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STUDY DESIGN The load in active and passive spinal components as well as the stability margin in standing postures +/- load in hands are studied using both computational model and in vivo studies. OBJECTIVE To investigate muscle activity, spinal loads, and system stability in standing postures. SUMMARY OF BACKGROUND DATA Study of the human trunk yields(More)
A hallmark of more advanced models is their higher details of trunk muscles represented by a larger number of muscles. The question is if in reality we control these muscles individually as independent agents or we control groups of them called "synergy". To address this, we employed a 3-D biomechanical model of the spine with 18 trunk muscles that(More)
BACKGROUND Comparative studies between single-joint electromyography (EMG)- and optimization-driven models of the human spine in estimating trunk muscle and spinal compression forces have not been conclusive. Due to associated implications in ergonomic applications as well as prevention and treatment managements of low-back disorders, there is a need to(More)
To resolve the trunk redundancy to determine muscle forces, spinal loads, and stability margin in isometric forward flexion tasks, combined in vivo-numerical model studies was undertaken. It was hypothesized that the passive resistance of both the ligamentous spine and the trunk musculature plays a crucial role in equilibrium and stability of the system.(More)
STUDY DESIGN In vivo measurements and model studies are combined to investigate the role of lumbar posture in static lifting tasks. OBJECTIVES Identification of the role of changes in the lumbar posture on muscle forces, internal loads, and system stability in static lifting tasks with and without load in hands. SUMMARY OF BACKGROUND DATA Despite the(More)
Despite the well-recognized role of lifting in back injuries, the relative biomechanical merits of squat versus stoop lifting remain controversial. In vivo kinematics measurements and model studies are combined to estimate trunk muscle forces and internal spinal loads under dynamic squat and stoop lifts with and without load in hands. Measurements were(More)
To circumvent the existing shortcoming of optimisation algorithms in trunk biomechanical models, both agonist and antagonist trunk muscle stresses to different powers are introduced in a novel objective function to evaluate the role of abdominal muscles in trunk stability and spine compression. This coupled objective function is introduced in our(More)
The role of intra-abdominal pressure (IAP) in unloading the spine has remained controversial. In the current study, a novel kinematics-based approach along with a nonlinear finite-element model were iteratively used to calculate muscle forces, spinal loads, and stability margin under prescribed postures and loads measured in in vivo studies. Four coactivity(More)
BACKGROUND The ratio of total lumbar rotation over pelvic rotation (lumbopelvic rhythm) during trunk sagittal movement is essential to evaluate spinal loads and discriminate between low back pain and asymptomatic population. METHODS Angular rotations of the pelvis and lumbar spine as well as their sagittal rhythm during forward flexion and backward(More)
BACKGROUND An improved assessment of risk of spinal injury during lifting activities depends on an accurate estimation of trunk muscle forces, spinal loads and stability margin which in turn requires, amongst others, an accurate description of trunk muscle geometries. The lines of action of erector spinae muscles are often assumed to be linear despite the(More)