Body Fluid Loss in Costa Rican Runners During a 21K Run

Abstract

The present study was pursued in order to determine the level of involuntary body fluid loss in a non-random sample of Costa Rican top long-distance runners, during the 1988 La Gloria half-marathon race. Forty subjects were measured before and after the race, for Body Weight, Resting Heart Rate, Blood Pressure and Oral Temperature. During the competition they ran at 80 ±5% of their predicted Maximum Heart Rate, finishing in 82 ±8 minutes; the temperature was between 29° and 26.3°C, and relative humidity between 60 and 62% (average WBGT = 25.65°C). Subjects were instructed to restore fluids ad libitum. Differences in blood pressure and body temperature were not statistically significant for p=.05. Both RHR and BW showed a statistically significant difference at p=.05. Average body fluid loss was calculated as 2.2 kg (3.61% of average total body weight), exceeding for the average and each individual the threshold for involuntary dehydration. It was concluded that none of the subjects restored body fluid loss properly. This confirms previous studies where runners showed very little knowledge about proper rehydration procedures.