Biomechanics and Anthropometry Flashcards

The 'reach envelope' concept in workstation design refers to:

Answer: The three-dimensional zone within which a worker can reach comfortably without harmful postures

The reach envelope defines the three-dimensional space within which a worker can access tools, controls, and materials while maintaining acceptable postures, used to guide optimal placement of work objects.

Maintaining a neutral spine posture during lifting is biomechanically advantageous primarily because it:

Answer: Distributes spinal loads more evenly and reduces localized stress concentrations

Neutral spine posture distributes compressive, tensile, and shear forces more uniformly across vertebral structures, reducing peak stress concentrations that occur with extreme flexion or extension.

In the NIOSH Revised Lifting Equation (1994), the Asymmetry Multiplier (AM) accounts for:

Answer: The angular displacement of the load from the sagittal (midline) plane

The Asymmetry Multiplier reduces the Recommended Weight Limit based on the angle between the midsagittal plane and the line connecting the load's horizontal position, penalizing twisting during lifting.

According to biomechanical principles, increasing the horizontal distance of a load from the lumbar spine by a factor of two will:

Answer: Double the moment (torque) that must be countered by back muscles

Torque equals force times moment arm; doubling the horizontal distance (moment arm) doubles the torque that lumbar extensors must generate, substantially increasing spinal compression forces.

Functional anthropometric data is preferred over static data for workstation design because:

Answer: Functional data captures the actual body dimensions and clearances needed during task performance

Functional (dynamic) data reflects real-world postures and movements, capturing how body dimensions change during actual task execution, making it more directly applicable to workstation layout decisions.

The action limit (AL) in the original NIOSH Work Practices Guide (1981) was set at approximately what compressive force on L5/S1?

Answer: 2,700 N

The 1981 NIOSH Work Practices Guide set the Action Limit at approximately 2,700 N compressive force at L5/S1, below which most healthy workers could safely perform lifting tasks without administrative controls.

Which anthropometric design strategy is most appropriate when a single fixed dimension must serve a diverse population and adjustability is not feasible?

Answer: Design for the extreme user that creates the greatest risk or demand

When adjustability is not possible, the correct strategy is to design for the extreme user whose body dimensions create the most critical constraint (e.g., clearance designs use the largest user; reach designs use the smallest user).