i think the "breathing" issue is urban mythology. i think ventilation is rarely an issue in bike positioning. i think "opening up the lungs" is a proxy for other things, like, opening up the hip angle so that a mechanical advantage can be gained over the resistance that needs to be overcome.
elbows in tight, position too stretched out, armrest drop too low, are all problems, or can be problems. i just don't think they're usually problems of ventilation. of course, it's easily tested with a fit bike and a spirometer. still, even if a position caused a drop from, say, 4 liters of air per inhalation to 3.9 liters, you'd still have to demonstrate that uptake was compromised.
i'm not stating this as a fact, rather as an opinion. it's a guess, and my guess may be inaccurate. but i haven't seen anything yet that suggests that ventilation is the determiner of TT positions to the degree people seem to think they are.
That's a very good point. TT's are almost never at VO2max effort, so compromising more than a few % of maximum breathing might not be an issue.
Regarding the stretched position... I found this on the Team SKY website.
contrast to the 2009 TdF photo
He looks pretty far forward perched on both saddles. Perhaps more so for the TdF? It could also be a longer saddle. Though it does look like he is farther aft in his overall position and more "stretched out"... I wonder if this is an aerodynamic advantage?
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