Physiological interdependence of the cardiovascular and postural control systems under orthostatic stress.

The cardiovascular system has been observed to respond to changes in human posture and the environment. On the same lines, frequent fallers have been observed to suffer from cardiovascular deficits. The present article aims to demonstrate the existence of interactions between the cardiovascular and postural control systems. The behavior of the two systems under orthostatic challenge was studied through novel adaptations of signal processing techniques. To this effect, the interactions between the two systems were assessed with two metrics, coherence and phase lock value, based on the wavelet transform. Measurements from the cardiovascular system (blood pressure), lower limb muscles (surface electromyography), and postural sway (center of pressure) were acquired from young healthy adults (n = 28, men = 12, age = 20–28 yr) during quiet stance. The continuous wavelet transform was applied to decompose the representative signals on a time-scale basis in a frequency region of 0.01 to 0.1 Hz. Their linear coupl...