20-minute test: heart rate result disagrees with pace and power?

Tagged: , ,

Viewing 3 posts - 1 through 3 (of 3 total)
  • Author
  • #21007

    I just completed a 20-minute time trial and am looking at the results in power, pace, and heart rate after running them through the calculator—and comparing them to my performance in actual day-to-day running in terms of both pace and power, the numbers just seem to be way off.

    • My average HR for the final 15 minutes was 180bpm. (That is roughly what I expected: on my last half marathon for which I have data, my peak 20-minute HR was 177bpm, and it averaged 179bpm on a Relaxed 5k Time Trial workout in mid-September.)
    • My average power over the whole time trial was 383W (per data from my Garmin HRM-Pro Plus strap).
    • My average pace was 6:15/mile.

    This gives me a LTHR of 180bpm, a LTP of 365W, and a LTPace of 6:35/mile. However, when I compare this to actual real-world Z2 work of late, it is wildly out of whack. The targets that gives would be:

    • HR: 146–162 bpm
    • Pace: 8:39–7:34/mile
    • Power: 277–321W

    On actual runs, though, I am fairly consistently turning in ~7:30/mile with my HR in the 148–152bpm range and power in the 345-355W range (e.g. exactly those on a 100-minute endurance run last week).

    What’s more, that puts my Z5 HR at 189+, and that’s very nearly my max HR. Meanwhile, I can run 5:30/mile for a minute and see my HR sitting in the mid-180s, not somewhere north of 190, even though that’s the Z5 range per pace according to this.

    For a previous test, I had previously been incorrectly remembering and taking 95% of the HR value, which in that previous test put the HR number at 172. That maps much more closely to the pace numbers I am seeing, but even there the power numbers would be weirdly low by comparison. (Mind: I run on the Colorado Front Range and there’s never less than 200 feet of climb in any run I do from my house, but I would expect down to balance up for that.)

    Long story short, I have no idea what to make of the test results or the data! Input very much welcome.


    Oh, and for whatever it’s worth: the 20-minute test also gives me a meaningfully slower pace value than my most recent half marathon performance, which was a 1:26:30 and gives me a threshold pace of 6:26/mile and a Z2 range of 8:28–7:24/mile, which much more closely matches my actual experience on Z2 runs!

    Leyla Porteous


    Training Metrics can certainly be over-whelming and confusing – and this is why we recommend picking a metric that makes sense to you and is consistently reliable for training purposes.  Testing is just an opportunity to set/adjust training zones or you to train to (and these are pretty wide ranges that will vary in output in differing environments and conditions). These zones are designed to allow you to get the most out of your training and avoid potential over-training.

    Looking at your results from your most recent 20min time trial and the pace and heart rates efforts you are seeing I don’t see a big discrepancy with training data there other than your power metric – which given the big difference between your training data and your testing data I would say that is some sort of recording error or inconsistency (where are you taking your power info from – Garmin or a Stryd pod).  For the Pace to HR, again this why we recommend choosing pace or power to train to, as it’s not uncommon to see wider variance in HR data in training and testing due to external factors such as excitability, temperature, fatigue, caffeine etc.  Heart rate also has a lag and it’s difficult to reach your true max heart rate outside of a testing/racing situation.

    HR: 146–162 bpm  – 148–152bpm

    Pace: 8:39–7:34/mile – ~7:30/mile

    Power: 277–321W –  345-355W range

    You will not always see a perfect match up between pace/power and HR due to the issues I mentioned above with Heart rate as a training metric.  Choosing pace or power to train to is a better option, then keeping an eye on HR (or RPE) to ensure that you are not drifting across your HR zones (which can happen when it’s hot, terrain, or fatigue).

    Here is a resource which covers what I have mentioned above in more detail. But in short for now, I would recommend only updating training zones if you have noticed a significant change in your metrics, ie HR very low to pace indicates pace threshold can be lifted or the opposite where HR is consistency high to pace, then pace zones may need to be dropped.

    Intensity Guidelines for 80/20 Running

    Hope that’s helpful in explaining zones setting and training zones/metrics.

    Coach Leyla





Viewing 3 posts - 1 through 3 (of 3 total)
  • You must be logged in to reply to this topic.
Posted in


You must be logged in to create new topics and to reply to topics.