David C. Viano, Ph.D., Joseph D. McCleary, Dennis V. Andrzejak, and David H.
Institute for Preventative Sports Medicine and Orthopedic
Surgery Associates, Ann Arbor, Michigan, U.S.A.
The use of batting helmets in baseball has substantially reduced the
incidence of head injuries, and softer baseballs have been developed to further
reduce the risk of injury for an unprotected head. This study utilized a 5th
percentile Hybrid Ill female dummy, which is similar in size to a 10-12-year old
child, to evaluate the effectiveness of various softer baseballs. A pneumatic
gun accelerated the balls to a speed of 60 mi/h (27 m/s). Head impacts were
delivered frontally on the forehead or between the eyes and laterally on the
temple. Peak resultant head acceleration and head injury criterion (HIC) were
significantly lower with the softer baseballs. Using logist analysis of the
forehead HICs, the risk of head injury was 20% with an official hardball versus
12-16% with softer baseballs, a 4-8% lower increment in injury risk. The risk of
injury was higher using head acceleration and for the temple impacts, however,
the range in effectiveness of the softer baseballs is smaller than predicted
from the National Operating Committee on Standards for Athletic Equipment
(NOCSAE) test procedure. Since the NOCSAE procedure was developed for helmeted
impacts, there may be a lack of biofidelity for unprotected head impacts. The
force of impact was 2.5-18.0 kN and was significantly lower with the softer
baseballs. The results of this study indicate that the softer baseballs reduce
the risk of head injury, but not to the degree previously claimed. Additional
work is needed to determine the actual range of effectiveness in pre venting
sport-related injuries in children.
Key Words: Baseballs - Head impact - Reduced injury.
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