Info on workout CFo21

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    I just completed workout CFo21 as part of the level 3 Half Ironman plan. It’s got 30mins warm up the 10x1min in Z5, then 55mins in z2.

    I would like to understand more about the objectives of this workout (it’s hard). My thoughts are:

    1) build maximal Aerobic Power with the 10x1min z5 intervals (for me that’s around 335watts)

    2) fatigue the legs early in a longer aerobic Z1/Z2 ride, building muscular endurance

    3) get the legs to learn how to process lactic acid on a long ride

    Is this correct or something else?



    David Warden


    Your inquiry comes just as I am finishing up a presentation on interval training for our upcoming San Diego clinic next week. See section 4.1 and 4.2 of for the benefits of those CFo21 (Zone 5, HIIT) intervals. That meta study says it better than I can.

    You’re right on on #1, but those short CFo intervals don’t really promote your #2 and #3. The RCI and CCI series do a better job of promoting your #2 and #3.


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