Difference between male and female workers lifting the same relative load when palletizing boxes

Area of Science:

• Occupational Biomechanics
• Ergonomics
• Human Movement Science

Background:

• Previous studies noted sex-based differences in manual material handling (MMH) lifting techniques.
• These differences, particularly in posture and coordination, were initially attributed to strength disparities.
• A key question remained whether these technique variations persisted when lifting loads relative to individual strength.

Purpose of the Study:

• To investigate if female workers maintain distinct lifting biomechanics compared to males when handling loads adjusted for their respective strengths.
• To determine if observed sex-based differences in lifting technique are intrinsic or solely due to absolute load differences.

Main Methods:

• Participants performed box lifting tasks from a pallet.
• A dynamic 3D linked segment model estimated net moments at L5/S1.
• Kinematic variables and task duration were analyzed to compare male and female lifting strategies with relative loads.

Main Results:

• Lifting task duration and cumulative loading were similar between sexes when using relative loads.
• Significant differences persisted in interjoint coordination patterns between male and female workers.
• The distinct coordination pattern observed in females with absolute loads was replicated with relative loads.

Conclusions:

• Sex appears to be a significant factor influencing lifting technique, independent of absolute or relative load.
• The female interjoint coordination pattern may place greater strain on posterior passive tissues during ground lifts.
• Further research is needed to identify the underlying reasons for these sex-specific biomechanical patterns to develop targeted injury prevention strategies.