*** many thanks to Tony Hchaimé for this blog post ***

I went for a run a few nights ago and could barely keep my heart rate under control:  the Dubai summer is officially here:  heat, humidity, smog, and the perils of air conditioning.

This coincides with a number of questions I've received recently from beginner as well as "elite" amateur endurance athletes regarding the optimal nutrition and hydration strategy for hot weather training.

After all, who among us hasn't suffered through heat-induced cramps, stomach problems, bloating, and bonking when training / racing in the sandpit summer?  I know I have! And I still make mistakes with that...

Let me start with a small reminder from basic school biology: do you remember the process of osmosis?  You get 2 liquids, separate them with a membrane.  Add some some salt or any other mineral to one.  So now one of the liquids has a higher concentration of minerals than the other.  As time passes, the "clean" liquid will pass through the membrane into the "concentrated liquid", until both liquids have equal concentration.  How cool is that??!  Ok, now keep that in mind, we'll come back to it later...

Water serves 3 main functions for the endurance athlete:

1.  Temperature regulation

2.  Maintaining cellular chemical balance

3.  Aiding in digestion (to be addressed in separate article)

1.  Temperature Regulation

Mechanism:  sweating. Yes, not pleasant, but that's why we can outrun a gazelle over a day-long run...

Sounds simple enough, no?:  When sweating, the water evaporating from the skin cools the skin down, hence cooling the blood in the tiny blood vessels (capillaries) under the skin, and hence cooling the rest of the body.

Not so fast.

This works great in mild and dry weather, where the humidity in the air isn't low.  Remember that school biology lesson we started with about osmosis?  Well when humidity is high, the air is "concentrated" with water molecules, and "doesn't want to take more", this slows down dramatically the evaporation of sweat off your skin. Result:  less cooling.

Your body's reaction:

  • Stage 1: uh oh, this sweating thing isn't working very well, let's try and sweat some more --> you start sweating more, so this means losing more and more water, which needs to be replaced
  • Stage 2: dammit! Even this higher level of sweating is not cooling me down! That's it! I'm shutting down non-essential units.  HELLO CRAMPS!

This scenario is not uncommon among athletes, even smart ones. They say things like:

  • I ran with a fuelbelt and was drinking water all the time!"
  • "I took electrolytes all the time" (more on that later)
  • But I was still cramping and my heart rate was going through the roof! What's going on??"

Make sure you hydrate properly...

Well, a couple of things are going on:

a.  Yes you're drinking more and more water, which is replacing the sweat you're losing.  So your problem is not getting dehydrated by loss of water.

b.  The water you're drinking from your fuelbelt is warm and getting warmer by the minute by being in the sun/heat and / or close to your body, so effectively you're warming your "insides" with every sip of water, thereby negating any benefits you're getting from sweating.

c.  Yes you're taking electrolytes, which is great since they are essential for your muscles to function, and you're losing them when sweating... but the question is, are you taking too many electrolytes?

This is a good time to talk about how water helps in maintaining your cellular chemical balance.

2. Maintaining cellular chemical balance

a.  Some essential minerals (and water) are needed for our muscles to function properly (won't go into cellular chemistry here, email if you want to know more!).

b.  Those minerals are lost with sweating.

c.  Cells (nervous and muscle fibres) are sensitive to swings in their cellular chemistry (including availability of those minerals).

d.  Replacing those minerals is simple enough: taking electrolytes during hot weather training/racing.

So what could go wrong? Why do athletes suffer from cramps even when taking electrolytes (I'm guilty too, check out my Abu Dhabi race report!!).

Well there are 2 scenarios:

Scenario 1: Not taking any electrolytes

  • You sweat, losing water and minerals;
  • You drink tons of water to replace sweat;
  • Your stomach fills with nice clean water.

RESULT: Remember that osmosis thing?

{water in stomach, low concentration} ==> ||Stomach Wall/Membrane|| ==> {blood, high concentration}

Your stomach wall is the "membrane", on one side you have a "low concentration liquid, the water in your stomach", and on the other you have a "high concentration liquid, your blood".  Because of osmosis, water will move through the stomach wall into your blood stream. This causes your blood to get diluted (becomes lower concentration).

Now you have:

{diluted blood, low concentration} ==> ||Cellular/muscle Wall/Membrane|| ==> {Cells in muscles and nervous system / high concentration}

So what happens now, is water will Flood the cells, diluting the minerals. Cells are now hit with a "double whammy": they're losing minerals from sweating, and the flooding of water is causing whatever minerals are left to get diluted further!  They start shutting down or "mis-firing". HELLO CRAMPS!!!

Ok, so you say, fine, I'll take as much electrolytes as I need. Well yes, but again, not so fast, because there is such a thing as taking TOO MANY electrolytes! It's not easy to keep a balance.

Scenario 2: taking too many electrolytes

  • You're smart / experienced enough to know that water alone doesn't work
  • You start popping salt tablets like crazy
  • Yet you still cramp!!! WTF!!!!???

Well here's "WTF":

Remember that osmosis thing?  Now imagine the situation we have in Scenario 1 above is reversed. You take SO MANY electrolytes that the water in your stomach now is higher in concentration than your blood.

{water in stomach, high concentration} <== ||Stomach Wall/Membrane|| <== {blood, low concentration}

So what do you think happens now?  That's right!: the higher concentration in your stomach is drawing water out of your blood and into your stomach!!! By the same token, now your blood is super concentrated, and draws water out of your cells! and that, ladies and gentlemen, is how one can get dehydrated even when drinking water... when you overload with electrolytes, it's no longer water, it's highly concentrated liquid that's actually pulling water out of your entire body and into your stomach!

Result: cramping, and bloating (ugghh hate that feeling!), liquid sloshing around your stomach... not fun, especially on the run.


Well that's all well and good, but what do I do about it??  Well, a solution isn't really a workable solution unless it's simple right? There is no "fool proof" method, but here are my suggestions:

  • #TIP1:  Don't overload on salt the days before training / racing. Here's a tidbit: our typical diet (even healthy ones) have 5x to 8x the recommended daily salt intake. AND, our body does store a lot of that.
  • #TIP 2:  be careful when taking electrolytes: you want to take in the minimum to maintain osmotic balance. So start with 1 tablet / hr, then increase.  It's a learning process, and eventually you'll find the right balance for you (each body is different).
  • #TIP 3: chose a balanced electrolyte: some products out there have way too much salt compared to other minerals.  What happens is that even if you take a tiny bit, and the concentration of minerals in your stomach is "balanced", you will have such a high concentration of "salt" that it creates an osmotic imbalance and draws water out of your blood/cells.
  • #TIP 4: be aware of your drinks! Remember, sports drinks (Gatorade, etc) are by design concentrated (due to sugar contents), and by having them in your stomach you're increasing the concentration. If you want to drink them, just be aware of that when taking electrolytes on top. My personal strategy is to drink only water when racing / training - I take my calories and electrolytes separately.
  • #TIP 5: drink cold water: whenever you can.  Drinking cold water cools you from the inside, cools your blood and organs.  This is even more critical on humid days where the sweating mechanism isn't doing much to cool you down.
  • #TIP 6:  do NOT overhydrate!  On very hot days, it's tempting to guzzle down cold water.  Remember, you need to keep the liquid in your stomach balanced.  Too much water causes an imbalance (see Part 2/Scenario 1 above) - do a "Sweat Test" to determine your sweat rate (call/email for details).
  • #TIP 7:  don't forget to hydrate while swimming in the summer.  While you may think that you're not sweating, you are! and you're losing minerals too! So for hard/long swims, replace those lost fluids/minerals
  • #TIP 8:  hydration doesn't stop when you stop training. Stay well hydrated throughout your day, before and after training to maintain that infamous osmotic balance...

Happy Training,