I’m not an obsessive, just interested, but as i have a garmin with HRM that I use to map my rides, I might as well also collect the data, and so have been for a couple of years.

I’ve estimated max heart rate three ways in the past; 220-age; by beasting myself on the biggest hill I can find and seeing what the biggest number is before it all goes black; and doing a 30min time trial to get an approximation of threshold and multiplying that up. They all give me a number within a few beats of each other, so i figure the answer is around there. So far so good. On a normal ride, when twatting about racing mates, i usually get up to or close to this number. 175 for sake of argument, with a threshold at about 145-150.

Until fairly recently – last 4 months or so, I don’t seem to get close. Will be crunching some data later but as a comparison, the highest I’ve seen is 169, and I wanted to die at the top of that.

And so yesterday on the commute home, I tried a refresh of the lactate number (OK, not a full 30min effort, but based on perceived) – finding the tipping point between as fast as i can sustain, and where performance starts to drop off. I then on the last hill started to ramp up from this perceived threshold to end up on close to maximal effort (I’ll admit, just short because I don’t like fainting in rush hour traffic). I got 142 as a threshold, and 162 as a max. The 142 isn’t so far off, but the 162 is way below previous, and has also dropped significantly vs this year’s 169 max.

And while you can say i didn’t try hard enough, both segments on Strava were pb’s.

Now, i might be 2 years older (I recall two birthdays, vaguely), and also possibly a bit fitter (suspect) – but any reason why my heart rate numbers seem to be so much lower?

Bottom line – is this a sign that I’m going to die?

Replaced the battery in the HRM strap? Might be getting a bit off as it runs out.

It could be that your initial measurements were too high and you’re now seeing true values. For example, my average HR is a few beats higher around times where I’ve not been getting enough sleep, when I’m stressed, or on rides where I’ve had a lot of coffee beforehand. Lifestyle changes affect your hormones and that, in turn, can affect your heart rate readings.

The fitter you get the harder it is to actually achieve your max heart rate. Think of the extremes, your regular couch potato will likely reach their max next time they decide to head to the fridge for another beer. A top athlete will have to be at or near a world record pace and still have a few beats in the bank.

This is one of the reasons why HR is a poor data point around which to build training programmes. As has been explained to me by a sport science lab, your HR, including your max, your zones and so on, is really quite variable.

For instance, the total range I have seen over the last three years for my HR max is 191 at one end and 183 at the other, and the ‘real world’ max i’ve seen recently, i.e. the max I usually/commonly get when racing, is only around 177.

The 191 reading is almost ‘ghost like’; I’ve only ever seen it twice, and on both occassions fleetingly enough to make me think it was an error reading, although on both occassions it did come right at the end of a long hard turbo session.

My 183 reading was taken in the sports science lab. At the same time however, they also did blood gas analysis and blood lactate readings during a ramp test.

There was another thread about Lactate Anaerobic Threshold testing that questioned what it told you that you did’t already know and your question around HR max is a good insight to the answer.

It told me that at anything above 267 watts at my current (at the time) level of fitness, I would be riding on borrowed time.

That was a very precise figure; there’s no ambiguity to it and it and in the absence of any additional training, that will always be a constant, regardless of what my heart is doing.

At least that’s how it was explained to me.

Gone on a diet, or cut a food stuff out of your diet?

I don’t think you’re measuring like with like? To be consistent you need to measure on the same course with the same regime.

Other things conspire to change HR data. The straps can be unreliable (especially ‘soft’ luxury straps, static/cold weather can cause mayhem and you may be tired, hot, dehydrated etc which will all elevate HR.

I understand all that, but I’m not comparing a single number from 2 years ago to a single number now. What i’m seeing is consistent with what I’ve been seeing the last few months; the numbers i built from 2 years ago were consistently there or thereabouts up until a few months ago.

So no, it’s not ‘under lab conditions’ but there is enough other variability in there that any single factor is likely to have been smoothed out (hot vs cold, tired vs fresh, ill vs not, and so on)