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sean costin
human power expert

Lesotho
2005 Posts

Posted - 01/11/2010 :  20:34:39  Show Profile  Reply with Quote
I'm still trying to figure out why an upright position can produce more power than recumbent and I have a theory about why this is the case. I think is has something to do with subtle movement that the upright position allows the rider to make with upper body, the hips and mid section. This movement is severely restricted with the fixed seating position characteristic of recumbents.

I'm thinking of designing a dynamic seat that can pivot to take advantage of these muscles.

Anyone have similar thoughts?

Sean

johntetz
Starting Member

USA
6 Posts

Posted - 01/11/2010 :  21:40:07  Show Profile  Reply with Quote
Sean wrote;

>I'm still trying to figure out why an upright position can produce more power than recumbent. .....
>the upright position allows the rider to make with upper body, the hips and mid section.
......Sean the HPA folks have measured both upright and recumbent positions. It was important to reduce drag so they spent some efort making measuremnts. First tests indeed showed the recumbent position produced less power but with constant (every day) training the recumbent rider was able to produce the same power as the up right position.

This appeals to my pet therory that the up right rider is using the same bike muscles on a daily bases (walking, climbing stairs etc) which has a tendency to keep them from loosing muscle tone. Where as the recumbent rider is not using the recumbent muscles as much on a daily bases therefore loosing more muscle tone.

John Tetz
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calfeenated
recumbent enthusiast

USA
226 Posts

Posted - 01/11/2010 :  22:30:31  Show Profile  Reply with Quote
Glad to hear that you have been thinking about this Sean,

I remember at some BM event in years past Sam W had an SRM on his road bike and in the Varna. In the 1/4 mile drags I saw a crazy number of 1500+ peak watts on his upright and we know what he can do in a Varna.
I couldn't get my head around why the numbers were so hugely different.

I have long wondered if you can get a longer power stroke in an upright position or if the difference was due to gravity.
Sean, I'd be interested to know your thoughts on well...Gravity's effect on power.
You have stated on several occasions the effect of forces when cornering on the velodrome and how that effects your power. In an extremely reclined position gravity is pulling your legs down at almost 90 degrees to the axis of which you are providing power from.
That's got to steal power from somewhere but how much?

When you are standing on the pedals of an upright, gravity is pulling everything down. Plus you can pull UP simultaneously while you are pushing down on the pedals. Plus your body weight. You want proof that this matters? Try doing that exercise upside down! The only thing that has changed is the direction that gravity is in relation to your riding position. And lets say that you can only generate 25% of the power while upside down...What effect will rotating your body position back 10 degrees? or 20, or 90 etc...
I have also long wondered if there is a way to determine how much energy is required by ones body just to turn the pedals over and not generate ANY power to the wheels. Think about it, your going downhill on your favorite bent and your freewheeling, generating ZERO power to the wheels but you are expending energy just spinning the pedals, and the moment you hit the bottom of that hill and you are still freewheeling but gravity is starting to pull your legs down allot more than it had been you are going to expend allot more energy to keep spinning even though you are generating ZERO power to the wheels.

Try hammering nails in different positions related to gravity. The force required to drive the nail into the board remains the same regardless but you will expend a huge amount more of energy to do this 90-120-180 degrees from vertical because of where your mass is in relation to gravity.

Anyone else having similar thoughts?


Mark.
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Hadden
recumbent enthusiast

United Kingdom
208 Posts

Posted - 01/12/2010 :  02:03:31  Show Profile  Visit Hadden's Homepage  Reply with Quote
I find I can produce higher peak powers on my recumbent.

Simon sanderson http://www.bhpc.org.uk/simon-sanderson.aspx http://www.youtube.com/my_videos http://www.flickr.com/photos/bhpclub/sets/72157604828238682/
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Tedd Wheeler
New Member

USA
74 Posts

Posted - 01/12/2010 :  05:46:01  Show Profile  Reply with Quote
On an upright, when you get up and "honk", you are using a much wider range of muscles including your arms and back, so you can produce more peak power than on a recumbent. I find that while honking my heart and lungs will quickly limit my performance because they can't provide enough oxygen to all those muscles. On the other hand, I'm finding my legs to be the limiting factor on my Gritters/trainer and I have trouble keeping my heart rate up.

I believe the above applies, but to a lesser degree while seated on an upright.




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alevand
human power expert

USA
3278 Posts

Posted - 01/12/2010 :  05:55:31  Show Profile  Visit alevand's Homepage  Reply with Quote
My theory is lactic acid builds up in the leg muscles when they are elevated due to lower blood pressure. I tried a test on my recumbent trainer. Measure watt output with arms down low and with arms raised over head. More power with arms over head because more blood in legs. I don't know if it is true will all muscles or just legs, it would be interesting to test arm endurance also.

C:
Tony Levand
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25hz
human power supergeek

Canada
1223 Posts

Posted - 01/12/2010 :  06:17:47  Show Profile  Visit 25hz's Homepage  Reply with Quote
I think the benefit of gravity on an upright is greatly underestimated. The only way to put force on the pedals of a bent is to push with the legs - and this can be augmented by pulling with the arms, but at the expense of firing a lot more support muscles in the core. It's even harder if you "bridge" as you hold your torso up against gravity. On a DF though, even with no leg strength at all, a stiff leg can utilize the help of gravity to stand on the pedal and let gravity push their body weight down onto the pedal, all at fairly low cost of effort compared to the energy a bent rider would have to expend to apply the same pedal force using nothing but leg strength. As mentioned, pulling on the handlebars increases the force even more. It'd be cool if a test was done to compare max DF seated force to max standing, and max standing with pulling. The ability to rack the upright left and right, and further increase the pedal pressure by levering the pedal up against the foot while the leg, body weight and gravity are pushing it down is another power advantage that can't be emulated on a bent. I think that either the aerodynamic benefits of bents are understated and more than the oft quoted 30% or in our minds, we underestimate how much effort it really takes to overcome air drag at higher biking speeds. The interesting thing is, that kids, who have little or no care, or understanding of physics, or the geometry of cycling, will intuitively stand when they need more power, and rack the bike left and right to increase their power output.

Gravity approaches max effect on a bent when the pedals approach the dead spots. While it helps (in theory) to push the front foot down, it's working against the rear foot coming up, and when applying power, the legs are moving at a tangent to gravity. Physics tells us the net effect will be negative when comparing the help and hindrance gravity provides. On a DF, the dead spots are pretty much free from the effect of gravity, and gravity is helping push down on the pedal, while pushing against the rear foot coming up. Again, comparing the foot going down, to coming up, the net gain from gravity will be negative. But, which pedalling action (with no body english involved) does gravity have more of an effect on (either positive or negative)? Recumbent legs or upright legs? Also, on a DF, you can add body weight by simply standing, which you can't add on a bent. You can also add pulling with the arms that is also augmented by gravity, whereas the pulling on a bent is limited to pretty much straight muscular strength. The line of force generated by pulling like that on a bent is more direct because the lines created by joining hand - shoulder - BB is a smaller angle than the same combination on an upright, but I think this doesn't so much "add" a benefit on a bent, as much as it reduces a defecit (the defecit being the lack of gravity's help). When the smoke clears though, the max power generation on a bent comes from leg strength plus arm pull, while on an upright comes from leg strength plus arm pull plus body weight/gravity. Now, if you add all that to that the physiology and performance differences in a recumbent body compared to an upright body, the fact that a bent rider can do so well, with so much less power being apparently produced, means that somewhere, when comparing DFs to bents, something, or a bunch of somethings are being over or underestimated.

I think a big help would be to get a strong rider who rides DFs and bents. Put them on an indoor track, or even an outdoor velodrome with suitably mild conditions. Get a lowracer and a DF, close in weight, and equipped with power meters. Have him do max power tests on the DF with legs only, standing, and standing with pulling (ie racking the bike from side to side like they're sprinting). Might be hard to separate the "standing" and "standing + pulling". Then, have him do max power on a bent with legs only, and then legs with pulling. Compare and see what the results say.
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randy
recumbent guru

727 Posts

Posted - 01/12/2010 :  08:34:24  Show Profile  Reply with Quote
quote:
Originally posted by alevand

My theory is lactic acid builds up in the leg muscles when they are elevated due to lower blood pressure. I tried a test on my recumbent trainer. Measure watt output with arms down low and with arms raised over head. More power with arms over head because more blood in legs.



I believe the second part of this statement. Raising your torso (seat angle) has the same effect. I don't believe it has anything to do with lactic acid buildup, though. I think it's simply a matter of delivery. I believe a full, upper body corset would boost performance on a recumbent provided it didn't impede breathing too much.

I think it's important not to mix up aerobic and anaerobic power when discussing this. I believe anaerobic power is affected much less by the recumbent position.
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Upright Mike
human power expert

USA
3813 Posts

Posted - 01/12/2010 :  09:12:32  Show Profile  Reply with Quote
Sean,

I have not been able to go as fast on my recumbent as I've gone on my upright with the old bodysock - yet. With recumbent training I hope to change that. I know that I can put out more power on my upright, it shows in my One Hour times being better on the upright. On my recumbent coast-down tests shows that it is faster than my upright. I agree with the statements above, that the weight of the legs is beneficial to adding power to each pedal stroke on an upright.

Edited by - Upright Mike on 01/12/2010 16:34:30
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Larry Lem
human power expert

South Sandwich Islands
2529 Posts

Posted - 01/12/2010 :  10:35:32  Show Profile  Reply with Quote
Don't laugh too hard at my power output, but..

recumbents, 7 years of training (not at all intense by racing standards)
dual 406 FWD lowracer, Garneau Prologue helmet, Fiesta Island 20 km TT, 29:00, 205 W avg

upright, 3 months of the same training, end of 2008 (mostly to acclimate to position) Softride Powerwing, nose of seat 50 mm ahead of bb (highly illegal), old Profile aerobars (elbows 2" further aprart than they should be), Casco Warp 2 helmet (because I couldn't keep my head up to warrant a longtail helmet) CH Aero cover rear, Specialized Tri-spoke front, Fiesta Island 20 km TT, 33:01, 232 W avg (coincidentally, 232W avg the week before at Piru).

I make 15% more aerobic power on the upright without too much training, but am 4 minutes slower over a flat 20 k in modern-day TT position compared to my small-wheel lowracer. Maybe I could get it down to 3 minutes with more position refinement. More importantly for this thread, the higher aerobic power was not due to training.

Larry Lem
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sean costin
human power expert

Lesotho
2005 Posts

Posted - 01/12/2010 :  12:00:16  Show Profile  Reply with Quote
You have to look at Larry's numbers seriously. My evidence is much more anecdotal, but if you have ever ridden against a comparable upright rider on the climbs, or on computrainer races where wind resistance is not a factor, you know that you are giving up something by be being recumbent. For most of us I think it is around 30 watts on continuous efforts.

Think about what it would be like to run without using your arms. Take a look at some seated climbing videos of the Tour de france. You see a swinging of the upper body left to right and a slight bobbing of the head and shoulders and perhaps a little rocking in the saddle. This is something we cannot do since we are fixed in recumbent position. I think these body oscillations of the upper body are similar to the way we use our arms to run. They are reinforcing or counter acting lower body movements.

Perhaps similar to a fish or a snake, we initiate an oscillation to one side of our body near the head and it carries through to the end of the body.

Sean

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randy
recumbent guru

727 Posts

Posted - 01/12/2010 :  12:35:36  Show Profile  Reply with Quote
quote:
Originally posted by Larry Lem



I make 15% more aerobic power on the upright without too much training, but am 4 minutes slower over a flat 20 k in modern-day TT position compared to my small-wheel lowracer.



Larry,

do you know how much power you lose in the DF TT position compared to the more open, normal position? That makes the difference between DF and recumbent climbing power even greater.
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randy
recumbent guru

727 Posts

Posted - 01/12/2010 :  12:46:57  Show Profile  Reply with Quote
quote:
Originally posted by sean costin

You have to look at Larry's numbers seriously. My evidence is much more anecdotal, but if you have ever ridden against a comparable upright rider on the climbs, or on computrainer races where wind resistance is not a factor, you know that you are giving up something by be being recumbent. For most of us I think it is around 30 watts on continuous efforts.

Think about what it would be like to run without using your arms. Take a look at some seated climbing videos of the Tour de france. You see a swinging of the upper body left to right and a slight bobbing of the head and shoulders and perhaps a little rocking in the saddle. This is something we cannot do since we are fixed in recumbent position. I think these body oscillations of the upper body are similar to the way we use our arms to run. They are reinforcing or counter acting lower body movements.

Perhaps similar to a fish or a snake, we initiate an oscillation to one side of our body near the head and it carries through to the end of the body.

Sean





Sean,

you can produce "x" amount (a lot) of wattage during the sprint. What is preventing you from producing that much wattage during a TT? Is it due to lack of stability in the recumbent position? Of course not, it's due to lack of oxygen in the working muscles. In other words, if recumbent instability doesn't prevent you from putting out over a thousand watts during the sprint it sure isn't preventing you from putting out 400 watts during a TT.

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steamer
Starting Member

USA
43 Posts

Posted - 01/12/2010 :  13:01:16  Show Profile  Reply with Quote
quote:
Originally posted by randy

quote:
Originally posted by alevand

My theory is lactic acid builds up in the leg muscles when they are elevated due to lower blood pressure. I tried a test on my recumbent trainer. Measure watt output with arms down low and with arms raised over head. More power with arms over head because more blood in legs.



I believe the second part of this statement. Raising your torso (seat angle) has the same effect. I don't believe it has anything to do with lactic acid buildup, though. I think it's simply a matter of delivery. I believe a full, upper body corset would boost performance on a recumbent provided it didn't impede breathing too much.

I think it's important not to mix up aerobic and anaerobic power when discussing this. I believe anaerobic power is affected much less by the recumbent position.



http://jap.physiology.org/cgi/content/abstract/75/5/1962

This study might back this idea up too. I have only read the abstract, though. Whether or not it's lactic acid specifically that is the problem, or some other metabolic inhibitor, I dunno. The exact mechanism makes me wonder as well, but it sure does seem that the body's ability to move oxygen, nutrients, lactic acid, whatever around from the blood to the muscle cells is fundamentally affected by posture (or perhaps more precisely stated, their positions relative to the heart).

Tom
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randy
recumbent guru

727 Posts

Posted - 01/12/2010 :  13:10:56  Show Profile  Reply with Quote
quote:
Originally posted by steamer

(or perhaps more precisely stated, their positions relative to the heart).



Absolutely. Unfortunately, raising the heart (past a certain degree) is the aerodynamic kiss of death.
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Larry Lem
human power expert

South Sandwich Islands
2529 Posts

Posted - 01/12/2010 :  13:31:56  Show Profile  Reply with Quote
I've trained with the PowerTap on the upright bike in a more upright position, but never raced with it in an upright position. I need to race in the TTs to make an honest, comparable, half hour-long effort. I lack the discipline to hold my level of effort that high for that long during training.

Beluga recumbent position is much more upright than my lowracer. I ran one test at Piru and Tom Amick did as well the following month about 3 years ago. I expected the more-upright recumbent position (more closed shoulder-hip-bb angle) to produce more power. But our power outputs were about the same as on our more-layed back lowracers. Mine was 195 W. That led me to conclude that shoulder-hip-bb angle did not have that much effect on aerobic power. Later, I ran 2 more tests with the Beluga experimenting with the partial fairings and power was 188 and 198 W. So again, same output as on my normal lowracer.

Larry Lem

Edited by - Larry Lem on 01/12/2010 13:36:12
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steamer
Starting Member

USA
43 Posts

Posted - 01/12/2010 :  13:49:21  Show Profile  Reply with Quote
quote:
Originally posted by randy

quote:
Originally posted by steamer

(or perhaps more precisely stated, their positions relative to the heart).



Absolutely. Unfortunately, raising the heart (past a certain degree) is the aerodynamic kiss of death.



So I guess it is yet again another variable that (ideally speaking) is adjusted to suit the kinds of speeds anticipated. Upright, closed angles for climbing, open laid back positions for the flats. The trouble of course, is that real world riding conditions (hills!) are constantly imposing different speeds on us. I know some folks have played around with 'adjust-on-the-fly' seat angles (one guy was on a Bacchetta, I think), but it might be tough to come up with reasonably simple mechanism that simultaneously adjusted the seat position back and forth to maintain a constant maximal leg extension as the seat angle was varied.

Tom
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randy
recumbent guru

727 Posts

Posted - 01/12/2010 :  14:39:53  Show Profile  Reply with Quote
quote:
Originally posted by steamer



So I guess it is yet again another variable that (ideally speaking) is adjusted to suit the kinds of speeds anticipated. Upright, closed angles for climbing, open laid back positions for the flats. The trouble of course, is that real world riding conditions (hills!) are constantly imposing different speeds on us. I know some folks have played around with 'adjust-on-the-fly' seat angles (one guy was on a Bacchetta, I think), but it might be tough to come up with reasonably simple mechanism that simultaneously adjusted the seat position back and forth to maintain a constant maximal leg extension as the seat angle was varied.



I've done the shift-on-the-fly seat and it works really good. The key to making it work is placing the pivot point in the seat back a number of inches above the seat valley so as not to disrupt pedal to hip distance.
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randy
recumbent guru

727 Posts

Posted - 01/12/2010 :  14:46:08  Show Profile  Reply with Quote
quote:
Originally posted by Larry Lem

I've trained with the PowerTap on the upright bike in a more upright position, but never raced with it in an upright position. I need to race in the TTs to make an honest, comparable, half hour-long effort. I lack the discipline to hold my level of effort that high for that long during training.

Beluga recumbent position is much more upright than my lowracer. I ran one test at Piru and Tom Amick did as well the following month about 3 years ago. I expected the more-upright recumbent position (more closed shoulder-hip-bb angle) to produce more power. But our power outputs were about the same as on our more-layed back lowracers. Mine was 195 W. That led me to conclude that shoulder-hip-bb angle did not have that much effect on aerobic power. Later, I ran 2 more tests with the Beluga experimenting with the partial fairings and power was 188 and 198 W. So again, same output as on my normal lowracer.

Larry Lem



I'd guess that once you get past a certain closed angle on a recumbent you would run into the same problem (pinched off blood vessels in the hips) that DFers do in their TT position.

Last spring I trained in the closed position and it didn't produce very good results (Diablo Challenge). The year previous I trained in a relatively closed (except about ten degrees more open than last spring) and achieved my best power and speed results ever.
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steamer
Starting Member

USA
43 Posts

Posted - 01/13/2010 :  05:09:09  Show Profile  Reply with Quote
quote:
Originally posted by randy

quote:
Originally posted by steamer



So I guess it is yet again another variable that (ideally speaking) is adjusted to suit the kinds of speeds anticipated. Upright, closed angles for climbing, open laid back positions for the flats. The trouble of course, is that real world riding conditions (hills!) are constantly imposing different speeds on us. I know some folks have played around with 'adjust-on-the-fly' seat angles (one guy was on a Bacchetta, I think), but it might be tough to come up with reasonably simple mechanism that simultaneously adjusted the seat position back and forth to maintain a constant maximal leg extension as the seat angle was varied.



I've done the shift-on-the-fly seat and it works really good. The key to making it work is placing the pivot point in the seat back a number of inches above the seat valley so as not to disrupt pedal to hip distance.



That sounds pretty cool. Good point about the pivot location. Do you have a picture of this bike? Is this one that you are currently riding? How much do you actually adjust on the fly during rides?

Tom
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alevand
human power expert

USA
3278 Posts

Posted - 01/13/2010 :  05:33:10  Show Profile  Visit alevand's Homepage  Reply with Quote
I just pull up on the handlebars to sit up on hills. My arms are stretched out normally. Some claim moving bb is good for climbing.

C:
Tony Levand
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randy
recumbent guru

727 Posts

Posted - 01/13/2010 :  08:15:09  Show Profile  Reply with Quote
quote:
Originally posted by steamer



That sounds pretty cool. Good point about the pivot location. Do you have a picture of this bike? Is this one that you are currently riding? How much do you actually adjust on the fly during rides?



Yes, they're on my blog ( http://fogcom-randy.blogspot.com ) for January of 2008. At the very least I would switch to the up position at every stop sign or light. Makes a world of difference for take-offs.
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purplepeopledesign
recumbent guru

Canada
689 Posts

Posted - 01/13/2010 :  11:41:42  Show Profile  Reply with Quote
Two days ago I rode my junk bent to go meet someone. The snow was a little too slippery so yesterday, I rode my mountain bike to the post office. Much better traction and control, but after, my calves were surprisingly sore. It could be that upright and off the saddle puts in the extra lower leg training that translates into more power?

:)ensen.

Those who claim to be making history are often the same ones repeating it.

Video of my trike
http://www.youtube.com/watch?v=MdSLRD_2vzc
Photos of my trike
http://www.flickr.com/photos/purplepeople/
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sean costin
human power expert

Lesotho
2005 Posts

Posted - 01/13/2010 :  20:39:52  Show Profile  Reply with Quote
Randy,

I am not very knowledgeable with the circulatory system. I thought it was closed loop and that pressures are consistent. If I took my blood pressure with an arm cuff while standing, lying down and upside down, would my blood pressure change?

I don't know if you are right or not, but even if you are I think to assume that there is just one big reason for the loss in power fails to appreciate the complexity of the problem.

As far as sprinting goes, I don't think the example you presented proves anything. If I was an upright cyclist I might generate more power due to increased mobility. No athlete can continuously put out an anerobic effort. Isn't it more than just Oxygen. Processing the energy takes time. More flow, may not be any more helpful at some point. I'm getting out of my area of experise, so at the risk of saying something innaccurate I'll stop.

I'm not saying that the power difference between upright and recumbent cyclists is that large. Maybe 15%.

If your theory was true, then how is it possible that elite recumbent rowers can put out over 400W for 20 Minutes. wouldn't their system be taxed by gravity as you suggest? Or is it that increased availability of muscles is helping to produce more power.

I'm not sure where you get the idea about recumbent stabilty affecting power. I am just talking about creating seat designs to take advantage additional lower body movement that could help boost power.

Sean

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steamer
Starting Member

USA
43 Posts

Posted - 01/14/2010 :  05:36:40  Show Profile  Reply with Quote
quote:
Originally posted by sean costin

Randy,

I am not very knowledgeable with the circulatory system. I thought it was closed loop and that pressures are consistent. If I took my blood pressure with an arm cuff while standing, lying down and upside down, would my blood pressure change?

I don't know if you are right or not, but even if you are I think to assume that there is just one big reason for the loss in power fails to appreciate the complexity of the problem.

As far as sprinting goes, I don't think the example you presented proves anything. If I was an upright cyclist I might generate more power due to increased mobility. No athlete can continuously put out an anerobic effort. Isn't it more than just Oxygen. Processing the energy takes time. More flow, may not be any more helpful at some point. I'm getting out of my area of experise, so at the risk of saying something innaccurate I'll stop.

I'm not saying that the power difference between upright and recumbent cyclists is that large. Maybe 15%.

If your theory was true, then how is it possible that elite recumbent rowers can put out over 400W for 20 Minutes. wouldn't their system be taxed by gravity as you suggest? Or is it that increased availability of muscles is helping to produce more power.

I'm not sure where you get the idea about recumbent stabilty affecting power. I am just talking about creating seat designs to take advantage additional lower body movement that could help boost power.

Sean




The blood's absoluate pressure is elevation dependant despite the system being a closed loop (hopefully - I hate the sight of my own blood ). Engineers use the term "static head". The pressure a fluid exterts on the walls of it's container increase with the height of the fluid above the location being considered. Highest absolute pressures at the bottom, lowest at the top. Think of submarines and the concept of the "crush depth", for example. The mechanism for how this might affect blood circulation through the arteries or perfusion rates at the muscles (perfusion meaning the process of getting blood borne nutients in the arteries into the capillaries and then to the muscle cells) is what I don't understand.

The study abstract I included a link to basically provides evidence that upon a call for additional nutrients and oxygen to be delivered to the muscles at the beginning of lower body exercise, the body is slower to respond to the needs of the muscles when the body is in a recumbent position than when it is in an upright position. It is not entirely clear to me to what extent this indicates a fundamental relationship between perfusion rates between the different postures in a general sense (regardless of the time frames involved), or if, in fact, the differences are limited to a short period of time at the onset of exercise (which was the study's test potocol apparently).

It appears this does not try to explain what is fundamentally at work in producing these results. The fully study might speculate on that - not sure 'cause I don't have it.

I have fiddled around with my seat angles a lot over the last two years, and I have noticed that I DO climb better with a more upright seat. The trouble with that anecdote is that there could be other reasons why I have observed this that have nothing to do with arterial blood flow rates, muscle perfusion rates, etc.

Tom
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alevand
human power expert

USA
3278 Posts

Posted - 01/14/2010 :  06:55:51  Show Profile  Visit alevand's Homepage  Reply with Quote
It is a closed system ,but everyone has experienced getting dizzy when standing up too fast. When recumbent climbing feet are more elevated than on level ground.

C:
Tony Levand
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