Bike power zones | 80/20 Endurance

Bike power zones

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    Hi David,
    I am planning to do most of the Zone 2 rides (in the week/winter) on zwift and in the TT position. My current FTP (288 done as ramp test) was done on a road bike which which I presume is 15 to 20W higher than if I do the ramp test in the TT position.

    I realised with current FTP, the lower Z2 power is the same as power generated during my last 70.3 in October (211W on a 100% flat course in TT bike), so wondering if I should lower the FTP by 15-20W when im doing the Z2 rides in the TT position to make sure I dont go into the X zone. When I do the high intensity intervals I can push further and i can switch back to the higher FTP to make sure I get quality workout. What do you think?

    My power Target for the full IM is around 220 which is a step up from my latest Half IM power output of 211 this year.

    Thanks as usual

    David Warden


    This is a great question, really glad you asked it.

    This issue is at the root of looking at the purpose of each workout. Each workout’s goal can be categorized into increasing General Fitness goal or Specific fitness goal (some workouts target both, but at a minimum, each workout segment is focused on one of these two categories).

    Yes, TT position is going to generate less power than road position, and the aerodynamic tradeoff is always worth it. However, while 10-15 watts is a typical decrease in FTP in TT position, it’s different for each athlete. Can be as little as 5 and as much as 20.

    So, the best option is to have an FTP tested in TT position and get your precise zones for TT.

    Regarding the bike position when performing higher intensity intervals, it depends. If you are a Sprint or Oly athlete, a significant amount of your intervals should be done in TT, because that it the position you will race in (Specificity). If you are an IM or 70.3 athlete, you can maintain road position for all intervals, because you won’t be in TT position for Zone 3+ in your event. This gives you a better opportunity to increase General fitness.

    For either short or long athletes, at least half of your total cycling time should be in TT during the last 8 weeks of training.


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