May 10, 2006

Fluid Loss in Triathlon Doesn’t Harm Elite Athletes

NEW YORK (Reuters Health) - Athletes competing in an Ironman triathlon can experience some dehydration without developing a dangerous increase in the body's core temperature or impairing performance, a new study shows.

The report is the first in which Ironman athletes' temperatures have been evaluated throughout a race, rather than after they have completed competition.

Currently, the American College of Sports Medicine (ACSM) and other groups recommend that athletes replace all fluid lost during exercise to maintain performance and prevent dehydration and overheating, Dr. P.B. Laursen of Edith Cowan University in Joondalup, Western Australia and colleagues note in the British Journal of Sports Medicine. But recent studies have suggested that some dehydration may not interfere with performance.

To investigate, Laursen and colleagues monitored core temperature and hydration in 10 male triathletes competing in an Ironman event in Western Australia. The average age was 34 and all of the athletes had completed at least one previous Ironman competition in less than 10 hours and 30 minutes. Each swallowed a device known as a core temperature pill that allowed their temperature to be monitored remotely throughout the race.

The race included a 3.8 km (2.4 mile) swim, a 180 km (112 mile) bicycle race and a 42.2 km (26.2 mile) marathon run. During the race, the air temperature averaged 23.3 degrees C (about 74 degrees Fahrenheit), while humidity was about 60 percent.

On average, the researchers found, the athletes lost about 3% of their body weight or 2.3 kg (5.7 pounds), but their average body temperature increased just 1 degree Centigrade above normal.

The findings show, Laursen and colleagues say, that recommendations urging athletes to drink as much as possible during exercise may not necessarily apply to experienced athletes competing in an Ironman triathlon.

"Consequently, and in light of the evidence emerging in this field, it would seem prudent that the ACSM and others review and adjust their current fluid replacement guidelines so as to be aligned with more contemporary wisdom in this area," the researchers conclude.

SOURCE: British Journal of Sports Medicine, April 2006.