The Summer season takes place in June, July and August which are typically the three hottest months of the year. In addition to high temperatures, these months can also be some of the most humid. Adding this hot humid weather to long periods of outdoor activity can spell disaster. Dehydration, hyperthermia, hyponatremia, heat exhaustion, and heat stroke are just some of the negative health states that can be brought on by such conditions. Concerning dehydration, the loss of body mass of greater than 2-3% is the cut-off of most sport scientists for general safety. A loss of fluid and electrolytes beyond 3% has been shown to decrease motor performance. Fatigue has been shown to set in earlier under such conditions as well as decreased motor function. More importantly, however, is the increased the risk of heat related injury.

Heat is not the only factor in hydration with hot, humid conditions. The body’s natural cooling mechanism is for heat to rise from the core, through the bloodstream, and eventually to the surface of the skin through sweating. The evaporation of this perspiration leads to the actual cooling of the body. High humidity does not allow effective evaporation as the air is already high in water content. So, the body continues to perspire in a vain attempt to cool the body. This leads to increased electrolyte depletion. Sodium and potassium are removed from the body via sweat at advanced rates. Under such conditions, over a prolonged period of time, drinking excessive water may lead to a condition known as hyponatremia. This potentially lethal condition is marked by a dangerously low level of sodium in the blood. Hyponatremia most often occurs during prolonged activities such hard outdoor work,such as bailing hay, or long sporting events such as marathons where people sweat profusely in hot, humid conditions and hydrate excessively with inadequate sodium replacement such as drinking too much water. This condition may deplete sodium to such an extent that there is a significant drop in blood pressure and an increased rate of respiration. If this condition persists, death may eventually result.

What can be done to prevent hyponatremia and other heat related conditions? The first step in understanding adverse environmental conditions and hydration is knowledge. This includes knowledge of basic hydration practices and personal knowledge of yourself. When conditions are especially hot and humid it pays to monitor your body mass. Excessive loss of body mass through perspiration should be prevented by ingesting an adequate amount of fluid before, during, and after prolonged activity. The best and easiest place to store fluid is in the body, so several hours before an activity in hot, humid weather include fluid and electrolytes. A sports drink or salt added to a meal should do the trick. Also, immediately before an activity in this kind of weather an additional cup or two of fluid should also be consumed, though not so much that you become overfull. During the activity, continue with fluid consumption as indicated by perspiration and body mass loss, not thirst, as thirst is an unreliable indication of hydration state. After your activity, any fluid lost through perspiration should be replaced. Two cups per pound of body mass loss is a good rule to follow. In addition to monitoring your body mass, behavior and motor coordination should all be taken into consideration for general health status. Last, when in doubt, always consult a physician or qualified health professional.

To make your Summer activity as safe as possible make sure that hydration and environmental conditions are considered. Everyone needs to understand the basic principles of hydration and body cooling both in normal and extreme weather conditions. Make sure that you consume not only adequate fluid, but also adequate amounts of electrolytes before, during, and after an activity. Last, to ensure the health and safety you and your loved ones, pay careful attention to behavior to see if everyone is acting appropriately or if closer examination for a heat related illness is warranted. With these few simple steps, you will be well on your way to having a fun and active Summer season.

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