Friday, 16 September 2011

Part 1: Sweat, Salt and Minerals

Hello all!  Well, after a three week hiatus, we are back in action.  Sorry for the delay on this post- I recently started working from two great clinics (Price Health Centre and New Hamburg Wellness) which have taken away from my precious blogging hours.  Apparently, to my surprise, working two jobs takes up more time than not working at all.  

Stuff On Sweat

Today's blog is in light of the fact that I, along with a number of fellow riders, are going to attempt to do a 160+ km bike race this Sunday in Collingwood.  This race will surely be a great deal of fun, in a "I can't wait until it's over" kind of way.  However, one thing that many of my fellow riders have been discussing is how to handle their fluid and salt balance during a 5+ hour event such as this.  So, today's blog will be a summary of the basics behind keeping yourself hydrated, while Part 2 will discuss how to maintain your salt balance.  

How Much?

It has been shown that on average, athletes sweat at a rate of 1-2L/hour.  There is obviously a huge variability here, and it has actually been shown that in some more extreme cases, an athlete can lose 4L of sweat per hour.  Nevertheless, a general rule of thumb to follow, as recommended by the American College of Sports Medicine is:

Athletes participating in events lasting more than 40 minutes should consume 5-8 ounces of fluid for ever 15 minutes.  

Google tells me that is about 150-240 mL for every 1/4 hour you are competing. This protocol seems pretty basic, and easy to follow.  However, during a race or any other type of athletic event, it is easy to get caught up in the moment and forget to ingest adequate fluids.

Dehydration happens all the time, even to pros.  Sure, you will always drink some liquid- but maybe your 15 minute drinking intervals turn into a 20 minute intervals.  Now, you are consuming 15 ounces per hour instead of 20 ounces.  This may seem insignificant at the time, but it is quite the opposite.

How Important IS Water?

Water plays a number of roles in the body.  During exercise, one of the key functions that it is used for is heat dissipation via evapostranspiration (which is essentially me trying to sound smart- but heat is carried via water from within muscles and other deep tissues to the skin's surface, where it can evaporate). In fact, this process of sweating is one of the reasons why our ancestors made such  great hunters, which you can read about in my article on persistence hunting.  However, as we lose water while we sweat, we also lose are ability to cool off, and eventually our ability to perform:
  • With a 2% loss in water, we start to lose the ability to regulate our body temperature (but performance is ok)
  • With a 3-4% loss in water, some studies have shown up to 30% impairment of muscle performance
  • With a 6+% loss in body water, heat stroke starts to occur (body temperature going over 42 degrees, internal organs starting to "cook," overall not a healthy thing)
Two More Tips

While any water is better than no water, it has been shown that there are a few tricks to enhance how quickly water is absorbed into your system.
  • Research shows that cold water is absorbed more efficiently than water at room temperature.
  • Your sports drinks should NEVER contain more than 8% sugars.  If higher than 8%, there is a significant decrease in how quickly water is absorbed from your intestines into your blood stream.

So, that is all for Part 1 on maintaining your salt and water balance.  Overall, it is a fairly straight forward topic, but also very important for obvious reasons.  The key things to keep in mind include:
  • Drink 5-8 ounces of fluid every 15minutes                                                                                           
  • Cold water is best
  • Never more than 8% sugar in your sports drinks
With the next post, we'll get to the salt.


Convertino VA, Armstrong LE, Coyle EF, Mack GW, Sawka MN, Senay LC Jr. et al. American College of Sports Medicine position stand: Exercise and fluid replacement. Med Sci Sports Exerc 1996; 28(1): 1-7

Nutritional Aspects of Athletic Performance, Dr. James Meschino D.C., M.S., ND, 2008, Pages 20-24

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