Hydrating in the Summer 2019

Here’s exactly what you need to know about how much fluid it takes to stay hydrated when it gets hot!

We are in the thick of summer here in Tennessee and the heat and humidity are becoming stifling. Long gone are the early spring and winter rides where 2-3 bottles would be enough for a 4-5 hour ride, and say hello to water stops every 45’-1 hour.  If you are thirsty, or stop sweating it’s already too late. Your HR will climb, your power will drop and potentially dangerous heat stroke can ensue. But is there a way to still ride and enjoy yourself when conditions get like this? There sure is! By observing sweat rate, being diligent about your hydration, and with a bit of patience you can get used to riding in heat and even enjoy some extra training adaptation because of your efforts. 

Start with Sweat Rate  

Any time I have an athlete struggling with the head this is where I start.  People are blown away by how much water they actually lose when the temps start climbing!  I’ll never forget when I first did a sweat rate test a few years after transplanting from Michigan to Tennessee.  I had drank 13 bottles on the ride. It was just a steady endurance day, 5 hours, and when I weighed myself after it i was 10 pounds lighter than when I left!

This was so incredibly eye opening. That is about 20 pounds of sweat, just riding endurance, about 5lbs of water per hour, would mean I need to attempt to get up to 5 bottles per hour when the heat index is over 90 degrees. Granted this was one of the hottest days I had EVER ridden in, but I never forgot it. 

Sweat rate is highly individualized, ranging from <1 Liter per hour to some outliers being above 5 Liters per hour!  Coming up with a personalized plan for hydrating in the heat means you are going to have to do a little bit of homework!

 First, you will need to have a home scale. Get on the scale and figure out your pre-workout weight.  Go for a ride at least 60 minutes that has some good aerobic intensity in it, and when you return home, get back on the scale and measure the difference. You are going to want to take your sweaty kit off because the kit is going to be drenched at this point and would affect your measurement. From there, add the weight in water you took in during the ride, weight difference and volla you have a pretty good ballpark sweat rate!

 Doing this 5-6 times with different length rides can really help you zero in on how much you sweat at different intensities, or at different temperatures. As you adapt to the heat, age, or gain/lose fitness this sweat rate might even go down or up a bit, so it’s worth checking out a few times every season at a minimum.


Everyone has heard of sodium, but did you there are 6 other kinds of electrolytes? 

  • Bicarbonate

  • Calcium

  • Chloride

  • Magnesium

  • Phosphate

  • Potassium

  • AND Sodium

“Electrolytes are substances that dissociate in solution and have the ability to conduct an electrical current. These substances are located in the extracellular and intracellular fluid. These electrolytes play an important role in maintaining homeostasis” (1) These electrolytes are essential minerals for our nervous system and muscles to function properly. Long story short if  you dont supplement electrolytes and just drink water when training, fatigue will come on sharp and swift much sooner, and it’s really hard to come back from that. 

That feeling of being unable to push the pedals hard, a sharp rise in heart rate, and the dreaded cramps are all tell tale signs that you have gotten behind on your hydration.  Consuming water alone just won’t cut it. Your body needs all the help it can get when you are trying to maintain homeostasis under the physical stress of exercising when it gets really hot out.  In addition to water we are losing a few different kinds of electrolytes through our sweat too, and supplementing for that loss can greatly prevent fatigue from setting in too soon.

How much is the right amount? Well that depends on you again. It’s fairly easy to establish sweat rate, but figuring out your electrolyte loss rate per hour is more individualized, and BOTH depend on the intensity and heat you are trying to operate at.  In general, the more water you take on, the more electrolytes you should be taking on as well.  

Knowledge is Power

Remember that we are all going to be a little different. Genetics, fitness level, heat index, and heat conditioning all play a combined role in how quickly dehydration will set in, but the fact is it will catch us all if we aren’t careful! With a little experimentation and practice you can start to better understand exactly what it takes for YOU to perform at your best in the heat.  Take a few minutes before and after your next training session or race and write it down in your training journal or on Training Peaks so that the next time you head out the door to do some suffering you know exactly what your body will be craving so you can crush those intervals and keep improving.

Still have questions? Contact us we are happy to help!


1. https://www.ncbi.nlm.nih.gov/pubmed/7965369

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