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tongskie01 
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Joined: 29 July 2011 Location: blackpool Status: Offline Points: 11 |
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 Posted: 24 February 2012 at 4:46pm |
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i can certainly say based on my experience that matching the cranks with the leg length can help with knee problems. being 0nly 5'4'' tall i have to changed my crank from 175mm to 155 especially when i started to develop knee pains after doing a lot of hills. this is probably trying to spin faster with longer cranks to keep up speed so that i dont fall over especially on a lowracer.. but i did have to lower down the gear inches coz i could spin faster with the shorter cranks. never had any problems with my knees now.
i believe that the brain senses the pressure that you put on the muscles on every pedal stroke. that is why changing to shorter cranks will feel strange and uncomfortable at first and may reduce speed. this is due to the fact that short crank=less torque. spinning on same gear i can say, short crank=more pressure on muscles on each pedal stroke when compared to longer cranks. so brain tells body gear down to match muscle strength. |
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absolute beginner
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Joined: 03 May 2011 Location: UP NORTH Status: Offline Points: 17 |
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Posted: 24 February 2012 at 12:15pm |
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Hi All!
Sorry if Quote1 is incorrect or misleading. I have found a piece in Mike Burrows book which is relevant to Quote2 and the relationship between perception and changes of physiological state. Mike writes about meeting Frank Lienhard at the '96 IHPVA Championships. "Frank did not win any races so there were no overnight conversions. Some while later I met Frank riding his regular road-going LB (laid back) also now fitted 110mm cranks, because as Frank discovered, you body/brain take a while to get used to them, and are not so happy about changing back, either. Most surprising though, Frank was going as well as ever, without any aerodynamic benefit other than slightly less air being stirred up by the feet." "taking a while to get used to it" The muscle fibres not needed for turning 110mm cranks are being relaxed to assist increasing effiency of movement. "not so happy about changing back" The muscle fibres not needed are at some stage of the atrophic process. Which when completed would make the change appear permanent. "going as well as ever" The muscle fibre economic requirements are improving the efficiency of movement. Mike goes on to explain how having fitted shorter cranks to his sons' cycle and then his own, he couldn't get used to them because of the number of different bike he was riding at the time. Physiologically Mike's body wouldn't have had time to make the required muscle fibre adjustments to get used to short cranks which may have felt awkward and/or uncomfortable because of the other muscle fibres needed to push varying crank lengths are still being involved in some level of activity. Perception of the benefit of short cranks may just be in the mind. If you have converted, did you change your cadence to match expectation? Did your knees benefit as result of the shorter crank or the increase in cadence? Did you adjust your gearing needs to help with increase in cadence or were you pushing the same gears for the same/increased speeds? Would we like a study to investigate the time scale associated with the muscle fibre changes required for getting used to short cranks? From relaxation to atrophy, and on to increased efficiency. From initial installation of cranks through to the final result which in some cases racing. A measure of the change of mind too? Is there an optimum crank length or do we just adapt? I do. Frank may already be able to answer this study as he has already undergone his own version. I am finding the body to be remarkable and adaptable structure. The harmony required between the nervous system and power producing muscle fibres is astounding. I look forward to more debate on this subject. All the best! |
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too fat for too long, time to get fit again!
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GeoffBird
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Joined: 20 September 2005 Status: Offline Points: 2384 |
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Posted: 23 February 2012 at 8:22pm |
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A probably sacrilegious and possibly irrelevant comparison:
Petrol-fuelled engines generally produce more power by reving higher (but you have to keep the reciprocating mass low). It's often said that Diesel engines are great because they have much more torque, but they also rev much slower, so need to be geared up, reducing torque at the wheels. The real advantage of Diesels is their even 'spread' of torque across the rev range. Perhaps older bodies are more like diesel engines (sorry Andrew) - they certainly cough and splutter more - and younger bodies more like motorbike engines? Humans and IC engines are after all both heat engines - their efficiency figures are remarkably similar. People of our age should, however, be reasured that for a number of years, The LeMans 24 Hour race has been won by a diesel-engined car  Martin Widget-Wingnut will hopefully be along in a minute to expand on this comparison, 'cos engines aren't my strong-point. PS: Good to hear from you Mr Tigwell! Oh, and John - XL Quest? You must be VERY tall. Edited by GeoffBird - 23 February 2012 at 8:42pm |
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Right Time - Right Place - Wrong Speed
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Andrew S
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Joined: 14 March 2005 Location: Hornsea, UK Status: Offline Points: 2240 |
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Posted: 23 February 2012 at 5:07pm |
Another piece of anecdotal evidence: every morning I do the same run down a flat, straight cycle-track about 1km long. I try to keep one gear lower, i.e. a higher cadence, than I'm really comfortable with because I'm told it's good for me. Sometimes I just can't hold it to the end and change up a gear. Cadence drops but, simultaneously, my speed increases by around 1mph. I know fast cadence is supposed to be better, more efficient or whatever, but it's nuts to that in a race if it slows you down that much. What am I doing wrong?? |
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tongskie01
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Joined: 29 July 2011 Location: blackpool Status: Offline Points: 11 |
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Posted: 23 February 2012 at 3:08pm |
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not to forget that venous return of blood to the heart is influenced by muscle contraction.
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Adrian Setter
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Posted: 23 February 2012 at 12:42pm |
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It would be nice to have some some explanation of the theory behind the claim in point 1. The more generally-accepted wisdom is that high cadence at the same speed requires more oxygen. See NickM's earlier post, and this, I'm sure, was what Lance Armstrong (who achieved some degree of success riding at a cadence much higher than his rivals) meant when he wrote that it "puts greater demands on the heart and lungs" (or words to that effect). Reading and personal experience would support the idea that mashing a big gear slowly leads to a greater build up of lactate, not because more oxygen is required but because it restricts blood flow, so less oxygen can get to the muscles. Armstrong says he adopted his high cadence because it was less fatiguing,
For a person who is aready reasonably fit, there might be a lot of truth in point 2. A lot of stuff about exercise can be counterinuitive, which is why I'll be watching next week's Horizon.
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Challenge Hurricane - MicWic Delta (Front half) - Burrows Ratracer
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absolute beginner
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Joined: 03 May 2011 Location: UP NORTH Status: Offline Points: 17 |
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Posted: 22 February 2012 at 9:14pm |
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Hi All.
I'm quoting from a couple of books I've been reading lately. The first piece regards cadence and the second regards aerobic activity. I hope they are of interest.
1- Many new riders tend to underestimate the role of cadence and pedal at around 50-60 rpm, but pro racers won't go below 90 and some no less than 100. This is because mashing a big gear at a low cadence takes the cyclist into anaerobic exercise. A fast cadence in a lower gear consumes less oxygen and puts less stress on the leg muscles and knees.
2- Whether it's running, cycling, or a step class, the main reason it gets easier the more you do it, is not because of improved cardiovascular conditioning, but because of improved economy of motion. For the most part, it doesn't get easier because of muscular endurance, but because your body is becoming more efficient at that particular movement. You require less strength and oxygen than you did before, because your body's nervous system is adapting. Wasted movements are eliminated, necessary movements are refined, and muscles that don't need to be tensed are relaxed and eventually atrophied. This is why marathon runners will huff and puff if they cycle for the first time in years.
Aerobic training actually causes muscle wasting because the body is programmed to adapt to whatever demands we place on it. Long low-intensity aerobic training only requires the smallest and weakest, "slow twitch" muscle fibres to fire off again and again. the other, stronger and larger "fast twitch" muscle fibres are not necessary for the task and become a burden to carry and supply with oxygen. The body has no demand for the extra muscle beyond what is needed to perform a relatively easy movement over and over. So your body adapts by burning muscle. Even if you perform steady state training in conjuction with strength training, it will deminish any potential increase in lean body mass, especially in the legs. Aerobic training should only be used to develop movement proficiency when you are traing for a specific sport or event......
All the best!
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too fat for too long, time to get fit again!
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Dave Tigwell
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Joined: 19 October 2010 Location: West Cornwall Status: Offline Points: 9 |
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Posted: 22 February 2012 at 6:11pm |
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Hello People, I have noticed that my pedal cadence has come down from 96 to 83 over this off -season`s training as my legs have become stronger. This could indicate a need to run longer cranks at a higher gear perhaps, or is it six of one and half a dozen of the other. However, I`m convinced that this stuff is very particular to the individual rider. Would be interested to hear theories from clever people. Regards, Dave.
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dave T
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Warekiwi
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Joined: 22 February 2012 Location: Ware, UK Status: Offline Points: 44 |
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Posted: 22 February 2012 at 4:24pm |
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My Grasshopper was supplied with 152mm cranks -Sugino branded. They certainly seem to have saved my knees although initially they took a bit of getting used to. My Quest XL will come with cranks of a similar length as any longer would result in my knees touching the upper skin of the machine.
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QuattroVelo #13 (2016)now eQV!
Snoek#18 Too tight! Brompton P6- for shoppping! Vitus Escarpe eMTB for off-road fun. |
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GeoffBird
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Posted: 20 February 2012 at 8:25pm |
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Yehbut, Cavendish exceeded the elimination time a couple of time in last year's Tour ;-)
I know - so did a lot of other people (who are probably in the top 500 fittest athletes in the world)... |
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Right Time - Right Place - Wrong Speed
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Short Cranks
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Dave Tigwell wrote: