Cardio‐postural interactions and aging

Abstract

Introduction: Until recently cardiovascular and postural reflexes have been looked at as independent control systems. In this study we propose an interaction between these two systems, particularly in relation to the maintenance of venous return through skeletal muscle pump in conditions of impaired vascular control or increased venous pooling. We investigated this “cardio‐postural” interaction with aging. Methods: Healthy elderly and young subjects were tested in a sit to stand test. Mediolateral centre of pressure (COP) trajectory, as well as non‐invasive heart rate and blood pressure data were collected in two test conditions (eyes open or eyes closed) in randomized order. Data was collected in over a 10 minute period in two equal phases (sitting followed by standing). A power spectral density analysis was performed for mediolateral sway and BP for each subject. Results: Postural sway power was higher in elderly subjects with distinctive low frequency peaks (<0.1 Hz) that matched peaks found in blood pressure. Both COP and BP data had variation in the higher frequency range (0.15–0.25 Hz) that corresponded to respiration. The observed increase, with age, in postural sway in a region corresponding to low frequency blood pressure variation may represent an increase in skeletal muscle pump activity to maintain blood pressure in the elderly due to a reduction in baroreflex with age. Funded by Simon Fraser University.