Neuromuscular power question--for A. Coggan (or anyone else)

Discussion in 'Power Training' started by D-Yob, Jul 28, 2006.

  1. WarrenG

    WarrenG New Member

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    Well, for those of us who can sprint at least reasonably well, if I start a sprint on flat ground near my optimal cadence for this kind of test I rapidly go above that optimal cadence, thus my mention of doing it on an uphill to keep the cadence from going up too far.

    Practiced technique really can make a difference.
     


  2. WarrenG

    WarrenG New Member

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    No. Training to improve the length of your sprint could help a lot.

    Your peak power was close to 120 rpm's. Not unusual, but try to start your test closer to that cadence and see if that helps make the watts higher. Practice sprinting at rpm's from 110-130 will help too.

    Of course, by the end of a race you probably can't do the same high rpm's that you can during your rested test, so you'll have to decide which information is really the most useful to you.

    FWIW, I often do sprint training after other training in the session that is not easy.
     
  3. Billsworld

    Billsworld New Member

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    Thats similar looking to lots of mine. Different numbers though.
     
  4. Spunout

    Spunout New Member

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    Nope, quite similar to mine.
     
  5. acoggan

    acoggan Member

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    If that's the case, then you haven't met the criteria I described. You need to be going slower when you start, pick a bigger gear, or do the sprint uphill (as you do).
     
  6. acoggan

    acoggan Member

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    I think it's more indicative of the difficulty the PowerTap has in determining cadence when it's changing rapidly.
     
  7. Spunout

    Spunout New Member

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    Frenchy: Were you using crank or hub cadence?

    Mine: Hub cadence, hence the jerky response.

    Interesting: Our peak power occurs at about 115 rpm. So, should we try jumping from 115 rpm (slightly uphill) and then shifing for optimal sprinting performance? (where optimal perfomance for me is peak power and 5s power). I also have a goal to not lose speed at the end of a sprint.

    Remember, we're talking about two different things in this thread: Training sprinting and sprinting. In a competition situation I'd never wind up a 39x17 from a stop, but I do appreciate that it builds needed strength.
     
  8. WarrenG

    WarrenG New Member

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    Going slower or using a bigger gear results in a lower cadence. Doing it uphill tends to keep the cadence (and speed) about the same during the effort.
     
  9. Billsworld

    Billsworld New Member

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    That flat line at the 140 mark looks like the cadence might have gone into default mode. I have had the magnet fall off, and it still gave estimates. I was doing some high cadence sprints and PT kept giving me 141 for max cadence.
     
  10. fatrat

    fatrat New Member

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    How have you attached the magnet? The PT ziptie thing looked useless to me so I just took the magnet out and attached it to the crank with some araldite. Job done.
     
  11. stevevinck

    stevevinck New Member

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    Having read "the" book and looked at the power profiling I did some sprints today and reached for 900 watts (5 seconds).

    In the power profiling this gives me a rating of untrained :confused: ? Do I miss something or am I really that bad in sprinting

    treshold 288 watts
    75 kg for 1m82
     
  12. Spunout

    Spunout New Member

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    You're not a natural sprinter. That is what it tells you. But it can be trained to acceptable levels.
     
  13. WarrenG

    WarrenG New Member

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    Practice sprinting for a month and then see what it is. Maybe two times a week, do a few 10-12" sprints out of the saddle in something like 53x19, from various starting speeds, mostly on the flat but occasionally on a slight rise. Just 3-4 in a session, with about 4-5' minutes between sprints.
     
  14. acoggan

    acoggan Member

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    Try sprinting from a dead-stop in a 39x15, then post your file here.

    (PS: What sort of power/mass do you suppose it takes to cover 250 m in ~15.5 s from a standing start?)
     
  15. tigermilk

    tigermilk New Member

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    I'm thinking around 25 W/kg, or at least that's what my code spits out. Low ball estimate of 18.4 W/kg is no good (P/m=acc_avg*vel_avg+Fdrag*vel_avg/m, vel_avg^2=2*acc_avg*s). I'm in no jeopardy of hitting either value for 15.5 s.
     
  16. acoggan

    acoggan Member

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    Sorry, try it w/ an air density commensurate with ~1850 m.
     
  17. tigermilk

    tigermilk New Member

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    How about a heavier rider (200# rider+bike), 25 inHg, a rather pleasant day at altitude (60 F), a VERY good CdA for sprint position (0.33), and some lower rolling resistance (.004) which needs a whopping 2200 W for the effort?
     
  18. WarrenG

    WarrenG New Member

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    Does the rider get out of the saddle for the standing start? For how long?
     
  19. acoggan

    acoggan Member

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    Are you sure about those calculations? I was coming up with a really high power/mass, but not that high.
     
  20. tigermilk

    tigermilk New Member

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    To accelerate from a dead stop with constant power? Yes. I compared my results to http://www.analyticcycling.com/DiffEqMotionFunctions_Page.html and they are pretty much dead nuts on. Since the analyticcycling site and my code both solve the diff. eq., I have confidence the 2 independent models are getting the correct value.

    You can get a VERY SIMPLE estimate by basic physics

    1) assume constant acceleration - distance=.5*acceleration*time^2
    2) solve 1) for acceleration (a=2.08)
    3) accounting for only acceleration (i.e., no rolling resistance or drag), P=F*v=m*a*v
    4) use v=v_average=distance/time for an estimate, so v=16.12 m/s
    5) P/m=a*v=33.56 W/kg

    Admittedly, 33.56 W/kg is a bit high since you wouldn't have constant acceleration. Nonetheless, I'll stick by my numbers.
     
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