Thoracic Tolerance to Whole-Body Deceleration

Harold J. Mertz; Charles W. Gadd

doi:10.4271/710852

1971-02-01

Thoracic Tolerance to Whole-Body Deceleration 710852

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 47.0-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.

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Thoracic Tolerance to Whole-Body Deceleration 710852

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