Two-dimensional biomechanical model for estimating strength of youth and adolescents for manual material handling tasks

The goal of this study was to quantify the variability of the three-dimensional kinematic and kinetic parameters describing the motion of the torso during the performance of sagittally symmetric lifting tasks. Subjects performed eight repetitions of simple lifting tasks described by three levels of coupling (poor, fair and good) and seven levels of load (4.5, 9, 13.5, 18, 22.5, 27 and 31.5 kg). The three-dimensional, time dependent position, velocity and acceleration of the lumbar spine were monitored using the Lumbar Motion Monitor. These measures were then input into a dynamic biomechanical model which calculated torque about the L5/S1 joint in the sagittal plane. The results of the kinematic analysis showed significant variability in the magnitude of the peak velocity and acceleration in the sagittal plane and also showed significant motion in the transverse and coronal planes. The kinetic analysis showed an increase in the variability of the peak dynamic torque with greater levels of load but no coupling effect.

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Lifting Performed on Laterally Slanted Ground Surfaces

Proceedings of the Human Factors and Ergonomics Society Annual Meeting ◽

10.1177/154193120504901413 ◽

2005 ◽

Vol 49 (14) ◽

pp. 1325-1329

Author(s):

Zongliang Jiang ◽

Gwanseob Shin ◽

Jacklyn Freeman ◽

Stephanie Reid ◽

Gary A. Mirka

Keyword(s):

Material Handling ◽

Biomechanical Model ◽

The Body ◽

Time Dependent ◽

Whole Body ◽

Slant Angle ◽

Manual Material Handling ◽

Lateral Forces ◽

Outdoor Work ◽

Biomechanical Responses

Many outdoor work environments (e.g. agriculture and construction) require manual material handling activities on variable grade ground surfaces. Quantifying biomechanical responses for lifting under these conditions may provide insight into the etiology of lifting-related injuries. The aim of the current study was to quantify the effect of laterally slanted ground surfaces on biomechanical responses. Ten subjects performed lifting exertions (using a 40% of max load) while standing on a platform that was laterally tilted at 0, 10, 20 and 30 degrees from horizontal. During the lifting tasks the whole body kinematics were collected, which were later used in a dynamic biomechanical model to calculate the time-dependent moment about L5/S1 and the time-dependent lateral forces acting on the body segments. The results showed a consistent reduction in the peak dynamic L5/S1 moment (decreased by 9%) and an increase in the lateral forces (increased by 111%) with increasing slant angle.

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Two-Dimensional Symmetric Box Delivery Motion Prediction and Validation: Subtask-Based Optimization Method

Applied Sciences ◽

10.3390/app10248798 ◽

2020 ◽

Vol 10 (24) ◽

pp. 8798

Author(s):

Yujiang Xiang ◽

Shadman Tahmid ◽

Paul Owens ◽

James Yang

Keyword(s):

Cost Function ◽

Material Handling ◽

Optimization Method ◽

Joint Torque ◽

Two Dimensional ◽

Computationally Efficient ◽

Inverse Dynamic ◽

Manual Material Handling ◽

Research Outcome ◽

The Cost

Box delivery is a complicated manual material handling task which needs to consider the box weight, delivering speed, stability, and location. This paper presents a subtask-based inverse dynamic optimization formulation for determining the two-dimensional (2D) symmetric optimal box delivery motion. For the subtask-based formulation, the delivery task is divided into five subtasks: lifting, the first transition step, carrying, the second transition step, and unloading. To render a complete delivering task, each subtask is formulated as a separate optimization problem with appropriate boundary conditions. For carrying and lifting subtasks, the cost function is the sum of joint torque squared. In contrast, for transition subtasks, the cost function is the combination of joint discomfort and joint torque squared. Joint angle profiles are validated through experimental results using Pearson’s correlation coefficient (r) and root-mean-square-error (RMSE). Results show that the subtask-based approach is computationally efficient for complex box delivery motion simulation. This research outcome provides a practical guidance to prevent injury risks in joint torque space for workers who deliver heavy objects in their daily jobs.

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