Exercise-induced trace mineral element concentration in regional vs. whole-body wash-down sweat


Journal Title (Medline/Pubmed accepted abbreviation): Int J Sport Nutr Exerc Metab
Year: 2011
Volume: 21
Number: 3
Page numbers:233-239
doi (if applicable):

Summary of background and research design

Hypothesis: The authors did not state a specific hypothesis, but noted that the skin patch method, while practical for field studies, has not been validated against whole body wash-down for measurement of electrolytes such as calcium, magnesium, copper, manganese, iron, and zinc. The purpose of this study was to compare these two methods with these particular electrolytes.

Subjects:There were 4 male and 4 female well-trained athletes (runners, cyclists, and triathletes, mean age=36 y, mean body mass=72 kg, mean body surface area=1.84 m2)

Protocol:The subjects performed 90 min of exercise on a cycle ergometer in a heated (30° C) laboratory.  At 20 min into exercise a sterile patch was applied at anterior midthigh.  Then, 30 min into exercise, one patch each was placed on the upper chest, scapula, forehead, and posterior midforearm, in that order.  The subjects’ clothing had been previously washed with deionized water to remove minerals.  The cycle ergometer and subjects were enclosed in a plastic housing to catch all unevaporated sweat.  The subjects were rinsed with 5 L deionized water with ammonium sulfate immediately after completing the exercise.  All clothing, towels, heart rate monitor, and other items the subject touched were collected for analysis of electrolytes.
 
Summary of research findings
  • The 5-site  patch collection method overestimated the sweat calcium, magnesium, and copper concentrations by 32, 48, and 33%, respectively.
  • No individual patch site or the 5-site method was significantly correlated with whole-body wash-down sweat concentrations for calcium (R = -0.21, P = 0.65), magnesium (R = 0.49, P = 0.33), or copper (R = 0.17, P = 0.74).

Interpretation of findings/Key practice applications

The authors concluded that the patch method was not a validated surrogate for whole-body wash-down technique for the measurement of sweat calcium, magnesium, or copper. The concentrations of these electrolytes in sweat are very small and do not usually represent much of a concern relative to quantitatively more significant electrolytes (e.g., sodium) for exercising athletes. However, the measurement of these electrolytes in sweat forms part of the basis for which dietary requirements of these electrolytes are developed.

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