By the time you begin to read this article, the “Dog days of summer” will be upon us.  Outdoor activity during this time of the year needs to be planned so that you stay out of the hottest part of the day which can lead to dehydration illness.   If you are planning to be outdoors, exercising, performing lawn activities, i.e; cutting the grass or gardening, or working, you need to stay hydrated.  When performing activities between 10 am and 4 pm, you need to be aware of your fluid loss and replacement.  The vast majority of healthy people during normal activities throughout the day adequately meet their daily hydration needs by letting thirst be their guide.  However, for individuals with higher than average fluid intake requirements, thirst is not a true guide of fluid loss and replacement needs.  Daily fluid intake fluctuates for those in hotter climates and those that are more physically active.  The Food and Nutrition Board of the Institute of Medicine (IOM) reports that healthy adults consume enough water from drinking fluids (about 80%) and eating food (about 20%) to maintain health and proper physiological function.  The American College of Sports Medicine (ACSM) and the National Athletic Trainers Association (NATA) recommend active adults drink before, during, and after exercise or other outdoor activities.    Although Americans consume eight to 12 grams of salt daily on average and the IOM recommending no more than 3.8 grams of salt each day, the ACSM and NATA recommend that athletes, instead of cutting back on salt intake in their diets, that they liberally salt their food and consume sports drinks.  Athletes that compete in hot weather conditions need sodium in their diet to help replenish the loss of large amounts of sodium in sweat to ensure proper fluid balance in the body.


During exercise, 80% of total heat removed from the body is by sweat evaporation.  The evaporation of sweat is an effective way the body dissipates large amounts of heat to help keep the core body temperature regulated.  High levels of heat and humidity severely limit the exercising body’s ability to dissipate heat as well as a lesser conditioned athlete is more at risk to experience heat related illness.  Dehydration resulting from the failure to adequately replace fluids during exercise can lead to impaired heat dissipation, elevated body core temperature, and increased stain on the cardiovascular system.  Classification of heat related illness include heat cramps, heat fatigue, heat exhaustion, and heat stroke, with the latter being a medical emergency.  Athletes should know how to acclimate their bodies to hot weather training and competition as well as those who work or perform leisure activities in the heat. 


Fluid intake recommendations are as follows: eight 8oz glasses of water the previous day before activity, 16 oz of water 2 hours prior to activity, 8-10 oz of water 10-15 before activity, drink 8-10 fl oz every 10-15 min during exercise, and drink 20-24 fl oz water for every pound of body weight lost during activity.  If exercising longer than 90 minutes, drink 8-10 fl oz of a sports drink (with no more than 8 percent carbohydrate) every 15 - 30 minutes. Research has also shown that people will drink more of a lightly flavored sports drink that contains sodium than they will water.  You should avoid caffeinated and alcoholic beverages while performing strenuous outdoor activity as these beverages act as diuretics and will increase the level of dehydration.  Carbonated beverages should also be avoided as they may be irritating to the stomach and cause you to drink less.


Heat related illness can be serious if the proper hydration during outdoor activity is not done.  For all of us that work, play, and compete outdoors, we need to make sure that we plan to stay well hydrated.  Remember to rest often and in shade to allow our body to cool down.