Analysis of Postural Instability in the Upright Position on Narrow Platforms and the Interactions with Postural Constraints

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.

Training Postural Balance Control with Pelvic Force Field at the Boundary of Stability

“…Perturbations were enacted as a pull on the trunk lasting 600 ms. During this time, the subject's COM was forcibly moved in the direction of the pull leaving them close to the boundaries of their BOS at the end of the perturbation. At this point, the COP-COM distance was minimized and thus, the ability of subjects to generate any restoring torque using the ankle strategy was minimal because the COP-COM distance is directly proportional to the restoring torque [31,32]. In the first few hundred milliseconds of the perturbation, when the COP-COM distance is maximal, we observed that subjects tried to use an ankle strategy but quickly changed to the hip strategy once the perturbation started.…”

Relationship between Upper Body Mass and Trunk Segment Control for Stability during Single-Leg Standing

“…The one-leg standing posture is difficult to control with CoP effectively due to the narrow support surfaces on the left and right sides 26) . This may be why no In conclusion, it was shown that differences in upper body segments and mass control strategies affect CoM-TLL and CoP-Freq.…”