Humans are thrill-seekers and what better thrill than a death-defying roller coaster ride? The adrenaline rush that comes from the sharp twists and turns cause us to seek bigger and faster rides. However, the forces exerted on us during a ride impact the human body beyond just providing a fun time. Depending on the speeds and accelerations of the ride, body parts such as the neck, brain, and spine are affected or may even be injured. Therefore, it is important to know potential risks before chasing the next ride.
The human body is heterogenous, meaning body parts have different shapes, densities, and composition. Therefore, each part will respond in an unique way due to changes in acceleration and its specific resonant frequency. This is the frequency a part will naturally vibrate at when disturbed. For example, the frequency range for the head is 20-30 Hz. If this is reached, dizziness can result. The frequency of the eyes is 25 Hz, and if this is reached, vision blurriness may occur. However, softer body parts allow for damping or reduction of the impact of forces due to their viscoelastic nature and ability to absorb energy, which can help minimize adverse symptoms caused by the ride.
Two important terms needed to understand roller coaster dynamics are jerk and snap. Jerk is the change in acceleration over a given time interval, and snap is the change in jerk changes over a given time interval. Both these dynamics can cause bones to break if the forces and acceleration exerted on a ligament are rapid enough. Also, if ligaments are subjected to repetitive jerks, this can lead to fatigue or eventual failure.
Most importantly, however, roller coaster rides affect both the brain and spine, two of the most important body parts. A study was conducted on two healthy adult males to observe changes to the brain and skull during a roller coaster ride, and a case series was conducted on spinal injuries caused by the Rattler roller coaster in Six Flags, San Antonio, Texas.
In the first study, the maximum angular velocity (the speed an object rotates) of the ride was 9.9 rad/s with the maximum brain surface displacement being 4.0mm. The study concluded that for this ride, the effect on the brain was slightly less than a mild soccer header, but more than daily activities, such as running.
In the San Antonio, Texas case series, there were 138 spinal injuries between March 1992 and October 1993. Of the injured, 71% suffered a cervical disk injury. The cervical disk is similar to a cushion that absorbs shock to the neck and head, which can get injured due to rapid accelerations or whiplash. Unfortunately, this study concluded that there is not a minimum threshold where serious injury to the spine may occur since it greatly depends on the makeup of the individual, the speed of the ride, and any preexisting conditions.
The rapid accelerations and changing forces during a roller coaster ride contribute to its thrilling experience, but if the forces exerted on the human body are strong enough, injury can occur. Therefore, make sure to ride at your own risk.