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Research Papers

Reliability of Impact Forces, Hip Angles and Velocities during Simulated Forward Falls Using a Novel Propelled Upper Limb Fall ARrest Impact System (PULARIS)

[+] Author and Article Information
Timothy A. Burkhart

Departments of Industrial and Manufacturing Systems Engineering and Kinesiology,  University of Windsor, Windsor, ON, N9B 3P4, Canadaburkha3@uwindsor.ca

Don Clarke

Department of Kinesiology,  University of Windsor, Windsor, ON, N9B 3P4, Canadadclarke@uwindsor.ca

David M. Andrews1

Departments of Kinesiology and Industrial and Manufacturing Systems Engineering,  University of Windsor, Windsor, ON, N9B 3P4, Canadadandrews@uwindsor.ca

1

Corresponding author.

J Biomech Eng 134(1), 011001 (Feb 09, 2012) (8 pages) doi:10.1115/1.4005543 History: Received August 22, 2011; Accepted December 08, 2011; Posted January 19, 2012; Published February 08, 2012; Online February 09, 2012

Previous forward fall simulation methods have provided good kinematic and kinetic data, but are limited in that they have started the falls from a stationary position and have primarily simulated uni-directional motion. Therefore, a novel Propelled Upper Limb fall ARest Impact System (PULARIS) was designed to address these issues during assessments of a variety of fall scenarios. The purpose of this study was to present PULARIS and evaluate its ability to impact the upper extremities of participants with repeatable velocities, hand forces and hip angles in postures and with vertical and horizontal motion consistent with forward fall arrest. PULARIS consists of four steel tubing crossbars in a scissor-like arrangement that ride on metal trolleys within c-channel tracks in the ceiling. Participants are suspended beneath PULARIS by the legs and torso in a prone position and propelled horizontally via a motor and chain drive until they are quick released, and then impact floor-mounted force platforms with both hands. PULARIS velocity, hip angles and velocities and impact hand forces of ten participants (five male, five female) were collected during three fall types (straight-arm, self-selected and bent-arm) and two fall heights (0.05 m and 0.10 m) to assess the reliability of the impact conditions provided by the system. PULARIS and participant hip velocities were found to be quite repeatable (mean ICC = 0.81) with small between trial errors (mean = 0.03 m/s). The ratio of horizontal to vertical hip velocity components (∼0.75) agreed well with previously reported data (0.70-0.80). Peak vertical hand impact forces were also found to be relatively consistent between trials with a mean ICC of 0.73 and mean between trial error of 13.4 N. Up to 83% of the horizontal hand impact forces displayed good to excellent reliability (ICC > 0.6) with small between trial differences. Finally, the ICCs for between trial hip angles were all classified as good to excellent. Overall, PULARIS is a reliable method and is appropriate for studying the response of the distal upper extremity to impact loading during non-stationary, multi-directional movements indicative of a forward fall. This system performed well at different fall heights, and allows for a variety of upper and lower extremity, and hip postures to be tested successfully in different landing scenarios consistent with elderly and sport-related falls.

FIGURES IN THIS ARTICLE
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Copyright © 2012 by American Society of Mechanical Engineers
Topics: Force , Reliability , Errors , Motion
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Figures

Grahic Jump Location
Figure 1

The major structural components of the Propelled Upper Limb fall ARrest Impact System (PULARIS). Forward motion of the PULARIS would occur from the left to the right.

Grahic Jump Location
Figure 2

Example of a quick release mechanism used to suspend and release participants from the inverted lower track of PULARIS. The quick release is engaged by an electrical impulse from the computer to release the shackle (thereby dropping the participant) via an internal plunger of the solenoid that acts in the direction of the dashed line.

Grahic Jump Location
Figure 3

Experimental setup of a straight-arm 0.10 m fall of an un-instrumented participant just prior to release. The directions of the hand force components Fx, Fy, and Fz are included for reference.

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