Evaluation of Thoracic and Lumbar Accelerations of Volunteers in Vertical and Horizontal Loading Scenarios

There are exposures of the body to accelerations in the lumbar and thoracic regions on a regular basis with everyday activities and exercises. The purpose of this study was to evaluate the response of the thoracic and lumbar regions in human volunteers subjected to vigorous activities. A total of 181 tests include twenty volunteers subjected to four test scenarios: “plopping” down in a seat, a vertical jump, a vertical drop while in a supine position, and a vertical drop while seated upright in a swing. Each of the latter three activities included three severity levels with drop heights ranging from 25 mm to 900 mm. Volunteers selected represent the anthropometry of the general population including males and females at a wide range of weights (54 to 99 kg), heights (150 to 191 cm), and ages (26 to 58 years old). Instrumentation for each volunteer included tri-axial accelerometers attached to custom-fit mounts that were secured around the lumbar and upper thoracic regions. Subjects impacted an instrumented rigid force plate with forces ranging from 950 N to 14030 N. The time to peak load, peak values, and relative timing of the accelerations are reported. From the force and acceleration measurements approximate stiffness values are provided for the lumbar region with the initial loading up to 25% of peak force at close to 18 N/mm and reaching close to 90 N/mm in the stiffer region. Analyses of acceleration data as a function of drop height, subject variables, and activity level are also presented. Including a range of activities that produce accelerations from 0.6 G to 24.0 G, these 181 tests are beneficial in understanding the range of accelerations that do not cause injury. Moreover, a study of the parameters indicated activity level has the greatest influence on the magnitude of the accelerations of the spine compared to other variables in the study.