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Hydrate Yourself for Summer Training

By Marni Sumbal

hydration Depending on where you live, the summer months generally bring hot and/or humid training conditions. Because your body will sweat as a safeguard to control the temperature of the body, it’s imperative that you do your part and focus on your individual hydration, caloric and electrolyte needs in order to keep your body in good health as you train to maximize performance.

In order to reach optimal performance gains in the summer, one must learn to tolerate the heat without sacrificing form. Therefore, if you can control the environment in which you train, it’s recommend that you focus first on training adaptations and then to acclimate to the heat in the 7-14 days leading up to your A-race.

For most athletes, sweating feels incredibly uncomfortable. But for good reason, your body relies on evaporative cooling as the primary mechanism to decrease surface body temperature and prevent overheating. During activities in the heat, the cardiovascular system works overtime in order to provide blood to the working muscles as well as increasing blood flow to the skin for cooling. Unfortunately, if one area of the body is receiving more blood than the other, performance will be compromised.

While the temperatures may be similar in two different regions of the country, relative humidity is the most important factor having a direct relationship to sweating and cooling. Perhaps the lucky athletes are those who train in areas of low humidity and welcome a nice breeze to keep the body from overheating. As for the rest of athletes training in high humidity, they are all too familiar with wet clothes and high heart rates during the first ten minutes of training outdoors.

Because high humidity causes sweat to evaporate more slowly than in low humidity, it is suggested to avoid constantly drying off your skin with a towel if you are a light sweater, as your body’s primary method of cooling is through evaporation. If you are a heavy sweater, dripping sweat will require a higher sweating rate so be cautious as to adjust your intensity in order to reduce the risk for heat illness.

Since it is likely that a triathlete will train and/or race in hot and humid temperatures at some point during the summer months, sweat loss is of concern during your training sessions. Heat may cause athletes to lose up to .5-2 L/hr of sweat (1), depending on body size (surface area), training environment, diet and ability to meet hydration and electrolyte needs. Considering that fluid replacement is affected by fluid volume, energy content and osmolality, it is recommended to consume between 24-28 ounces of fluid per hour during training and racing and to not overhydrate with water. An optimal carbohydrate solution is necessary in order to meet individual calorie and electrolyte needs, so keep in mind liquid calories are essential in ensuring a successful race day performance.

Additional tips for training/racing in the heat:

1) Train and race in clothing that promotes evaporation from the skin. Lightweight, loose-fitting clothing will allow more air to pass over the body for an added cooling effect. Avoid dark clothing which absorbs light rays and promotes radiant heat.

2) Hydrate at regular intervals during training and racing. As the intensity increases during training/racing, there is a simultaneous demand for blood flow and delivery of oxygen to working muscles. While the working muscles are receiving blood to sustain energy during exercise, the same blood must go to the skin, in order to help dissipate heat. By drinking every 10-15 minutes during exercise, the metabolic response to exercise will not be compromised as you hydrate your cells and meet fluid requirements.

3) Take your time while acclimating to the heat. Do not expect to perform at the same intensity/heart rate throughout the acclimation period. Be smart and adjust training intervals to allow for higher than normal heart rates. Additionally, acclimatization to the heat does not reduce your risk for dehydration. Though the body can become more efficient at cooling the body, acclimatization does not train your body to need fewer fluids (or calories) than recommended.

4) Focus on electrolytes, not just sodium. Most sport drinks will provide sodium and potassium to cover your basic electrolyte needs. However, search around and compare products, as the most advantageous sport drinks will provide a full panel of electrolytes (ex. sodium, potassium, calcium, magnesium, chloride) in an effective quantity, to keep you hydrated, regulate blood pH and control proper nerve and muscle function.

Source: Sawka MN, et al. (2007). American College of Sports Medicine position stand: Exercise and fluid replacement. Med Sci Sports Exerc., 39377– 390. 

Marni Sumbal, MS, RD, is a Certified Sports Nutritionist (CISSN) and holds a certification by the American Dietetic Association in Adult Weight Management. She is a Level I Certified USA Triathlon Coach, a 4x Ironman finisher and an Oakley Women ambassador. Marni is currently training for her second Ironman World Championships in Kona, Hawaii. Marni enjoys public speaking and writing, and has several published articles in Lava Magazine, Hammer Endurance News, CosmoGirl magazine and Triathlete Magazine. She also contributes monthly to and To contact Marni, email or visit

The views expressed in this article are the opinion of the author and not necessarily the practices of USA Triathlon. Before starting any new diet or exercise program, you should check with your physician and/or coach.