Power Based Workouts are slower comparing to Pace | 80/20 Endurance

Power Based Workouts are slower comparing to Pace

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    I received my Stryd recently and continued to using Pace based Maintenance workouts to get Stryd CP autocalculated.

    I did 20 mins test on top of that. I got absolutely the same HR and very close Pace LT as were before and Power LT data as well.

    Surprisingly, autoCP and 20 min test based Power LT are very-very close to each other for me. I did not forget to reduce results by 5%. It was only 1W difference.

    After than I started workouts based on Power, rather than Pace. And I realized that I became slower. I mean, if I tried to keep same pace, no matter of wind, or gentle hills, or surface (asphalt or park roads or whatever). And now all these factors increasing power (while same pace) and force me to slow down to be on the required zone. I mean my average 30 mins RF workout pace reduced from something around 5:15 min/km to around 5:40 min/km if I want to keep my Z1 and Z2 in required power ranges. HR is also lower than usually as it’s very aligned with Pace zones.

    Is it correct behavior and I need to get used to that or I shall retest myself for Power? I was doing test on barely flat asphalt road (as I always did before for HR and Pace). Shall I add some hills and different roads I’m usually doing my runs?


    And maybe there is another way to test power if i know my LT pace?
    Maybe same as for Pace if you know HR? Something like running on LT pace for some time on flat surface till power is not stabilized. Just in case I need to retest.

    Matt Fitzgerald

    You best me to it! That’s exactly what I was going to suggest. It’s the best way to get zones to align in different metrics.


    Thank you very much for your response! Will try to retest today.


    Did test today. Warm-Up and then 5 mins on LT pace. Average Power is 3% higher (262 W instead of 254 W) than what been tested previously. As power curve pretty flat comparing to pace or HR I believe it will make my zones aligned.

    Matt Fitzgerald

    Thanks for the report.


    Hi Matt,

    My initial too slow statement was based purely on Z1-Z2 races and 20 minutes test. Meaning below LT runs.
    However, after running intensive runs including Z4 and Z5, namely RFF49 and RFR5 I have another observation.
    What I found, no matter if I put 254 or 262 (or average 258) as FTP – Z1 and Z2 runs are still quite easy and slow comparing to pace based ones. On other side Z4 and Z5 runs are really hard and require much faster pace comparing to pace based zones.

    As an example using 258 W as FTP and 4:35 min/km as my tested LT Pace for zones configuration. Runs are on more or less flat terrain, no hills.

    Z1 upper one shall be on 196 W and 6:02 min/km. With 196 W I can get something around 6:25 min/km only.
    Z2 upper one shall be 227 W and 5:16 min/km. Here it’s closer but still around 5:25 in average with 227 W
    ZX – not tested
    Z3 here is where I am almost 100% on range and thresholds aligned on both lower and upper ranges for pace and power.
    ZY. It’s only 5 seconds wide for pace and 8 W for Power. Just comparing to Z3 which is 16W and 20 seconds wide. 1/2 difference in Power and 1/4 in Pace. Cannot understand why.
    Z4. Here it’s starting to get hard. To keep 266 W which is lower Z4 threshold for me, I need to run with pace around 4:20, but not 4:30 as zones calculators states. This is something manageable. But if I want to stay somewhere in the middle of Power based zone it’s hard to keep long – I need to stay very close to Z5 Pace based.
    Z5. That was tough today on RFR5. 3:59 which is my Z4-Z5 threshold is even not close Z5 in terms of power. It’s actually on top quartile of Z4. And I am hitting 310 W (lower Power based zone threshold) is on about 3:30 min/km instead of 3:59. And this is not the pace I can keep for 5 mins. For now it’s only short 1 min sprints for me.

    I’ve read following thread very carefully: https://www.8020endurance.com/topic/hr-vs-power-vs-pace-vs-gap-an-experiment/?

    If I’d go with pace as main metric on flat terrain and convert that to Power as advised, it looks like I need to make zone Y little bit narrower (100-102) and probably decrease Z4-Z5 border to something closer to 116%-118% instead of 120%.

    I want most effective training, of course, as any athlete probably.

    Shall I forget about Pace zones, break my habits, stick with Power zones and just run slower on Z1-Z2 and push harder on Z4-Z5? Or shall I adjust zones manually to make them aligned? What is your view and advice on that?

    Matt Fitzgerald

    The truth of the matter is that it is impossible to create zones that align perfectly across all metrics with all athletes. The relationship between HR, pace, and power is unique for each athlete. This gets at the reason elite endurance athletes dispense with zones altogether and train by a combination of feel and specific targets depending on the session type. For example, a cyclist will do intervals at their critical power, which is a particular wattage, not a zone.

    I’m not saying zones are bad, just that you have to use them as a thinking person, which you are indeed doing. Either one of your proposed solutions will work fine. If it were me, I would go with the latter, but in a more informal way, gradually learning over time which wattage aligns with my vVO2max, my critical velocity, my half-marathon pace, etc.


    Hi Matt,

    Thank you for your response and support on this. Will try to do all the required adjustments.
    I like concept of power based trainings as independent metric, seems forme some fine tuning and getting used to is required.


    Another findings after another few days of training.
    Seems main problem was with calibration of Stryd. It was showing lower distance and pace accordingly. After a calibration to 102.1 seems pace and power zones became aligned as given in 80\20 zones calculator and there is no need to edit something manually. Really amazed with 80/20 zones concept.
    I switched back to pace based workouts as Garmin works with structured pace based workouts natively, however I’m using 80/20 Run Zones application on Garmin showing both Pace and Power data on single screen and trying to align to Power rather than Pace as main indicator.
    Actually for first few seconds moving to new zone I do switch using pace (due to few seconds delay in power data) and then trying to keep correct Power zone.
    Stryd is giving some delay and on top of that if I put real time Power it gives a lot of noise in case of very small ups and downs (few meter long), so I am using 5-10 (still playing with most comfortable numbers) seconds averaging that also brings some delay during switching zones indication.
    This is not an issue for long 1-2 zone workouts but might be an issue if I use purely power for high intensity intervals.

    I do not pretend that my method fits everyone, I am also getting used to that and finding most suitable way of using Power. But I hope my findings would be useful for novice power based plans and\or Stryd users.

    Matt Fitzgerald

    Thanks so much for sharing your experience. I should have thought of the calibration thing. This is the downside of not being able to run right now due to my health. I’m not using Stryd, and there’s just no way to make up for the absence of ongoing personal experience.

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