The dehydrated athlete - hydration tips

Many factors contribute to the total volume of fluid lost from the body on a daily basis - environmental conditions, size/surface area of an individual, metabolic rate, physical activity load (ex. frequency, duration, intensity), sweat loss, diet composition and volume of excreted fluids. 

The daily fluid loss in cool weather (less than 70 degrees F) can be around 2300 mL (with much of that as fluid lost in urine) whereas in warm/hot weather (above 85 degree F weather) it can total 6600+ mL (with most of that lost as sweat). 

Once again, as mentioned in my previous post, relying on thirst to initiate daily water (or sport drink consumption during workouts) is a false recommendation to ensure adequate fluid consumption. I hear it over and over again that athletes feel that they don't need to drink because they aren't thirsty but then when they do feel thirsty, they do not provide themselves with opportunities for frequent drinking and it becomes uncomfortable to fully replace what was lost earlier in the workout/race. When the body is already dehydrated, performance is not only already declining but there is already considerable strain on the body to digest and absorb adequate electrolytes and fluids and carbohydrates. 

There are many physical benefits of training. But because almost all athletes in the Northern Hemisphere train throughout the summer in hot temperatures, minimizing dehydration is critical to receiving the adaptations to following a training plan. 

By developing a fluid replacement program that prevents excessive dehydration, you provide your body with the following benefits:

-Lower heart rate
-Higher stroke volume
-Higher cardiac output
-Higher skin blood flow
-Lower core temperature
-Decreased RPE
-Improved performance

Every time you start, continue on or finish a workout dehydrated, you put yourself at a competitive disadvantage to other athletes who are maintaining hydration status OR you are limiting your full athletic potential as an athlete (and risking serious health consequences). 

Without going into estimating sweat loss/rates, here are a few very simple tips to ensure that you are not sabotaging workouts with improper hydration. 


-Understand the warning signals of dehydration 

-Plan your hydration strategy before a workout (rather than waiting until the last minute)

-Drink ~5-7 mL per kg body weight 4hours before exercise (appropriate for afternoon workouts or races) OR 17-20 ounces of water 2-3 hours before workouts/races. 

-Drink 7-10 ounce water 10-20 min before workouts/races (in addition to above recommendations if you have 3 hours before your workout/race) 

-Add additional electrolytes (in a well formulated pill/powder) like sodium, chloride and potassium to pre workout/race fluids when exercising in warm environments (or for long durations).
NOTE: Glycerol has been promoted to help with hyperhydration. Glycerol is a WADA banned substance and should not be used by athletes (it also comes with dangerous side effects).
-Avoid drinking large volumes (more than 30 ounces in the 3 hours prior to a workout/race) before a workout/race which can cause GI discomfort, low blood sodium levels or excessive urine production.
-Plan to bring fluids/electrolytes/sport drinks with you for the start of your workout (generally at least 1 hour of running and 2-3 hours of cycling and 1 hour of swimming) so that you do not have to ration your fluid supply. Plan to stop as needed so you can voluntarily drink as needed. 

-According to the Institute of Medicine (2005), daily fluid needs are ~3.7L (or 130 ounces, 16 cups) for men and ~2.7L (95 ounces, 12 cups) for females. Around 20% of daily water intake is from water in food (so long as you consume a wholesome diet) so around 80% of your fluid intake should be directly from  fluid ingested. 

-In warm environments when you anticipate sweating (indoors or outdoors), start your workout with a comfortable full stomach full of fluid. 

-Be consistent in training with fueling/hydration during workouts.
-Always have fluids/sport drink with you and plan to refill bottles along your route/course. 

-Practice consuming liquids while you are working out - specifically running while drinking and grabbing bottles from cages while cycling. 

-1 mouthful of fluid is around 1 ounce. I suggest to take 2-3 swallows every time you drink from a bottle while cycling and 1-2 sips every time you drink from a cup/flask while running. 

-Bring money in the case you need to stop for fluids while cycling. Always have enough fluid on your bike to last 1 hour of cycling and enough fluid to last 30 minutes of running.
-Record body weight before and after workouts. You want to avoid losing more than 2% body weight and you do not want to weigh more after your workout. Any weight lost during a workout is not fat, it's fluid! You do not want to be proud of your weight loss during workouts as it can affect your health and performance. Some weight loss is fine but be mindful of signs of dehydration. You can estimate sweat loss/fluids needs with basic calculators or get yourself tested in professional lab. 

-Better hydration = better performance = better health. Aim to consume frequent intakes of fluid (sport drinks) starting around 15 minutes into your workout/race and be consistent throughout your entire workout/race. Prioritize liquid calories and vary your flavors so you prevent taste bud fatigue (ex. choose a different flavor drink for running versus cycling and if riding more than 4 hours, opt for 1-2 bottles of a different flavor than your other 2-3 bottles).
Drink no more than 10 ounce fluid every 15-20 minutes (best as 4-5 ounces every 10 minutes).

-Put more fluid in your stomach than on your head. Use cold water to cool yourself but don't go long periods without drinking. 

-In the case of GI upset or a sloshy stomach, slow down for 5-15 minutes and consume additional sodium with a little water to help empty contents from gut. Diarrhea will increase electrolyte loss so be sure to stay up with sport drink consumption during and post workout/race in the case that you experience loose stools while working out/racing. 

-Drink on a schedule, don't wait until you are thirsty. You are better off drinking earlier in a workout/race when your body temperature and heart rate are more controlled. 

-Hydrating with a sport drink that contains carbohydrate, electrolyte and water before and during workouts/races will help replaces losses and provide your body with sustainable energy. 

-Post workout, consume around 16-24 ounces for every lb of body weight lost during the workout. DO NOT consume all fluids at once. Start with an electrolyte rich beverage of around 16 ounces and aim to replace weight loss (in ounces) within 4-6 hours post workout.
For example, if you lost 5 lbs in a workout, aim to consume 80 ounces of fluid in a 4-6 hour time period in the form of an electrolyte beverage, recovery drink, food and water. 

If you find that you struggle with hydration or consuming adequate fuel during workouts or races, consult with a sport RD to help you fuel smarter in your athletic development. 

Information in this blog collected from Sport Nutrition: A practice manual for professionals. By Christine A Rosenbloom, PhD, RD, CSSD and Ellen J Coleman MA, MPH, RD, CSSD.