The amount of energy dissipated away from or returned to a child falling onto a surface will influence fracture risk but is not considered in current standards for playground impact-attenuating surfaces. A two-mass rheological computer simulation was used to model energy flow within the wrist and surface during hand impact with playground surfaces, and the potential of this approach to provide insights into such impacts and predict injury risk examined. Acceleration data collected on-site from typical playground surfaces and previously obtained data from children performing an exercise involving freefalling with a fully extended arm provided input. The model identified differences in energy flow properties between playground surfaces and two potentially harmful surface characteristics: more energy was absorbed by (work done on) the wrist during both impact and rebound on rubber surfaces than on bark, and rubber surfaces started to rebound (return energy to the wrist) while the upper limb was still moving downward. Energy flow analysis thus provides information on playground surface characteristics and the impact process, and has the potential to identify fracture risks, inform the development of safer impact-attenuating surfaces, and contribute to development of new energy-based arm fracture injury criteria and tests for use in conjunction with current methods.
Peter L. Davidson (Corresponding Author), Suzanne J. Wilson, and David J. Chalmers are with the Injury Prevention Research Unit, University of Otago, Dunedin, New Zealand. Barry D. Wilson is with the Institut Sukan Negara, Bukit Jalil, Sri Petaling, Kuala Lumpur, Malaysia. David Eager is with the Faculty of Engineering and Information Technology, University of Technology, Sydney, Australia. Andrew S. McIntosh is with the Australian Centre for Research into Injury in Sport and Its Prevention, Monash University, Victoria, Australia.