A human body support, such as a chair, has a plurality of support segments that are arranged in an array. Each support segment has a protrusion elevation that is independently variable and controllable in its distance of protrusion elevation against the supported human body. A sensor is connected to a human body on the support and senses a human body parameter that can indicate the presence of drowsiness. A controller analyzes the sensed parameter to detect whether the sensed parameter is within a range indicating the presence of drowsiness. The controller applies a wave of varying segment protrusion elevation against the human body in response to the detection of drowsiness. The wave progresses in a direction from an inferior location on the human body toward a more superior location. Alternatively, a wave of electrical stimuli is applied by similarly positioned electrodes and causes periodic tightening and relaxing of proximate muscles.