Or,
what a difference two hours earlier and 15 degrees cooler make!
Basically,
I hit the wall--at Mile 8. The entire run just felt different. Temperature at finish
was 91F, with humidity still near 80. Looking back, obviously, I should have
started earlier that morning--by at least couple hours. It wasn’t quite heat
exhaustion during the back half of the run; but there were perhaps intimations
of it. Dehydration? Probably. The usual 22 oz Nathan bottle I carry on long runs definitely wasn’t enough. And, had I not fortuitously run by a water
fountain at a local park, I would have run dry and likely run into trouble.
Definitely need to better plan for refills! Before the shower, the scale showed
a seven-pound weight loss, which seems to be within the average of two pounds of sweat per hour of intense activity. The recovery of the lost
pounds was fairly quick, as typical, within a couple days or so.
The
entire run felt different, but the back half decidedly so. I was into some new,
Twilight Zone-like territory. Ears felt waterlogged. Voice sounded foreign.
Skin grew a layer of salt crystals. It didn’t even occur to me at the time that,
being evidently a salty sweater, my body was running low in sodium.
In
previous hard runs, my legs would partially recover by walking, and I’d be able
to run a stretch before the next walk. This time, the legs didn't recover by
walking; they continued to feel fatigued. In my mind at the time was the
Potomac Marathon coming up in five weeks; so, I decided to not chance it and
walk the last three miles home. Over the back nine miles, I walked about half
that distance in total. Cadence (stride rate) was 142/min; usually it’s 168-174.
Total time was about an hour longer than usual for 19 miles.
The
body acclimates to heat, from a number of physiological adaptations, including
integrated thermoregulatory, cardiovascular, fluid-electrolyte, metabolic and
molecular responses, over a period of about one to two weeks. (See,
e.g., Armstrong, 1998; Nielsen, 1998; Prazak, 2014; Sawka et al., 2016; and Chong and Zhu, 2017, a review.) So,
if I had run the 20 miles on August 12th in similar conditions, I
probably would have done better. (August 12th was over the same
route, just a mile longer.) But, by far, the big difference between the two
runs of August 5th and 12th was 15-degree cooler! The
result was a two-minute faster average pace. (For comparison, the July 29th run in
California was done in cooler and drier conditions.)
The
following nomogram from Cheuvront et al. (2010) shows the effect of temperature
on marathon pacing. My pacing as a function of temperature accords fairly well
with the chart.
If
endurance, according to Alex Hutchinson in his book, Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance, is “the struggle to continue against a mounting desire to stop," then I lost
that struggle on August 5th. Perhaps, in such conditions, I should have
stayed closer to home and run my usual long run route (three miles from home at
its farthest).
In
fact, such a struggle was the August 5th run that, for the first
time ever, I made a nine-minute Starbucks pit stop at around Mile 18 to get
coffee; which greatly helped getting me through that last mile! (Btw, my TomTom
watch has a nice auto-pause feature, which produces an average pace based on
actual activity, not including, e.g., time in a Starbucks getting coffee.) The guy who
made it to the barista just ahead of me had some kind of complicated order. With
my ears "waterlogged," I only caught a few words: can you add ...
caramel ..., I can't do that, but I can ... Standing right next to him, I was
thinking, hey buddy can you hurry up I just want to order a tall coffee and get
out of this way-too-air-conditioned place (for a sweat-soaked runner). I
suppose I was fortunate, the way I must have appeared, that the police wasn’t called
on me. But, then again, if my skin had a somewhat darker hue from all those summer months of running ...
