Alterations in head dynamics with the addition of a hockey helmet and face shield under inertial loading.

The effect of a hockey helmet and face shield on the head and neck during inertial loading was studied. A Hybrid III Anthropometric Test Dummy (ATD) was struck from both the front and rear by a spring-loaded, instrumented striker moving at 2.9 ms-1. Data were collected from a triaxial force transducer mounted at the atlanto-occipital (a-o) junction of the ATD, a load cell in the striker, and by cinematography (250 fps). Angular kinematics of the head and moments of force about the a-o junction were determined along with impact force levels. When compared to a bare-head condition, the addition of a helmet and face shield caused an increase in head angular displacement (20-40%) but did not affect head angular acceleration. Axial and shear forces at the a-o junction did not change appreciably with the addition of a helmet and face shield. A triphasic pattern was evident for the neck moments including a small phase which represented a seating of the headform on the nodding blocks of the uppermost ATD neck segment, and two larger phases of opposite polarity which represented the motion of the head relative to the trunk during the first 350 ms after impact. No substantial differences were apparent between the helmeted and non-helmeted trials. The magnitudes of forces and moments found in the present study were well within tolerance levels reported by others (Melvin, 1979; Cheng et al., 1982). It was concluded that the increase in angular displacement of the head, with the addition of a helmet and face shield, does not place the wearer in a position of increased risk of cervical spine trauma.