Monday, August 24, 2015

Marathon Training Update from Dr. Brandon Larkin; "Choose Your Own Adventure--The Long Run of Doom!"

Do you remember the “Choose Your Own Adventure” book series?  Huge in my life as a child.  I read every one of them.  Several times.  (That was the point, you know.)

Just in case you were not a purveyor of children’s literature in the eighties and have no idea what I’m talking about, CYOA was a collection of books in which you determined the plot.  The stories started out harmless—a regular kid having a regular day.  Heck, it could have been you.  In fact, it was you!  Some crazy sequence would occur and you were smack dab in the middle of a volcano.  And you drove the plot—“Choose option 1 to hike up the stairs to get away from the smoldering lava, turn to page 25.” Or choose option 2 to jump over the liquid fire, turn to page 44.”  Eventually you’d either win the day….or get killed.  But the beauty part was that if you got killed, you just start over and make a different pivotal decision.  And if you were in a pinch, you could just peek ahead and look for “THE END” on your chosen page, then flip back because those two words were pretty much a death sentence.  But you would only do that if you were a big ol’ cheater.

So let’s play “Choose Your Own Adventure—Long Run of Doom”

You’re on a 16-miler around the hills of beautiful Queeny Park.  It’s beautiful scenery, but as usual, it’s hot and humid.  Kind of like running in the Mekong Delta.  (See what I did there?)

You’re half way around your fourth four-mile loop, and your running buddy, Suzi, is starting to sag a little.  She’s been cramping for the last couple of miles, but now she’s starting to get dizzy and confused, and she’s throwing up.  She looks rough.

Do you:

1: Start pushing fluids.  She’s been drinking the whole run, but it’s hot and she’s sweating something fierce.  It must be dehydration.

2: Try these salt tabs you bought last week.  And how about an ambulance?

Suzi’s been drinking Nuun and Gatorade non-stop for two hours, so more salt probably isn’t the answer.  She needs more fluids, right?

You choose option 1.  (Just do it.  The story works better that way.)


Nice job. Some friend you are.


Fortunately, especially for Suzi, I’m going to let you turn back and choose option 2.  But wait, why does she need salt? You would have thought she would have had plenty of salt from the sports drinks.  Turns out you were wrong. 

Suzi is suffering from exercise-associated hyponatremia (EAH).  Because of the steamy forecast, she prehydrated all day yesterday and this morning with water and sports drinks.  This caused the concentration of sodium in her blood to decrease and the continuous drinking during the run made it even lower—dangerously low. 

So where did Suzi (and you—you’re not off the hook yet) go wrong?  She followed the dogma of overhydration.  The one that tells athletes to drink and drink and drink.  And then drink some more.  Gotta keep hydrated to replace the fluids lost by sweat, right?  And that means drinking like a fish, right?

Well, wrong.  In fact, too much water during exercise can be incredibly dangerous.  And even replacing fluids with an electrolyte containing beverage like Gatorade or Nuun isn’t safe.  These sports drinks are more dilute than your blood, so they’re considered “hypotonic.”  That means that drinking them will not increase the sodium concentration in your blood.  Rather, it makes things worse.

Too much water or sports beverages over an extended period can cause hyponatremia, or low sodium concentration in the blood.  We replace lost fluids when we drink it, but not enough of the sodium is replaced, and the blood in our body becomes diluted. Hyponatremia can be incredibly dangerous, even deadly. 

So there needs to be a balance, but do we really know how much to drink and what to drink and when to drink it during a prolonged bout of exercise?

Fortunately, new guidelines about this topic are hot off the presses, having been published in the July 2015 issue of the Clinical Journal of Sports Medicine.  It’s an 18-page article that I’m going to distill down into one sentence for you. (It’s OK.  I like reading this stuff. You’re welcome.)

Lean closer. Here it is: “Drink when you get thirsty.” 


Now, some believe that this strategy is a sure path to dehydration, but based on the research, we know that the thirst sensation is a finely tuned mechanism for maintaining normal fluid concentration.  It does a pretty good job of protecting against excessive dehydration.  And while controversial, most of the research supports that mild levels of dehydration (up to 2-3% of body weight) are tolerable and don’t overly affect performance.  The only concern here is in extreme environments or with especially aggressive prolonged activities that may lead to rapid dehydration.  In these cases, drinking to thirst may not be enough.  But situations like this are pretty rare.  (Think ultramarathons and Ironman Kona.)

If you want to be a little more scientific about it, pre- and post-exercise weights are a good way to determine the total amount of fluid to replace.  The goal should be to replace enough fluid to maintain a consistent weight or to come in a little less after exercise.  You should NEVER weigh more.  This method is relatively involved, as we don’t often have a scale readily available after completion of a run.  And it doesn’t account for the weight of the non-fluid nutritionals you put in your body during a long run or of the, ahem, other substances that leave your body during pit stops.  (Insert your favorite poop joke here.)

If you’re technologically inclined, there are apps into which you can feed the ambient temperature and humidity, your weight, and other important data to get a handle on your fluid requirements.

But here’s the deal.

Your body already does this.  Really well.  Without wifi.  The body is filled with receptors that monitor your fluid volume and electrolyte concentrations—in real time.  And these receptors give constant feedback to your brain about the situation on the ground.

And you know what it does when your internal fluids start to drop too low?  Your body, supercomputer that it is, says to your brain, “Hey! You know that water bottle sloshing around on that belt down there?  Use it, dummy.”

Your body makes you feel thirsty, so you drink.  And that’s that.  If you drink according to thirst, you stay hydrated in a safe way. 

So if our buddy Suzi had just been drinking when she was thirsty and not freaked out about the heat, we wouldn’t be in this mess.  (So, let’s blame her.)

Now, I mentioned salt supplements as an option above.  A quick note: Salt supplements can help replace depleted sodium.  In fact, oral sodium is the treatment for hyponatremia out in the field before an affected athlete can get to the hospital.  Studies recommend 4 bouillon cubes in a half-cup of water for anyone exhibiting signs of mild EAH. (Yum.) 

What they don’t recommend is more sports drinks.  The benefit of the sodium in these beverages is far outweighed by the volume of fluid it takes to deliver it when you drink.  So Gatorade isn’t going to fix anything.  And if you still overdrink while you’re taking salt supplements, you can still get EAH.

At any rate, overhydrating by constantly drinking during a prolonged bout of exercise increases the risk of hyponatremia and is potentially disasterous.  So stop doing it.  Drink when you’re thirsty.  And don’t forget to pack your bouillon.

Suzi will thank you.

THE END, for real. 

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