Fainting, or syncope, during a high-thrill amusement park ride is a temporary loss of consciousness caused by a brief lack of oxygen-rich blood reaching the brain. This event, or the preceding feeling of lightheadedness known as pre-syncope, occurs when the body struggles to maintain adequate blood flow against the extreme, rapidly changing physical forces of the ride. This loss of consciousness is typically brief, resolving almost immediately once the forces stabilize or subside.
G-Force Effects on Blood Circulation
The primary mechanical reason people pass out on rides is the manipulation of blood flow by intense acceleration forces, measured in Gs. A positive G-force (+Gz) is experienced when a ride accelerates upward or bottoms out a drop, pushing the rider down into their seat. This force acts along the body’s vertical axis, increasing the apparent weight of blood and pushing it toward the lower extremities, a phenomenon known as blood pooling.
The heart and brain are located at the top of this vertical column. The greater the G-force, the harder the heart must work to pump blood upward against that increased resistance. When G-forces exceed the body’s ability to compensate, blood return to the heart decreases, and the supply of oxygenated blood to the brain is reduced. This temporary lack of oxygen, known as transient cerebral hypoxia, causes riders to experience a loss of vision, often starting with tunnel vision or “greying out.” This precedes a full blackout and subsequent loss of consciousness, referred to as G-Induced Loss of Consciousness (G-LOC).
Ride designers typically limit the maximum positive G-forces to a safe range, generally between 4 and 6 Gs, but the duration of the force is more significant than the peak. G-LOC usually requires a sustained force of around 4 to 5 Gs for several seconds, but amusement park maneuvers rarely maintain peak G-forces for more than three seconds. Conversely, negative G-forces (-Gz) occur during the crest of a hill or a sudden drop, creating a feeling of weightlessness. While less common, extreme negative Gs can cause an excess of blood to rush to the head, leading to a “redout,” where vision turns reddish due to increased pressure in the eye capillaries.
The Vagal Response and Sudden Stress
A separate, non-mechanical cause of syncope on rides is the body’s neurological overreaction to intense fear or sensory input, known as vasovagal syncope. This reaction is triggered by the vagus nerve, a major component of the parasympathetic nervous system that regulates the heart and blood pressure. The extreme sensory overload, anxiety, or excitement of a high-thrill ride can cause an abrupt surge of activity in the vagus nerve.
This sudden vagal stimulation results in a rapid drop in both heart rate and blood pressure, causing circulation to falter momentarily. The brain senses the reduction in blood supply and initiates a temporary shutdown to protect itself, leading to the brief fainting spell. Vasovagal episodes are a common cause of fainting in many non-ride scenarios, such as the sight of blood or intense pain. The extreme environment of a roller coaster can serve as a trigger for susceptible individuals, sometimes happening the moment the ride launches due to shock and anticipation.
Factors Increasing Susceptibility
While G-forces and the vasovagal reflex are the direct causes of passing out, several individual factors can lower tolerance and increase susceptibility to syncope. Dehydration is a common contributing factor, as it reduces overall blood volume and makes the body less capable of maintaining blood pressure during high G-force maneuvers. Fatigue and low blood sugar can also impair the body’s compensatory mechanisms, making it easier to experience symptoms like “greying out.”
Certain medications, particularly those that affect blood pressure (such as diuretics or some antidepressants), can heighten the risk of syncope. Individuals with naturally lower blood pressure or pre-existing heart conditions are also more prone to G-induced or vasovagal episodes. Tolerance for G-forces is variable, meaning the same ride will affect riders differently based on their unique physiology and current physical state.
Tips for Staying Conscious on High-Thrill Rides
Riders can take proactive steps to increase tolerance for high-G environments and minimize the chance of syncope. Remaining well-hydrated and avoiding riding on an empty stomach are simple ways to maintain adequate blood volume and stable blood sugar levels. Tackling the most intense rides earlier in the day when the body is less fatigued can also be beneficial.
Employing specific breathing and muscle-bracing techniques can counteract the effects of positive G-forces. Aviators often contract the abdominal and leg muscles, sometimes combined with a grunt or yell, to physically push blood back toward the heart and brain. Another method is to lift your body slightly against the seat restraint during peak G-forces to resist the downward pooling of blood. Focusing on the track ahead and keeping the eyes open helps the brain synchronize visual input with the inner ear’s balance signals, reducing sensory confusion.