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Training with Heart Rate & Power

Balancing the information acquired from Virtual Power or a power meter with that which you obtain from the myriad heart rate recording methods available nowadays can be a bit confusing.

In this article, we'll try to help you understand some of the more frequent power/heart rate mismatches by explaining some power and HR feedback fundamentals and then explaining some ways in which the two interact.

Heart Rate 

It's important to keep in mind that heart rate readings can fluctuate on a daily basis. General fatigue, incipient illness, day-to-day stress, dehydration, quality and quantity of sleep, caffeine intake, training stress and other factors can influence your heart rate.

In the case of impending illness an elevated heart rate can even be used as a warning sign to back things off a bit, maybe rest a bit more, but again is an illustration of how sensitive HR is to numerous internal and external factors.

These demonstrations of why HR-based training is problematic are not to imply that it's without merit.

Athletes who know their bodies and have years of training history can often associate their perceived levels of exertion (RPE) with HR abnormalities and circumvent training errors, but these athletes are in the minority.

For most riders, HR becomes more usable when associated with power output. This too involves a learning process but one that's more straightforward than the RPE/HR relation. 



You've probably heard the phrase, "Watts is watts", and while statements like these are often maddeningly obvious and meaningless (not to mention grammatically incorrect), this one effectively pushes the point that you can't cheat power numbers. 

One day you can hit 300 watts and the next day you can't. You're seldom left mystified by the host of potential bodily and environmental influences that might be affecting your power, rather you just know you're tired. 

But what happens when you're heart rate tells you one thing but your power indicates another?


Underestimated FTP 

If your workouts, especially workouts near and above FTP, just don't seem very demanding then it's likely that you have an underestimated FTP. Further evidence of this too-low FTP value are evident when your HR doesn't rise to the expected level.

Underperforming on an FTP test is not uncommon; in fact, I've yet to meet a rider who nailed his/her first FTP assessment. Due to this assessment learning curve, many first-time or early testers won't perform to the height of their abilities.

As a result, their FTP is underestimated and consequently, their HR is lower than expected at nearly all work levels. 


Indications You Underperformed

If the workout's intensity classification indicates a gut-wrenching set of intervals, e.g. Intense or Insane, yet you're sailing through them wondering when things will get challenging, you've probably underestimated your FTP.

If your next reassessment grows by leaps and bounds, you probably underestimated your FTP the first time around and things are about to get a lot more demanding with your new, more accurate FTP estimate.

Often, riders finish an initial assessment and feel like they still have a lot of gas left in the tank, or they'll start the assessment interval at a much higher power output than they finish with.

In both cases, the FTP estimate is likely to be low, probably too low to raise the subsequent workouts to the appropriate effort level and this can have a minor to major effect on the training response you derive from a later set of workouts or even an entire training plan.


What If I Held Back Too Much?

Riders who have underestimated their capabilities during their FTP test have two options.

Option 1 is to retest and work harder.

Option 2 is to incrementally increase your FTP by 5-10 watts over the course of your next couple/few rides until your HR (assuming you're rested and fresh) is more in line with your LTHR and associated percentages.

A third option for riders new to training with power is quite a bit more work but lends itself really well to making your training as effective as possible. By using the first ride of each week during the first two to three weeks to do an FTP test, you'll better learn to evenly pace your effort over the course of 8 or 20 minutes. 

Discrepancies between your actual FTP and the FTP your tests yield can be mitigated by learning how to properly pace and push yourself during the extent of a test interval. This is something that comes with experience, and doing an FTP test at the top of each week for two to three weeks would help bring about such skills.


Other Common HR/Power Discrepancies

If you notice a heart rate that's below what it should be based on the power you're putting out, this is a good indication you're overreached. But overreaching is a necessary component of improvement and it only becomes a problem when it doesn't relent.

You can only overreach for so long before, worst case, you start dangerously venturing into overtraining territory or, best case, you continue to train a tired body and fail to see any noticeable improvements in fitness. Time to rest.

If workouts that once seemed impossible or at least very demanding are becoming more tolerable and maybe even a little too manageable, you're right on track but it's time to consider your next assessment. 

For example, your power may be right on track but your HR is a little lower than you'd expect it to be, you're breathing a little more easily and another minute isn't quite as intimidating as it once was. This is the difference between improvement and overreaching too far. 

In both cases, your HR is lower than expected but in the case of fitness improvement, your power is on track, i.e. steady graphs and on-target numbers. But with with overreaching, your power output is erratic or falling and you can't seem to hit your numbers as consistently as you once did.

Learning these subtle differences can be the difference between increasing and decreasing your training load, and as a result, can be the difference between building and losing fitness. 

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  • Avatar
    Michael Van Ness

    I am in the middle of week five of low volume sustained power base. I retested using the 8 minute test and added to my ftp. Black was easy, but I absolutely hit the wall on the fourth set of Stevens. As I am new to this type of training, is failure on these hard workouts to be expected from time to time or do I need to dial back my ftp? Thanks.

  • Avatar
    Mario Tello

    Hi guys, my problem is that for easy workouts, my heart rate seems to be higher than expected (a recovery ride might look like an endurance or tempo effort) but for example, I did Foerster ( and I had to hit VO2 max, but instead I got to Tempo. Another thing, my HR is always lower in the trainer than on the road (I did 5x3 min hard, with a minute rest in between intervals a couple days ago, one day after Foerster) and I got readings over 167 bpm. What is going on?

  • Avatar
    Darden Mueller

    @Mario There are a couple things going on here. First lets go over your workout "Foerster" If you look closely you can see that your HR slightly elevates throughout the workout. Since the intervals are rather short with rest periods, this does not allow your HR to increase further than tempo. HR is a lagging indicator of effort, so it's difficult to get your HR up too high on workouts with frequent rest.

    Your recovery workout "Dans" has longer intervals allowing your HR rise past tempo. A longer interval allows your HR to increase more so than a short high powered interval.

    It is quite normal to see your HR higher indoors than compared to outdoors. A lot has to do with Thermoregulation. The environment you're riding in requires your body to invest more energy into cooling itself down. Thus increasing your HR.

    Finally it is important to note that several factors can influence where within a zone your HR sits. Factors like age, level of conditioning, years of experience, pain tolerance, impending illness even -point is, there are a lot of factors so it's on the shoulders of each rider to determine his/her capabilities & limitations.

    I hope this helps!

  • Avatar
    Mario Tello

    Thanks so much Darden! I was affraid I was on my way to overtrain! even running I cannot go lower than 130 bpm on easy efforts... I was a swimmer, turned triathlete. I swim a lot slower than before, and I cannot bring my HR up in the water (It is usually around 150 bpm for hard efforts, while I used to go to 180). Running gets me around 170 for LTHR and the bike is my worst sport (but becoming better thanks to TRAINERROAD!) :)
    I use a fan when doing indoor training, I guess I need a bigger one :)

    Should I bring my FTP down so I can be in sync with my HR? or should I keep the wattage where my tests suggest? I have done the 8 minute test many times, and the 20 min just once


  • Avatar
    Darden Mueller

    We don't really recommend the 8 minute test for LTHR testing since the shorter intervals don't really give the heart enough time to level off. If you want a more accurate LTHR and HR zones, you could do the 20 minute test which is a more accurate measure because of the interval structure.

    If you're up to it, you might want to re test with the 20 mint test. I know these are know where near enjoyable, but if you're concerned about becoming more in sync with HR targets that may be the best way to go.

  • Avatar
    Huw Duggan

    As stated above, your HR can be (actually is) a great indication of your state of recovery and if you are serious about your training you should check out Myithlete and all to do with HRV. It's proven to be extremely accurate and can only assist serious trainers with when to train hard and when to back off.

  • Avatar
    Mario Tello

    Hi all! Thanks for the replies. I took the 20 minute test and now the readings are more accurate against my "real" LTHR. I can train the swimming and running more accordingly (I still have a lot of work to do on the bike) :)
    I've done another 8 min test since that 20 min one, changed FTP a little bit, but not the LTHR, and results are consistent, so I'll keep it that way.

  • Avatar
    Anthem Dogma

    One might also mention heart rate and heat issues. Especially pronounced in basement environment, when air cooling not so effective. At least, my heart rate dropped by 12points or so when I installed fan powered from the rollers I ride. Not sure, all agree, just my experience.
    Thanks for great plans!

  • Avatar
    Tony Daniel

    8 weeks ago I started base and after the 8 minute power test my estimated FTP was 99W and the power zones more or less matched my heart rate zones.

    2 weeks ago I started phase 2 of base and redid the 8 minute power test which increased my estimated FTP by almost 50% (147W). Training in the endurance zone according to the new power zones now means that my HR is much higher, first session it was mainly in the Tempo zone and during my last session it was way above, being only a couple of beats below, and sometimes above my lactate threshold HR and I couldn't finish the ride. I've just started the medium volume traditional base 1. My legs are killing me this morning which, as I understand, shouldn't be the case during base training!

    I've been on and off the bike due to one bug or another (bloody kids!) and when I did the test I was fresh back after a week off. During the 8 minute intervals during the test I went all out to the point of almost being sick at the end. Did I simply work to hard?

    My question is should I...
    1. Reduce my FTP so that my HR more closely follows my power zones or
    2. Continue using my current FTP in the hope my HR zones catch up?
    3. Redo another test, maybe the 20 minute test this time?

  • Avatar
    George Leonard

    Would love to see this thread progress more...

    Id guess/expect that with the first ftp test you are most probably under... and the HR might be a bit higher, not use to the training, as you get fitter, and the legs get more use to the power output things become easier, leading to a lower HR. Then you redo the FTP, allot more accurate now... leading to "harder" training/ higher load represented most probably by a much higher HR compared to the first "block" after your first FTP test.

    as time goes by and you get fitter I'd HR to drop, but also remember, we all get older, which implies lower MAX HR's. implying we won't hit those higher numbers, but this will be over time/years, so more for someone very experienced with years of data.

  • Avatar
    Bob Clifton

    I'm 75, so numbers about my HR are in a different range from most folks here. Also, I'm new to structured workshops, tho I feel good a few hours after, so I like it. I believe I understand why power rather than HR is used as a metric in the program, but I don't have a power meter off the trainer so HR outside at least gives me a little info.

    What I don't understand is why on an inside ride the "time in zone" numbers are radically different for the same ride, depending on whether it's HR or power. For instance, on my Tunnebora, the power chart says I was 43% in Sweet Spot, 6% in Threshhold, and 0% in VO2Max, which sounds like the intent. The HR chart for that identical ride says I spent 2% in Sweet Spot, 38% in Threshold, and 20% (12 minutes) in VO2Max. The zones bear the same names, and TR scaled both zones from my first 2 x 8 FTP test, which I felt was in the ball park.

    I ask because if I set my Garmin HR zones to the same values as TR's HR zones, it will see 10 minutes in my Sweet Spot (power) as a 10-min all-out sprint, which would probably kill me. Why such a different interpretation of the same ride? Or maybe I'm asking how TR scales the HR zones for a particular rider, and did I somehow mislead it.

  • Avatar
    Janis Svarpstons

    I can not find answer in help center or blog, and I see above that somebody else have such question. The question is if the "output" data of watts and HR when doing the workout should fall in the same zone? Just started using Trainerroad and did Ebbetts. As I use ergo trainer, the power is adjusted automatically in each interval. However when doing interval 3 and 4 my heart rate hit the top and I even had to stop. And indeed that according heart rate I was in higher zones then in power zones. Maybe my ftp test was wrong I got too high FTP?

  • Avatar
    George Leonard

    Don't worry to much about HR, as long as you're healthy and the heart is happy thumping away at that pace just work on the Power.

    I have the same, even for lower zone exercises my HR goes to the mathematical max quickly and just flat lines there for the entire duration of the workout.
    Normal logic is as the heart gets stronger the HR drops, the muscle gets stronger so it pumps more blood per cycle, mine seems to have said, nah... it will just keep pumping the lower volume and increase the revs.... :)


  • Avatar
    Sam Lin

    @Michael Van Ness This is a very late reply as I was doing some research about LTHR and saw your post.

    Stevens has a Intensity Factor of 0.91. It consists 5 sets of 6-minute 105% FTP intervals with only 2 min of recovery in-between sets. If you set your FTP properly it is supposed to be difficult, supposed to feel like hit a wall at set 4-5. Total interval time is 30 minutes. Similar to doing the 8 Minute Test twice. Except that the 8 minute test has very long rest in-between the 2 intervals.

    From time to time workout incomplete feeling the need to dial back is normal. I would suggest keep the FTP unchanged for 1-2 weeks before you decide to dial it down.
    Incomplete workout due to tireness can be caused by many variables. I list some below:
    - Not enough recovery from previous workout(s).
    - Too many rest days from previous workout.
    - Nutrition/hydration prior to workout
    - Nutrition/hydration during workout
    - Mental physical stress level from life. (I am serious)

    Last time I adjusted my FTP and I did Tray Mountain, a 90 min workout with 3 x 20-minute 85% FTP intervals. The last interval felt like a massive wall as I was about to bonk. The cool glucose powder drink, fan in air conditioned room, CTXC 90 min youtube outdoor cycling video, and techno music kept me going but it was hard. Yes there will be times we are unable to complete some workouts. Nutrition/hydration, ample recovery, ample cooling. are the key. Music can keep you pumping but that is secondary.

  • Avatar
    Josh Carrier

    Hi folks. I've just recently started using a HRM and I'm noticing my HR seems to be consistently higher than my power zones, by quite a large amount. I haven't yet done an FTP test with the HRM (I've done several without) - not sure if TR uses that data to make your HR zones more customized to you?
    I'm finding that my workouts are completely manageable - I'm working hard on some of them (like I should), but I'm never close to bailing out and I'm often needing harder workouts so I bump the intensity 3-8%. Before you tell me to retest FTP - I'm doing that every 4-6 weeks :-) and my FTP is jumping quickly. The point is though, I'm handling the workouts and my RPE is entirely at the level I'd expect; the unexpected part is my HR seems far higher that I would feel it should be based on both power zones and RPE - I notice this especially during the 'easier' workouts during rest weeks, etc.
    If I was 'stronger' than my FTP test results were showing, I'd be expecting the opposite (HR would be lower than power zones).

    Here are some examples:
    Hard workout. Most of time spent in Threshold power, but HR was in VO2Max. Not a big disconnect between the 2, but noticeable:

    Easy workout. Most of the time spent right on the cusp of Tempo/Sweetspot, but HR was on cusp of Threshold/VO2max. I felt completely comfortable but apparently my heart was just pumping away!

    Can't stress enough that my RPE tells me there's a massive difference between the 2 workouts, but HR for the 'easy' workout is far higher than I'd expect.
    Also, possibly related, I notice my HR jumps to around 120bpm VERY quickly when I jump on the bike at super lower wattages during warmup(~150w in my case) when I barely feeling I'm touching the pedals, almost no effort at all. Dunno if this is normal.

    Anyone able to provide some clarity as to what's happening?

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