Dancing with Dirt – and the Physiology of a Good Long Run

19 Jul

It’s HOT!  How hot is it??  It so hot, I could go to my hot yoga class to cool off!  (ba-da-bam-cymbol crash)  But, really, I’m neither joking nor exaggerating.  It is currently hotter than what yuppy-spa-goers pay for to open their sweat glands and release their chi.  Hmmm – funny I don’t see anyone running out into their yards taking advantage with a good vinyasa!

But I digress.  Our current heat wave – and the pain of running in it – has me thinking about just what our bodies can take!  Recently I got talked into running in the trail race from Hell.  No, really, the race originated in Hell, Michigan – but we ran the Wisconsin version in Devils Lake State Park.  A 60 mile relay for a team of 5.  We each ran three legs up and down hills, through forests and ravines, across prairies, and even up a creek.  I actually ran the shortest distance on our team, coming in with just under 10 miles – and I was darned pleased with the training it took me to manage that.

must...not...get...passed...by...old...dude... (Photo credit - not me! - Thanks M Reetz)

Early on the morning of the race, as we were still snug in our tents at the race base, a starting buzzer went off.  Hours before our own.  Before the day dawned a group of (I assume crazy) runners took off to conquer the hills and miles we would later distribute between the 5 of us.  The ultra marathon would cover 50 miles of the nastiest terrain, climbs, mud pits of the whole race.  Never before have I felt wussier for running a mere 9+ miles over some hills and through a creek!

How is this even possible?  This question is also came up in our recent group paper (seriously a great read, why don’t more articles start with tales of polar explorers – and then offer scientific explanations for their demise?).  The author bridged some interesting species gaps by studying the feats of both cross-continental migrating animals, and ultra-distance human athletes.  They talked about physiological constraints that limit the amount work that is actually possible for our bodies, and the ecological conditions that led most to evolve to choose not to push it quite that far.  Turns out the physiological limitations – like heat stress, how much energy we can take in to balance what we burn, etc. – are pretty incredible!  Animals are physically capable of overexerting ourselves to extreme proportions – maybe even up to 8 or 10 times our resting energy outputs.  But most animals “realize” that fitness is better and life is longer if we take it a little easier.  So most never push that hard.  And those who really go great distances – i.e. maintaining huge exertions for long periods of time – top out at much lower levels of energy use – about 4 to 5 times our resting rate.

So what about those crazy ultra-runners?  I have a long way to go before even considering myself an ultra-jogger!  But I thought I’d see what it takes for an average-sized lady to run a 50 mile ultra trail marathon.  (Note – this is a super simplification, and we’re not even considering the stress of heat on a July afternoon, and we’re assuming our runner has enough water and goopy energy shots to maintain hydration and energy balance all day – she probably doesn’t!).

  • An average adult female requires about 1700 calories per day just to maintain herself.  (this is the resting energy requirement or “basal metabolic rate”)
  • Over a full day that’s about 71 calories needed every hour.
  • She’ll burn about 105 calories per mile of running at a slow and steady pace.
  • But she’ll burn closer to 150 calories per mile on a hilly hike.
  • So we’ll guestimate a mid range and say that over the course of the race she burns about 125 calories per mile.
  • She runs 50 miles!
  • That’s 6,250 calories for the day!
  • And the top notch runners were finishing in around 10 hours or even less! (obviously our ultra gal is top notch)  (side note – our relay team finished in about 10 and ¼ hours – getting to swap out for fresh runners every few miles!)
  • So that means she burns about 625 calories per hour during the race.
  • That’s over 8.75 times the resting energy rate for this runner!!

Way to go ultra-runner!  You’ve pushed the limits of possible animal exertion!  And exceeded anything that could reasonably be maintained for much longer!

As for our own little relay team – well, we won – chairs!

DWD relay team and our prize! (Photo credit - not me! Thanks J Chipault)

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