2006 Annual Report 4a.List the single most significant research accomplishment during FY 2006. Sweat Mineral Losses in Youth During Controlled Exercise We performed the first study to evaluate mineral concentrations from specific sites on the bodies of youth and adolescent athletes during physical activity. The principal finding was that sweat mineral concentrations differed by sex; mineral concentrations were greater in males than females. Collaborators from Gatorade Sports Science Institute (Barrington, IL) recruit members of elite youth soccer teams to wear unobtrusive sweat collection patches during training sessions. This preliminary information is important in planning future studies to assess the impact of surface mineral losses on mineral nutritional status of humans. This work is related to Human Nutrition Action Plan 107 and addresses the area of Nutrient Requirements. 4b.List other significant research accomplishment(s), if any. None 4c.List significant activities that support special target populations. None 4d.Progress report. This report serves to document research conducted under non-funded cooperative agreement #58-5450-5-107N between ARS and Gatorade Sport Science Institute. Additional information can be found in the report for the parent project 5450-51530-009-00D Micronutrient Roles in Physiology and Health. Another study is underway to develop a standard reference material for use in analysis of human sweat samples. The only available reference material with a similar matrix as sweat is an NIST water standard. However, the mineral concentrations are not in the same ranges as those found in human sweat. Thus, there is a critical need to develop this standard for future research.