Validity/reliability of sweat analysis by whole-body washdown vs. regional collections

Six subjects (25.3 +/- 3.3 yr, mean +/- SD) exercised for 60 min at 42 +/- 4 [low (L)], 55 +/- 6 [moderate (M)], and 67 +/- 4 %VO2max [high (H)] in a moderate environment. Sweat collected from upper back (UB), lower back (LB), midchest (MC), stomach (S), and thigh (T) areas as well as by whole-body washdown (W) was analyzed for urea nitrogen (N). With the exception of the L where all regional measures were similar, all sites overestimated W (several significantly, P less than 0.05). Regression analysis estimations of W (mg/h) from regional collections were as follows--L: W = 0.727 (S) - 1.366(UB) + 1.181(T) + 65.470 +/- 29.5, R = 0.90; M: W = 0.598(MC) - 0.649(UB) + 0.244(LB) + 43.238 +/- 30.4, R = 0.99; H: W = 0.274(S) - 0.560(T) + 0.223(MC) + 131.104 +/- 4.3, R = 0.99; All Intensities: W = 0.497(MC) - 0.483(T) + 0.112(LB) + 69.554 +/- 31.5, R = 0.96. W recovery of exogenous urea N applied to each subject's body was 98.3 +/- 2.7% (mean +/- SE). Interinvestigator reliability coefficient (r = 0.511) was significant (P less than 0.01) but relatively low and the between investigator urea N recovery (93.3 +/- 3.7 vs. 103.2 +/- 3.5%) was significantly different (P less than 0.05). Repeated W determinations by the same investigator were not different (P greater than 0.05), but intrainvestigator reliability coefficients differed widely (0.385 vs. 0.820). Together, these data indicate that W solute recovery can be high; however, both inter- and intrainvestigator reliability can vary.(ABSTRACT TRUNCATED AT 250 WORDS)