Thursday, July 31, 2014

How To Stay Hydrated During Long Workouts In The Heat

The heat and humidity of summertime in Wilmington is INTENSE!  For the record I'm not complaining at all b/c I'd much rather it be hot than cold, but it has raised some discussion recently among the athletes that I work with about how to stay hydrated on long workouts in these conditions. And after a few of these talks, I feel like this is a blog-worthy subject.

The heat and humidity of the hot summer months increase an athlete's likelihood of becoming dehydrated and can make training and racing feel much more difficult.  In high environmental temperatures (>80 degrees) heat cannot dissipate from the body as effectively, and in humid conditions (>50-60% humidity) sweat is not wicked away from the skin efficiently to provide the cooling sensation it is supposed to.  In these instances, not only are the body's self-cooling mechanisms impaired, but greater amounts of fluid are lost due to increased rates of sweating.  Dehydration can lead to decreases in speed, strength, stamina, mental capacity (including willpower) and overall performance, as well as increased perceived level of exertion and risk of injury.  Plus, large amounts of sodium losses via excessive sweating can contribute to muscle cramping.  In the worst case scenario, heat exhaustion or potentially fatal heat stroke could ensue.  Thus, it is EXTREMELY important to stay on top of your fluid intake in hot weather!
Here are some guidelines for you to follow and some tips for you to try.  Trust me, spending some time figuring out how to prevent yourself from becoming dehydrated is going to give you a huge one-up on the other guy you are competing against who hasn't given adequate attention to this important component of training/racing.

Before Exercise
*Adequately hydrate yourself 24 hours prior to exercise.  Duh.  For athletes who are training multiple times per day, you should think of yourself as being in a perpetual state of rehydration for the next workout.  

*Monitor the color of your urine.  Any former college athlete remembers the pee charts on the backs of the bathroom stalls that explain what your urine should look like!  For the non collegiate athletes out there I'll fill you in on what you missed - your urine should be pale yellow and without any strong odor.  Dark yellow/orange or foul-smelling urine is an indicator of dehydration!

*To ensure optimal hydration before a workout or race, drink 14-20 oz of fluids 3-4 hours prior to training.  This allows enough time to void any excess fluid before competition. 

*Plan to measure your sweat rate.  Why is this important?  Because of this graph (excellently hand-reproduced by myself):

This was a study where men walked on a treadmill at 3.5 mph at 2.5% grade for over 6 hours.  Each hour (x axis) they measured rectal core temperature (y axis).  The men depicted by the solid line (top line) did not drink any water, the men depicted by the solid line with circles (middle line) drank water as they were thirsty, and the men depicted by the dashed line (bottom line) drank water equivalent to their sweat output.  What this shows is that you cannot rely on thirst to adequately hydrate yourself.  At roughly 3.5 hours into the experiment the men who did not drink any water had a rectal temperature of 102, which is equivalent to the zone of impending exhaustion.  Those who drank water to thirst were a little better off, and didn't hit this point until 5.5 hours into the experiment.  However, the men drinking in accordance with their sweat rates, were able to completely stave of the zone of impending exhaustion!!!  Clearly the thirst mechanism will not lead you to drink enough to make up for your fluid losses!  What this means for you is that you should measure your sweat rate & here's how you do that:

1.  Weigh yourself without any clothes prior to exercise.
2.  Keep track of how much fluids you drink during exercise.
3.  Weigh yourself without any clothes after exercise.
4.  For each pound lost, add 16 oz fluid to your hydration plan. 

During Exercise
*Plan to drink 24-48 oz per hour.  Larger individuals and those who sweat a lot will be at the higher end of this range.  The best way to figure out where you fall within this range (or if you are above this general range) is to measure your sweat rate.  You sweat rate will be different in different environmental conditions and across different sports.

*Aim to consume 400-800 mg sodium per hour.  400 mg sodium per hour is generally a good amount of sodium to aim for.  For example, one PowerGel contains 200 mg sodium.  Therefore, if you are consuming 2 PowerGels per hour you will automatically reach the target of 400 mg sodium per hour.  However, if you are a salty sweater (i.e. someone who ends up with dried white salt all over their black biking shorts after a ride - and not because you peed on the bike), are exercising in extreme heat (>80 degrees and/or >80 percent humidity), or are sweating a lot, you should aim for up to 800 mg sodium per hour.  The best way to get this additional sodium is through sports drinks or salt tablets.  I have used LavaSalts before and had good success with those. 

*Keep in mind the signs and symptoms of dehydration:  dry mouth, chills/goose bumps, discomfort, dizziness, headache, accelerated heart rate, loss of appetite, impatience, and sleepiness.  Do not try to beat the heat.  If you start to notice these symptoms, slow down or stop and get some fluids because otherwise things will progressively get worse:

Here is what can happen when x% of body weight is lost as fluid:

1% - Thirst threshold & threshold for impaired exercise thermoregulation leading to decrement in physical work capacity.

2% - Stronger thirst, vague discomfort and sense of oppression, loss of appetite

3% - Dry mouth, increasing hemoconcentration (thicker blood), reduction in urinary output

4% - Decrement of 20-30% in physical work capacity

5% - Difficulty in concentrating, headache, impatience, sleepiness

6% - Severe impairment in exercise temperature regulation, increased respiratory rate leading to tingling and numbness of extremities

7% - Likely to collapse if combined with heat and exercise

After Exercise
*Weigh yourself and consume AT LEAST 16 oz of fluid for each pound lost in order to adequately rehydrate yourself.

*Reach for salty snacks like pretzels & V8 juice because the sodium will help improve fluid retention.

*If you find that you have gained weight, you drank too much

*Continue to monitor your urine and rehydrate for the next workout.  Failing to properly rehydrate will impair your next workout and prevent you from getting the most out of your double day.  

*Having a headache and feeling like crap later in the day is a sure sign of inadequate hydration!

Some Final Tips
*Never leave the house without fluids when running in the heat, no matter how short your run is.

*Do not plan your run around pre-planted water bottles - this will inevitably lead to dehydration.  Instead, carry bottles or a camel back with you and plan your run around places that you know you'll be able to re-fill, such as convenience stores, gas stations, hotels, water fountains, neighborhood pools/clubhouses, etc.

*Mentally prepare for and be ok with going at a slower pace.

*Seek out routes w/ shade.

*Do your workouts early morning or late evening to avoid the hottest hours of the days.

*Reduce body fat to decrease your natural thermal insulation.

*Carry a debit card with you so that you can purchase more fluids as needed.

*When all else fails, go old school --> find a garden hose and use it to refill your bottles!

Time for me to go run 10 miles ... guess I'll take my fuel belt (sigh). 

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