Some people faint often, negatively impacting quality of life. Fainting occurs when the heart cannot pump enough blood to the brain. Standing still pulls blood into the lower body reducing its return to the heart. However, even when standing still, our body sways and these movements may prevent fainting by pushing blood to the heart. Water drinking might also help by stretching the stomach, raising blood pressure. Also, seeing blood/having blood drawn can cause fainting, suggesting the brain may trigger a faint, not the heart. We will examine: i) the role sway plays in fainting, ii) if fizzy water drinking wards off fainting, and iii) brain activity during emotional triggers. Using wearable sensors, we will compare heart rate, blood pressure, and sway patterns in the lab and in soldiers who faint on parade. We will test if drinking fizzy water increases blood pressure more than still water. We will also compare blood pressure, heart rate, and brain activity in fainters and non-fainters while participants watch a video of a blood draw to show the role of the brain in initiating faints. These studies will help us better understand fainting, relieving the healthcare burden and improving quality of life for people who faint.