Measurement of accelerations experienced by rough stock riders: A model for examining acceleration-induced head injuries in astronauts

Head injuries result in significant morbidity in rough stock rodeo events. Concussions are the most common injury sustained by rough stock riders, representing 50% of all major injuries. A pilot study conducted in 2007 examined head acceleration experienced by two rough stock riders. Ear-mounted tri-axial accelerometers showed a maximum of 26 G experienced by the bull rider, while the bareback rider experienced 46 G. An aim of the current study was to expand upon this pilot study by examining head acceleration experienced by 10 bull riders and 10 bareback riders during the 2009 Houston Livestock Show and Rodeo. Riders were outfitted with two earplugs, one measuring tri-axial linear acceleration and the other tri-axial angular rates. On average, bareback riders experienced a statistically-significant increase in linear acceleration in the x and z axes compared with bull riders. Bareback riders also experienced a statistically-significant increase in angular acceleration in the x and y axes. There was no difference seen between bareback and bull riders in linear head acceleration in the y axis, and the difference in angular rates experienced in the z axis did not reach statistical significance. Another population at risk for injuries due to repetitive acceleration is astronauts. The Russian Soyuz spacecraft can expose astronauts to high accelerative forces during re-entry and up to 10 G during ballistic re-entry. Soyuz landing impact has reached 17 G. The new NASA Aries launch vehicle is predicted to experience thrust-oscillation problems that may affect crew health. A second aim of this study was to apply the test procedure, hardware, and knowledge gained at the rodeo toward the development of a protocol for measuring head acceleration experienced by astronauts. The first step will be implementation of the study hardware and protocol in centrifuge training. Once validated, the hardware and protocol can undergo flight certification for testing on Russian and U.S. spacecraft. This would provide invaluable insight into launch loads, vibration, reentry and impact loads to ensure crew health in the new vehicle design.