Hydration and Physical Activity
Exercise,  Hydration,  Nutrition

Quick Tips About Hydration And ExerciseThis article is a 7 min read

Hydration and fluid replacement is critical to athletic performance (1). I’m not talking about your walk in the local park, but intensive activities that last longer than 1 hour. I hear many theories on how much water one should drink during sporting events and many are “one size fits all” in nature.

Intense activities lasting longer than an hour will require a specific re-hydration strategy. This applies for both hot and cold environments. It is clear that starting your exercise session dehydrated is one of the leading causes of heat-related illness.

When hydration bladders first came out, like many people, I ran out and got one. I mean, really, the thought of not having to hold a bottle and having water ready via a tube was too good. I see people I hike using these bladders like IVs. Almost never taking them out of their mouth. Constantly sucking water. But since the time I bought mine I’ve reconsidered the use of this as a hydration solution. If you read on I’ll tell you why and what the science is telling us about hydration.

Dehydration makes you clumsy and stupid

Being clumsy and stupid is not the way to be while engaging in high-performance activities.

A water loss equivalent to 2% or more of body mass appears to reduce endurance exercise performance in both temperate and hot environments, especially when the duration of exercise is around 90 min or more (1,2).

Research on high-level soccer players has shown as little as 2.4% body mass loss is associated with a 5% loss in skills performance. In other studies, dehydration was associated with a reduction in power output, speed, and running times (2). It must also be noted that low levels of dehydration impacts cognitive function and mood (3). Not re-hydrating can make you mentally / physically slow and cranky.

Why worry about hydration?

Well, it’s fairly simple. Dehydration can reduce performance and increase the risk for heat and cold related illness. Even in the absence of heat or cold illness, you can experience, simple dry mouth or more seriously, weakness/fatigue, dizziness, headaches, poor sleep, constipation, and palpitations (feeling that the heart is jumping or pounding) (1). So staying hydrated keeps you moving and healthy.

However, remember this, excessive over-drinking should be avoided because it can also compromise physical performance and health (1). In rare cases, people who drink too much water may reduce blood sodium levels and experience a condition known as hyponatremia (see symptoms here), or in high-performance activity, exercise-associated hyponatremia (EAH), which can be fatal or leave you simply feeling bad in sub-clinical states (4).

How much to drink?

This is a bit tricky. You’ll need to consider several factors such as age, gender, body size,  weather/climate, duration of your outing, the weight being carried, the speed of travel, terrain, and foods you are eating (dehydrated foods have little or no water were fresh fruits have lots). Keeping the above in mind will give you a general idea of how often you should be drinking on a given outing and if you need to mix in a sports drink.

But most of all knowing your body and its thirst indicators may be critical.

New guidelines (2015) published in the Clinical Journal of Sports Medicine recommends drinking when thirsty (4). The guidelines specifically say:

Given that excessive fluid consumption is a primary etiologic factor in EAH, using the innate thirst mechanism to guide fluid consumption is a strategy that should limit drinking in excess and developing hyponatremia while providing sufficient fluid to prevent excessive dehydration”.

In other words, using your bodies natural system of thirst recognition to guide you. However, in this writer’s opinion, it may not “hold water” in environments where thirst perception is altered and one can lose 3 – 8% of body mass quickly (5).

So what to do?

  1. A common recommendation includes hydrating before your activity. Drinking about ~2–3 mL·lb of water or sports solution at least 4 hours before you engage in your activity will pre-hydrate you (1). Start your activity hydrated.
  2. Consume 7-10 oz of fluid 10-15 minutes before your activity (during warm-up).
  3. Become an expert regarding your body. Know the early signs of your own thirst. You can follow the link below for an interesting way to tell if you are hydrating enough during exercise. This article has some good information of how to gauge the amount of water you’ll need during exercise.
  4. Drink 28-40 oz every hour during exercise.
  5. Bring foods that contain a higher water content. Fruits are good food/water sources. Foods with water will absorb slower and provide other nutrients.
  6. Use watered down performance drinks to help replace lost nutrients. Events longer than 90 minutes may benefit from carbohydrate replacement.
  7. Keep an eye on your pee. If it is starting to look like apple juice (it should look like lemonade), drink-up!
  8. Assess your trip route and figure out how much water you need to have at any one time. You may be able to refill along the way which means carrying less weight.
  9. Never ignore thirst.
  10. Rehydrate after an intense performance. Within 2 hours post exercise, 24 oz for every pound lost due to sweat. Many athletes fail to hydrate enough or cannot hydrate enough due to the nature of the activity.

The amount of water you should carry depends on several factors.

First how long and what type of activity are you engaging in? A relatively short 1-hour volleyball match or a 2-day ultra-endurance race?  Water management becomes tricky during the latter. Are going to be near dependable water sources for much of your event? If so you may be able to travel with one 1 liter bottle filled and resupply with a filter or other quick purification method when needed. Carrying less water means carrying less weight. But if your water supplies are suspect (meaning dry) carry more water. Always err on the safe side.

You can save weight by ditching the Nalgene type bottles in favor of a simple 1-liter spring water bottle. Another option is using a filter/drinking system like the Sawyer Mini Water Filter which acts as a filter and hydration bladder system. We are playing with it in the field now.

Healthy water

Out in the backcountry? Unless you have all the water you need, which you can during short events, you’ll want a way to keep your water resupply safe. Having refill stations during races is important. But during backcountry pursuits, the hiker/athlete may have to rely on natural water sources. I have to admit, I drink from high mountain streams. Hot and tired I take a handful. But nothing more.

There are a lot of reasons why people get sick in the backwoods and most of it is probably due to poor hygiene in camp or on the trail. Yes, they pee or poo and do not “wash”. Heck, I see 50% of men in public toilets not washing, gross. In the backcountry, this is something that a simple antibacterial wipe could prevent, so carry a few. Ya, you gotta go sometime during a 3-day race/trip. Having said this, all water should be suspect, some more than others.

The simple rule of thumb is: Treat and/or filter your water. There are many ways to do this from tablets, filters, boiling, and even UVGI sterilization. But that’s another post.

References on hydration and exercise

1. Nutrition and Athletic Performance. Medscape. Mar 01, 2009.

2. Maughan, Ronald J., and Susan M. Shirreffs. “Development of individual hydration strategies for athletes.” International journal of sport nutrition 18.5 (2008): 457.

3. Casa, Douglas J., et al. “11 Hydration for High-Level Athletes.” Nutrition for Elite Athletes (2015): 249.

4. “Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference.” LWW. Clinical Journal of Sports Medicine:, July 2015. Web. 22 Oct. 2015. <http://journals.lww.com/cjsportsmed/Fulltext/2015/07000/Statement_of_the_Third_International.2.aspx>.

5. “Cold Weather Increases Risk Of Dehydration.” Cold Weather Increases Risk Of Dehydration. UNH Media Relations, 28 Jan. 2005. Web. 22 Oct. 2015. <http://www.unh.edu/news/news_releases/2005/january/sk_050128cold.html>.

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