Threshold testing in the new 2021 marathon plan | 80/20 Endurance

Threshold testing in the new 2021 marathon plan

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  • #10130

    Hi there
    My partner is working with the new 2021 Marathon plan (pace as the metric) but i cannot see anywhere through the workouts, indication of retesting. Obviously this is important to ensure workouts are executed at the desired intensity, but I’m struggling to see where they are.
    I am following an Ironman plan and there is opportunity on it to test each easy week (not that i want to put myself through those every three weeks or any benefit to that but option is there)
    Please can you clarify so I can best guide her

    David Warden


    This is addressed in our document Intensity Guidelines for Triathlon but I have included the relevant section below for your convenience:

    Threshold Testing
    Because your fitness level and lactate threshold can change quickly, it’s important to keep your thresholds and zones current throughout the training process by retesting your lactate threshold every few weeks. Repeating your chosen field test in every recovery week (recovery weeks fall ever third or fourth week in our 80/20 Triathlon plans) is the theoretical ideal. As a practical matter, however, this is onerous for many athletes.

    Fortunately, your 80/20 training plan includes Swim Time Trial (STT), Cycling Tempo (CT), and Running Tempo (RT) workouts that may serve as zone testing sessions. Most of these sessions feature Zone 3 effort that are less than 20 minutes in duration. Advanced athletes can replace these workouts with the 20-minute time trial described above. Another option is to use the “backing in” method of verifying running threshold pace or cycling or running threshold power. Because LTHR changes less than TP and rFTP over the course of a training plan, you can retest either of these variables in the context of CT and RT workouts featuring Zone 3 efforts as short as 10 minutes by adjusting your effort until your heart rate levels off at your previously determined LTHR and observing the pace or wattage that corresponds to it.

    Alternatively, the Talk Test can be performed during any Foundation Run or Recovery Run whenever you feel that you have “outgrown” your current zones and act as a provisional threshold until more formal testing can be done.

    Also note that if you are an intermediate- or advanced-level athlete and you use heart rate as your primary intensity metric, you probably don’t need to update your zones very often. This is because LTHR doesn’t change a lot with changes in fitness once you’re past the beginner (or starting-over) phase. What you will find as you gain fitness is that you run faster and faster at the same heart rates. Indeed, one simple way to update your pace or power zones is to do a test where you run at your current known LTHR and identify the corresponding pace/power, then plug this number into the appropriate calculator. For example, if you know that your LTHR is consistently stable at 160 BPM but you notice that you’re running faster at any given HR lately, do a run where you lock into a heart rate of 160 BPM and note the corresponding pace/power. Say your pace is 7:07/mile at this HR. This, then, is your approximate Threshold Pace. It’s best to do this particular test within the context of a scheduled run that targets Zone 3.

    Note that CT and RT sessions occur less frequently in the L2 and L3 plans because 1) the high volume of these plans makes frequent high-intensity/high-duration testing risky, 2) we assume advanced athletes have a longer training history and are already confident in their lactate threshold, and 3) advanced athletes tend to experience smaller changes in lactate threshold than do beginner athletes. But if you ever feel you’re “outgrowing” your zones, feel free to insert one of the easier testing options into your next recovery week if it does not already contain a CT or RT session.


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