Abstract
Background: Loss of balance is a considerable risk factor for workers while using ladders, because they are required to maintain static postural balance on platforms of a restricted size. This study observed center of mass (CoM) and center of pressure (CoP) behaviors and evaluated the effects of the platform depth (anterior–posterior length) and working postures. Methods: Eleven male participants stood on four platforms with depths ranging from 6 to 15 cm and maintained their positions for 60 s while performing or not performing other tasks (object holding, upward viewing, or both simultaneously). The kinematics were analyzed on the sagittal plane based on the inverse pendulum model. Results: The absolute moving range for the CoP–CoM linearly increased with the decreasing platform depth, and the working postures affected the slopes of the linear fits. The relative range of CoP–CoM displacement on narrow platforms was highly correlated with the subjective sense of instability. Conclusions: Monitoring the CoP is effective for a better understanding and evaluation of static postural balance. This study’s findings contribute to improving the design of work equipment through the use of wider platforms that are robust against the effects of working postures.
Highlights
Loss of balance during work is a serious problem, because workers who lose their balance risk slips, trips, and falls as well as other workplace accidents [1,2]
The neck angles during the object holding (OH)&upward viewing (UV) postures showed similar trends with the UV postures, whereas the trunk and hip angles were similar to the OH postures
The absolute ranges of the center of pressure (CoP) and CoP–center of mass (CoM) displacement increased linearly with the narrowing of the platform depth, whereas that of the CoM was constant with the platform depth
Summary
Loss of balance during work is a serious problem, because workers who lose their balance risk slips, trips, and falls as well as other workplace accidents [1,2]. Hsiao and Simeonov [19] summarized the elements that affect balance control during roofing work as the following three factors: environmental, task-related, and personal factors These factors affect the sensory inputs of the worker and can disturb postural stability. Working postures during tasks affect the static postural balance [2], which is destabilized by tasks, especially by particular postures such as reaching [25], body movement [26,27], load holding [17,28,29], external loading [30], and mental workload [31,32] These are considered to be task-related factors for human postural stability [19]. To examine the upright postural stability on the narrow platforms, kinetic analysis was performed using the inverse pendulum model with both the CoM and CoP, because postural perturbation due to postural displacements induces body acceleration
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