THE DEVELOPMENT AND VALIDATION OF A THREE-DIMENSIONAL VISUAL TARGET ACQUISITION SYSTEM TO ASSESS THE PERFORMANCE EFFECTS OF HEAD SUPPORTED MASS

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Authors
Derouin, Aaron
Keyword
Fitts' Law , Head Supported Mass , Whole-Body Vibration , Human Performance , Time-optimal Head Movements
Abstract
Rotary-wing aircrew in Canada and abroad experience a myriad of occupational risk factors that contribute to neck pain. Most functional assessment approaches relevant to evaluating aircrew neck pain are too reliant on static outcome measures and do not consider scanning tasks routinely required of aircrew. The primary goal of this dissertation was to describe the development and design of the three-dimensional visual target acquisition system (3D-VTAS) to facilitate the evaluation of dynamic, fast, goal-oriented head movements using a Fitts’ task paradigm. The secondary goal was to utilize the system to explore and understand how task familiarization affects performance and test-retest reliability, how added head supported mass (HSM) affects performance, and how the combined factors of HSM and whole-body vibration (WBV) influence performance, kinematics and muscular demand. The first study describes the development of the system, which included various system verification and validation activities. As anticipated, changes in index of difficulty appropriately influenced target acquisition time. Relative to movement planes of the head, we found that axial head rotations (yaw) produced the fastest target acquisition times compared to the sagittal plane (pitch) and two off-axis movement trajectories. After accounting for within-day familiarization, between-day test-retest reliability of the system achieved fair to excellent intraclass correlation coefficient results. The second study reports on the influence of operationally relevant HSM (helmet and night vision goggles) on three 3D-VTAS performance outcome measures (target acquisition time, time to move off target, and error index). Compared to the unloaded condition, added load to the head degraded performance and increased the time to move off target. The third study investigated the combined effect that operationally relevant HSM and vertical WBV have on 3D-VTAS performance, kinematics, and neck muscle activity. Exposure to WBV degraded performance. Peak muscle activity during off axis movements were consistently above 50% of maximum voluntary contraction for the right upper neck extensors; potentially indicative of muscular strain. In general, the results of these studies illustrate the potential of the 3D-VTAS to facilitate the assessment of rapid aiming head movements and thus understand the influence of HSM and other occupational risk factors on performance and function.
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