Gregory G. Knapik

article

Development and testing of a moment-based coactivation index to assess complex dynamic tasks for the lumbar spine

Peter Le, Alexander Aurand, Jonathan S. Dufour, Gregory G. Knapik, more

Clinical Biomechanics > 2017 > 46 > C > 23-32

Many methods exist to describe coactivation between muscles. However, most methods have limited capability in the assessment of coactivation during complex dynamic tasks for multi-muscle systems such as the lumbar spine. The ability to assess coactivation is important for the understanding of neuromuscular inefficiency. In the context of this manuscript, inefficiency is defined as the effort or level...

article

Validation of a personalized curved muscle model of the lumbar spine during complex dynamic exertions

Jaejin Hwang, Gregory G. Knapik, Jonathan S. Dufour, Thomas M. Best, more

Journal of Electromyography and Kinesiology > 2017 > 33 > C > 1-9

Previous curved muscle models have typically examined their robustness only under simple, single-plane static exertions. In addition, the empirical validation of curved muscle models through an entire lumbar spine has not been fully realized. The objective of this study was to empirically validate a personalized biologically-assisted curved muscle model during complex dynamic exertions. Twelve subjects...

article

Prediction of magnetic resonance imaging-derived trunk muscle geometry with application to spine biomechanical modeling

Jaejin Hwang, Jonathan S. Dufour, Gregory G. Knapik, Thomas M. Best, more

Clinical Biomechanics > 2016 > 37 > C > 60-64

Accurate geometry of the trunk musculature is essential for reliably estimating spinal loads in biomechanical models. Currently, many models employ straight muscle path assumptions that yield far less accurate tissue loads, particularly in extreme postures. Precise muscle moment-arms and physiological cross-sectional areas are important when incorporating curved muscle geometry in biomechanical models...

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A biologically-assisted curved muscle model of the lumbar spine: Model structure

Jaejin Hwang, Gregory G. Knapik, Jonathan S. Dufour, Alexander Aurand, more

Clinical Biomechanics > 2016 > 37 > C > 53-59

Biomechanical models have been developed to assess the spine tissue loads of individuals. However, most models have assumed trunk muscle lines of action as straight-lines, which might be less reliable during occupational tasks that require complex lumbar motions. The objective of this study was to describe the model structure and underlying logic of a biologically-assisted curved muscle model of the...

article

A biologically-assisted curved muscle model of the lumbar spine: Model validation

Jaejin Hwang, Gregory G. Knapik, Jonathan S. Dufour, Thomas M. Best, more

Clinical Biomechanics > 2016 > 37 > C > 153-159

Biomechanical models have been developed to predict spinal loads in vivo to assess potential risk of injury in workplaces. Most models represent trunk muscles with straight-lines. Even though straight-line muscles behave reasonably well in simple exertions, they could be less reliable during complex dynamic exertions. A curved muscle representation was developed to overcome this issue. However, most...

article

An EMG-assisted model calibration technique that does not require MVCs

Jonathan S. Dufour, William S. Marras, Gregory G. Knapik

Journal of Electromyography and Kinesiology > 2013 > 23 > 3 > 608-613

As personalized biologically-assisted models of the spine have evolved, the normalization of raw electromyographic (EMG) signals has become increasingly important. The traditional method of normalizing myoelectric signals, relative to measured maximum voluntary contractions (MVCs), is susceptible to error and is problematic for evaluating symptomatic low back pain (LBP) patients. Additionally, efforts...

article

Musculoskeletal disorder risk during automotive assembly: current vs. seated

Sue A. Ferguson, William S. Marras, W. Gary Allread, Gregory G. Knapik, more

Applied Ergonomics > 2012 > 43 > 4 > 671-678

Musculoskeletal disorder risk was assessed during automotive assembly processes. The risk associated with current assembly processes was compared to using a cantilever chair intervention. Spine loads and normalized shoulder muscle activity were evaluated during assembly in eight regions of the vehicle. Eight interior cabin regions of the vehicle were classified by reach distance, height from vehicle...

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Use of a personalized hybrid biomechanical model to assess change in lumbar spine function with a TDR compared to an intact spine

Gregory G. Knapik, Ehud Mendel, William S. Marras

European Spine Journal > 2012 > 21 > 5 > 641-652

Total disc replacements (TDRs) have been employed with increasing frequency in recent years with the intention of restoring natural motion to the spine and reducing adjacent level trauma. Previous assessments of the TDRs have subjectively measured patient satisfaction, evaluated sagittal range of motion via static imaging, or examined biomechanical loading in vitro. This study examined the kinematics...

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Musculoskeletal disorder risk as a function of vehicle rotation angle during assembly tasks

Sue A. Ferguson, Williams S. Marras, W. Gary Allread, Gregory G. Knapik, more

Applied Ergonomics > 2011 > 42 > 5 > 699-709

Musculoskeletal disorders (MSD) are costly and common problem in automotive manufacturing. The research goal was to quantify MSD exposure as a function of vehicle rotation angle and region during assembly tasks. The study was conducted at the Center for Occupational Health in Automotive Manufacturing (COHAM) Laboratory. Twelve subjects participated in the study. The vehicle was divided into seven...

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Loading along the lumbar spine as influence by speed, control, load magnitude, and handle height during pushing

William S. Marras, Gregory G. Knapik, Sue Ferguson

Clinical Biomechanics > 2009 > 24 > 2 > 155-163

Low back loading and risk associated with pushing activities have been poorly understood. Previous studies have demonstrated that increases in anterior/posterior shear forces are primarily initiated by antagonistic coactivity within the torso. Yet, few studies have considered the range of activities that might contribute to the antagonistic coactivation and subsequent spine loading.Twenty subjects...

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Search results for: Gregory G. Knapik

Development and testing of a moment-based coactivation index to assess complex dynamic tasks for the lumbar spine

Validation of a personalized curved muscle model of the lumbar spine during complex dynamic exertions

Prediction of magnetic resonance imaging-derived trunk muscle geometry with application to spine biomechanical modeling

A biologically-assisted curved muscle model of the lumbar spine: Model structure

A biologically-assisted curved muscle model of the lumbar spine: Model validation

An EMG-assisted model calibration technique that does not require MVCs

Musculoskeletal disorder risk during automotive assembly: current vs. seated

Use of a personalized hybrid biomechanical model to assess change in lumbar spine function with a TDR compared to an intact spine

Musculoskeletal disorder risk as a function of vehicle rotation angle during assembly tasks

Loading along the lumbar spine as influence by speed, control, load magnitude, and handle height during pushing

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Search results for: Gregory G. Knapik

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