Heat and heart rate

davetri

I race the Rev3 this past weekend and I was hoping to crush it, but the course had other ideas. My power meter didn't work for the race , so I had to rely on HR. I held back on the bike and ride the hills conservately, but I still had a disastrous run. I could not get my HR below 150 even when I slowed down and walked the hills. I am trying to figure out what went wrong. Can heat play a huge role in heart rate? Thanks

tgarson

I think we have a lot more knowledgeable HR athletes here than myself, but I'd chime into to say that heat *definitely* can play a huge role in heart rate, especially in how heat often leads to dehydration which leads to an elevated HR.

To try and make sense of the numbers though, what is your LTHR? (or some approximation of it)

Steve West

Trevor is correct heat can have an adverse impact HR. But there are others as well. The big ones are

Heat
Humidity
Hydration status (including rapid weightloss prerace)
Fatigue
Illness
Emotional state, ie - apprehension & excitement (positive energy), or anxiety (negative energy)

It can be very hard to know why HR behaves oddly on some days and not others. The longer you track your HR in realtime and after the fact, the better you get at identifying potential causes on specific days. But that is the trouble with HR. There are way to many outside and inside variables to get a clear answer.

Al Truscott

Posted By Dave Couture on 06 Jun 2013 08:54 AM
I could not get my HR below 150 even when I slowed down and walked the hills. I am trying to figure out what went wrong. Can heat play a huge role in heart rate? Thanks

HR goes up even more than usual in heat because you're trying to increase blood flow to the skin to cool off your overheating core ... Blood is taking heat from your insides and trying to offload it at the surface, using sweat evaporation as an aid. If this doesn't get your core temp into a safe zone your brain is smart enough to then make you slow down, walk or even stop to,literally save your life. More here in the wiki ...

http://members.endurancenation.us/Resources/Wiki/tabid/91/Default.aspx?topic=Heat+Acclimatization

davetri

Thanks guys, It looks like my LTHR=169. I think I might of pushed a little to hard in the heat. I learn something new every time I race.

cgres123

And that is what it's all about learning how to be the best you can be under all race day circumstances. If it was hotter than it was for the race the situation would have been a whole lot more challenging.

There are many things to keep you going even under the strain of the heat. You could hit the watch and do a 3 on 1 min off run, a 2 to 1 or a 5 to 1 etc, etc... That is the Galloway method of running. He advocates for every 5 degrees over 60 slow your run down by 1 min. I have a hard time with that math.
Others in Haus might use a percentage thing 2 - 10 per say. That has worked for me in training however it catches up to me between 4 - 6 miles then I need to slow down even more.
Next up is staying high Z3 low Z4 HR no matter what the speed then neg split your run as by then you will have figured out your pacing.
Best of luck

tim cronk

Posted By Al Truscott on 06 Jun 2013 04:42 PM

{HR goes up even more than usual in heat because you're trying to increase blood flow to the skin to cool off your overheating core ... Blood is taking heat from your insides and trying to offload it at the surface, using sweat evaporation as an aid. If this doesn't get your core temp into a safe zone your brain is smart enough to then make you slow down, walk or even stop to,literally save your life.}

This is brilliant but of course there are exceptions and some people do have the ability of pushing themselves into the danger zone... I believe the key to be in tune with your RPE and to NOT rely on HR. 

For an example my FTP tests yield LTHR of 168-175 and 5K tests usually 175 give or take ....I ran the 2012 Boston Marathon  in 90+ degrees in 3:36 with an average HR of 168....Glad I never looked at it as I would have thought that was impossible , of course I was hot but I never felt in danger and just paid attention to heat management and RPE.

 

 

rmiller

Dave -

I learned a valuable lesson at Quassy as well with regards to the heat - use ice water at the aid stations liberally. As Al said, your body uses blood for a multitude of things, one of which is cooling. More blood to cooling = less blood for transport of fuel to muscles. So in addition to staying well hydrated to keep your blood plasma volume up, use anything at your disposal to keep your core temperature down. At multiple aid stations, I simply ran up to them, took my hat off, pointed to someone holidng a couple cups of ice water, and said 'toss it'. They threw it in my face and on my torso, and I'd notice that instantly my HR would plummet - and it would stay down for a good couple-few minutes, which was a good way to the next station. Between that and walking the uphills (they were brutal - no point in running up them when it wasn't terribly faster), I learned a lot about heat dissipation and heat management in that race.
David also brings up the good point about Galloways adjustment for heat. Same basic principle - keep your body from overheating.

jimmy augustine

just ran over lunch today in 95deg san antonio heat. I was 25sec/mi slower than my morning run a few days back and my avg HR was 162 vs 154. It seems like in the heat, heart rate is just faster regardless of pace. I like using RPE as well though because in the heat running for an hour or so at 165bps is not nearly as hard as running at 165bpm in 40 degrees.

cgres123

I think I'd take the 40 degrees running :0