A field study was performed using freestyle aerial ski jumpers to determine the incidence of head impact (slapback) and to record head acceleration data during slapback episodes for the 1994–1995 and 1995–1996 winter seasons. A total of 382 slapbacks were recorded from 2,352 jumps for an observed slapback incidence of 16.2%. Head acceleration data were recorded for 5 slapback events. Maximum head acceleration magnitudes for the 5 impacts ranged from 27 to 92 gs and impact durations ranged from 12 to 96 μsec. Standard severity indices including the Gadd Severity Index and Head Injury Criteria were calculated from the resultant acceleration signal and ranged from 57 to 223, and 21 to 159, respectively, which are considered low in terms of life threatening injury levels.
M.D. Mecham is with the Orthopedic Biomechanics Institute in Salt Lake City, UT. R.M. Greenwald is with the Orthopedic Biomechanics Institute and the Department of Exercise and Sports Science at the University of Utah, Salt Lake City, UT. J.G. Macintyre is with Orthopedic Specialty Hospital in Salt Lake City, UT. S.C. Johnson is with the Department of Exercise and Sports Science at the University of Utah, Salt Lake City, UT. Address correspondences to R.M. Greenwald, National Institute of Sports Science and Safety, 222 Richmond Street, Suite 109, Providence, RI 02903.