Changes of Hemodynamics due to White Noise Stress according to the Extents of Obesity

Abstract

This study aimed to determine a range of adequate body fat percent from its relations with the change in hemodynamics when white noise was loaded as a stresser, taking special notices on the relationships between obesity and hemodynamics and between hemodynamics and stress. The 87 females subjects aged 18 to 24, students of a women's junior college, were divided into four groups according to body fat percent measured in this study: obesity group (≥ 30% body fat), borderline group (25-30%), adequate group (20-25%), and emaciation group (<20%). The results of the experiments about the effects of white noise stress on changes in blood flow rate, systolic blood pressure, and pulse rate among the four groups were summarized as follows. First, there were no inter-group differences in changes of systolic blood pressure and pulse rate. Second, the response time to the peak value in blood flow rate (which was defined as the time duration to the time of peak value after white noise was loaded) was the shortest in the obesity group and the longest in the borderline group. Third, the recovery time in blood flow rate (which was defined as the time duration from the response time to the time when the rate was recovered to the initial level) was the longest in the obesity group and the shortest in the borderline group. The latter two findings demonstrated that flexibility of hemodynamics to noise stress was low in the obesity group and high in the borderline group. It was also noted that there were no significant differences in any indicators between the borderline group and the adequate group. It is thus suggested that the adequate fat percent of young adult females (when the response time to the peak value in blood flow rate is treated as the determining factor) is 25-30%, that is higher than 20 - 25% as the previously reported adequate level.