The Effect of Wood Chip Surface Depth on Peak Force During Impacts

Jonathan S. Lee-Confer ^*

• University of Arizona, Tucson, United States

Objective: Playgrounds are essential for children's physical, social, and mental health. However, only 4.7% of playgrounds meet safety standards for wood chip surface depth around playground structures. This study aimed to quantify peak force attenuation at safety-compliant (9-inch) versus non-compliant (5-inch) wood chip depths.Methods: Wood chip layers of 5 inches and 9 inches were placed on a calibrated force platform.A 4.54-kg10-lb medicine ball was dropped from a consistent height onto the wood chips, and peak forces and time to peak force were measured.Results: The 9-inch wood chip layer significantly reduced peak forces compared to the 5-inch layer, showing a 44% reduction (p < 0.001). No significant differences were observed in time to peak force between the two conditions (p = 0.46). Discussion: Compliant wood chip surface depths reduce impact forces substantially, emphasizing the importance of routine inspection and maintenance of playground surfaces to safety standards. This practice can help minimize injuries in children resulting from playground falls.What is already known on this topic -Wood chips are widely used to reduce injuries at playgrounds and are essential for fall impact attenuation.What this study adds -This study quantifies a 44% reduction in peak force when wood chip surface depth meets safety standards, offering critical insights into their protective capacity.How might this study affect research, practice, or policy -These findings highlight the significant impact of maintaining playground wood chips at safety-compliant depths, supporting the need for updated maintenance strategies and policies to enhance playground safety.