Running in the heat questions

I sympathize!

I live and train in South Florida and the H&H is brutal from about late May when the rainy season kicks in until early November.  Those of us who run down here do so early.  Really early.  Not that the H&H is absent early, but that it is not as high as it will be later and if you add the direct sun to the mix ... not good.  People are often out at 3:30 to 4 AM to get their 20 mile training runs in before the sun comes up.

Anyway, I typically go into what I call my "Summer Slowdown" somewhere around June.  I lose about 20 to 30 seconds per mile on my paces.  The reason that most give for this is the your body has to direct more and more of the oxygen and nutrients to keeping the skin as cool as possible - thus less oxygen is available for the legs to use in running.  It can be mentally tough to run those slower paces.  I have to keep telling myself "This is not my "true" pace.  It'll come back in the Fall".

But the good news is, if you persist in training when the weather is tough, when Fall comes you will not believe how well you will run.  I've had most of my Best Races in the Fall, up north, after training all summer in the H&H.

Bill

For hot days, I would go with a loose tech tee.  You forget the sun will also make you feel hotter.  Also, once you sweat or put water on yourself, the wind will help cool you off.  If it is really humid out, I think no shirt feels best, because you won't be sweating normal and as much air on you skin will feel better.  If its hot and humid out, a tank top works well for me.  You get some cover from the sun and some exposed skin.  Of course hot and humid are just horrible runs. You might as well call them junk miles unless you are heat training. I would avoid both hot/humid days.  I got heat exhaustion from just 1-2 miler once.  I didn't drink enough water that day.  It took me 6 hours in AC with ice on my heat to not feel hot.  A friend of mine's kid almost died from heat stroke running HS track, it was only a 1 miler.

Here is a tip that tells you if you need to stop running during these days.  While you are running, stop for 10 seconds, if your face and ears feel hot, call it a day.  You won't feel the heat when you run because of the cooling effect, but this will tell you when you should stop.

Dropping from 7:30-8:00 pace to 10:00-10:30 pace seems to be a little too much, but I am not an expert by any means . 

I think what you should do all depends on which races you are planning to do. For example I am doing the IMTX this May 19th. Even though the race starts at 7:00am, it is obvious that almost everybody will be running during the hottest time of the day. 

Ahh Spring on BT when the threads about gloves, snow and trainers, turn to talk of heat stroke and lbs lost from sweat.

Run early or run late, but not running in the heat pretty much means not running in Houston.  You just have to do it, and I do suggest som runs around the time of day when you will be on the run course on the race.

I can't stand a shirt normally when it is hot but it is usually compression if it lasts at all.  I just got a desoto skin cooler shirt over the winter that is suppose to help keep you cool when it is wet.   It kind of looks like something one would wear to an S&M party... but anyone running in Houston in the summer is kind of belongs at those parties anyway.

I'm going to give it a try soon and see if that is better than no shirt.

Ahh Spring on BT when the threads about gloves, snow and trainers, turn to talk of heat stroke and lbs lost from sweat.

Run early or run late, but not running in the heat pretty much means not running in Houston.  You just have to do it, and I do suggest som runs around the time of day when you will be on the run course on the race.

I can't stand a shirt normally when it is hot but it is usually compression if it lasts at all.  I just got a desoto skin cooler shirt over the winter that is suppose to help keep you cool when it is wet.   It kind of looks like something one would wear to an S&M party... but anyone running in Houston in the summer is kind of belongs at those parties anyway.

I'm going to give it a try soon and see if that is better than no shirt.

The afternoon heat here in FL is my biggest incentive to get up and run in the relative cool of the  morning. 

I normally train by HR, but as Sue said, cardiac drift throws that out of kilter in the heat, so I just go by RPE.  More than once I've just packed it in and walked home when I got too hot.

I also worry about sun exposure, so I wear a shirt and hat 99% of the time.  If I've going more than a couple of miles I usually throw some sunscreen on my face, neck & arms. Sometimes I'll even wear a light-weight long-sleeve dry-fit shirt to keep the sun off my arms.

Mark

I'm going to go against my fellow Floridians and say I run in the late afternoon, after 5:30 or so in the summer. I don't like to run in the morning when it is brutally humid, the sweat just does not evaporate.

In the afternoon, there is almost always a sea breeze and while hotter, the humidity is much more bearable. I run a route that brings me back to my car after about three miles and I stock up on ice in a baggie and cold water. Put the ice in your hat and rub the bag on you and it feels much cooler. As the ice melts in the bag I pour it over my head. After three more miles, back to the car for more ice and gatorade. I am usually completely soaking wet after four miles on my summer runs.

 Body Glide is your friend.

The HeatGear or DeSoto Skin cooler stuff works better in lower humidity also.

5 seconds per mile per degree is pretty extreme.  6-10 seconds per 10 degrees (F) is more common.

To answer your question:  When your core temp starts to rise, the body pumps blood to the skin to carry the excess heat from the core (vital organs) to the skin, where it is dissipated with the help of sweat. Part of your aerobic capacity is thereby used up in the act of cooling, and so is not available to contribute to the act of running.  So, you slow down.

To some extent, you can acclimate, so the first hot days of the year are typically the worst (IME).  But to a large extent, this effect is unavoidable.

I don't think you can peg a specific amount of seconds per mile for each degree of temperature.  It's not linear.

I started working out in the dry Dallas heat last year when it was over 110F.

I plan on running in the heat again this year,as I felt that it helped me a lot to go faster in the cooler times.

Though I did carry a camelbak onlong runs.

Overall I felt that running in the heat with extra wheight helped me a lot to improve endurance and mentally to push through.

hromero - 2012-04-12 12:55 AM I have a few questions about running in high temps. I noticed my pace drops about 10 seconds per degree F with the same HR. Why is this? How can I minimize it? I love science and knowing why my body does what it does. Off course higher outdoor temp equals higher core temp. But why does higher core temp have to equal lower pace so dramatically? Also, at what point do you say this is torture and unproductive and take it to the treadmill. I live in south Louisiana so the treadmill in the AC is very tempting. I realize I will not get better in the heat unless I run in the heat but at what point does the pace get so slow that it is a waste of time? Which would produce better fitness gains? Option 1 - run in the heat at a 10:00 to 10:30 pace? Or option 2 - run on the treadmill at a 7:30 to 8:00 pace? My logic is telling me that I get a better workout when I run faster, but is that the case? Now.... Before all you hard core outdoor only running types start harping on me for not spending time in the heat to acclimate, let me say that I work outside in the heat all day so I am definitly accustomed to my environment. Also, if you have never been to south Louisiana in the summer then there is no way to fully understand how bloody hot it gets down here. 90 with 50% humidity is one thing and 90 with 100% humidity is a whole different thing. BTW it gets much hotter than 90

Correction, your core temp does not rise, and if it does it is by a very minimal amount. 

This is correct.  I was just making the point that the OP's report seems extreme.  Jack Daniels has published some numbers based on his observations (and they pretty much comport with my own observations of, granted, just myself).  The relationship is not linear, though it isn't massively non-linear either.  They're in his book, and probably available online as well.

bcagle25 - 2012-04-12 10:38 PM

hromero - 2012-04-12 12:55 AM I have a few questions about running in high temps. I noticed my pace drops about 10 seconds per degree F with the same HR. Why is this? How can I minimize it? I love science and knowing why my body does what it does. Off course higher outdoor temp equals higher core temp. But why does higher core temp have to equal lower pace so dramatically? Also, at what point do you say this is torture and unproductive and take it to the treadmill. I live in south Louisiana so the treadmill in the AC is very tempting. I realize I will not get better in the heat unless I run in the heat but at what point does the pace get so slow that it is a waste of time? Which would produce better fitness gains? Option 1 - run in the heat at a 10:00 to 10:30 pace? Or option 2 - run on the treadmill at a 7:30 to 8:00 pace? My logic is telling me that I get a better workout when I run faster, but is that the case? Now.... Before all you hard core outdoor only running types start harping on me for not spending time in the heat to acclimate, let me say that I work outside in the heat all day so I am definitly accustomed to my environment. Also, if you have never been to south Louisiana in the summer then there is no way to fully understand how bloody hot it gets down here. 90 with 50% humidity is one thing and 90 with 100% humidity is a whole different thing. BTW it gets much hotter than 90

Correction, your core temp does not rise, and if it does it is by a very minimal amount. 

Core temp is variable, though you're right that it doesn't change a whole lot, at least not if you are going to stay alive.  The point is that the body has mechanisms to maintain it within acceptable limits when conditions threaten to raise it unacceptably, an important such mechanism being pumping blood to the skin.

There's a lot of debate about some aspects of these mechanisms, including an interesting current debate about the extent to which humans are capable of 'selective brain cooling'.  But the basic point is not in dispute:  when it's hot, your heart has to work harder to keep the body cool, and that's work that is 'stolen' away from running faster.

Experior - 2012-04-12 10:07 PM

bcagle25 - 2012-04-12 10:38 PM

hromero - 2012-04-12 12:55 AM I have a few questions about running in high temps. I noticed my pace drops about 10 seconds per degree F with the same HR. Why is this? How can I minimize it? I love science and knowing why my body does what it does. Off course higher outdoor temp equals higher core temp. But why does higher core temp have to equal lower pace so dramatically? Also, at what point do you say this is torture and unproductive and take it to the treadmill. I live in south Louisiana so the treadmill in the AC is very tempting. I realize I will not get better in the heat unless I run in the heat but at what point does the pace get so slow that it is a waste of time? Which would produce better fitness gains? Option 1 - run in the heat at a 10:00 to 10:30 pace? Or option 2 - run on the treadmill at a 7:30 to 8:00 pace? My logic is telling me that I get a better workout when I run faster, but is that the case? Now.... Before all you hard core outdoor only running types start harping on me for not spending time in the heat to acclimate, let me say that I work outside in the heat all day so I am definitly accustomed to my environment. Also, if you have never been to south Louisiana in the summer then there is no way to fully understand how bloody hot it gets down here. 90 with 50% humidity is one thing and 90 with 100% humidity is a whole different thing. BTW it gets much hotter than 90

Correction, your core temp does not rise, and if it does it is by a very minimal amount. 

Core temp is variable, though you're right that it doesn't change a whole lot, at least not if you are going to stay alive.  The point is that the body has mechanisms to maintain it within acceptable limits when conditions threaten to raise it unacceptably, an important such mechanism being pumping blood to the skin.

There's a lot of debate about some aspects of these mechanisms, including an interesting current debate about the extent to which humans are capable of 'selective brain cooling'.  But the basic point is not in dispute:  when it's hot, your heart has to work harder to keep the body cool, and that's work that is 'stolen' away from running faster.

Most people think when their bodies can not get ride of the heat fast enough, their core body tempo is rising. It's more of a effect on your cardiac output then it is with your core temp rising.