Power vs HR zones

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    Hi – I’m new-ish to running and 80-20. I’ve been running for about 6 weeks on 80-20 plans with a Stryd pod and am concerned that running the power zones is holding me back too much. Warmups in zone 1 I find I’m almost being overtaken by pedestrians and keeping in zone 2 is a struggle because I feel like I’m compromising my running stride to keep the voice from saying ‘slow down’ continuously. When I look at my data for all of my runs I also find that even for the longes zone 2 foundation or depletion run, my heart rate is firmly planted in zone 1 – perhaps creeping into zone 2 for the last 5 minutes.

    I’ve calculated my CP twice – through both a 10K and a talk test and got fairly consistent values. I snuck the CP up a couple of W by being a bit optimistic on the talk test but that’s not materially making a difference.

    At 49 and looking to run a marathon next year after a 25year break from running, I’m sure I’m not standard (and I am definitely slow!) – how good should the link between HR and power be across all ages and capabilities?

    I’m concerned the power zones are going to hold me back from getting as fit as I can – I’m certainly running much slower than before I got the stryd (but feeling better daily for it).

    Any thoughts or advice welcomed.


    Since you’re new, you should conduct an all-out 20 minute time trial. Your zones may still be somewhat slower than you’re used to, but you’ll have more and better confirmation that they’re right.


    I was going to recommend the 20 minute all out test as well @wrspoon.

    It’s really the only test that links all three metrics in one test.

    Intensity Guidelines for 80/20 Running

    The talk test is good for a quick check to see if anything has shifted. The 20 minute test is definitely uncomfortable but will give you the best eval of where the threshold value is for the 80/20 system.

    The main reason you do 80% slower is to have the energy to do the 20% intense portion. The 80 will likely feel slower but the 20 should definitely feel like a little challenge.

    Hope that helps


    I have to agree with Richard. Sometimes running with power seems too easy. I always see some spill of power into higher zones, but I get reasonably good correlation with heart rate in the lower zones.

    Since you have faith in your heart rate threshold you might want to run your workouts by heart rate while you build up some history on the Stryd platform. You can set up a Stryd power data screen on you watch and monitor both power and heart rate (or pace) during workouts to learn how your metics vary in different environments and situations. I personally found that approach very effective for learning purposes. I now let Stryd calculate my CP and it seems to work just fine.


    Thank you all for the suggestions. I was aware that moving to 80/20 and onto power as key metric would make things go slower and there are benefits to that – not so sore legs next day etc. But it really did seem too slow…..

    Did the 20min threshold test today and yes, got a 10% bump in my Critical Power and threshold paces but only a slight (2bpm) bump in LTHR. Hopefully that will make things line up better going forwards (gonna have to run faster though!).

    – I’ve seen the documentation say that Stryd auto CP calculation should be off as it messes with the ability to use the app. Specifically:

    [quote]Align your Thresholds in Powercenter with TrainingPeaks

    The Stryd platform will provide users with an Auto-Calculated Critical Power (CP) by default. However, if you are following an 80/20 training plan and using either the Stryd Workout App for the Garmin watch or the Stryd Apple Watch app to perform the 80/20 structured workout then you should disable Auto-Calculated CP in the Stryd mobile app and manually set your Stryd CP to match the threshold run power (rFTP) being used in TrainingPeaks. If the threshold run power used in TrainingPeaks does not match your Stryd CP then your power targets for workouts shown in your Stryd account and on your watch will be different than what is prescribed in TrainingPeaks. [/quote]

    I haven’t challenged this but it doesn’t make sense to me as TP pushes the required wattages through as numbers not zones (I believe – as stryd app only has 5 zones, not the 7 of 80/20). Do you find using the autocalculated value from Stryd messes with your training plan?



    I had the issue using the Stryd App, the FTP in TP was ‘overrode’ by the Stryd App when doing the workout.

    The main reason it is turned off is that 80/20 Endurance uses a CP20 for it’s program. Stryd doesn’t specify which CP they are using (CP20, CP30, CP40, CP60). Therefore, if it autocalculated it could be using the wrong zones for the 80/20 Endurance program.


    Richard / Gerald

    Hopefully the coaches don’t toast me for this… I tend to get geeky about this stuff, but I am a believer in the 80/20 philosophy.

    Here’s what I do, and why…

    I use Training Peaks and 80/20 Training Plans as my principal tools for planing and conducting training. I use the Stryd Power Center to track my power based workouts – but the zones and reports are maintained with Training Peaks. Yes, there are differences between the Stryd Power Center and Training Peaks, but both are good tools.

    Heart Rate, Pace, and Power all have their particular strengths and weaknesses. Heart Rate is the best measure of cardio-vascular effort, but it has limited value as workout intensity increases into anaerobic efforts. Pace is great for performance measurements, but it fails in hilly terrain, heat, wind and in other circumstances. Power is a great measure for output, but it doesn’t reflect internal adaptations except by inference.

    You can test and get a good point estimate of your estimates on a given day, that’s fine. I choose to use the Stryd tool to decide my critical power. The Stryd calculation is based on workouts I have been doing, and I believe it is an accurate estimate based on the training I have been doing. This because as you progress you are constantly training and detraining different aspects of your fitness. Yes, Stryd and 80/20 have different zone partitions, but it really doesn’t matter if you stick to just one. – I choose Training Peaks as my preferred tool for controlling my training because it offers the flexibility to work with heart rate, pace, and power. I manually take the feedback from Stryd and enter it into my Training Peaks profile.

    I really don’t care that there are differences. I want to execute my workouts at the 80/20 prescribed intensities and I want a consistent tracking of Training Stress.

    Specific adaptations I am making are:

    1. Recovery Runs are converted to power, this to assure that I do not creep into anaerobic works even a little bit – for example, it means I walk up hills.
    2. Long runs are converted to power for the same reason recovery runs.
    3. Foundation runs are converted to heart rate. This to assure I am exercising for cardio-vascular adaptations. I make an exception if I have a foundation run after a hard workout, it that case I convert to power for the same reasons as above.
    4. Zone’s three and four are varied for heart rate, power, or pace depending on the particular circumstances. Sometimes just to assure that I am training lactate tolerance, and other times for pacing or environmental considerations.
    5. High intensity intervals of short duration are best monitored with power – it is simply more responsive.

    Bottom line, for me, the technology is available and provide suitable tools in order to achieve the best possible results with 80/20 periodization. But, none is perfect yet…

    Richard/ at 49 you’re just a kid – don’t worry about age. Your best years are yet to come.


    I’m 49 and I got back into running in 2018, after a really long break. You can definitely get it back!

    I’ve read a few comments about Stryd’s auto-CP. This is fine as long as you’re giving it the right information. I’m using one of Steve Palladino’s marathon training plans and he suggests doing the following max effort runs:

    – 10 seconds
    – 2 minutes
    – 10 minutes
    – 20 minutes (or 5K)

    Having all of these represented on the power curve will help.


    Thanks everyone for the replies and encouragement. Tried out the new power settings and it seems more natural than it was so hopefully that makes a difference. I did actually increase plan levels in order to combat the ‘too easy’ feeling so I’ll see how it goes then might decide to drop back one. What is curious is that the Stryd app has dropped a predicted marathon time by about an hour based on the 20 minute flat out and a foundation run yesterday. I think that’s rubbish – the old estimate already seemed out of reach let alone an hour faster! Reinforces that I don’t like the Stryd app as its buggy, user unfriendly and seems wildly variable in what its telling me over the last 6 weeks.

    – thanks for the detailed explanation. As a lay observer what you write makes intuitive sense and although I’ll probably just stick to power for now, you’ve given me lots of food for thought. Also an excuse to turn off the Stryd app and focus on something like Work Outdoors which gives far better data to allow me to check how the metrics are comparing on any given run.


    I would suggest doing a couple of shorter runs to balance out your power curve. Something like 10 minutes, 2-3 minutes, and then 10-20 seconds.

    All Stryd predictions are based on the power curve. The power curve is helpful, but it’s not human and it’s not intuitive. You have to give it the right information for it to work properly. The steeper the slope of your power curve, the lower your CP will be. On the other hand, the flatter the slope is, the higher your CP will be.

    Because you most likely don’t have any short best effort runs in the past 90 days, I would guess that your power curve is artificially flatter than it should be. I hope I’m making sense here and not sounding crazy!


    Thanks @alancraig – makes sense. I also referee Australian Rules football in Canada/USA which probably also disrupts the algorithm as it’s about 80 minutes of a mix of flat out sprinting, jogging, walking and running backwards (I wonder how the pod deals with that!). Sometimes multiple games a day.

    It does look a very flat curve at the moment….


    I am going to defend the Stryd race predictions. I find it very accurate for race estimating. As with any algorithm, it is only as good as the data it is being fed. I would recommend only using it on training runs; not when you are refereeing. Just my two cents based on my experience.


    Stryd predictions have been pretty realist – except for yesterday.

    I also saw a huge jump in predictions, totally unrealistic… The anomaly has been corrected as of today. Rats!


    I find this a more than relevant topic, and think it’s a pitty that untill now no coach has replied.
    Since a few months, I run with power. I love it. Nevertheless I have somewhat the same experience: I conscientiously follow the power-zones during a training, and find that looking at my heart rate zones afterwards: they lag.
    (All zones are retrieved from a recent 20′ all-out time trial.)
    E.g. for my non-foundational runs of last week: sunday: target was 10′ in Z3, HR zones show 6.5′ in ZX (remaining max Z2); friday: target was 12′ in Z4, HR zones show 6′ in Z3 and 10′ in ZX (remaining max Z2); tuesday: target was 9′ in Z5, HR zones show 2′ ZY, 7.5′ Z3, 5′ ZX remaining max Z2). (Ok, I am familiar with the fact that the higher the zone, the more HR will lag behind, HR is inappropriate for measuring interval-training. However, this is insufficient as an answer, since also in a steady 10′ Z3 exercise this phenomenon (lower HR zone) occurs.)
    So general observation: 80/20 endurance says to particularly avoid ZX and ZY (besides for specific prepatory training), so would I have done my training as I did, but watched my HR zones instead of my Power zones, I would have thought I was training incorrectly.
    My training plan proceeds smoothly and several indicators (a.o. Garmin’s VO2-max and general feel) suggest I am making nice progression. Moreover, I am not the kind of athlete that gets his kicks of becoming sick by doing sprints in HR Z5, so the somewhat smoother power zones are also therefore fine by me 😉
    All this would suggest, what probably Stryd and power adepts will endorse, that power zones are really the better way of targetting your training instead of HR zones. What then with all these training-talks about working with and around your lactate threshold HR? Should we forget all that? Does lactate threshold power and the therefrom calculated power zones really replace LTHR and its corresponding HR zones?
    On this, I would have liked to hear some comment of the 80/20 pro’s.

    David Warden

    All, great discussion here, I appreciate the participation.

    I regret the coaches can’t comment on each topic. The forum both allows us to scale answers, but also crowd-sources them. Particularly when there is a healthy discussion and competent answers like we have here, we’ll reply on our community of experts (and if coaches reply to every topic, it actually discourages participation).

    Or, think of it this way. In another year we’ll have 2-3x the number of posts that we have today. Like all forums, there is a limit where the forum outgrows the creator and we have to turn to the community.

    However, we’ll always be involved in some respect whether it’s responding to 10, 20 or 50% of the topics. Personally, I’m thinking an 80:20 balance of participants:coaches would be about right… 😉

    Anyway! While I’m here I might as well weigh in. I believe there are two main themes. One, power zones feel too low and 2, power zones are not aligning to HR zones. I think the other athletes have covered ways to address this really well already, but let me try and summarize.

    original concern was the perception of low effort for Zone 1 and 2. Let’s imagine that underneaththeradar has a run FTP of 250 watts, as established by the 20-minute TT (263 watts for 20 minutes less 5% = 250- watts).

    With an FTP of 250, the top of Zone 2 is 220 watts, or a 16% reduction in power between the top of Zone 3 and the top of Zone 2. Candidly, it is puzzling that a 16% difference in output is the difference between a walk and an 20-minute sprint. That’s an exceptionally narrow power range for running. I can’t fully answer it, but the most likely answer is that the FTP test was underperformed, and that actually FTP is considerably higher than 250 (in this example).

    Also, remember that when Zone 1 is called for, you can use Zone 2. While the boundary between Zone 2 and X is empirical, the boundary between Zone 1 and 2 is somewhat arbitrary. Both are easy and interchangeable. So, if you are struggling with Zone 1, feel free to use Zone 2 (and vice versa).

    But, underneaththeradar, you can solve this mystery for us! It’s been 2 months since your original post! What is your current running with power experience? Did you sort out the correct FTP?

    On the second question regarding the alignment of HR and Power, HR and Power will only align under the following circumstances:

    1. That you identify HR and Power in the same test
    2. That your subsequent training is performed in an environment similar to where the test was performed.

    If you performed an FTP test outside at 80 degrees and ended up with an FTP of 275 and LTHR of 170 bpm, that won’t hold up if you run inside at 68 degrees. That same 275 watts will be a HR of 160 in that cooler, indoor condition.

    HR is a product of the environment as much as it is an indicator of effort. Sleep, temperature, time of day, when you last ate, stress, indoor, outdoor, all influence HR for a given output.

    I’ve seen this in action in the lab. An elite runner came in and ran 16kph at 70 degrees and had a HR of 160. The same runner came back a week later and ran 16kph at 90 degrees and had a 180bmp. That’s one beat per degree for the exact same output.

    I’ve been coaching for only about 12 years, but the biggest improvement I and my coached athletes experienced was when I decided to



    heart rate.

    Hear rate is cheap, plug and play and easy to explain. It’s also unreliable. If you have access to Pace and Power, use them. Don’t get me wrong, there are times when HR is a helpful measure, and I use it occasionally for an athlete. But, using HR when you have Pace and Power is like using a divining rod when you have ground penetrating radar.

    Stan, I think you said it best when you said, “but watched my HR zones instead of my Power zones, I would have thought I was training incorrectly.” You’re instinctively recognizing the problems with using HR.

    Consider dropping HR altogether for 2 months, don’t even put on the HR monitor. Most athletes who do this never go back.

    Did I miss anything? (long thread!)


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