The course is divided into three phases. The first phase consists of physical training AZD2281 purchase and learning Army values and policies. The second phase involves weapons training and various assault courses. The final phase involves field exercises and the evaluation of skills taught during the first two phases. Physical training activities during BCT include road marching, distance running, and sprinting. Soldiers also participate in muscle strength training activities, including calisthenics, sit-ups, and push-ups. Military activities include obstacle courses, didactic Adriamycin classroom instruction,

and standing in formation [11]. Comprehensive measures of the ambulatory activity experienced during BCT have been reported elsewhere [12]. During physical training activities, which typically occur in the early morning (0500-0700) hours, Soldiers are required to wear uniforms consisting of shorts and short-sleeved shirts. At all other times Soldiers are generally required to wear the Army Combat Uniform (ACU), which consists

of boots, long pants, long-sleeved shirts, and caps. While wearing the ACU, only the hands and face are exposed to sunlight. Although the use of sun protection is recommended during BCT, data regarding the use of such products was not collected during this study. Blood was collected from fasted Soldiers by antecubital venipuncture, processed on site, AZD3965 purchase frozen, and shipped to USARIEM or the Pennington Biomedical Research Center (Baton Rouge, LA) for further analysis. Serum 25(OH)D (Immunodiagnostic Systems, Fountain Hills, AZ) and PTH (Siemens 2000, Los Angeles, CA) levels were determined using commercially available immunoassays. Self-reported ethnic characteristics were used to separate subjects into 3 groups (non-Hispanic white, n = 39; non-Hispanic black, n = 24; Hispanic white, n = 11) for statistical analysis. Statistical analysis was performed using the Statistical Package for the Social Sciences v. 15.0 (SPSS Inc., Chicago, IL). A two-factor ANOVA with repeated measures was used to test for main effects of both ethnicity and time, as well as ethnicity-by-time interactions in 25(OH)D and PTH. When a significant

ethnicity-by-time interaction was observed, post hoc analyses with Bonferroni adjustments were conducted to identify within- Guanylate cyclase 2C and between-group differences. Significance was set at P ≤ 0.05 for all tests. Results Overall, mean 25(OH)D levels declined during BCT (72.9 ± 30.0 vs 63.3 ± 19.8 nmol/L, P < 0.05, Figure 1A). Ethnicity affected changes in vitamin D status (ethnicity-by-time interaction, P < 0.05); 25(OH)D decreased (P < 0.05) in non-Hispanic whites, and in Hispanic whites, but did not change in non-Hispanic blacks (Figure 2A). Furthermore, mean 25(OH)D levels were lowest (P < 0.05) in non-Hispanic blacks at both time points. In the total study population, PTH levels increased over the course of BCT (36.2 ± 15.8 vs 47.5 ± 21.2 pg/mL, P < 0.