  Protective headgear effects measured in the laboratory may not always
translate to the field. In this study, we evaluated the impact attenuation
capabilities of a commercially available padded helmet shell cover in the
laboratory and field. In the laboratory, we evaluated the efficacy of the
padded helmet shell cover in attenuating impact magnitude across six impact
locations and three impact velocities when equipped to three different helmet
models. In a preliminary on-field investigation, we used instrumented
mouthguards to monitor head impact magnitude in collegiate linebackers during
practice sessions while not wearing the padded helmet shell covers (i.e., bare
helmets) for one season and whilst wearing the padded helmet shell covers for
another season. The addition of the padded helmet shell cover was effective in
attenuating the magnitude of angular head accelerations and two brain injury
risk metrics (DAMAGE, HARM) across most laboratory impact conditions, but did
not significantly attenuate linear head accelerations for all helmets. Overall,
HARM values were reduced in laboratory impact tests by an average of 25% at 3.5
m/s (range: 9.7 - 39.6%), 18% at 5.5 m/s (range: -5.5 - 40.5%), and 10% at 7.4
m/s (range: -6.0 - 31.0%). However, on the field, no significant differences in
any measure of head impact magnitude were observed between the bare helmet
impacts and padded helmet impacts. Further laboratory tests were conducted to
evaluate the ability of the padded helmet shell cover to maintain its
performance after exposure to repeated, successive impacts and across a range
of temperatures. This research provides a detailed assessment of padded helmet
shell covers and supports the continuation of in vivo helmet research to
validate laboratory testing results.
