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Juerg Feldmann

Fortiori Design LLC
Posts: 1,530
I got a nice test sent in to me  or better a challenge from a friend.
 His challenge to me was :
 I did some bike fitting and I like you top tell me what i changed in this customer  a few times in a row. I changed from 2  different position position one and than back to position 2. What did d I changed. Moxy was mounted on vastus lateralis.
  First of all this is great and  this is not the first challenge as Roger sent me a challenge form another source  asking us what  we can ready out of the moxy data's. We never got a real direct feedback on whether we where right but as I told him , that he manipulated with an " unnatural way the result  he kind of asked some more questions but we never got a clear answer. Which means  perhaps we where not that wrong.
 So I will try here as well.
 The picture below is the challenge  an the PP below is the answer.
 I will mail what the U d means to the Challenger  and see, whether I was close to  what he did.

Attached Images
Click image for larger version - Name: per_train_thb.jpg, Views: 16, Size: 63.51 KB 


Fortiori Design LLC
Posts: 65
Ill take a crack at this, because, IF I am right, this will open a can of worms about the rational behind time trail positioning in cycling (something that is already under debate or should be). The up and down dynamics are the result of changing positions from an upright position to a time trail down position. Why does this happen? Amazingly finding studies that discuss this is quite hard, from a baseline point of view this study identifies some groundwork for the changes.

Alveolar oxygen uptake and femoral artery blood flow dynamics in upright and supine leg exercise in humans

  1. Maureen J. MacDonald
  2. J. Kevin Shoemaker
  3. Michael E. Tschakovsky, and 
  4. Richard L. Hughson

+Author Affiliations

  1. 1 Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
  • Submitted 3 July 1997. 
  • Accepted in final form9 July 1998.


We tested the hypothesis that the slower increase in alveolar oxygen uptake (V˙O2) at the onset of supine, compared with upright, exercise would be accompanied by a slower rate of increase in leg blood flow (LBF). Seven healthy subjects performed transitions from rest to 40-W knee extension exercise in the upright and supine positions. LBF was measured continuously with pulsed and echo Doppler methods, andV˙O 2 was measured breath by breath at the mouth. At rest, a smaller diameter of the femoral artery in the supine position (P < 0.05) was compensated by a greater mean blood flow velocity (MBV) (P < 0.05) so that LBF was not different in the two positions. At the end of 6 min of exercise, femoral artery diameter was larger in the upright position and there were no differences inV˙O 2, MBV, or LBF between upright and supine positions. The rates of increase ofV˙O 2 and LBF in the transition between rest and 40 W exercise, as evaluated by the mean response time (time to 63% of the increase), were slower in the supine [V˙O 2 = 39.7 ± 3.8 (SE) s, LBF = 27.6 ± 3.9 s] than in the upright positions (V˙O2 = 29.3 ± 3.0 s, LBF = 17.3 ± 4.0 s;P < 0.05). These data support our hypothesis that slower increases in alveolarV˙O 2 at the onset of exercise in the supine position are accompanied by a slower increase in LBF.

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