we are never objective observers of ourselves.

im just trying to even imagine the mechanics of how it could restrict breathing. its not physically taking up space that my chest is trying to expand into, to have my elbows narrow.

---

---

Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

I'm talking more about power over a few minutes rather than 20 minutes, though even over 20 minutes it becomes an issue with varying terrain where you need short periods of much higher power. I know I am pulling on the bars quite hard for my 1 minute max power, my peak pedal force is around 150% of my bodyweight, so it isn't surprising to me that I need to do that. I'm hundreds of watts down on power if I try to do an effort like that in the aerobars. Perhaps I should be pulling up more with the other foot to cancel out the force, I'd have thought that unless you do that, applying a lot of force with one leg is always going to move your body away in the opposite direction? I must be doing something wrong because I find it very very hard to cycle at 476W for any duration at all in the TT position, whereas Wiggins does it for 19 minutes. But on the hoods pulling against the bars I can sustain 476W for a few minutes.

I just did this -- I can breathe MUCH more deeply with my elbows at shoulder width than with them touching. I have a 40-41" chest, though, and with my elbows touching, it's the stretch across my back that limits how deeply I can breathe. With my elbows at shoulder width, it's my chest/diaphragm that limits it. Elbows about 6-8" apart is almost the same as elbows at shoulder width.

Now, whether or not this makes a difference when riding at threshold, I can't say. But certainly for some people elbow width is going to affect their ultimate breathing ability.

Asad

if we're to assign cause to a drop in power, i think we have to separate fit coordinates from ventilation. it may be that narrowing elbows restricts ventilation, and that this restriction in ventilation further restricts uptake. but this is just intuited on your part. it's not proven.

i have no doubt that discomfort on the bike affects power. i just question whether your power-restricting-discomfort comes from a lack of ability to take in a full inspiration, or whether your power-restricting-discomfort comes from an inability to rest comfortably aboard a bike, with an economy of motion, allowing you to concentrate your efforts toward producing power.

---

Dan Empfield
aka Slowman

maybe my lungs are tiny.

would explain some things ;)

---

---

Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

I'm obviously in the Jack Mott camp on this one as I have no difference if I'm riding a 6 mile TT or a 112 mile TT, going steady on the flats or pulling hard over a little rise. More aggressive and tighter works for me with regard to speed and power. But I think this is another great example of 'viva la difference.' It wouldn't be any fun if there was one set of equipment or position that was clearly the only way to go. Part of the fun of this great sport is experimenting with different 'stuff' to see what works best. I've been doing this for 20 years and for the first time ever, I feel like I have my bike and position dialed in perfectly. Next month, I'm sure I'll be coveting something new and different (btw, put me down for a huge fan of the Sky TT helmet!).

I'm in the process of fitting a new rig, and the shop had me do _exactly_ that test, because I can set the pads as narrow as I like, with no discomfort. However, and obviously this is personal, there was zero doubt that the narrowest setting restricted my breathing.

But isn't the bigger performance issue related arm width likely to be how your arms line up w/ the rest of your body, especially your hips and knees (and ability to shield them from the wind)? My understanding is that there is no clear rule on narrower=more aero, because the 'optimal' width for the pads depends on other measurements, too, which are different for different bodies.

I am pretty sure the difficulty in breathing based on elbow position is an individual thing. My room mate in college could not make his elbows touch at shoulder height (in front of him). The subject came up as I was trying to explain why his breaststroke form sucked. I can do it easily and thought that everyone else could too. I'm pretty sure that someone who can't make their elbows touch will also have trouble breathing when their elbows are closer together on the bike.

You are absolutely correct, my assertion is not proven. But, I have experiences and testing that lead me to believe it is a reasonable (and not disproven) hypothesis. So I will take my admittedly anecdotal evidence and weigh it against the evidence you have brought forward. Wait, what evidence is it that you are presenting here?

---

---

Erik
Strava

again, i don't doubt that a change in your position causes you to lose power. i'm questioning your certitude as to causation. as to my evidence, my evidence that you lack evidence is your lack of evidence. that's my evidence. i'm not asserting causation.

just, over the years i keep hearing an impingement on one's "breathing" put forward as the cause proximal to a lack of power. i'm very suspicious of this. if i take you at your word - and i do - that a change in position caused a drop in your power, then all you and i know is that the change of position caused a drop on your power. the further mechanics behind your loss of power is still a mystery. you can guess it's that your ventilation was compromised. maybe so. but i think there's big room for doubt.

my only point here is that people should stop taking for granted that moving the aerobars too low; moving the elbows too close; impinges breathing. such changes make you uncomfortable. it might impact on the mechanics of how you push down on the pedals. it may very well cause a reduction in power. but it's an unvalidated leap to say the change in position decreased your ventilation which in turn caused a decrease in power.

---

Dan Empfield
aka Slowman

In my experience, the narrow elbow positions (regardless of aerobar height), coincide with both a decrease in power and a corresponding feeling of not getting enough air. I admit it is not an objective measure, but I don't think one should call it "no evidence". That many other people experience the same sensation is curious.

I guess I'm equally suspicious of the nebulous "change in mechanics" explanation.

Maybe I could borrow that neat machine my asthma doctor had me blow into to measure lung capacity...

---

---

Erik
Strava

Phil, that's because you are a triathlete playing with the roadies. Triathletes are "buffer", you stick out like a sore thumb in the peleton.
;-)

Ha! And here I was thinking I was a swimmer playing with all the triathletes:-) Way to much fun to be had out there to limit myself to one sport. Now it's Tuesday night, get yourself to PIR and come play with we roadies.

Also, I can't escape the irony that after the best part of 25 years Shimano have applied "PROtotype" to a wheel that was a genuine Du Pont prototype in the late eighties.

Obviously not an issue...

Perhaps the trendy "ultra-aero-covered-stem" cable routing is superfluous.

le sigh....

I'm wondering if "the most aero athletes " for armstrong means less drag becouse of smaller frontal area and less speed [cd is dependent on speed as one factor]; and yeah, that helmet looks like it would generate a lot of turbulance in the back!

---

res, non verba

The word on the street is Cd does not change from 15-35mph. I guess you could run the reynolds number calculations if you want

---

Ride Scoozy Electric Bicycles
http://www.RideScoozy.com

The street is wrong, aerodynamic drag increases exponentially; if you double the speed the drag increases fourfold

---

res, non verba

familiarize yourself with the terms in the equation: http://www.grc.nasa.gov/...airplane/drageq.html

Cd is not drag force. D is drag force.

also quadratic is not the same as exponential.

Surely the trick is to just breathe more frequently - a la Gary Hall Sr.

"Cd" is the coefficient of drag (ie, how 'sticky' a given surface appears to the wind, a function of the object's shape and surface, or "form drag" and "surface friction") and is by definition a constant with respect to velocity, and thus does not change, not only within a range, but across all apparent wind speeds.

But the poster's math is correct (2x the speed = 2^2 = 4x the drag): the drag created by an object, of a given surface area and with a given Cd, increases with the square of the velocity (which as jbp notes is an exponent, but not "exponential").

For those that enjoy math and find it annoying hard work to increase their ground speed, the really harsh reality is that the power required to move an object through a viscous medium at a given speed is proportional to the speed times the drag. Since drag increases quadratically with velocity, required power increases with the cube of velocity (2x the speed = 4x the drag = 8x the power). Which is of course why the absolute speed differences between say a high level amateur and pro get small relative to their large differences in power output on a TT course, while their speed difference on a steep hill is enormous.

Hard not to notice that he is riding an Osymetric chainring in both pictures.

---

Thomas Craven
Osymetrican
Owner/Evangelist
OsymetricUSA.com
info@osymetricusa.com

I believe we assume a constant Cd. This may be an valid assumption most of the time (and it certainly makes calculations easier) but isn't it possible for the coefficient to change depending on the speed as a result of some kind of interaction with the air?

edit:

http://en.wikipedia.org/wiki/Drag_coefficient

"In general, is not an absolute constant for a given body shape. It varies with the speed of airflow (or more generally with Reynolds number). A smooth sphere, for example, has a that varies from high values for laminar flow to 0.47 for turbulent flow."

We assume the coefficient is constant much in the way we assume a spherical cow...