Researchers are seeking 25 females (non-smoking, ages 18-39) that take monophasic, combined (estrogen and progesterone), oral contraceptive pills and do aerobic exercise three or more times a week to participate in two trials (five total visits) involving exercise in the heat. Total time commitment is roughly seven hours. Participants receive body composition, bone density, personal sweat rate and a $100 Amazon gift card when the study is completed. Please contact Whitley Atkins at wcatkins@uark.edu if you are interested.