Feasibility of Sweat Collection by Whole Body Washdown in Moderate to High Humidity Environments

Abstract

When sweat rates are sufficiently elevated, i.e., in high ambient temperatures or during exercise, due to potential losses of sweat by runoff, the whole body washdown technique of sweat collection is considered invalid in all but low humidity environments. This paper describes a modification of this technique that makes its use possible in moderate to high humidity environments. During exercise, sweat loss by runoff was minimized by maximizing evaporation of sweat (subjects wore little clothing and electric fans were utilized) and by drying the surface of the body when sweat became excessive (with small hand towels). Sweat rate was calculated from weight changes with appropriate corrections. Total sweat content and concentration of urea N were determined from the rinsings of the body, hand towels, and clothing. To validate this procedure, runoff sweat that was not collected was estimated from the weight change of collecting towels positioned under a bicycle ergometer. Eight subjects exercised at ∼ 60% VO_2max for 30 min in 22.6° ± 0.46°C (X¯ ± SD) and 66.1% ± 2.34% RH. Volume of sweat secreted was 581 ± 31 ml (1.162 ± .062 l·h^-1; X¯ ± SE). Sweat content of the collecting towels (corrected for evaporation loss) was 4.675 ml (0.8%) of total sweat rate), indicating that it is possible to prevent significant sweat loss with this procedure. Moreover, we have found that this procedure can be employed with little difficulty at exercise intensities up to ∼75% V̇O_2max, in RH of ∼70%, and with sweat rates as high as 1.65 l·h^-1. This procedure requires inexpensive and readily available equipment and, therefore, should enable sweat collection by whole body wash-down in all laboratories, even those without humidity control.

Key words

Sweat solute concentration - sweat rate - runoff sweat - regional sweat - sweat urea N - exercise