WHOLE-BODY SWEAT COLLECTION IN HUMANS - AN IMPROVED METHOD WITH PRELIMINARY DATA ON ELECTROLYTE CONTENT

Previous methods used to collect human sweat for electrolyte analysis have been criticized because they involve only regional sampling or be cause of methodological problems associated with whole body-washdown t echniques. An improved method for collection of whole body sweat from exercising subjects is described. It involved construction of a plasti c frame that supports a large plastic bag within which the subject exe rcises. The subject and the equipment are washed with distilled, deion ized water before exercise begins. After exercise is completed, tile s ubject and equipment are again mashed with water containing a marker n ot present in sweat (ammonium sulfate). Total sweat loss is calculated from the change in body mass, and the volume of sweat not evaporated is calculated from dilution of the added marker Recovery of added wate r was 102 +/- 2% (SD) of the added volume, and recovery of added elect rolytes was 99 +/- 2% for sodium, 98 +/- 9% for potassium, and 101 +/- 4% for chloride. Repeated trials (n = 4) on five subjects to establis h the reproducibility of the method gave a coefficient of variation of 17 +/- 5% for sodium, 23 +/- 6% for potassium, and 15 +/- 6% for chlo ride. These values include the biological variability between trials a s well as the error within the method. The biological variability thus appears to be far greater than the methodological error. Normal value s for the composition of sweat induced by exercise in a hot, humid env ironment in healthy young men and women were (in mM) 50.8 +/- 16.5 sod ium, 4.8 +/- 1.6 potassium, 1.3 +/- 0.9 calcium, 0.5 +/- 0.5 magnesium , and 46.6 +/- 13.1 chloride.