Biomechanically determined hand force limits protecting the low back during occupational pushing and pulling tasks

Area of Science:

• Occupational biomechanics
• Ergonomics
• Industrial safety

Background:

• Existing pushing and pulling guidelines rely on subjective psychophysical data.
• There is a need for objective, biomechanically-based limits for these tasks.
• Lumbar spine loads during pushing and pulling are critical factors for injury prevention.

Purpose of the Study:

• To establish objective, biomechanically-determined hand force and torque limits for occupational pushing and pulling.
• To assess spinal loads during various pushing and pulling exertions.
• To compare new biomechanical limits with existing psychophysical recommendations.

Main Methods:

• Sixty-two subjects performed standardized pushing and pulling tasks in a controlled laboratory setting.
• An electromyography-assisted biomechanical model estimated lumbar spine loads.
• Hand force and turning torque were measured using specialized transducers, and analyzed with mixed modeling.

Main Results:

• Exertion type, direction, and handle height significantly impacted spinal load, hand force, and torque.
• The study developed biomechanically-derived hand force and torque limits.
• These new guidelines are up to 30% lower than current psychophysical limits, offering greater protection.

Conclusions:

• Biomechanically-determined guidelines provide a more objective basis for assessing pushing and pulling risks.
• The new limits, particularly for straight pushing, are more protective than existing recommendations.
• Practitioners should adopt these guidelines for improved workplace risk assessment and design.