This study examined the effects of 3 days of estrogen supplementation (ES)
on thermoregulation during exercise in premenopausal (20-39 yr) adult women
during the follicular phase of the menstrual cycle. Subjects (11 control,
10 experimental) performed upright cycle ergometer exercise at 60% of maxim
al O-2 consumption in a neutral environment (25 degrees C, 30% relative hum
idity) for 20 min. Subjects were given placebo (P) or beta-estradiol (2 mg/
tablet, 3 tablets/day for 3 days). All experiments were conducted between 6
:30 and 9:00 AM after ingestion of the last tablet. Heart rate, forearm blo
od flow (FBF), mean skin temperature, esophageal temperature (T-es), and fo
rearm sweat rate were measured. Blood analysis for estrogen and progesteron
e reflected the follicular phase of the menstrual cycle. Maximal O-2 consum
ption (37.1 +/- 6.2 in P vs. 38.4 +/- 6.3 ml.kg(-1).min(-1) in ES) and body
weight-to-surface area ratio (35.58 +/- 2.85 in P vs. 37.3 +/- 2.7 in ES)
were similar between groups. Synthesis of 70-kDa heat shock protein was not
induced by 3 days of ES. Neither the threshold for sweating (36.97 +/- 0.1
5 in P vs. 36.90 +/- 0.22 degrees C in ES), the threshold for an increase i
n FBF (37.09 +/- 0.22 in P vs. 37.17 +/- 0.26 degrees C in ES), the slope o
f sweat rate-T-es relationship (0.42 +/- 0.16 in P vs. 0.41 +/- 0.17 in ES)
, nor the FBF-T-es relationship (10.04 +/- 4.4 in P vs. 9.61 +/- 3.46 in ES
) was affected (P > 0.05) by 3 days of ES. We conclude that 3 days of ES by
young adult women in the follicular phase of their menstrual cycle have no
effect on heat transfer to the skin, heat dissipation by evaporative cooli
ng, or leukocyte synthesis of 70-kDa heat shock protein.