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.