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FTP test as pseudo wind-tunnel test???

William JenksWilliam Jenks
in General Training Discussions

 I did two FTP tests about two weeks apart (long story why...doesn't matter).  I'm trying to use them as free wind-tunnel data. 

Test 1:  220 W, 15.3 miles, 21.9 mph

Test 2: 225 W, 15.8 miles, 22.6 mph

The course was exactly the same and the timing was the same to within a few seconds (42 minutes).  I don't remember the wind being much of a factor either day, but I can't swear to it.  In any case, the course is out and back, turning around during my 2 minute break. Today, I used zero aero bling (helmet, wheel, whatever).  I am pretty sure the same last time, but if anything, I would have been wearing the helmet at the slower test.  (I don't think so)

In between the two tests, I did an adjustment, lowering my elbow pads 12 mm, and I'm trying to figure out if the change is meaningful.  (The good thing is that dropping the pads made me more comfortable, not less.)

If I do the math right, the measured change in wattage should increase my velocity by 1.1% (=0.2 mph), but I actually got 0.7 mph benefit.

it seems like that kind of difference should be out of experimental error, and I should take this as verification that the change in position is a benefit.  But I wonder if anyone has had any experience doing this kind of thing and knows how much the scatter really is.

Thanks!

Comments

  • mgraffeomgraffeo
    Lots of noise in your conclusion. Was the road perfectly flat, or was there a slight elevation change, which would account for a big part of the difference? Wind, even small, can also produce an effect.

    There is a technique you can use which involves a multi-loop course. I have some info on it, but will have to dig it out. IMHO, I don't think you can draw a lot from the data you have.

    Mike
  • William JenksWilliam Jenks
    Yes, lots of noise and no it's not perfectly flat. But it is identical (except for the fact I went farther out on the same out and back).
  • John StarkJohn Stark

    Agree with Michael.  The other variables can include how much you slept the nights before, what you ate, your recovery level from prior days workouts, yada, yada, yada.  I know you know all this.  No way to make any type of meaningful conclusion.

    Upside is you are more comfortable in the lowered position. 

    Would love to see what Michael digs out.  I like to geek out on this stuff if/when I have the time.

  • Chris GChris G

     Hard to draw any conclusions from that sort of test.  The "home windtunnel testing" done by Tom A and some of the STers is fairly interesting but sounds like a LOT of work. Also best done in a big culvert.  Even a teeny bit of wind change [less than you can really perceive] throws it all off.  Unless you have a lot of free time on your hands I think you would be better off just doing more training or swimming or something.

    All that said, If it feels faster and you went faster sounds like a good change.

  • William JenksWilliam Jenks

     OK, fair enough. Just didn't know how big a deal modest wind effects etc would be. Thanks. Not clear to me what difference fatigue etc would make because you can normalize for differential power. Within reasonable limits, velocity goes as the square root of power in the 20 mph region, all else held equal. I'm sure there's lots of places to find the equations, but they are here.

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