When determining if water temperature is too low or too high for open water swimming competitions, knowledgeable experts around the world agree that a variety of factors and conditions – both in the water and in the air – should be taken into consideration by race directors, medical personnel, safety staff, athletes, coaches and parents.

On the high end of the scale where hyperthermia (elevation of one’s core body temperature above normal) is a risk, swimming in a competitive race in 30°C (86°F) in a still body of water with 100% humidity and bright sunshine can lead to trouble.

On the other hand, swimming in a competitive situation in the same water temperature in a moving body of water with currents and breaking waves in a light mist on an overcast day leads to a significant reduction in hyperthermia risks (as long as the athletes are not wearing constrictive wetsuits).

As Dr. Jim Miller of the FINA Sports Medicine Committee states, “When the question comes up regarding water temperature by itself, there will not likely be an absolute. The athlete is being affected by all of the conductivity factors – radiation, conduction, convection and evaporation. There are some equations used around the world that take these factors into consideration. These formulas start with a water temperature and then have points added or subtracted based upon the other variables.

There is also the equation that gives a total temperature (water plus air) stating that above or below a certain level that the open water swimming event should be modified, moved or canceled. This [formula that combines water and air temperatures] is an easier method for event directors since they are dealing with absolute numbers and not factoring in how fast water is moving or overcast versus sunshine or humidity. This method is not perfect, but it at least takes into account two different variables [that impact the physiology of the athlete].”

From the standpoint of all stakeholders in the sport of open water swimming and triathlons, these combined parameters are better than merely judging from water temperature alone. “They are user friendly for event directors who have forecasts for the event day,” said Dr. Miller. “This would allow race organizations flexibility and move a starting time to earlier or later in the day if bright sun were forecast for the race time.”

And race directors face a myriad issues on how to monitor the conditions. “We will always have issues of where do you take the temperature of the water. For FINA competitions, the water temperature is measured at 40 cm below the surface of the water in the middle of the course. While this works for a loop or triangle course, it is clearly meaningless in a linear [point-to-point] course.”

But with more and more experience, information-sharing and enhanced guidelines, the sport’s race directors and safety officers should be able to determine the proper conditions to conduct their races. Of the over 4,000 open water races around the world, there are always a few hundred races that are modified, postponed or canceled due to a variety of climatic conditions.

What is vitally important is for athletes and coaches to prepare themselves for the appropriate conditions prior to the race. There are occasionally medical problems especially when athletes place themselves in situations where they have little or no practice or acclimatization to the conditions. Therefore, while 30°C (86°F) may be tolerable to some, there are many others – especially those who are overweight and older – where higher temperatures place an inordinate amount of stress on their bodies.

As the sport continues to blossom, more and more science, research and empirical data gathering will be conducted. As a start, it would be enlightening to measure the body temperature of athletes immediately after races, especially in highly competitive or longer swims where water temperatures extremes (i.e., under 15°C or over 28°F) are experienced. The information has to start from someone and it would be very interesting to see what the global open water swimming community can gather to determine what is best for all.

Copyright © 2011 by Open Water Source