Abstract
The purposes of this study were to investigate the effects of two different sitting positions on the hemodynamic responses and the autonomic nervous function in healthy men. Fourier analysis of R-R interval may be used to characterize low- and high- frequency components (LF and HF) attributable to sympathetic and vagal influences, respectively. We analyzed R-R interval variability, blood pressure and pressure rate product (P.R.P.) of 5 healthy young and 5 healthy elder subjects before and during the posture change from supine to sitting position. The postures were kept in a sitting position with the aid of a backrest or without one for 10 minutes. Total power of R-R variability tended to be lower in the aged subjects than in the young subjects during supine position, but the hemodynamic responses did not change between elder and young subjects. Blood pressure, heart rate and P.R.P. increased during sitting position, especially without the backrest. HF/Total power of the younger subjects during sitting position decreased. LF/HF in the young subjects, increased during sitting position, but not in the elderly subjects. It is suggested that the different response between the elder and younger subjects might be due to some disability in autonomic functions with age.
