As a health and fitness professional, there are many different elements you need to consider when programming for your clients, including your clients’ goals, physical limitations and the environment in which they are exercising. In this blog, we’ll cover how to keep your clients safe while exercising in the heat. A client who does not take precautions when exercising in the heat may be at risk for developing heat-related illness, which may be amplified if he or she is not adequately hydrated, wears excessive clothing, or is overweight or obese. Excessive clothing and fat each have the potential for trapping heat in the body and preventing it from escaping, which can increase body temperature. Under normal conditions, body temperature will rise about 2-3° F during exercise, but heat injuries will usually occur when heat loss is compromised. Heat combined with humidity is the most stressful environment in which to exercise because the large amount of water in the air means that sweat will not readily evaporate, which decreases the efficiency of the bodies most effective cooling system. So what do you need to know as a trainer? First, it’s important to have a good understanding of the heat index chart. You don’t need to memorize it, but you do need to understand the relationship between humidity and temperature (conditions become more dangerous as humidity and heat increase). You must also be aware of the signs and symptoms of heat exhaustion and heat stroke as well as the initial treatment for both. Here are some tips to offer your clients before they begin exercising in the heat: Begin exercise in the heat gradually as acclimatization typically takes seven to 10 days. Always wear light-weight, well-ventilated clothing. Wear light-colored clothing if exercising in the sun as white reflects heat better than other colors. Never wear non-breathable clothing. Cotton is a good choice for exercising in the heat because it readily soaks up sweat and allows for evaporation. Replace body fluids as they are lost. Recording daily body weight is an excellent way to prevent cumulative dehydration. Air movement is critical for adequate cooling. For more information on exercising in the heat please refer to chapter 2 of the Essentials of Exercise Science manual.