Causality in the cardio-postural interactions during quiet stance

Cardiovascular and postural systems are understood to interact with each other to maintain equilibrium. Prolonged standing is known to induce postural sway, pre-syncope symptoms and muscle fatigue. Prior work has shown the presence of interactions between the cardiovascular and postural systems during quiet stance. The cause-and-effect relation between the representative signals of the two systems remains to be established. This preliminary work presents a study to identify the causal relationship between the blood pressure waveform (BP) and resultant center of pressure (COPr) as well as between systolic arterial pressure (SAP) and COPr signals during quiet stance. A 5 minute sit-to-stand experiment was conducted for 7 healthy young participants to acquire data for the SAP and COP signals.