Motion control, motion sickness, and the postural dynamics of mobile devices.

Drivers are less likely than passengers to experience motion sickness, an effect that is important for any theoretical account of motion sickness etiology. We asked whether different types of control would affect the incidence of motion sickness, and whether any such effects would be related to participants' control of their own bodies. Participants played a video game on a tablet computer. In the Touch condition, the device was stationary and participants controlled the game exclusively through fingertip inputs via the device's touch screen. In the Tilt condition, participants held the device in their hands and moved the device to control some game functions. Results revealed that the incidence of motion sickness was greater in the Touch condition than in the Tilt condition. During game play, movement of the head and torso differed as a function of the type of game control. Before the onset of subjective symptoms of motion sickness, movement of the head and torso differed between participants who later reported motion sickness and those that did not. We discuss implications of these results for theories of motion sickness etiology.

Body load and the postural precursors of motion sickness.

Physical properties of the body affect the control of standing body sway. One example occurs when loads are added to the body, such as occurs when wearing a backpack. Other research has shown that subjective symptoms of motion sickness are preceded by differences in body sway between individuals who later report motion sickness and those who do not. In the present study we asked whether loads worn on the body would affect relations between body sway and motion sickness. We measured standing body sway without load and then with loads worn at the shoulders or thighs. Then participants were exposed to potentially nauseogenic visual motion stimulation while wearing shoulder or thigh loads. We measured body sway continuously during exposure to visual motion. Thirteen of 36 participants (36%) reported motion sickness. Body sway was affected by loads and by load position, consistent with previous research. Also consistent with previous research, sway differed between well and sick participants both before and during exposure to visual motion stimuli. In addition, during room motion the well and sick participants responded differently to loads. The results are consistent with the hypothesis that physical properties of the body can affect relations between body sway and motion sickness.