A volunteer was impacted at velocities up to 4. 6 m/sec. (15 ft./sec.) with a 10 kg (22. 1 lb.), 15. 2 cm (6 in.) diameter padded impactor. Force-time, de'flection-time and force-deflection data are presented for these impacts showing a maximum force of 1. 67 kn (376 lbs.) and a maximum skeletal deflection of 4. 6 cm (1. 80 in.). The maximum chest compression is about the same at 4. 4 cm to 4. 6 cm (1. 72 to 1. 80 in.) at all impact velocities.
The force-deflection curve reaches a plateau where there is relatively little change in force for a large change in deflection after which there is a large change in force with little change in the maximum deflection. There is considerable hysteresis, and the force drops to zero while there is still appreciable skeletal deflection.