Accession Number : ADA332062

Title :   Use of Biomarkers to Optimize Heat Acclimation in Women.

Descriptive Note : Annual rept. 25 Sep 96-24 Sep 97,

Corporate Author : IOWA UNIV IOWA CITY

Personal Author(s) : Gisolfi, Carl V.

PDF Url : ADA332062

Report Date : OCT 1997

Pagination or Media Count : 20

Abstract : The effects of estrogen supplementation (ES) on heat acclimation was studied in 14 premenopausal females (18-35 yrs old) randomly assigned to either ES or placebo (P) groups after being matched for VO2 max, percent body fat, and body weight/surface area ratio. Four days after the onset of menstruation they performed 2-h bouts of treadmill exercise (35-45% VO2 max) daily in the heat (450C, 20% RH) until acclimated. On day 2 of the menstrual cycle, subjects ingested either 13-estradiol tablets (6 mg/day) or placebo tablets, for 7 d. Based on thermal and circulatory measures, 11SP70 synthesis, and days to achieve acclimation, we conclude that ES, as performed in this study, had no effect on heat acclimation. ANIMAL STUDIES: In the animal study, rats received daily subcutaneous injections of estradiol (10 ug/100 ml/g b.w.). One group underwent a daily exertional heating protocol (trained) and a second group served as sham controls (untrained). Within each group, 3 subgroups were utilized to assess the time course of potential alterations: (a) 4-day, (b) 8-day, or (c) 12-day. On the final day of a protocol, rats underwent a heat tolerance test consisting of treadmill exercise at 21.5 m/min at 350C until colonic temperature (Tc) reached 40.40C. In general, rats in the trained group had lower body weights, reduced resting Tc'S, attenuated heating rates, and increased run times to 40.40C (P<0.05) than their untrained counterparts. These results were primarily manifested in rats trained for 8 or 12 days compared with the 4-day treatment group. These studies demonstrate that the combination of exertional heat exposure and estradiol treatment, when compared to estradiol supplementation alone, enhances thermotolerance in rats exercising at a high ambient temperature.

Descriptors :   *ANIMALS, *FEMALES, *ACCLIMATIZATION, *ESTROGENS, *HEAT TOLERANCE, TEST AND EVALUATION, HORMONES, EXPOSURE(GENERAL), RATS, HIGH TEMPERATURE, RATES, PLACEBOS, CIRCULATION, DAILY OCCURRENCE, BODY WEIGHT, INJECTIONS(MEDICINE), SUBCUTANEOUS TISSUE, MENSTRUATION, TREADMILLS, TABLETS(CHEMICAL).

Subject Categories : Anatomy and Physiology
      Stress Physiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE