Part 2: Sweat, Salt and Minerals

What originally sparked interest in creating this 2 part series was the then-upcoming Centurion race in Collingwood.  As you may have noticed, I strategically posted only the 1st part prior to the race.  Shockingly, this strategy did not work as lots of fast guys still destroyed me.  Maybe they have race secrets they should be blogging about!  Nevertheless, a great day on the bike.  Check out Larry Bradley's race report to get a sense of what it was like to participate in the event.

When you ride for almost 5 hours over the course of 172km, fluid and salt balance undoubtedly play a vital role in maintaining performance.  The easiest way to waste valuable training is to refrain from taking in adequate amounts of either.  Last week's blog addressed how to maintain proper fluid balance, while today we will look at the salt.

Sodium

This is the mineral that is lost the most as we sweat.  As with everything else, there is obviously variation between athletes, but on average we lose about 1500mg per 1L of sweat lost.

So what happens if we lose too much sweat?  Well, the sodium outside of our cells will eventually be at a much lower concentration than the electrolytes inside our cells.  As a result, our body tries to balance things out, allowing water to travel into our cells.  As the cells fill up with too much fluid, early symptoms such as disorientation and shortness of breath can take place leading to more serious complications such as coma and even death.

As a general rule of thumb, you should consume 1g of sodium for every 1L of fluid you consume.

Fortunately, sports drink companies typically have this figured out, and their products meet this criteria.

Potassium

Contrary to what a lot of information out there shows, potassium is not an absolute requirement during athletic events.  It is easily replenished via the regular consumption of fruits, vegetables or fruit juices. 

While sodium is the main electrolyte located outside of cells, potassium is the main electrolyte within cells.  This is essentially why it is lost to a much lesser degree while sweating.  Potassium debt is a rare occurrence, and it is typically only seen in those who are malnourished or who are suffering from chronic diarrhea or related conditions.

Other Minerals

Just because we are on the topic, I would also like to remind people to keep a close eye on three very important minerals: calcium, magnesium and iron.  While these minerals are not lost in sweat, athletes who undergo strenuous training are much more susceptible to developing deficiencies.  Calcium and magnesium are both imperative for building and maintaining strong bones, while iron is a key component of the oxygen-carrying hemoglobin within our red blood cells.  Low levels of any of these three minerals can therefore result in osteopenia and anemia.

To prevent this from happening, ensure that you are consuming at least 1000mg of calcium per day (depending on your age and gender) with at least 600 IU of vitamin D.  Magnesium is found in an array of foods including nuts, grains and green leafy vegetables.  The recommended daily allowance is about 400mg/day, and a well balanced diet is usually sufficient in achieving this.  Iron balance is a more complicated issue due to the variation seen based on age and gender, but a well balanced diet high in meat or meat substitutes will help ward off its deficiency.  For more details on iron, see the National Institute of Health website.  In general, you should pay attention for symptoms such as chronic fatigue and stress fractures as a mineral deficiency may be at play. 

Closing 

So, in the end, the only mineral you really need to worry about on race day is sodium.  A healthy, well balanced diet plays an important role in maintaining adequate mineral levels within your body on a more long term basis.  BUT, on race day, remember:

1g of sodium for every 1L of fluid you consume.

Next time we will be switching gears a little bit, and will be looking at the effects of exercise on the brain.  Until then!

References:

1) Frissell, RT, et. al., 1986. Hypoenatremia and ultramarathon running. JAMA. 255: 772-774.

2) National Institute of Health: Office of dietary supplements. http://ods.od.nih.gov/ Accessed Sept 27th, 2011

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



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.

Summary

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.


References:

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