Heat exhaustion?

Weekends are my LSD—long slow distance—days.  That’s when I log my longest run of the week.  Last week I did 17.5 kilometers.  I wanted to do 20 kilometers yesterday.  LSD runs are supposed to be the bedrock of any marathon training schedule.

But yesterday, everything went bad.  I usually do my running in the morning, but I woke up at 5:30 am hungry and I was hesitant to eat before running.  If I ate my usual breakfast, that meant I would hit the road at about 7:00 am.  I calculated a 2.5 hour run so I would still be running when the sun began scorching the pavement.  Moreover, my Garmin watch was out-of-whack, suffering again from that irritating “reverse-charge” syndrome.   I opted to move my LSD run to later in the afternoon, figuring that the temperature would be cooler.

At 3:00 am, clouds hovered in the sky, threatening rain.  A downpour during an LSD run would be glorious!   I strapped on my hydration belt and began my run.  All I had was one banana as my on-the-run fuel and one 200ml bottle.

And no, it didn’t rain.  I know it rained elsewhere and as a result the air was humid and sticky.  There was no wind to cool me down.  I began to feel my body temperature rise.  I welcomed the brief gust of air when cars would pass me by but it wasn’t enough.  At first I downed water by the mouthful, but at the 10K point I started to conserve water.  The thought that constantly entered my mind was the James Franco character is 127 hours.   My heart rate was elevated, not at cardiac-arrest level, but I was surprised that even at a comfortable pace my heart rate was close to maximum level (you know, that “220-minus-age” level).   I was running slow and I planned to pick up the pace in the latter half, but I ended up slowing down.  By the time I hit 12K  my water bottle was empty.  I blanked my mind, trying to disassociate myself from that heavy, sluggish feeling.  My legs were still strong, my breathing was far from laboured, but my body temperature was feverish.  I was thirsty, my mouth dry.  I had a throbbing headache.   At the 16K point, mentally drained, I gave up, frustrated with myself, and walked the rest of the way home.

At home I gulped down glasses of water.  I have never been this parched after a run.   I still felt feverish and the cold shower helped alleviate it.   I didn’t have any sports drinks but I had a few sachets of hydration salts so I mixed those with water instead.  I began to feel weak and sleepy.  With about three electric fans blasting at me, I  closed my eyes, lay down on my bed, and tried to cool down.  I began to feel muscle cramps and had to periodically sit up to stretch.

So what happened?

I figured I must’ve suffered from heat exhaustion. The weakness, nausea, cramps are consistent with the symptoms of heat exhaustion.  Heat exhaustion happens when your body isn’t able to cool itself properly.  The body doesn’t cool itself by just sweating.  It’s the evaporation of that sweat that cools the body.  High humidity can prevent that sweat from evaporating.  It was a good idea that I stopped running—I could have ended up with a heat stroke!

Lessons learned: in a hot, humid day, bring adequate water bottles and constantly hydrate yourself!

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