An investigation of stability limits while holding a load

Area of Science:

• Biomechanics
• Human Factors Engineering
• Occupational Safety

Background:

• Understanding how load manipulation affects postural control is crucial for preventing injuries in manual handling tasks.
• Previous research has explored factors influencing balance, but specific data on load height and foot placement effects on functional base of support (FBOS) limits is limited.

Purpose of the Study:

• To investigate the impact of load height and foot placement on the functional base of support (FBOS) limits.
• To analyze the postural strategies employed by individuals when reaching their FBOS limits under different loading conditions.
• To provide quantitative data for designing safer materials handling environments.

Main Methods:

• Twelve young males participated in the study, performing reaching tasks with a 12-kg load at various heights (overhead, shoulder, knuckle) and unladen.
• Foot placements were varied between wide and narrow stances.
• Force platforms measured the centre of pressure (COP) excursion length and FBOS limits.
• 2-D motion analysis system recorded postural angles at the point of FBOS limit.

Main Results:

• Load height significantly influenced the posterior FBOS limit, with lower heights extending stability.
• Decreasing load height led to a reduction in the centre of pressure (COP) excursion length.
• Participants predominantly utilized a hip strategy to maintain balance as they approached their FBOS limits.

Conclusions:

• Load height is a critical factor affecting postural stability during manual handling.
• Lowering the load height enhances the functional base of support (FBOS) and reduces sway, indicating improved balance.
• The findings provide valuable quantitative insights for optimizing workplace design to ensure safety during load handling.