Psychological and Physiological Influences of A Head-Down Tilted Condition

The aim of this study was to evaluate psycho-physiological effects of two postures on emotional states, in relation to the autonomic responses obtained from measures of heart rate variability and salivary cortisol. This study compared a sitting posture with a 7 degree head-down-tilted (7° HDT) condition. The study assessed anxiety states during the HDT conditions. Twenty-eight healthy volunteers (university students) participated (age = 20.9±1.5). The participants were divided into two groups, high-anxiety and normal, based on state trait anxiety inventory (STAI) scores. A simple protocol for monitoring electrocardiograms (ECGs) was applied for all participants, such that they first quietly adopted the sitting posture for 20 minutes, followed by a subsequent 7° HDT posture was then assumed on a tilting bed for another 20 minutes. At the end of each period, a saliva sample was collected from the participant to measure cortisol concentration and salivary buffering action. Affect-grid scoring was applied to evaluate participant's emotional states. Heart rate variability was calculated to evaluate the balance of autonomic nervous system activities (LF/HF). When the HDT posture was assumed, the high anxiety group showed significantly higher salivary cortisol levels, increases in 0.39 ± 0.35 μg/dl from 0.24 ± 0.22 μg/dl (p