Surface contamination artificially elevates initial sweat mineral concentrations.

Several sweat mineral element concentrations decline with serial sampling. Possible causes include reduced dermal mineral concentrations or flushing of surface contamination. The purpose of this study was to simultaneously sample mineral concentrations in transdermal fluid (TDF), sweat, and serum during extended exercise-heat stress to determine if these compartments show the same serial changes during repeat sampling. Sixteen heat-acclimated individuals walked on a treadmill (1.56 m/s, 3.0% grade) in a 35°C, 20% relative humidity (RH), 1 m/s wind environment 50 min each hour for 3 h. Mineral concentrations of Ca, Cu, Fe, K, Mg, Na, and Zn were measured each hour from serum, sweat from upper back (sweat pouch) and arm (bag), and TDF from the upper back. Sites were meticulously cleaned to minimize surface contamination. Mineral concentrations were determined by spectrometry. TDF remained stable over time, with exception of a modest increase in TDF [Fe] (15%) and decrease in TDF [Zn] (-18%). Likewise, serum and pouch sweat samples were stable over time. In contrast, the initial arm bag sweat mineral concentrations were greater than those in the sweat pouch, and [Ca], [Cu], [Mg], and [Zn] declined 26-76% from initial to the subsequent samples, becoming similar to sweat pouch. Nominal TDF mineral shifts do not affect sweat mineral concentrations. Arm bag sweat mineral concentrations are initially elevated due to skin surface contaminants that are not removed despite meticulous cleaning (e.g., under fingernails, on arm hair), then decrease with extended sweating and approach those measured from the scapular region.

[1]  Samuel N Cheuvront,et al.  Sweat mineral-element responses during 7 h of exercise-heat stress. , 2007, International journal of sport nutrition and exercise metabolism.

[2]  P. Moretto,et al.  Nuclear microscopy: A tool for imaging elemental distribution and percutaneous absorption in vivo , 2007, Microscopy research and technique.

[3]  M. Nimmo,et al.  Acute effects of dehydration on sweat composition in men during prolonged exercise in the heat. , 2004, Acta physiologica Scandinavica.

[4]  S. Galloway,et al.  Effect of induced metabolic alkalosis on sweat composition in men. , 2002, Acta physiologica Scandinavica.

[5]  W. Crosby,et al.  IRON EXCRETION BY THE SKIN. SELECTIVE LOCALIZATION OF IRON-59 IN EPITHELIAL CELLS. , 1965, The American journal of pathology.

[6]  M D McNeely,et al.  Atomic absorption spectrometry of nickel, copper, zinc, and lead in sweat collected from healthy subjects during sauna bathing. , 1973, Clinical chemistry.

[7]  S. Galloway,et al.  Variations in Regional Sweat Composition in Normal Human Males , 2000, Experimental physiology.

[8]  J. Conn.  Electrolyte composition of sweat; clinical implications as an index of adrenal cortical function. , 1949, Archives of internal medicine.

[9]  D. DuBois,et al.  A formula to estimate the approximate surface area if height and weight be known , 1989 .

[10]  S. Yazar,et al.  Sweat Copper, Zinc, Iron, Magnesium and Chromium Levels in National Wrestler - , 2004 .

[11]  A. Kilding,et al.  Sweat Rate and Sweat Electrolyte Composition in International Female Soccer Players during Game Specific Training , 2009, International journal of sports medicine.

[12]  S. Yazar,et al.  Magnesium, Copper, Zinc, Iron, And Chromium Levels in Sweat of Boxers. , 2003 .

[13]  Mark J. Patterson,et al.  The reproducibility of closed-pouch sweat collection and thermoregulatory responses to exercise–heat stress , 2004, European Journal of Applied Physiology.

[14]  J A Stolwijk,et al.  Respiratory weight losses during exercise. , 1972, Journal of applied physiology.

[15]  A. R. Lind,et al.  Optimal exposure time for development of acclimatization to heat. , 1963, Federation proceedings.

[16]  Marshall Barnett Dunning,et al.  A Manual of Laboratory and Diagnostic Tests , 1980 .

[17]  P. Paulev,et al.  Dermal excretion of iron in intensely training athletes. , 1983, Clinica chimica acta; international journal of clinical chemistry.

[18]  C. Consolazio,et al.  Relationship between calcium in sweat, calcium balance, and calcium requirements. , 1962, The Journal of nutrition.

[19]  C. Weaver,et al.  Sweat mineral loss from whole body, patch and arm bag in white and black girls , 2003 .

[20]  Lindsay B. Baker,et al.  Comparison of regional patch collection vs. whole body washdown for measuring sweat sodium and potassium loss during exercise. , 2009, Journal of applied physiology.

[21]  S. Shirreffs,et al.  Whole body sweat collection in humans: an improved method with preliminary data on electrolyte content. , 1997, Journal of applied physiology.

[22]  J. Howard,et al.  Trace elements in the sweat of acclimatized persons. , 1994, Clinica chimica acta; international journal of clinical chemistry.

[23]  M. Sawka,et al.  Prior heat stress: effect on subsequent 15-min time trial performance in the heat. , 2009, Medicine and science in sports and exercise.

[24]  J. Stauber,et al.  A comparative study of copper, lead, cadmium and zinc in human sweat and blood. , 1988, The Science of the total environment.

[25]  D. D. Bois,et al.  CLINICAL CALORIMETRY: TENTH PAPER A FORMULA TO ESTIMATE THE APPROXIMATE SURFACE AREA IF HEIGHT AND WEIGHT BE KNOWN , 1916 .

[26]  S. Shimai,et al.  A modified, local sweat collector for warm and humid conditions , 2004, European Journal of Applied Physiology and Occupational Physiology.

[27]  O. Vellar,et al.  Studies on sweat losses of nutrients. 3. Calcium, magnesium, and chloride content of whole body cell-free sweat in healthy unacclimatized men under controlled environmental conditions. , 1968, Scandinavian journal of clinical and laboratory investigation.

[28]  A. Córdova,et al.  Effect of Training on Zinc Metabolism: Changes in Serum and Sweat Zinc Concentrations in Sportsmen , 1998, Annals of Nutrition and Metabolism.

[29]  P. Trumbo,et al.  Dietary reference intakes: vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. , 1998, Journal of the American Dietetic Association.

[30]  L. Hallberg,et al.  Iron losses in sweat. , 1986, The American journal of clinical nutrition.

[31]  Callum G. Fraser,et al.  Biological Variation: From Principles to Practice , 2001 .

[32]  C. Consolazio,et al.  Comparisons of nitrogen, calcium and iodine excretion in arm and total body sweat. , 1966, The American journal of clinical nutrition.

[33]  D. Maclaren,et al.  Iron, copper and zinc concentrations in human sweat and plasma; the effect of exercise. , 1988, Clinica chimica acta; international journal of clinical chemistry.

[34]  S. Cheuvront,et al.  Sweat iron and zinc losses during prolonged exercise. , 2002, International journal of sport nutrition and exercise metabolism.

[35]  G. R. Brisson,et al.  A simple and disposable sweat collector , 2004, European Journal of Applied Physiology and Occupational Physiology.

[36]  M. Chiba,et al.  Concentrations of trace elements in sweat during sauna bathing. , 2001, The Tohoku journal of experimental medicine.

[37]  Herman Brown,et al.  THE MINERAL CONTENT OF HUMAN SKIN , 1927 .

[38]  E. Haymes,et al.  Zinc loss in sweat of athletes exercising in hot and neutral temperatures. , 1993, International journal of sport nutrition.