Originally published in the 8/20/15 edition of Out There Monthly
As the temperatures heat up for the summer, many people find themselves reaching more frequently for their water bottles. As we look towards maintaining high performance and enjoyment of outdoor activities in the summer heat,, we need to be consistently aware of our hydration levels, particularly as our normal body functions result in the loss of a portion - most noticeable through sweating - of the 50-70% of our body weight that is made up of water each day.
Proper hydration can be estimated with three factors; urine output, thirst and body weight. Proper hydration can be identified by regular with a clear to light yellow color urine. Infrequent urination with dark colored urine and a strong odor can be an indicator of dehydration. Since thirst will present after the body is already in a dehydrated state, it is best to hydrate prior to feeling thirst. Significant body weight change after strenuous activity can indicate dehydration or over-hydration. Experiencing one of these indicators independently should lead you to consider dehydration, and any combination (or all three) increase the likelihood of dehydration.
There are two specific medical conditions associated with hydration and outdoor activity to be aware of when planning outdoor activities; dehydration and hyponatremia. Both conditions present with similar symptoms and are more common as the temperature and activity increase.
During high levels of exertion in warm environments individuals can lose up to 2 liters of water per hour. Although most of us will lose less water than that per hour, we still can easily lose water faster than we are able to rehydrate since our absorption rate is about .5 liters per hour. As the body becomes dehydrated, symptoms will start with increasing thirst, then increase to include fatigue, headache, nausea and decreased athletic performance. As dehydration increases, people experience dizziness and a decreased ability to sweat. If dehydration becomes profound, a person can go into shock.
The combination of sweating excessively and intaking more water than the body can process can result in a decreased sodium (salt) level in the body, a condition called hyponatremia. Hyponatremia most commonly develops from prolonged activity in warm environments while drinking plain water for fluid replacement. It can also occur from attempting to drink too much water in anticipation of high levels of activity or heat. As a person loses salt through sweat or decreases the balance of salt from over-hydration symptoms begin to present that are similar to dehydration. Fatigue and headache can be early indicators followed by muscle cramps. Increase in urine output (often clear) can also occur. In the extreme cases people experience personality changes and loss of consciousness.
The key to avoiding dehydration is to hydrate appropriately prior to the start of any activity. To avoid water issues onr upcoming adventures, plan on drinking consistently, but not excessively. Aim for consuming .25-.5L per hour. To avoid hyponatremia during high output activities, consider adding an electrolyte mix to plain water, but watch out for highly sugared electrolyte mixes that might be more akin to drinking a candy bar. If drinking plain water, plan to include small, frequent snacks that include sodium.
If symptoms of a hydration-related illness occur, proper treatment will start with understanding the history of food and water intake of the person affected. For a person with symptoms and a history of limited water intake, physical activity should be decreased and fluids encouraged at a rate of .5 liters per hour. If the affected person has a history of prolonged exertion and has been drinking plain water, consider hyponatremia and treat by discontinuing water consumption and slowly increasing the person’s sodium intake.