As we exercise, our bodies burn the calories that that we consume (i.e. carbohydrates, proteins and fats).  It is the breakdown of these calories and muscle movement that causes heat to build up and raise our core body temperature initiating the demands of the body to maintain its ideal body temperature of 98.6 degrees.  There are several ways that the body dissipates heat (skin and exhalation for example); however, the most complex system involves your ability to sweat.

Simply put, water molecules evaporate from your skin removing heat energy from inside your body, water molecules on your skin making you feel cooler.  The (endothermic) process of converting liquid to a gas is beyond the scope of this article; however, the ultimate goal is to maintain your body’s ability to efficiently dissipate heat during exercise.  What makes this process difficult is dealing with elements that we don’t have any control over – heat and humidity.

On hot days when there is little difference between the skin’s surface temperature and the ambient air temperatures, the skin provides only small cooling benefits – increasing the importance of sweating to rid your body of internal heat. In fact, when the temperature rises above 95 degrees Fahrenheit, you lose no heat at all from your skin – evaporation must to all of the work.  Humidity decreases your body’s ability to evaporate sweat because the air is already saturated with water vapor, reducing (and in some cases eliminating) the evaporation rate.  Though you and your gear/clothes may be saturated, it is not helping you in your cooling process – sweat must evaporate to remove heat from your body – plain and simple.  It is this concept that makes hydration so important; if you don’t have enough fluids to produce sweat you will over heat guaranteed (along with the negative side effects – performance and health wise).

On average, racers lose approximately 30-35 ounces of fluid per hour of exercise (the actual amount varies by body size, intensity & duration levels and heat/humidity levels).  There are numerous formulas floating around in the sports performance world regarding ideal food and fluid intake; however, keep in mind that there are three things that we need to evaluate regarding ideal performance nutrition: fluid intake (sports drink & water), electrolyte balance (sodium, potassium, calcium, magnesium) and calories (sources & amount).

5 Tips for Training and Racing in the Heat and Humidity

• Wear gear that facilitate the evaporation process (avoid cotton at all costs)
• Train at times that are relevant to your race (i.e. if you are going to be racing at 2:00 pm, then practice at this time “teaching” your body to acclimate to the heat & humidity
• Avoid over-hydrating on plain water; drink a sports drink that has a 4-6% concentration rate for optimal hydration levels. If the concentration rate is too high or too low, your body will not absorb your fluids and you may become nauseous
• Consume cold fluids; they absorbs faster than warm fluids; use insulated bottles to help you keep your fluids cold
• During hard training intervals in the heat, back off of the intensity for 30 seconds; it is like shaking your hands over a jump

Be sure to pay attention to external signs of heat stroke sequence:

Stage 1: Dry skin (indication that you have stopped sweating). If this occurs, stop the workout. You have hit a point where your fluid levels are dangerously low.

Stage 2: Cold chills (visible goose bumps) – Your body is attempting to capture your attention; you  crossed the danger line; performance is irrelevant.

Stage 3: Become lightheaded, get a headache or feel queasy –  You are so dehydrated that your core body temperature has reached a critically dangerous point; bodily functions are being negatively affected.

Stage 4: The top of your head feels like someone has put a hot skillet on your head; your head feels “hot” – You are literally “cooking” yourself from the inside out.  Long term problems could result if you continue.