After working my way to understand the benefits of taking 2 or 3 leisurely longer rides (ones in which I remain in Heart Rate Zones 3 or 4) for every brief all-out ride (in which I spend more time in Heart Rate Zone 5), I have been keeping an eye not on the absolute heart rate, but on the heart rate zone, inspecting the number every time I feel that my heart is starting to race.

[Edit 1: Why is it useful to keep track of one's HR? Let me quote a comment by Andrew Henle, who sounds like he really knows what he's talking about: "FWIW, riding hard like that all the time right at your threshold is a great way to get good at being mediocre. Getting FAST really requires riding a lot at about 1/2 to 3/4 threshold power to build your pure aerobic power." I don't have a way of measuring my power, and so I am taking the next best thing and using my HR, by remaining in HRZ 3 to 4. Is it unreasonable to assume there is a correlation?]

Every time I approach the 4.8-4.9 heart rate zone (yes, it's displayed as a fractional number), I calm my thrill down and ride more slowly.

Still, when I inspect afterwards how much time I've spent in each heart rate zone, I get numbers that are heavily skewed towards HRZ 5.

Zone    Heart Rate
1       00:00   
2       00:16   
3       11:52   
4       72:43   
5       91:22

Why is my HRZ 5 so high, even though I'm certain I have rarely, if at all, entered 5.0+. Is it the case that the "zone" measures from -0.5 to +0.5, and so HRZ 4 is really a count of the time spent in the interval [3.5, 4.4]? Is HRZ 5 really measuring 4.5 to 5.0?

Also, is there some special significance for the HRZ maxing out at 5? Is it, for example, a hint that remaining for a long time above 5 is somehow detrimental? What about racers? Don't they remain in 5 basically all the time?

In case it makes a difference, I'm using a chest heart rate strap with electrical connections.

The HRM is from Lezyne. It is wireless; smallish; has worked impeccably for about a year now; just about the only negative I can say about it is the little chill I get from the contacts when they first touch my chest, but that's presumably a necessity since it's electrical with metal electrodes, and it lasts only a moment. Plus the battery (a common Lithium disposable battery) drains extremely slowly.

Edit 2: Another way of asking the question is this: I have access to a Heart Rate Monitor, as well as to a cadence sensor and a speedometer, but not to a power meter. I have so far been using bar charts such as the one quoted above to check whether I did indeed remain in Heart Rate Zones 3 (or 4), as I intended. How can I ensure I remain in Heart Rate Zone 3 (or 4) using a Heart Rate Monitor?

On a bike we're rather lucky we can get four measurements. This Q&A ask the same if all we had were a heart rate measurement. In the context of cycling the additional issue is whether the three other meters can assist in determining the training zone.

  • 3
    This is a question about your heart rate monitor and its software, not really about bikes or even training. But to me those numbers look cumulative (which is a silly way to present them), or perhaps we should imagine that every zone in the first column is prefixed with "less than", or "up to" as decimals in the zone numbers don't really make sense. I've seen an indication of high/low in the zone, so perhaps that's what they're aiming at. How long was the activity you've shown the results for?
    – Chris H
    Commented Jun 1, 2021 at 18:33
  • 2
    I’m voting to close this question because it's not about bikes or cycling, but about the quirks of a heart rate monitor
    – Chris H
    Commented Jun 1, 2021 at 18:34
  • 3
    Also note that heart rate zones are all very well, but actually getting them correct is much harder than just doing percentages of a simply-calculated maximum
    – Chris H
    Commented Jun 1, 2021 at 18:35
  • 1
    160 minutes in Zones 4 and 5, How were your zones established?
    – mattnz
    Commented Jun 1, 2021 at 21:32
  • 4
    @Sam - If you are using Zones calculated by the device, they are wrong. All the ways to calculate HR zones require you to do stuff, and stuff that 'hurts' like working out your lactate threshold heart rate. If you can maintain Zone 5 for more than 5 minutes, its not zone 5. If you are in zone 4 for more than 30-45 minutes, you will know it and have more will power than most if you last that long. Max Hr, LTHR and Zone boundaries are very individual and change with fitness and age, to get meaningful numbers you have to run though some tests.
    – mattnz
    Commented Jun 2, 2021 at 1:35

3 Answers 3


It's most likely that your bike computer is using your age to determine a maximum heart rate and then determining some zones based on that. This is common practice amongst devices that use HRM data, and equally commonly wrong.

I answered this in a similar question before:

Max HR isn't a particularly useful metric. Not only is it particularly difficult to measure/estimate, but it can't be used to accurately define training zones, as there are large variations between individuals with regards to % of MHR they can sustain for various durations. It can even change for an individual based on their current state of training.

Basing zones on Lactate Threshold Heart Rate (LTHR) is a much more useful metric for determining appropriate training zones. The most common way to determine LTHR is by performing a 30 minute solo time trial as if it were a race, and taking the average HR for the last 20 minutes of the effort. https://www.trainingpeaks.com/blog/joe-friel-s-quick-guide-to-setting-zones/

Finally, you can (and should) use RPE (Rate of Perceived Exertion) alongside heart rate to try to ensure you are in the correct zone. Numerous effects such as fatigue, caffeine and even time of day can have a large impact on HR, so learning how zones feel is very useful. For example i find if I'm no longer able to breathe through my nose, i've moved into Tempo zone.

Here's a very handy chart: ICA zone chart

  • 1
    Basing zones on Lactate Threshold Heart Rate (LTHR) is a much more useful metric for determining appropriate training zones It's certainly better than using a percentage of the 220 - age wild-ass-guess "max hr", but using a percentage of your LTHR to establish training zones can still be off, and for some it can be way off. As @mattnz alluded to in his comment, you really need to do full VO2 max testing. And for the cost of that you can probably get yourself a decent power meter and just train with power... Commented Jun 2, 2021 at 10:08
  • What does RPE stand for?
    – ojs
    Commented Jun 2, 2021 at 10:12
  • @ojs Rate of Perceived Exertion - updated answer to clarify
    – Andy P
    Commented Jun 2, 2021 at 10:13
  • @AndrewHenle But AndyP also is saying, I think: to ensure you remain in zone 3, get a power meter and measure your functional threshold power. Now the question to you is: this requires both getting a power meter and doing a VO2 max test to figure out one's (maximal) FTP. What am I missing?
    – Sam7919
    Commented Jun 2, 2021 at 10:33
  • 1
    @AndrewHenle I am not certain that a full VO2max test would get the OP a better way to set their training zones. They would get ... their VO2 max? Isn't % of LTHR the best guess available to the OP given no power meter?
    – Weiwen Ng
    Commented Jun 2, 2021 at 12:37

Answering the question as written at the time of answering and avoiding all side tracks about the meaning of the zones: Whenever you find yourself above the target zone, slow down. When you are below the target zone, ride harder. To avoid overshooting the target, do the changes gradually, do not jump to full stop or maximum effort right away. If you go right over the target zone at the beginning and can't get to the zone, start with a slow warmup and approach the target zone from below.

  • 1
    But how is one supposed to recognize that he/her is "above the target zone" and "below the target zone"? That is the whole point of this question. Commented Jun 2, 2021 at 13:01
  • 1
    By looking at the HRM. Of course I could have missed some detail that prevents the OP from doing so...
    – ojs
    Commented Jun 2, 2021 at 15:08
  • I'm with @ojs on this one. When I first started using an HRM, some time in the mid 1990s, it would beep when I dropped below or went above the target range that I set (eg 150-180). So I just work harder or less. I also think that OP is reading the numbers wrong or making some mistake understanding the equipment.
    – jqning
    Commented Jun 2, 2021 at 17:00
  • @Sam whilst a power meter is the gold standard, I actually did quite the opposite to saying 'forget about it and get a power meter'. I told you how to get the best approximation of zones without a power meter
    – Andy P
    Commented Jun 2, 2021 at 23:06
  • 1
    BTW, the zone 1 isn't usually about resting heart rate, because the HRM is supposed to be used for exercise, not for resting.
    – ojs
    Commented Jun 3, 2021 at 5:28

I guess the data you are seeing and posting here are "zone" not in the sense of "Heart Rate Zone" (let's call them HRZ) but in the sense of some proprietary "manufacturer(r) Training Zone " (let's call them MTZ).

Probably your sensor is recording HRZ, then the page where you visualize the data is doing some processing to calculate the MTZ. Then it can be anything, it can be that MTZ = 4 if HRZ is between 3.5 and 4.4, it can even be that MTZ = 5 if HRZ = 1 ... that would make sense with yor MTZ = 1 being null, since you stated that you never crossed HRZ 4.8/4.9 .

Then, given the data you posted, it can be everything, it can even be cumulative, as someone commented, in the sense that

  1. MTZ = 5 means simply HRZ >0.5,
  2. MTZ = 4 is HRZ > 1.5,
  3. MTZ = 3 when HRZ > 2.5

and so on ...

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