Several issues ago, we discussed over hydration and the problems it can cause, and how to avoid it. With the heat of summer on the horizon, and endurance running events held at altitude and higher temperatures, we need to acclimatize our bodies before jumping from the frying pan into the fire. Winter temperatures will soon wane, and it would be good for your body to know how to prepare for an event where you expect it to be hot and dry throughout the race.
Since no two bodies and their metabolic requirements are alike, lets determine how much water we actually perspire and respire off during a workout or long run.
- First we will need your bathroom scale. Weigh yourself naked prior to your run. Weigh your full water bottles that you will take with you on your run.
- Run your complete work out, as hard as you would run in the event, try and keep the same pace.
- Now weigh yourself again naked, note your weight – now weigh your water bottles again.
- Determine what your weight loss was in respiration and perspiration, and take into account the weight of the water that you consumed.
- Now you should have determined your personal rate of consumption of liquids over time or distance, or fluid expenditure.
- This should give you a thumbnail estimate of whether you are hydrating enough or over hydrating, and how much water your body needs throughout the race.
- For every pound that you lost, you need to replace 16 to 20 ounces of fluid and electrolytes to get back to where you started.
It is important that you sweat to cool your body’s core temperature. The areas that you will sweat the most, is the area that will cool your body off the quickest, so it is important that it is allowed to be exposed to evaporation as you run. Your back and your chest/torso will give up the most heat, and reduce your core temperature most effectively. In other words, wearing a hydration pack on a very hot race versus water bottles in each hand may hinder your body’s ability to give up heat and cool your core temperature. Secondary to your torso are your armpits, your groin and your neck, closest to your carotid artery.
***Using one of the new DPMR bandanas with ice and ice water will help tremendously in keeping your core temperature in check.
How soon should I start pre-hydrating before a race?
Studies with ParaRescue Jumpers, deployed from cooler climates to say Afghanistan, determined that pre-hydrating 8 to 12 hours prior to deployment into an arid and or humid environment, was helpful in keeping their plasma volume adequate to stay ahead of dehydration.
Carbohydrates contain a higher amount of water than proteins, so the old carb loading adage, up to 3 days prior to an event will also help keep plasma volume optimal for starting your event in hot temperatures.
Without losing you further, I’ll stop here for now. If you have any questions that you would like a more in depth answer to, please don’t hesitate to message me. I could go on for hours as you can tell!
Best of luck to all of you trail animals this season…be safe, stay hydrated, and have fun!
~Spike
Spike- I’m going to have to disagree with you slightly on this one but it’s mostly with the title and not the content. The data that pre-hydration or staying hydrated prevents heat related illness is pretty weak. You do need to listen to your thirst more as you do sweat more and fluid requirements do go up. However, most heat related illnesses are more related to intensity of exercise and wet bulb globe temp than hydration.
Yes, quite right Dr. Andy. I wrote the title, got short on time for deadline, and didn’t finish my complete thought. I completely agree that listening to your thirst is most important for individual requirements, and not listen to marketing strategies. Had I taken more time to write a complete article, it would have included heart rate monitoring in an arrid environment, say a sauna, at temps ~ 85°F…Taking 220 minus your age x (90-92%)= Target heart rate…perform for 10 minutes, increasing time each day by 10% for 7-10 days for heat acclimatization, and taking your wet bulb temp (humidity) into account as well. Also important, core temp must not exceed 107°F, but we are talking military extremes at this point. Thank you so much for reading my article, and giving valuable feedback. ~Spike