda Carfrae

Julia Gajer

Gina Crawford

These women would really benefit from going to shorter cranks, IMHO. Of course, Mirinda is "fast enough" and probably has sponsorship issues. My guess is she won't consider this until she starts losing. Hard to get the very elite to change what got them there. (Edit: These are 3 of the top 15 women pros at Kona. Imagine how awful the positions are of the average age-grouper woman.)

Dave, doesn't care about aerodynamics because he lives in the mountains and he doesn't want to spend the money necessary to outfit his bike so he can climb on shorter cranks. I don't think Dave has done a very "systematic" testing program but he has, at least, tried, and thinks he races longer with longer cranks, at least for the kind of courses he tends to race on.

Courtney Ogden has been on shorter cranks for several years now and won IM WA on 145's. We recently had a back and forth and I think he is going to try to go even shorter.

I was just at a triathlon camp where I put all the campers on 170 cranks and then put them on 145's. About 80% of them, when they first got on 145's got a big smile on their face and would say something like "this is so much easier" (despite the fact they were usually at a higher power). two thirds of the people in this camp were women. Some needed to go even shorter. Anyhow, my recommendation is that people experiment and find out what is best for them. If they do that I don't care where they end up. If they won't do that then they may be missing out on some free speed but, at least, I tried.

 

[FrankDay]

Re: Re:

Well I just swapped in a set of 170mm cranks for the ancient 177.5mm cranks that were on my old mountain bike turned gravel grinder. Interestingly enough my max 20 minute power and heart rate at that power are still exactly the same. Go figure????????

Hugh

How did your position change? If aero got better and power didn't change then this is an improvement. Going fast isn't all about power.

 

[faster]

My experience is without a powermeter or heart rate moniter. Used lengths, 170, 172.5, 175, 177.5, 182.5 & 185. When climbing I am looking to get out of the saddle a lot more to push the crank over on 175 and under. I struggle to stay seated with these lengths. I have also only cramped the VMO muscle with these shorter lengths as it never happens with longer. 185 was quite long but doable. For me as a recreational rider staying seated and riding like a steam engine is very satisfying. It is harder to sprint with longer cranks as the circle is just too big for me to maintain the required force but every other aspect is better. I also recruit my glute strength a lot more, all perceived of course.

 

[Captain Serious]

Re:

^ have you noticed or perceived any speed difference with the different lengths?

 

[faster]

Re: Re:

^ have you noticed or perceived any speed difference with the different lengths?

Yes. Currently using 177.5 cranks atm which I can maintain a faster cruising speed for longer, a lot longer. I'm fresher after a ride too as I assume I'm using more muscles but they aren't going to failure like I experienced with short cranks. Thoroughly recommend it. Maybe not for crit type racing as it's too big a circle to turn in a sprint. I'm 179cm with an 88.8cm inseam using shimano size 44 shoe.
I have 180mm cranks ready to install once the campag tool turns up.

 

[Captain Serious]

Re: Re:

^ have you noticed or perceived any speed difference with the different lengths?

Yes. Currently using 177.5 cranks atm which I can maintain a faster cruising speed for longer, a lot longer. I'm fresher after a ride too as I assume I'm using more muscles but they aren't going to failure like I experienced with short cranks. Thoroughly recommend it. Maybe not for crit type racing as it's too big a circle to turn in a sprint. I'm 179cm with an 88.8cm inseam using shimano size 44 shoe.
I have 180mm cranks ready to install once the campag tool turns up.

Thanks.

Your crank length 'history' and body dimensions are similar to mine. I've bored the people on here with my story many times, so here's the short version:

I'm 182 or 181cm (I think I've shrunk ), with long-ish legs (~89cm inseam) and size 43 feet.
I got right into the long crank thing about ten years ago, and bought 180s. At first I loved them, so I bought another 2 sets for my other main bikes and used them exclusively for almost a year. I thought I had a secret weapon.

After several months, they started to *** me a bit; I was regularly getting off the seat to "get on top of" them, and I could never find a comfortable position, especially after about 90 mins of riding. I was constantly adjusting the height and fore-aft position of my saddle. When I eventually had some persistent medial knee pain in both knees, I got rid of them after having some great rides on some old 175s.

When I "restocked" my bikes (5 or 6, at the time ), I found many more deals on 172.5s than 170s or 175s, so rode 172.5s for ages.

However, there were times when I missed the long cranks, especially when riding off the saddle over short hills or our out of corners in races, so I put some 177.5s on one bike.

Then I read all the stuff about short cranks and getting more aero, etc, so I experimented with 165s, 167.5 and 170.
I was probably no faster or slower on any different length, but the 165s feel odd, so I rarely use them.

 

[CoachFergie]

New data...

http://journals.lww.com/acsm-msse/Fulltext/2016/05001/Triathlon_Cycling_with_Shorter_Crank_Lengths_at.2107.aspx

 

[JayKosta]

Thanks for the link about crank length tests.

I don't understand the speculation about slower muscle contraction -
"may change mechanical advantage at the hip and knee allowing the muscle to contract slower through the pedal stroke"
eventhough the cadence remained about the same.
" Cadence and all ventilatory parameters were not significantly different between CL trials (p > .05)"

Can anyone explain why muscle contration would be slower at the same cadence?
Is a larger portion of the crank rotation used for the 'downstroke' so the muscle contration rate is spread over a longer time period?

Jay Kosta
Endwell NY USA

 

[sciguy]

Re:

[quote="JayKosta

Can anyone explain why muscle contration would be slower at the same cadence?
Is a larger portion of the crank rotation used for the 'downstroke' so the muscle contration rate is spread over a longer time period?[/quote]

Jay,

If the cadence is the same for two crank lengths, the pedal velocity and therefore foot velocity and therefore muscle shorting velocity will be less for the shorter crank as it's following a smaller circumference circle. Interestingly, in my own case when moving from 175 to 165mm cranks my cadence has actually decreased rather than increased as one might expect. Perhaps it's part of the aging process kicking in in my mid 60s but my FTP is just as high as before the switch to shorter cranks.

YMMV,

Hugh