Volume 5, Issue 6 (June 2008)

    Head Kinematics During Experimental Snowboard Falls: Implications for Snow Helmet Standards

    (Received 16 August 2007; accepted 11 May 2008)

    Published Online: 2008

    CODEN: JAIOAD

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    Abstract

    A study by Nakaguchi and Tsutsumi [“Mechanisms of Snowboarding-Related Severe Head Injury: Shear Strain Induced by the Opposite-Edge Phenomenon,” J. Neurosurg, Vol. 97, 2002, pp. 542–548] showed that 68 % of all snowboarders’ head injuries were associated with backward falls, with beginner and intermediate snowboarders constituting the majority of the injured. We previously fabricated a test apparatus that replicated the fall kinematics of a snowboarder during a back-edge trip. A Hybrid-III anthropomorphic test device (ATD) outfitted with a snowboard and snowboarding gear was accelerated to a typical intermediate snowboarder’s speed (30.5 ± 1.5 kph) and tripped resulting in a backward fall that terminated in a head-to-slope impact. This test protocol produced repeatable fall kinematics under realistic on-slope conditions. In this study, we characterized the fall kinematics and quantified head velocity in order to evaluate the helmet energy management requirements associated with a back-edge trip. Digital high-speed video recorded at 500 frames per second was used to quantify the snowboarder’s head kinematics: (i) prior to the trip; (ii) during trip phase; (iii) during free fall; and (iv) at ground impact. Translational energy of the ATD was rapidly converted to a combination of linear and angular energy during the trip phase. Although the speed of the ATD’s center of gravity decreased during the trip phase, the test data showed the absolute speed of the head increased rapidly during the fall as a result of the body’s induced angular rotation. The mean head velocity normal to the slope increased from approximately zero at fall initiation to as much as 37.1 kph during the fall (122 % of the initial velocity), and was 29.1 kph at snow contact (95 % of the initial velocity). Resultant head velocity peaked at 54.3 kph (178 % of the initial velocity), and was 38.2 kph at snow contact (125 % of the initial velocity). The data presented here may be useful for assessing drop height requirements for snow helmet evaluations.


    Author Information:

    Richards, Darrin
    Exponent Failure Analysis Associates, Phoenix, AZ

    Carhart, Michael
    Exponent Failure Analysis Associates, Phoenix, AZ

    Harrington Department of Bioengineering, Arizona State University, Tempe, AZ

    Scher, Irving
    Exponent Failure Analysis Associates, Los Angeles, CA

    Thomas, Reed
    Exponent Failure Analysis Associates, Phoenix, AZ

    Hurlen, Natalie
    Exponent Failure Analysis Associates, Phoenix, AZ


    Stock #: JAI101406

    ISSN: 1546-962X

    DOI: 10.1520/JAI101406

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    Author
    Title Head Kinematics During Experimental Snowboard Falls: Implications for Snow Helmet Standards
    Symposium 17th Symposium on Skiing Trauma and Safety, 2007-05-19
    Committee F27