Autonomic Nervous System Activity in Young Subjects Exposed to Orthostatic Posture and Emotional Visual Stimuli: A Pilot Study

Heart rate variability (HRV) reflects autonomic nervous system (ANS) activity and provides insight into physiological and emotional regulation. Evaluating HRV during postural and emotional challenges may help characterize autonomic adaptability in healthy individuals. HRV was recorded in 24 young medical residents (17 females, 7 males; mean age 27.04 ± 1.97 years) during four conditions: rest, orthostatic standing, and exposure to positive and negative emotional images. Each session lasted five minutes. Anxiety and depression were assessed using the Hospital Anxiety and Depression Scale. Heart rate increased significantly only during standing, consistent with sympathetic activation with postural change. Spectral and normalized HRV parameters (nLF, nlf, LF/HF, and normalized coherence) were lowest at rest and increased during standing and emotional image exposure, particularly in males. Parasympathetic indices showed opposite trends. Emotional image exposure did not produce significant differences between positive and negative valence at the group level; however, sex- and anxiety-related patterns emerged. Females with anxiety showed increased heart rate during positive image exposure, whereas non-anxious females exhibited higher heart rate responses to negative images. Orthostatic challenge elicited the strongest autonomic response, whereas emotional visual stimuli induced subtler, sex- and anxiety-dependent autonomic modulation without overall changes in heart rate. These preliminary observations suggest that anxiety and sex may be associated with differences in cardiac autonomic regulation in young healthy adults. These results should be interpreted cautiously, given the pilot design, the small sample size (N = 24), the imbalance between sexes, the exclusion of the depression subgroup from inferential analyses, and the use of non-validated emotional visual stimuli