Hydration & Heat Survival Guide

Congratulations!  We at Memorial Sports Medicine Institute would like to welcome you to the Sunburst.  By participating in the race, you made a great choice in making exercise part of your life.  Regular exercise is an important part of maintaining and improving your personal health.  

Participation in the Sunburst has grown over the last few years.  There are 4 different races, the Marathon, Half Marathon, 10K, and the 5K run/walk.  While these races are very different, they all share one thing in common:  The most common injury we see in the tent each year are those related to hydration (both under- and over-hydration) and heat-related issues.  The good news is that these injuries are preventable by taking a few extra measures during your training and during the race.  The next few sections are dedicated to providing you with tips on how keep yourself from visiting us at the tent this year.

1. Weigh yourself before and after exercise, especially those lasting more than 30 minutes in duration.  One should weigh themselves several days in a row, in the morning, to establish a baseline body weight that represents euhydration (which means steady-state hydration).  Fluid intake should be about 24 oz. for every pound lost.  You must drink more than you have lost in order to cover what you will lose through urination.  This fluid should be consumed in small amounts, as consuming large amounts will result in the majority of it being lost through urine.  Rehydration with an electrolyte drink showed benefit in recovery times as well when used for rehydration.  Water is still adequate to rehydrate yourself, especially if you are exercising only one session per day.
2. Dehydration: of as little as 2% of body weight can significantly impair performance in a race.  The longer the race, the more significant the impairment.  It is important that when you train for longer times (> 30 min), you should prehydrate with either water or an electrolyte-containing sports drink. Try different fluid volumes while you are training to see what works best for your body.  Excessive amounts can lead to stomach discomfort during exercise. 
3. Prehydration:  One should drink 5-7 ml/kg of body weight approximately 4 hrs prior to athletic competition.  If no urine is produced, one should consume 3-5 ml/kg about 2 hrs prior to the event.  Consuming beverages with some sodium will help to stimulate thirst and retain the fluids consumed. 
4. Fluids during Exercise:  This greatly depends on your body weight and the speed you run at.  Slower and lighter runners will require less fluid than heavier, faster runners will. Runners should consume between 400 ml and 800 ml per hour.  Consuming fluids with electrolytes such as sports beverages can help replace sweat losses, the sodium can stimulate thirst, and carbohydrates provide energy.
5. Overhydration: you can also drink too much fluids, which can produce a lowering/ dilution of your blood's electrolytes especially sodium.  The results can be just a catastrophic as severe dehydration, including arrythmias, seizures, confusion, decreased performance, etc.
6. Acclimatization: for about 5 to 10 days before the race, you may want to see what the daily temperature, humidity, and cloud cover is  here in South bend is at 6 a.m. and 12 p.m. (race times).  You should try to simulate these conditions in your last week of training.

The above information is taken from the American College of Sports Medicine Position Stand on Exercise and Fluid Replacement.