A human body support, such as a chair, has a plurality of electrodes arranged in an array and spaced longitudinally with respect to the human body. The array extends from an inferior position to a more superior position along the body. A sensor measures a parameter of the human body that is capable of indicating the presence of drowsiness. A controller has an input connected to the sensor for receiving a signal representing the sensed parameter and has outputs connected to each of the electrodes. The controller detects whether the sensed parameter is within a range indicating the presence of drowsiness and applies a wave of electrical stimuli against the human body in response to detection of a sensed parameter within the range. The electrical stimuli cause periodic tightening and relaxing of proximate muscles as the wave progresses in a direction from an inferior location on the human body toward a more superior location.
