Fig. 1

Subject selection process. Fifty-three female university students were surveyed, with 23 excluded after not meeting the inclusion criteria. For the remaining 29 students who agreed to participate in the study, their menstrual cycles were checked, and 7 were excluded because of cycle abnormalities. Of the 21 students who completed measurements, 2 with cycle abnormalities, 2 with monophasic basal body temperatures, and 2 with measurement errors were excluded. A final total of 15 female university students with biphasic basal body temperatures and normal menstruation were included