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ABSTRACT: The Personnel Armor System for Ground Troops (PASGT) Helmet is a
standard infantry helmet that provides ballistic protection from fragmenting
munitions to the head, temples, ears, and neck. Originally type-classified
in the late 1970's and fielded in early 1980's the current fielded PASGT is
made of Kevlar 29® and weighs between 3.1 lbs. extra small and 4.2 lbs.
extra large U.S. Army Soldier Systems Command (SSCOM), 1998. The outcome of
studies related to the performance of job tasks in different environments
will determine how the needs of soldiers are being met by this system. Many
of the improvements and modifications made to the original design of the
PASGT helmet are the results of feedback from soldiers in the field who
tested the equipment. The Land Warrior IHAS system is different from the
current PASGT helmet in design technology and weight, and will require
intense training to ensure soldiers needs are being met.
The Personnel Armor System for Ground Troops (PASGT) Helmet is a
standard infantry helmet that provides ballistic protection from fragmenting
munitions to the head, temples, ears,and neck. Originally type-classified
in the late 1970's and fielded in early 1980's the current fielded PASGT is
made of Kevlar 29® and weighs between 3.1 lbs. extra small and 4.2 lbs.
extra large U.S. Army Soldier Systems Command (SSCOM), 1998.The Integrated
Helmet Assembly Subsystems (IHAS) is part of the Land Warrior System (LWS).
The IHAS uses advanced materials to provide ballistic protection at less weight than the current
helmet shell. The IHAS's helmet-mounted computer and sensor display are the soldier's interface with
the other subsystem and with the digital battlefield. Through the helmet-mounted display,
the soldier can view computer-generated graphical data, digital map, intelligence
information, and troop locations. The Night Sensor Display will integrate a
helmet-mounted display with an image intensifier for access to the computer. This sensor/display assembly
flips up for flexibility and electrical compatibility between day and night displays. The
helmet is also designed to provide safe functioning in day and night and at
nuclear, biological, and chemical environments with an inner helmet
surface allowing for ventilation and deformation during impact SSCOM, 1998. The design
of the IHAS does not restrict the user's range of motion and movement of the head to any extent
that would prohibit successful completion of mission – critical tasks.
®Kevlar is a registered trademark of E.I. Du Pont de Nemours & Co., Inc., Wilmington, Delaware. Use
of trademarked names does not imply endorsement by the U.S. Army but is
intended only to assist in identification of a specific product.
Helmet Size and Weight
The weight of the helmet configured with the Land Warrior IHAS is between 3.1 lbs. and 5.4
lbs. The weight of the PASGT helmet is between 4.5 lbs. and 6.0 lbs. a
difference of 6 ounces when compared to the LWS. The weight of the PASGT
helmet identified a direct correlation to an increase of potential work
related muscularskeletal WMSD injuries to the head and necks of soldiers
during performance of functional job tasks. Soldiers' reported during wear
of the current PASGT helmet an increase of pressure on their head and that
helmet was too heavy USARIEM, 1997. This chart illustrates proposed changes
in the IHAS helmet weight for the LWS:
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Sizes
Maximum Weight (lbs.) + 1.5 lbs. (LW) Gear
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Psychophysical/ Human Factors
Psychophysical/human factors relates to a person's ability to “rate the perceived strain”
stemming from the physical work performed and to judge whether or not the
strain is personally acceptable for safe performance of that task
(Kromer,1997). The weight of the helmet is a potential risk factor in
movements required for mission critical tasks that include the following:
- Standing, kneeling, crawling, or maintaining a prone position.
- Moving the head up and down and side to side.
- Looking over the shoulder.
- Moving of helmet during task that are specific to certain military occupational specialties (MOS 11B,11M,12B,13F,91B).
- Fatigue of neck muscles during sustain wear of the IHAS helmet with equipment.
Biomechanics
Biomechanics applies to the static and dynamic effects to the soldiers' body from vibration and
impact associated with wear of the helmet. The evaluation of weight
distribution and center of gravity in the helmet system helped to achieve
maximum helmet comfort and to reduce neck strain. Physical demands required
in MOS-specific tasks should be evaluated relative to the potential for
developmentof repetitive strain disorders. The most common musculoskeletal
disorder involves the neck and is associated with intervertebral disc
disorders. The following table shows potential conditions identified in the
International Classification of Diseases (ICD-9 Codes) related to helmet wear.
Code Condition
Comment
722.0
Displacement of the intervertebral disc
Positive association
722.11
Displacement of thoracic
Positive association
intervertebral disc
722.71
Intervertebral disc disorder/myelopathy
Positive association
cervical region
722.91
Other and unspecified disc disorders
Positive
association
cervical region
722.92
Other and unspecified disc disorder
Positive association
thoracic region
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Anthropometry
The LWS IHAS in human body dimensions will fit the 90th percentile male and
female. The design of helmet system will ensure safe and effective use by the soldier during all
environmental and operational conditions U.S. Army Soldier and Biological
Chemical Command (SBCOM), 1999.
Ergonomic Recommendations
The SBCOM has completed the first phase of the written for approved modification to the
PASGT helmet and integration of the IHAS in the LWS. The ergonomics focus
should involve identification of potential risk factors associated wear of
the helmet and recommendations for reducing risks.
Although specific ergonomic risk factors have not been determined, soldiers should receive
training in wear of the helmet relative to weight distribution of the helmet
center of mass during job task associated with specific MOS's identified in
the table below:
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MOS Job
Title
Physical Demands
11B
Infantryman
Very Heavy
11M Mechanized
Infantryman Very Heavy
12B
Combat Engineer
Very Heavy
13F Cannon
Crewmember Very Heavy
91B Medical
Specialist
Moderately Heavy
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Training should also include:
- Individual or group training in movement over different terrain.
- Fitness training in upper extremity (neck & thoracic) muscle strengthening.
- Training in technical skills workload stress to reduce risk factors associated in job
task performance levels i.e. ( Medical Specialist litter carry casualty
lifts while maintaining proper posture of head and neck with weight of LW
IHAS).
The outcome of studies related to the performance of job tasks in
different environments will determine how the needs of soldiers are being
met by this system. Many of the improvements and modifications made to the
original design of the PASGT helmet are the results of feedback from
soldiers in the field who tested the equipment. The Land Warrior IHAS
system is different from the current PASGT helmet in design technology and
weight, and will require intense training to ensure soldiers needs are being met.
- U.S Army Soldier System Command, “Personnel Armor System Ground Troops (PASGT)
Helmet”, Program Manager (PM) Soldier, 1998,<http://www-sscom.army.mil/pmsoldier/index.html (January,1999).
- Kroemer, K.H, “Ergonomic Design of Material Handling System” Screening Material Handlers.
Englewood Cliffs, NJ, Prentice Hall, (6), 90-91, 1997.
- Amoroso, P. and M. Yore, “Analysis of Military Occupational Specialties and
Hospitalization,” U.S. Army Research Institute of Environmental Medicine (USARIEM)
Technical Report (TR97), 1997.
- U.S Army Soldier and Biological Chemical Command, “Fragmentation Helmet,
Lightweight Marine Corps,”(USARIEM) and Natick Research Center Draft Report, 1999.
For more information about USACHPPM computer workstation assessments, contact
services@ergoworkinggroup.org
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