30-min Threshold Field Test | 80/20 Endurance

30-min Threshold Field Test


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  • #8533

    Hi! I’m relatively new to 8020 running and am loving it so far. I have a question regarding the threshold field test for heart rate, power, and pace. They are all 30 minutes, and my understanding is that the threshold values are for what your body can maintain for 60 minutes. Why is the test only 30 minutes?

    My concern is that I’ll be training too strong in Zones 1 and 2 and end up in that dreaded in-between zone (I think you call it X). I know I can just train in the lower end of the zones and that’ll fix any problem, but I’m curious to understand the thinking behind the 30-min test.

    Thanks so much!

    David Warden

    Eldon, welcome!

    Although lactate threshold is in fact the intensity which can be maintained for an hour, the 30-minute test is commonly used for self-field testing because an observed test will produce higher output than an unobserved test. This is not a “tree falls in the woods” philosophical issue, but an actual athletic phenomenon where performing a test while being watched increases output by around 5%. Therefore, a 30-minute test done alone will likely have the same result as a 60-minute test in the lab. In other words, a 30-minute test unobserved equals a 60-minute test observed.

    This has another advantage, in that most of your training will take place unobserved as well, which allows the thresholds results and application of the corresponding zones to align.

    Of course, there is a range in which athletes respond to being observed. We’re likely robbing or rewarding athletes who would fall well outside the normal range. But, given that we have to accommodate a “typical” athlete in all decisions when writing a plan or protocol, we’re comfortable with using 30 minutes.

    There is also a practical side to this decision. A 60-minute test is impractical to perform regularly (every 3-4 weeks). It’s difficult enough to do 30 minutes. Plus, the recovery time from a 60-minute test is significant.

    Finally, the 30-minute test has proven to be effective. We can get 98% accuracy out of a 30-minute test, perform it more frequently, and reduce risk of injury from adopting this shorter protocol.



    Thanks so much for your detailed response!

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