Sudden increase in max training heart rate

I read one peer reviewed paper in some medical journal that analyzed the accuracy of optical-based heart rate measurements on the wrist. The error was up to 8% and not much lower than 4% at best. This is just from my memory, but if we assume that the accuracy that they report is relative to your heart rate rather than relative to full scale, then:

If your heart rate is actually 180, then you would see anything from 173-187 on your watch, at best. You could see anywhere from 166-194.

So, you seeing 185 on your watch when you expect to see 180 is not significant. It’s well within the accuracy of the measurement technique that you are using.

I read one peer reviewed paper in some medical journal that analyzed the accuracy of optical-based heart rate measurements on the wrist. The error was up to 8% and not much lower than 4% at best. This is just from my memory, but if we assume that the accuracy that they report is relative to your heart rate rather than relative to full scale, then:

If your heart rate is actually 180, then you would see anything from 173-187 on your watch, at best. You could see anywhere from 166-194.

So, you seeing 185 on your watch when you expect to see 180 is not significant. It’s well within the accuracy of the measurement technique that you are using.

Thanks for the reply.

My point is that I've been using the watch for nearly a year, and have only seen 180 twice before. Once during my 10K PR where it spiked briefly at 180, and once on a bike ride where I destroyed myself going up a 33% gradient. During both efforts I knew I was working really hard and close to or at my limit.

This week, however, I've seen a 180bpm recording on three consecutive days of pretty moderate efforts. Each around 5-10 minutes of my PR with around 100 metres of climbing thrown in over the 10 K distance (300 feet over 6 miles roughly). If I had seen the 180 reading on just one day I would have put it down to an inaccuracy, but to see it on three days in a row? Each of the 180 readings where all on the short hill sections, so it makes sense that my heart rate would spike at that point. I'm just surprised/concerned to see that it went so high.

I recorded my heart rate all day to see if my resting heart rate is elevated somewhat, and it has been around 48-52 all day, which is normal for me. I feel rested after a week of relative inactivity last week, but maybe I have some residual fatigue left over from my cycling tour over a week ago? I've searched Google, but I can't find any phenomenon relating to a sudden spike in a runner's training heart rate.

I guess I should say I was seeing 180-185 when I would be expecting to see 160-170. I regularly run the course I ran at the pace I ran, and those are the numbers I usually record.

Change in blood volume. Less plasma = higher heart rate, lower stroke volume (less blood pumped per beat) but usually the same cardiac output.

If you increase mileage or the weather gets warmer, you will see the reverse.

Thanks, I'll look into that. Hopefully it is normal.

What would cause a drop in blood volume? Are there common causes?

I haven't changed my training in any way, other than I've had two lost weeks (one week due to an intense cycling trip, followed by a mild week of hiking). The weather has got considerably colder.

dehydration is most common. HR can change in response to a variety of stimuli in addition to acute changes in blood volume. But, because your RHR is within your normal limits, I wouldn't be too concerned

From age 50 to 53 I achieved max heart rates of 212, 214, and 216. In each case it came after 4 months of careful aerobic base building. For two of those winters I spent three months pool bottom running doing 2 to 2.5 hour workouts. I built my aerobic base during the fall and winter months running 70 to 75 miles per week on soft hilly trails. I followed the MAF (maximum aerobic function) method, gradually increasing my pace while keeping my heart rate aerobic in a gradually increasing from 148 to 162. My favorite training pace was at 155 beats per minute.

When I hit 212, it was in a 1 mile straight road race with the first 600 meters being uphill and the entire race into a 17 mph headwind. I hit 200 bpm at the half mile mark, and finished at 212, with the time of 5:00.

On the other occasions hitting 214 and 216, both were in a late February hilly 10 mile road race, then I sprinted the last half mile.

For me the key was a long careful aerobic buildup. Each time when I started racing my heart rate would go up above 190 in the first race and I did not even feel tired at all. All I wanted to do was go faster. Gradually my steady heart rate and races would come down as I got into my racing season.

I'm a mile or 5,000 meters guy, though I have run as far as 50 miles. In a 5K race my heart rate never reached 190. The race just wasn't long enough. And I was running very fast for my ability, in the 16:30 to 17:30 range.

The highest heart rate I'd ever recorded before the training I described was 201 at age 30, and I did it in a circuit training workout blending weightlifting and cardio.

Just my experience to share with you.

Fogrunr wrote:

[quote]runandride wrote:

...In a 5K race my heart rate never reached 190. . .

It means you have lack of muscle power, and heart system developed much bigger than muscles. Not optimal development: want to run faster, not tired, feel good, but cannot increase the pace.

MAX HR doesn't increase with fitness, you may be able to sustain your max efforts longer and closer to it as you get more fit.

If the new max readings are short spikes it could be bad reading from the monitor. Maybe you aren't used to max efforts?

How old are you? 180 is low for a max HR unless you are over 45yo

I've had the same thing many times. After I take a long break, my heart rate is raised by about 10. For example, after the break I would "feel" like I'm running around 140bpm when it is indeed around 148-150bpm. Detraining has this effect on me, which I've witnessed quite a few times. Once I took a 2-3 week full break from running after running quite a lot in the preceding 3-4 months. After I started running again my HR was at a lot higher than before. At the peak of my training I could not pass 185bpm, but after the break I was running at 175bpm and was still feeling well under my lactate threshold. One day I got so fed up, I just ran as hard as I could, completely out of breath and hit 201bpm, 15 above what I could possibly have run a month ago! That was the first time I experienced it and now I know that when I first start running after a long break I will have my HR around 10bpm higher. As I get fitter it starts to go down, and eventually how I felt running at 155bpm becomes the same at 143bpm (generally after a few weeks later).

Years ago I read a peer-reviewed study from UBC that explained this phenomenon and suggested a difference of 2-4bpm in average if I remember correctly, though I don't remember the explanation nor the study.

Two other posters mentioned change in blood plasma and heat and I think they are right. Heat is a factor regardless of how fit or unfit/detrained you are, so that doesn't explain your situation assuming the temperature was similar in the low and high HR runs. Also stopping training (ie. detraining) might have some effect on blood plasma volume.

I wouldn't worry about it too much as I've had this happen to me many times. In fact, people who are in tune with their bodies who have a "feel" for a certain heart rate would probably notice this, though it might be just a couple bpm, whereas I (and perhaps you) are on the end of the bell curve with much higher heart rate difference between trained and untrained states that makes it more noticeable.

I'm quite familiar with the FR 45 and I agree with your assessment of its HRM. And no, you should not see anywhere close the HR you hit during a 10K PR during a 6.2 mile training run.

My guess is that your watch has developed an issue. The next time you see a high HR during an easy run, check your heart rate manually. If your heart rate really is that high, consult a doctor.

runandride wrote:

What would cause a drop in blood volume? Are there common causes?

I haven't changed my training in any way, other than I've had two lost weeks (one week due to an intense cycling trip, followed by a mild week of hiking). The weather has got considerably colder.

Most likely reason is that the cold weather and a mild training week has caused a reduction in fluid and sodium retention in your cells and blood plasma. Your red blood cell mass will be the same.

This is because you have been sweating less. It's an adaption to the cold weatveher and reduction in training volume.

Your HRM is picking up your cadence.

runandride wrote:

My point is that I've been using the watch for nearly a year, and have only seen 180 twice before. Once during my 10K PR where it spiked briefly at 180, and once on a bike ride where I destroyed myself going up a 33% gradient. During both efforts I knew I was working really hard and close to or at my limit.

This week, however, I've seen a 180bpm recording on three consecutive days of pretty moderate efforts. Each around 5-10 minutes of my PR with around 100 metres of climbing thrown in over the 10 K distance (300 feet over 6 miles roughly). If I had seen the 180 reading on just one day I would have put it down to an inaccuracy, but to see it on three days in a row?

Typically when an optical-based heart rate measurement is similar to cadence but not likely near actual heart rate, the watch is loose and responding to ambient light from outside reaching the detector rather than reflected light from the device that would indicate heart rate.

My original point was that you cannot be confident that your heart rate measurement of 180 and 185 indicate any difference in heart rate. They are the same. You can have some confidence that when you made those two measurements your heart rate was probably between 171 and 194.

My immediate thought is hydration as you could be slightly dehydrated and not know it. It's not only making sure your fluid intake is adequate prior to your session but also throughout the day as we all lose fluid due to temperature, use of caffeine, alcohol, etc.

OK, I found the source I mentioned in my earlier post.

https://pubmed.ncbi.nlm.nih.gov/10688280/

"While it is known that aerobic training decreases submaximal HR (HRsubmax) at a given absolute exercise workload, the general consensus is that maximum HR (HRmax) is relatively unaltered regardless of training status in a given population. It has not been seriously postulated as to whether HRmax can change modestly with aerobic training/detraining. Despite several sources stating that HRmax is unaltered with training, several studies report that HRmax is reduced following regular aerobic exercise by sedentary adults and endurance athletes, and can increase upon cessation of aerobic exercise. Furthermore, evidence suggests that tapering/detraining can increase HRmax. "

And here's another one:

https://pubmed.ncbi.nlm.nih.gov/17960504/

"HRmax is significantly lower in athletes compared with age matched sedentary counterparts. "

Both are peer-reviewed articles.

As I said I've observed this many times myself, my trained and untrained HR numbers have a difference of about 10bpm. I'd think for most people there is a difference but perhaps it's minimal for most to realize it.

This is correct and has been known for a long time. Why it isn't common knowledge is.... well it's just another one of those things that every athlete and exercise physiologist should know, but most don't.

stranger wrote:

Both are peer-reviewed articles.

As I said I've observed this many times myself, my trained and untrained HR numbers have a difference of about 10bpm. I'd think for most people there is a difference but perhaps it's minimal for most to realize it.

My max HR went from 200 to 185 and then 180 very quickly with intense training. But I'm also a mega responder to training (5k drop from 21 min to 16 min in 2 years). In people who don't train very hard or don't respond to it, changes in max HR will probably be a lot less since their heart and blood volume won't develop at the same rate. That change happened from almost no training to 4-5 hours/week. Further increases in training showed 0 change in max HR, even up to 10+ hours/week it's still around 180. So the change in max HR is probably due to beginner gains/going from rather sedentary lifestyle to somewhat active.

Also, I can only reach this HR with an extreme effort, full glycogen stores, good sleep etc. Also when it's too cold (shortly above freezing or lower) max HR levels off much earlier, I've leveled off at 171 during an all-out mile in 18F (but same speed as during normal weather), ~10 bpm below my actual max.