Determining 1 hour power

Discussion in 'Power Training' started by velomanct, Feb 28, 2004.

  1. velomanct

    velomanct New Member

    Dec 21, 2003
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    i want to find out what power i could do for a 40km/1 hour time trial, without actually doing one.
    i like doing an 8 mile time trial, which takes me about 20minutes.(this TT is very simular to a TT at a stage race that i am peaking for in july. so i like doing this TT every 2 or 4 weeks for practice. there is 400ft of climbing total, and the finish line is 60ft above the start.)
    is there a formula for determining 1 hour power from this 20minute time trial?
    the reason i don't want to do the full 40km is that such an effort is so hard on my body, especially at this time of year.
    i am looking to find my 1 hour power so i can set up zones.

    today i did the 20minute time trial with an average watts of 307.
    i am thinking that my 1 hour power would be 290watts.
    does this sound right?

  2. ric_stern/RST

    ric_stern/RST New Member

    Nov 11, 2002
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    If you want to know what you can do for a 1-hr TT, your best bet is to do one...

    Else, take a few watts off your 20-min effort (exact amount will vary person to person), or do an incremental test to exhaustion, and calculate your MAP. one hour TT power will most likely be 72 to 77% of your MAP.

    Be aware that your TTpower isn't a fixed number, it'll increase and decrease with training and detraining, and there'll be biological variation as well. Environmental and topographical factors will also impact on the result.

  3. acoggan

    acoggan Member

    Jul 4, 2003
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    You could do another TT of around 3 min duration, then plot work (in J) accomplished vs. duration (in s) for the two efforts and fit a straight line. The slope will be your critical power, which generally corresponds very closely to what people can maintain for a 40k in competition. (Alternatively, you could extrapolate the line out to your anticipated time, and divide the predicted work by time to arrive at a predicted power...but as Ric alludes to, there's enough day-to-day variability that such extra precision probably isn't necessary.)