Interval workout progression and choice | 80/20 Endurance

Interval workout progression and choice

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    When creating a training plan what drives the choice of which interval session to complete? When would you choose to lengthen the intervals vs repeating the same session or increasing the intensity?

    For example, lets take one threshold session on the bike for each of the coming weeks. I would plan to do 4×6′ week 1, 4×8′ week 2, and straight 24′ on week 3, all at equal power. This seems like a nice progressive overload. On the other hand would you choose to repeat the 4×6′ session and look to increase the average power output each time?


    David Warden

    S. Wow, what a great question. I don’t know if I can do it justice.

    As the co-author of the triathlon plans, I’m confident in the empirical evidence behind the interval:rest ratio and the interval intensity:duration ratio used in our plans. See Chapter 20 of the book Triathlon Science for a thorough review of why the intervals are structured this way.

    Your question, however, is the next step. What is the correct week-to-week progression of those interval sessions? This decision should be driven by the Principle of Specificity. In the early (General) phase of training, it’s better to maintain shorter, less frequent work intervals performed at the upper end of the zone in order to maximize thresholds and VO2. During the latter (Specific) phase of training, the work interval duration should be extended to more closely match the specific demands of your upcoming race. For some athletes, this is the lower end of the zone and for some the upper, it depends on abilities.

    These phases can be chained together as you have described, 4×6 to 4×7 to 5×6 minutes… all the way to 5×12 minutes of Zone 3 and 6×30 minutes of Zone X. In the General phase, you’ll know it’s time to increase the work interval duration if you are able to consistently maintain the upper level of the interval. At some point, you might get “stuck” and that’s OK. Regardless, you would want to move onto the Specific phase and start to perform longer work interval durations and intensities that mimic your race.

    For Sprint, Olympic, 5K and 10K athletes, the General and Specific phase intervals can be very similar (lot’s of Zone 3). For half marathon and longer, in the the intervals Specific phase should be quite different from the General phase, as Zone 3 is not a race pace for those longer distances.



    Excellent information. Thank you David!

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