Health Hazard Assessment (HHA)

 Hazard Category - Musculoskeletal Trauma

Last Updated: June 30, 2022
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​​Musculoskeletal Trauma

Coordinate with the Health Hazard Assessment (HHA) Program early in the acquisition process to eliminate or control health hazard exposures associated with musculoskeletal trauma. Subject matter experts from the Ergonomics Program provide input for HHAs related to musculoskeletal trauma.

Specific health effects vary based on the type of exposure. Increased stress placed on the musculoskeletal system may cause fatigue, chronic degenerative changes, chronic spine and/or neck injuries, and degraded performance. Injuries may occur by direct trauma, a single exertion (overexertion), or as a result of multiple exertions (repetitive trauma). 

Lift and Carry

The lift and carry of heavy components yields complex exposures producing levels of biomechanical stress that vary as a function of the load handled, postures used, and the frequency, duration, and periodicity of the physical activity employed. Other work-related factors may also lead to musculoskeletal trauma, such as pushing and pulling activities and non-neutral postures.  

Data Requirements
Provide the system description, including the weights and dimensions of all items weighing over 31 pounds  (lbs) that will be lifted. Provide a detailed use scenario (e.g., handling environment, required tasks and physical demands, frequency of lifts). 

Health Protection Criteria
MIL-STD-1472H contains design guidance for efficient handling. Maximum design weight limits based on lifting team size are provided.1 Reduction multipliers for lifting risk factors (e.g., lifting frequency, lifting height, load asymmetry) are considered in the determination of the safest load that a team is permitted to handle. Each item required to be manually lifted/carried should be labeled with their weight and lifting requirements.

Head-Supported Mass

A quantitatively descriptive property which represents the loading on the neck from wearing head protection systems that may affect Soldier performance and health. This term may also be used to refer to the helmet and helmet-mounted system components. 

Data Requirements
Provide the weight of the HSM component, center of mass offset, detailed use scenario (e.g., duration, frequency of use, vibration exposure), and operational baseline helmet configuration (e.g., MOS, aviation, ground).

Health Protection Criteria
Currently-approved health protection criteria are not available for health hazards associated with exposure to HSM for mounted or dismounted ground Soldiers. The U.S. Army Aeromedical Research Laboratory (USAARL) External Link developed performance and acute injury risk guidelines for Army aviation which describe acceptable ranges for mass properties of Army aviation-specific HSM.2,3 Medical and safety personnel, specifically those at the USAARL, are currently working to develop applicable health protection criteria. Completed studies establish preliminary performance guidelines; however, injury criteria are still being researched. 

As a result of the preliminary performance guidelines, it is recommended that the rear and forward offsets relative to the tragion notch be limited to -2 and 9.5 centimeters, respectively, and the preliminary maximum allowable helmet mass be limited to 2.5 kilograms.4

Load Carriage

The total loading on the body from carrying clothing and equipment. The load is typically carried over long distances or durations, and may be worn, affixed, or sometimes hand-carried. Load carriage has been associated with musculoskeletal trauma, and movements or exertions while carrying increased loads may elevate the risk of injury. Examples of systems requiring load carriage include body armor, backpacks, personal weapons, radio handsets, and other equipment attached to the body. 

Data Requirements

Detailed system and use scenario information are required to assess the risk of injury associated with load carriage (e.g., component size and weight, distribution of weight, diagram/picture, method of attachment to the body, backpack type or design (if applicable), other equipment worn and carried by the Soldiers using the system, distance and duration expected to carry load, required tasks while carrying load, environmental conditions).

Health Protection Criteria

MIL-STD-1472H provides design criteria for load carriage1. Individual portions of portable equipment shall not exceed 35 pounds, unless the individuals carrying the load do not need to maintain the pace of infantry movement. The total load carried (i.e., all equipment, clothing, and weapons) shall not exceed 30% of the user's body weight for close combat operations, or 45% of the user's body weight for marching. Additional MIL-STD-1472H design criteria provide suggestions for reducing the risk of musculoskeletal injuries (e.g., distribute and balance the load throughout muscle groups, design the center of gravity as close to the spine and waistline as possible, design the load to permit freedom of movement).

For more information and guidelines for assessing musculoskeletal trauma, see Technical Guide 351C, Health Hazard Assessor's Guide.


(1) DOD. 2020. MIL-STD-1472H. Department of Defense Design Criteria Standard: Human Engineering. External Link

(2) USAARL. 1998. Mass Requirements for Helicopter Aircrew Helmets (Report No. 98-14). Prepared by B.J. McEntire and D.F. Shanahan. Fort Rucker, Alabama. External Link

(3) AFRL. 1994. Vertical Impact Testing of Two Helmet-Mounted Night Vision Systems (AFRL Technical Report #AL/CF-SR-1994-0013). Prepared by C. Perry. Wright-Patterson Air Force Base, Ohio. External Link

(4) USAARL. 2019. Preliminary Head-Supported Mass (HSM) Performance Guidance for Dismounted Soldier Environments (USAARL Technical Memorandum No. 2019-11). Prepared by A. Madison. Fort Rucker, Alabama. (Note: Limited Release) External Link