Methodology for Evaluation of WIAMan Injury Assessment Reference Curves Using Whole Body Match-Paired Data.

Development of the Warrior Injury Assessment Manikin (WIAMan) capability has included the creation of injury assessment reference curves (IARCs) specific to under-body blast (UBB) loading mechanisms and injuries. The WIAMan IARCs were created from high-rate vertical loading tests of component post-mortem human surrogates (PMHS) and analogous components of the WIAMan anthropomorphic test device (ATD). Validation of the WIAMan IARCs is required prior to the WIAMan ATD being utilized for injury assessment in live-fire vehicle test events. A portion of the validation process involves evaluating the ability of the IARCs to predict injury at the system level (whole body). This study evaluates a methodology to assess the performance of the WIAMan IARCs using match-paired tests of whole body PMHS and the WIAMan ATD. The methodology includes a qualitative analysis designed to identify false-positive and false-negative ATD predictions, as well as a quantitative analysis that utilizes area under the receiver-operating characteristic curve (AROC) and Brier score indices to grade IARC performance. Three WIAMan IARCs were used to exemplify the proposed methodology and results are provided. Attributes of the false-prediction, AROC, and Brier score portions of the methodology are presented, with results indicating the new methodology is thorough and robust in evaluation of IARCs.

Initial electro-mechanical response to rearward perturbation.

The objective of this study was to examine the combined electromyographic (EMG) and mechanical response to a rearward perturbation and to separate the response into three categories: preset properties of the muscle, reflex changes to the muscle, and active changes to the muscle. We hypothesized that an active response is required to maintain balance on a moving platform. Eleven healthy adult subjects stood on a platform oscillating at three frequencies (0.75, 1.0, and 1.25 Hz). Ankle extensor EMG activity and ankle moment were analyzed and compared for initial movement cycles. Timing of events in EMG and moment data were examined to separate observed changes into the three categories. Results showed an initial rise in ankle moment as the platform started to move backwards, followed by a more rapid reflex increase. After a slight drop, ankle moment again rose due to active response. By the third cycle of platform movement, the EMG and moment were synchronized with the platform movement, maintaining the body in a desired posture. Initial preset properties of the ankle extensor muscles combined with reflex activity were not sufficient to maintain balance. Following an initial reflex reaction, further active control was required to match the timing of the ankle moment and the platform motion and avoid a loss of balance. This study provides new insight for the rehabilitation of postural deficits.