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 to 14 days leading up to your "A" race.
The Role of Sweat
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 increase 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.
How Much Should You Drink?
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 and 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.