N102-170 TITLE: Neck Load Simulation During Individual Warfighting Postures and Maneuvers

TECHNOLOGY AREAS: Biomedical, Human Systems

ACQUISITION PROGRAM: EMW-FY09-06 EC, Individual Warfighter Lightweight Protective System

OBJECTIVE: Develop a validated simulation for predicting neck loads during realistic and repetitive Warfighter tasks incorporating fatigue factors.

DESCRIPTION: The desire to protect the Warfighter’s head from higher ballistic threats has required the use of heavier and heavier materials. This headborne load creates a potential cause of intense fatigue or even injury while conducting normal dismounted military operations. Advancements in neck load evaluations, specific to these types of movements, are needed in order to improve helmet designs that are affected not only by added weight but also by the placement of headborne sensors and communications devices. As a Warfighter engages in common activities such as marching, crouching and running, the angle of the head relative to the body shifts so that not only do head-supported masses load the neck axially, potentially causing disk compression, but off-axis head orientation taxes the neck muscles, potentially causing muscle strains. This problem is accentuated by the fact that head-mounted gear may change during the course of an operation, and the appropriate placement of a piece of equipment on the helmet for a person in a marching stance might, for example, actually be injurious to a person in a prolonged crouch. A physics-based simulation tool is needed that would simulate neck loads while a Warfighter conducted common Warfighter movements while wearing various headborne equipment that varied in weight and placement. It would demonstrate the ability to optimize neck loads in order to reduce fatigue and injury while improving mobility, stability, and comfort. This simulation tool would include the ability to analyze adjustment strategies, such as minimizing neck torque by revising the placement of head-mounted gear or by changing head angle or amount of knee bending. The tool would advance current analytical capabilities relative to head-supported masses by adding and validating the fatigue component which does not exist in current models. This effort would use Government collected data for demonstration and validation. This effort would enable progress towards a mission-based optimization tool for designing or selecting headborne equipment. Initial work conducted under the "Validation of a Physics-Based Simulation of Warfighter Neck Load" study funded by ONR yielded a model based on limited experimental Army ARIEM data of Soldiers performing basic mission maneuvers with combat helmets (with and without NVGs). This model proved to be a fairly inaccurate predictor of load influence on the head and neck. While the initial model was not to the level of maturity required for engineers, designers and human factors personnel, the base model did provide a basis for continuing development as the indication are that a significantly more accurate predictive model can be achieved.

Phase I: Build and demonstrate a validated physics-based simulation that estimates neck load of a Warfighter engaged in at least three common mission tasks; such as marching, running, jumping, etc. This simulation should include the ability to accurately analyze neck load adjustment strategies and account for fatigue and the onset of potential injury. This basic and validated simulation tool will allow for further investigations to maximize warfighter performance and reduce injuries from over burdened muscular and skeletal systems.

Phase II: Using existing experimental bio-mechanics data and the validated simulation tool developed in phase I demonstrate the applicability of the tool by designing an improved helmet system (center of gravity, weight distribution and stability) and identify maximum loads the head/neck can carry over various durations and operational tasks without causing significant fatigue or injury (temporary or permanent). Simulation will demonstrate ability to optimize neck loads based on equipment design and individual movement.

Phase III: This tool can be used by military R&D and acquisition organizations to design and select protective headborne equipment. Phase III will seek to expand the scope of mission tasks to include more intense select mission functions (firing weapons, high impact insults, NVG compatibility and weight distributions and etc). Improved combat helmet design concepts developed under separate FNC funding will be incorporated into the simulations to optimize performance prior to user evaluations.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The sports industry can benefit by being able to evaluate and optimize protective headgear against fatigue or discomfort.

REFERENCES:
1 - Draft Final Report: Validation of a Physics-Based Simulation of Warfighter Neck Loads, U.S. Army Natick Soldier Center & Office of Naval Research, 20 pages (uploaded in SITIS 5/17/10).

2. PM-MERS study "Investigation of the Preferred Mass Properties for Infantry Headwear Systems."

3. ONR and Army study on "Validation of a Physics-Based Simulation of Warfighter Neck Load."
Ashrafiuon H, Alem NM, McEntire BJ. Effects of weight and center of gravity location of head-supported devices on neck loading. Aviat Space Environ Med. 1997 Oct;68(10):915-22. PubMed PMID: 9327117.

4. Buhrman JR, Perry CE. Human and manikin head/neck response to +Gz acceleration when encumbered by helmets of various weights. Aviat Space Environ Med. 1994 Dec;65(12):1086-90. PubMed PMID: 7872908.

5. McCloskey K, Esken RL. Evaluation of integrated night vision goggle (NVG) helmets under sustained +Gz. Aviat Space Environ Med. 1995 Feb;66(2):118-25. PubMed PMID: 7726774.
Manoogian SJ, Kennedy EA, Wilson KA, Duma SM, Alem NM. Predicting neck injuries due to head-supported mass. Aviat Space Environ Med. 2006 May;77(5):509-14. PubMed PMID: 16708531.

6. Sovelius R, Oksa J, Rintala H, Huhtala H, Siitonen S. Neck muscle strain when wearing helmet and NVG during acceleration on a trampoline. Aviat Space Environ Med. 2008 Feb;79(2):112-6. PubMed PMID: 18309908.

KEYWORDS: simulation; neck load; validation; biomechanics; headwear; helmet

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