title: The effect of heat acclimation on sweat microminerals: artifact of surface contamination.
abstract: Heat acclimation (HA) reportedly conveys conservation in sweat micromineral concentrations when sampled from arm sweat, but time course is unknown. The observation that comprehensive cleaning of the skin surface negates sweat micromineral reductions during prolonged sweating raises the question of whether the reported HA effect is real or artifact of surface contamination.
  
  
  OBJECTIVE
  To measure sweat mineral concentrations serially during HA and determine if surface contamination plays a role in the reported mineral reductions.
  
  
  METHODS
  Calcium (Ca), copper (Cu), magnesium (Mg), and zinc (Zn) were measured in sweat obtained from 17 male volunteers using an arm bag on Day 1, 5, and 10 of a HA protocol. To study the role of contamination, sweat was simultaneously (n = 10 subjects) sampled twice daily from a cleaned site (WASH) and unclean site (NO WASH) on the scapular surface.
  
  
  RESULTS
  Sweat Ca, Cu, and Mg from Arm Bag trended progressively downward from Day 1 to Day 10 of HA (p = .10-0.25). Micromineral concentrations from the WASH site did not change between Day 1, 5, or 10 (Ca = 0.30 ± 0.12 mmol/L, Cu 0.41 ± 0.53 μmol/L; Zn 1.11 ± 0.80 μmol/L). Surface contamination can confound sweat mineral estimates, as sweat Ca and Cu from NO WASH site were initially higher than WASH (p < .05) but became similar to WASH when sampled serially.
  
  
  CONCLUSIONS
  Heat acclimation does not confer reductions in sweat Ca, Cu, Mg, or Zn. When the skin surface is not cleaned, mineral residue inflates initial sweat mineral concentrations. Earlier reports of micromineral reductions during HA may have been confounded by interday cleaning variability.
authors.affiliation: U.S. Army Research Institute of Environmental Medicine, Natick, MA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Ely
authors.forename: Robert W
authors.initials: RW
authors.lastname: Kenefick
authors.forename: Samuel N
authors.initials: SN
authors.lastname: Cheuvront
authors.forename: Troy
authors.initials: T
authors.lastname: Chinevere
authors.forename: Craig P
authors.initials: CP
authors.lastname: Lacher
authors.forename: Henry C
authors.initials: HC
authors.lastname: Lukaski
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Montain
mesh_terms: D000064:Acclimatization; D000293:Adolescent; D000328:Adult; D016477:Artifacts; D002118:Calcium / Q000378:metabolism; D003300:Copper / Q000378:metabolism; D015444:Exercise; D006358:Hot Temperature; D006801:Humans; D008274:Magnesium / Q000378:metabolism; D008297:Male; D008903:Minerals / Q000378:metabolism*; D012867:Skin / Q000378:metabolism*; D017592:Skin Care; D013542:Sweat / Q000378:metabolism*; D013546:Sweating; D055815:Young Adult; D015032:Zinc / Q000378:metabolism
chemical_list: D008903:Minerals; D003300:Copper; D008274:Magnesium; D015032:Zinc; D002118:Calcium