# Lower heart rate at altitude ?



## Summit_Rider (Aug 29, 2006)

I just returned from a week of riding in Colorado at elevations of 9,000' to 12,000'. My heart rate seemed to be about 20 beats lower for the same perceived effort. I.E. at home elevations ( 2,500' - 5,000') my normal HR zones are 150 to 170 BPM, in CO my HR was 130 to 150 BPM max. for the same effort...? I took it easy for the first 2 days and seemed to adjust to the elevation as the week went on, but my HR still stayed low. Now that I am back home my HR is back at my normal rates . Is this normal or possibly a result of a poor VO2 max ?

Any ideas ?


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## ericm979 (Jun 26, 2005)

I noticed the same thing when I went to Colorado for the Mt Evans race. Even after a week at 5000', once I got above 10k' the HR that I could maintain gradually went down.

I'd expected HR to be unaffected by altitude, or to go up instead of down.

I was definately breathing hard- I stopped breathing for a moment to swallow a piece of clif bar at 12k' and nearly passed out- felt dizzy and got tunnel vision. I didn't try to eat after that.


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## JChasse (Sep 16, 2005)

I noticed the same thing, by about 10-15 bpm, when I moved to 7,000 ft in CO from sea level on the east coast. it's been 2 yrs now, and my "normal" range hasn't ever gone back up. 

It actually freaked me out, so the hr change and some other weirdness led me to have some pretty elaborate cardio testing done, but i'm told everything looks good (for a guy with a teeny motor).


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## bradXism (May 10, 2011)

Hasn't noticably happen myself. I would have thought it would have gone up to move oxygen to cells at the same rate. Once your hematocrit ,or red cells per volume, goes up, thenit may slow down.
The reason may be that the outside aire pressure pushing in is less and so would the return pressure to the heart. Starlings law dictates that more pressure to the left of the heart makes the rate increase. This is means pumping action of muscles that are contributing to moving blood thru the veins returning to the heart and increasing the pressure. I am taking a guess that a decreased outside pressure is enough to decrease the resistance...I am prepared for my guess to be shot full of holes but even being stumped would put a guess in.


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