High heart rate and no sweat -- heat exhaustion like symptoms

This is kind of an odd problem I am working through/seeing doctors. I’m curious if anyone here has had anything similar or has any ideas.

On 4 or 5 occasions over the passed two months I have had “heat exhaustion-like” outdoor exercise issues. Each time it happened (both running and biking) it was after significant zone 4/5 efforts. My heart rate remained high until I was in shade and pouring water on myself. Each time it was hot, but nothing I have not done before. I have also been sweating SIGNIFICANTLY less than I used to on my stomach, back, arms, etc. I still will sweat from my underarms and my head, more lightly though.

I recently re-did my FTP test and am showing my highest power levels to date. And I did a 100-mile ride last week at an average temp of 70degrees with no issues. I stopped a number of times to cool down, (more than usual) and I was slower than I have been previously, but I was able to finish with no problems.

I am a 30 year old male, generally ride 80-120 miles / week. Overall pretty fit and healthy (outside of this new issue).

All in all, my symptoms after a zone 4/5 workout are:

Prolonged high heart rate
Feeling of exhaustion and hot until I cool down
Substantially less sweat (I use to soak a shirt after a run, now its barely damp)
Skin feeling changes, more coarse (not a rash, but a different texture) – this happens when I begin an effort and I would be sweating
Swelling in the hands

Thanks for the help!

Do you live on a dry or humid place?

The more dry it is, the less sweat you will see…

I don’t have that problem in Florida. Every ride/run feels like a swim

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Get yourself a simple blood test and let proper docs (not web docs) decide. I never sweated much and overheated at times but got stronger if I avoided that before but I had an underlying problem which a simple blood test pointed the docs to. I’m sure you won’t have the problem but a simple blood test will rule it out altogether and put your mind at rest.

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Humid place. It seems to be a new/sudden change in my body’s response

Thanks for the response.
I goot blood tests done and am working with my doctor. Blood tests are all normal so far. This is my “wisdom of the crowd” shot.

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I had that happen once when I got dehydrated/heat exhausted. Went from sweating normally to completely dry skin and high internal temps and HR since the body had no way to cool. Not sure why it would continue to happen though

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I forgot, i got this skin rash on hottish days for the rest of that season(july onwards) and I avoided hot days in general so I may have just avoided relapsing symptoms.

Start with this 3 part ‘beat the heat’ series and see if you find something useful:

What helps me is pre-hydrating about an hour before going outside. Through trial and error I determined water with electrolytes is best for pre-hydration.

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Were you shivering and dizzy at all? When you say high HR are we talking above 100 bpm even when you’ve stopped exercising for a few mins and how does it compare to resting HR?

Heat exhaustion and stroke symptoms