Change in Maximum Heart Rate

If it's hot and humid, heart rate goes up.

I just did a scientific study of 1, this morning.

How do you mean, exactly? Are you looking for data that MHR improves or goes up with heat acclimation?

Jack Daniels Calculator wrote:

Maximum Heart Rate changing under extreme (hot/humid) environmental conditions.

I would also like to hear from anyone that has direct experience with this occurring.

Based on my data records, my Maximum Heart Rate increased by over 3.5% (i.e., 6 bpm) in the span of less than one month's time. I would have trouble believing that unless I had seen it for myself.

In summary:

I conducted two 12-min Cooper Tests in May of this year, hitting what I believed to be my Maximum Heart Rate in both tests*. (These are standard tests subjecting one to VO2max conditions.) One month later, during an extreme Time Trial lasting over 20 minutes in very hot and humid conditions, my Maximum Heart Rate was 1-6 beats/min higher, sustained over a period of approximately three minutes.

*Note, in one of the tests, there was a very brief spike (four seconds in duration) in Heart Rate of 3 bpm that I discounted at the time as likely data error.

Breakfast In Bed wrote:

How do you mean, exactly? Are you looking for data that MHR improves or goes up with heat acclimation?

Yes, essentially. I'm looking for scientific literature that discusses the topic where one's Maximum Heart Rate can change in a relatively short period of time (i.e., within the span of a few weeks.) We already know that one's Maximum Heart Rate will typically decrease with age (i.e., by a small amount per decade.)

For reference, I include below the HR traces from the last 12-min Cooper Test conducted on May 17, and the Time Trial conducted earlier this week:

You must be new to running? It's called dehydration and cardiac drift.

I'm well aware of cardiac drift and dehydration. What I'm referring to is a change in the Maximum Heart Rate. I would appreciate it if you can point to a scientific source that provides evidence of one's Maximum Heart Rate significantly increasing under those conditions?

Juicy Burrito Maker wrote:

If it's hot and humid, heart rate goes up.

I just did a scientific study of 1, this morning.

You can add me to the study!!!

Max HR is a near constant, and can’t be trained to get higher. However, your max HR may be lower when aerobically fatigued or sick. I will regularly get into the mid 190s during hard intervals, but have a hard time pushing myself out of the 170s at the end of a hard long run.

I’ve been experimenting with heat training, as I’ve read a few studies showing that running in the heat does elevate the heart rate, but not at the expense of extra muscular fatigue. The theory is that you are getting more bang for your buck doing your aerobic runs in the heat, as long as you do so safely.

When heat training (85-95 degrees F) my aerobic pace of 7:00-7:30 a mile will result in a consistent HR ranging between about 150 and 160 after the first mile. My body doesn’t seem to fatigue any quicker, I just breath a bit harder than normal and have the discomfort of the heat.

Before this experiment when I’d run in 65-75 degree weather, my heart rate would be more like 145-153 in this pace range.

I have ran a few aerobic runs in more ideal conditions (65-75 degrees) and have found now the heart rate stays between 140-148 in the same pace ranges. I haven’t been able to get a long distance time trial in, but I believe this indicates I am now in better aerobic shape than when I started this experiment about a month ago.

Hope this helps

I know that sub-maximal heart rate increases, for the same paces, under hot/humid conditions. I provide actual examples where one can see that occurring in this thread:

However, what I am specifically referring to here is one's MAXIMUM Heart Rate (which is typically thought to be fairly constant) increasing by as much as 3.5% in a short period of time. I'm also not referring to being able to hit one's Maximum Heart Rate due to fatigue.

Jack Daniels Calculator wrote:

I'm well aware of cardiac drift and dehydration. What I'm referring to is a change in the Maximum Heart Rate. I would appreciate it if you can point to a scientific source that provides evidence of one's Maximum Heart Rate significantly increasing under those conditions?

Look it up yourself. Sheesh! You spend enough time pontificating.

I've tried. Unlike you, there may be some actual degreed physiologists familiar with the literature reading the forum that are willing to offer some insight.

MaxHR may DECREASE with endurance training and then "rebound" as part of tapering.

Reaching MaxHR requires one to push oneself. Also, if this was a one-off, one second reading I would not call that MaxHR (peak HR). I think a better measure is highest HR over 60 seconds (using a rolling average).

It is conceivable one might not reach MaxHR because one did not push himself hard enough the first time. In terms of heat and humidity it could keep you from hitting the higher HRmax due to other fatigue factors.

Just an abstract...

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

Jack Daniels Calculator wrote:

I've tried. Unlike you, there may be some actual degreed physiologists familiar with the literature reading the forum that are willing to offer some insight.

Look up blood volume changes and plasma shift in response to running in hot and humid conditions.

Are you really too lazy to search for this stuff yourself for more than a few minutes?

I don't think there is a hard max heart rate number as there is no max cadence number for your legs. Heart rate also is different for different sports. You might think the wrong way with this and claim you hit the max and that it increased. I think you just experienced cardiac drift in the heat.

I experienced a large change 2 years ago at the same time I started rowing. My heart rate reduced 10 strokes on average over a 1-1.5 month time and it has been like that ever since. I run the same paces, so my max heart rate must have dropped 10 strokes and since the fitness is the same it must mean my stroke volume increased. I have found very little research on this...

I haven't seen any studies on this, but I think max HR is max. Determining MHR is a bit difficult, but I'd guess that an accurate measurement wouldn't vary by more than a couple of beats.

On the other hand, there are a LOT of reasons why an effort to reach MHR would not elicit true MHR... not running hard enough before attempting the MHR effort, running too hard before increasing pace to elicit MHR, not running long enough before the attempt, being fatigued from the day before, choosing the wrong pace to elicit MHR (either too fast or too slow).

In my case, I was tested at a university performance lab. Using their standard protocol, I finished the test in 15 minutes and only reached a MHR in the low 180s. I asked for a longer test. In two subsequent tests, I ran for 29 minutes and reached 189 and 190 respectively. At the time, I routinely hit 191 after a quarter-mile sprint finish at the end of 5k races.

Bro.

Your maximum heart rate didn’t increase. You just didn’t hit your maximum in the first two hit outs. It’s not rocket science. These 12 minute fancy tests might get you *close* to your max heart rate, but you probably had a little bit more of a gear to tap into. Maximum recorded heart rate is not the same as maximum possible heart rate. End of story, close the thread.

NerdBusters wrote:

Bro.

Your maximum heart rate didn’t increase. You just didn’t hit your maximum in the first two hit outs. It’s not rocket science. These 12 minute fancy tests might get you *close* to your max heart rate, but you probably had a little bit more of a gear to tap into. Maximum recorded heart rate is not the same as maximum possible heart rate. End of story, close the thread.

+1

My max hr has been steady for the last 5 years plus. Recently, I went 5 beats above this in two separate interval workouts.

I have no explanation, but just wonder if the recent covid vaccine had anything to do with this?

I completely agree with this. I think the process for calculating max heartrate is not super accurate and I also think there are a lot of variables that can throw an already inaccurate process off even more.