When a high-speed amusement park ride causes a temporary feeling of lightheadedness or tunnel vision, this is often the body signaling a brief disruption in blood flow to the brain. This sensation, commonly referred to as “greying out,” is the precursor to syncope, the temporary loss of consciousness. Syncope occurs when the brain is starved of oxygen due to insufficient blood supply. This article provides non-medical strategies to mitigate this physiological response and better enjoy intense acceleration rides.
Understanding the Cause: G-Forces and Blood Flow
The physical stresses that cause the feeling of passing out are known as positive G-forces, or +Gz, acting from the head toward the feet. During rapid upward acceleration or at the bottom of a large loop, the ride forces blood to pool in the lower extremities. The heart struggles to pump blood upward against this increased force, leading to a temporary reduction in oxygen delivered to the brain. This lack of oxygenated blood supply first causes a loss of peripheral vision, known as a “greyout,” followed by total vision loss, or a “blackout,” and finally, syncope.
The average person can tolerate sustained forces between +4.5 and +5.5 Gz before experiencing G-induced loss of consciousness (G-LOC). Most roller coasters apply these high forces for very brief periods, typically less than three seconds. Negative G-forces, experienced during moments of weightlessness or “airtime,” push blood toward the head but are generally not a cause of syncope. Understanding this mechanism provides the foundation for effective preventative measures.
Essential Preparation Before Boarding
A well-conditioned physical state before boarding a ride is the first step in increasing G-force tolerance. Dehydration thickens the blood and lowers overall blood volume, which significantly reduces the body’s ability to compensate for gravitational stress. Consistently drinking water throughout the day, and possibly including electrolytes, is important to maintain sufficient fluid levels.
Eating a light, balanced meal that is rich in carbohydrates helps maintain stable blood sugar levels, supporting the body’s energy demands during stress. Conversely, consuming a heavy, fatty meal may divert blood flow to the digestive system, negatively affecting the cardiovascular response. Diuretics like excessive caffeine and alcohol should generally be avoided as they promote fluid loss. Adequate sleep is also necessary, as fatigue impairs the body’s natural regulatory mechanisms for blood pressure control.
Counter-Maneuvers During High-G Sections
The most direct way to prevent syncope is to perform a simplified Anti-G Straining Maneuver (AGSM), adapted from techniques used by fighter pilots. This technique relies on tensing large muscle groups to restrict blood from pooling in the lower body. Riders should first ensure their head is firmly pressed against the seat’s headrest to minimize the distance blood must travel up the neck.
As the ride enters the high-G section, typically the bottom of a drop or a tight turn, the rider must maximally tense the muscles in the abdomen, thighs, and calves. This isometric contraction acts as a temporary compression suit, helping to elevate blood pressure in the upper body. Perform a specific breathing pattern simultaneously, often described as an “L-shaped” breath.
The breathing component involves taking a sharp, controlled breath and straining the chest and abdomen muscles while holding the air in for approximately three seconds. To prevent completely holding the breath, a quick, forceful exhalation and immediate re-inhalation must follow this strain. This rapid breath exchange should be performed every few seconds throughout the high-G exposure. The combination of intense muscle tensing and controlled straining helps force blood toward the brain, maintaining cerebral perfusion and preventing the onset of visual symptoms.
When to Skip the Ride
While these strategies are effective for healthy individuals, preventative maneuvers cannot fully compensate for certain underlying health issues. Individuals with known cardiac conditions, such as arrhythmias or heart failure, should avoid high-G rides entirely. Those with uncontrolled high or low blood pressure, severe anemia, or a history of recent concussions face an elevated risk and should exercise caution.
The body’s G-tolerance is also significantly reduced by temporary conditions. If a rider is feeling unwell, has a fever, is severely fatigued, or is noticeably dehydrated, the sensible choice is to skip the ride. These factors lower the body’s physical reserves, making it more susceptible to the physiological effects of intense acceleration.