Accumulation of super(2)H sub(2)O in plasma and eccrine sweat during exercise-heat stress

• Published in: European journal of applied physiology Vol. 108; no. 3; pp. 477 - 482
• Main Authors: Armstrong, Lawrence E, Klau, Jennifer F, Ganio, Matthew S, McDermott, Brendon P, Yeargin, Susan W, Lee, Elaine C, Maresh, Carl M
• Format: Journal Article
• Language: English
• Published: 01.02.2010
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-009-1223-2

The purpose of this research was to characterize the movement of ingested water through body fluids, during exercise-heat stress. Deuterium oxide ( super(2)H sub(2)O) accumulation in plasma and eccrine sweat was measured at two sites (back and forehead). The exercise of 14 males was controlled via cycle ergometry in a warm environment (60 min; 28.7 degree C, 51%rh). Subjects consumed super(2)H sub(2)O (0.15 mg kg super(-1), 99.9% purity) mixed in flavored, non-caloric, colored water before exercise, then consumed 3.0 ml kg super(-1) containing no super(2)H sub(2)O every 15 min during exercise. We hypothesized that water transit from mouth to skin would occur before 15 min. super(2)H sub(2)O appeared rapidly in both plasma and sweat (P < 0.05), within 10 min of water consumption. The ratio super(2)H sub(2)O/H sub( 2)O (D:H) was 47.3-55.0 times greater in plasma than in back sweat at minutes 10, 20, and 30 ( Delta D:H relative to baseline). At elapsed minute 20, the mean rate of deuterium accumulation ( Delta D:H min super(-1)) in plasma was 14.9 and 23.7 times greater than in forehead and back sweat samples, respectively. Mean ( plus or minus SE) whole-body sweat rate was 1.04 plus or minus 0.05 L h super(-1) and subjects with the greatest whole-body sweat rate exhibited the greatest peak deuterium enrichment in sweat (r super(2) = 0.87, exponential function); the peak super(2)H sub(2)O enrichment in sweat was not proportional (P > 0.05) to body mass, volume of the deuterium dose, or total volume of fluid consumed. These findings clarify the time course of fluid movement from mouth to eccrine sweat glands, and demonstrate considerable differences of super(2)H sub(2)O enrichment in plasma versus sweat.