A professional high diver, instrumented with accelerometers, performed sixteen dives from heights between 27-57 ft. For each dive he executed a 3/4 turn and landed supine on a 3-ft deep mattress which consisted of pieces of low density urethane foam encased in a nylon cover. Using FM telemetry, sagittal plane decelerations were recorded for a point either on the sternum or the forehead. Impact velocities and corresponding stopping distances for the thorax and the head were calculated from high-speed movies of the dives. For a 57-ft dive, the impact velocity of the thorax was 41 mph with a corresponding stopping distance of 34.6 in. The peak resultant deceleration of the thorax was 49.2 g with a pulse duration of 100 ms. The maximum rate of change of the deceleration of the thorax was 5900 g/s. No discomfort was experienced as a result of this impact. The maximum forehead deceleration occurred during a 47.3-ft drop and exceeded 56 g with a Gadd Severity Index greater than 465. This peak acceleration was the result of a localized impact to the skull produced by a hard spot in the helmet worn by Ross Collins and resulted in a brief, sharp head pain. The results obtained from these experiments are compared with whole-body tolerance data obtained by other investigators and a long duration acceleration tolerance level of 60 g with a pulse duration of 100 ms is recommended for the thorax in the A-P and P-A directions.
Abstract