Biomechanics Commons^™

Skills Learning In Robot-Assisted Surgery Is Benefited By Task-Specific Augmented Feedback, Srikant Vallabhajosula, Srikant Vallabhajosula, Timothy N. Judkins, Mukul Mukherjee, I. H. Suh, D. Oleynikov, K.-C. Siu

Journal Articles

Background: Providing augmented visual feedback is one way to enhance robot-assisted surgery (RAS) training. However, it is unclear whether task specificity should be considered when applying augmented visual feedback. Methods: Twenty-two novice users of the da Vinci Surgical System underwent testing and training in 3 tasks: simple task, bimanual carrying (BC); intermediate task, needle passing (NP); and complex task, suture tying (ST). Pretraining (PRE), training, and posttraining (POST) trials were performed during the first session. Retention trials were performed 2 weeks later (RET). Participants were randomly assigned to 1 of 4 feedback training groups: relative phase (RP), speed, grip force, …

Lower Extremity Kinematics During Walking And Elliptical Training In Individuals With And Without Traumatic Brain Injury, Thad Buster, Judith Burnfield, Adam P. Taylor, Nikolaos Stergiou

Journal Articles

Background and Purpose: Elliptical training may be an option for practicing walking-like activity for individuals with traumatic brain injuries (TBI). Understanding similarities and differences between participants with TBI and neurologically healthy individuals during elliptical trainer use and walking may help guide clinical applications incorporating elliptical trainers.

Methods: Ten participants with TBI and a comparison group of 10 neurologically healthy participants underwent 2 familiarization sessions and 1 data collection session. Kinematic data were collected as participants walked on a treadmill or on an elliptical trainer. Gait-related measures, including coefficient of multiple correlations (a measure of similarity between ensemble joint movement profiles; …

Oncology Section Task Force On Breast Cancer Outcomes: Scapular Assessment, Mary Insana Fisher, Pamela K. Levangie

Physical Therapy Faculty Publications

Background: Functional deficits and changes in scapular mechanics following breast cancer (BC) treatments have been documented. Scapular assessment is important when examining the shoulder in survivors of breast cancer to document the need for or effectiveness of physical therapy intervention. The Oncology Section Task Force on Breast Cancer Outcomes sought to identify scapular examination tools that can be recommended for routine use in individuals treated for BC.

Methods: A systematic review of the literature on scapular measures was conducted. Relevant studies were examined for psychometric properties and clinical usefulness. Each method was given a recommendation score based on the Breast …

Oncology Section Task Force On Breast Cancer Outcomes: An Introduction To The Edge Task Force And Clinical Measures Of Upper Extremity Function, Pamela K. Levangie, Mary Insana Fisher

Physical Therapy Faculty Publications

With the proliferation of outcome measures in the literature, many of which lack documentation of sufficient psychometric properties to justify use, it is difficult to document patient change or demonstrate effectiveness of interventions. The goal of the Section on Research’s EDGE (Evaluation Database to Guide Effectiveness) Task Force is to facilitate identification of valid and reliable tests and measures that reflect clinically important outcomes and are responsive to change for standard use across selected patient groups. This paper lays the groundwork for understanding the work of the Oncology Section’s Breast Cancer EDGE Task Force on clinical measures of shoulder function …

Degeneracy And Long-Range Correlations, D. Delignières, Vivien Marmelat

Journal Articles

Degeneracy is a ubiquitous property of complex adaptive systems, which refers to the ability of structurally different components to perform the same function in some conditions and different functions in other conditions. Here, we suppose a causal link between the level of degeneracy in the system and the strength of long-range correlations in its behavior. In a numerical experiment, we manipulated degeneracy through the number of networks available in a model composed of a chain of correlated networks over which a series of random jumps are performed. Results showed that correlations in the outcome series increased with the number of …

Formulation To Predict Lower Limb Muscle Forces During Gait, Gil Serrancolí, Jonathan P. Walter, Allison Kinney, A. Barjau, Benjamin J. Fregly, Josep M. Font-Llagunes

Mechanical and Aerospace Engineering Faculty Publications

The human body has more muscles than Degrees of Freedom (DoF), and that leads to indeterminacy in the muscle force calculation. This study proposes the formulation of an optimization problem to estimate the lower-limb muscle forces during a gait cycle of a patient wearing an instrumented knee prosthesis. The originality of that formulation consists of simulating muscle excitations in a physiological way while muscle parameters are calibrated. Two approaches have been considered. In Approach A, measured contact forces are applied to the model and all inverse dynamics loads are matched in order to get a physiological calibration of muscle parameters. …

A Miniaturised Spectrometer Device For The Detection Of Nitrogen Dioxide In An Urban Environment, Brian Devine

Doctoral

Monitoring of air pollutants, such as Nitrogen Dioxide (NO2), that are toxic or environmentally damaging is a key metric for environmental protection agencies worldwide. There is a constant need to develop new technologies and methodologies that provide real-time, low cost pollution measurements over a broad range of sampling sites, particularly in urban and industrial areas. Typically, detection of pollutants in urban environments is performed using a variety of techniques, many of which are expensive, require complex setups and are in fixed locations. The novel system presented in this thesis is designed for portable, low cost and in-situ detection of pollutants …

Center Of Pressure And The Projection Of The Time-Course Of Sitting Skill Acquisition, Joshua L. Haworth, Regina T. Harbourne, Srikant Vallabhajosula, Nikolaos Stergiou

Journal Articles

A normal time-course for the acquisition of sitting is essential. A delay in sitting may affect other developmental milestones, resulting in deficiencies in overall skill. Therefore, our aim was to identify variables whose measures at the very beginning of sitting would allow for the projection of the evolution of the sitting skill. Center of pressure data were collected from the postural sway of twenty-six typically developing infants while sitting on a force platform with a beginning ability to sit upright. Spatial, temporal and frequency variables of postural sway were obtained from both the medial/lateral and anterior/posterior directions of sway. Discriminant …

Multiple Sclerosis Alters The Mechanical Work Performed On The Body's Center Of Mass During Gait, Shane R. Wurdeman, Jessie M. Huisinga, Mary Filipi, Nikolaos Stergiou

Journal Articles

Patients with multiple sclerosis (MS) have less-coordinated movements of the center of mass resulting in greater mechanical work. The purpose of this study was to quantify the work performed on the body’s center of mass by patients with MS. It was hypothesized that patients with MS would perform greater negative work during initial double support and less positive work in terminal double support. Results revealed that patients with MS perform less negative work in single support and early terminal double support and less positive work in the terminal double support period. However, summed over the entire stance phase, patients with …

Optimization Problem Formulation For Predicting Knee Muscle And Contact Forces During Gait, Gil Serrancolí, Jonathan P. Walter, Allison Kinney, Benjamin J. Fregly, Josep M. Font-Llagunes

Mechanical and Aerospace Engineering Faculty Publications

The human body has more muscles than degrees of freedom (DOF), which leads to indeterminacy in the muscle force calculation. In this study, an optimization problem to estimate the lower-limb muscle forces during a gait cycle of a patient wearing an instrumented knee prosthesis is formulated. It consists of simulating muscle excitations in a physiological way while muscle parameters are calibrated.

Gait Variablility Is Altered In Older Adults When Listening To Auditory Stimuli With Differing Temporal Structures, Jeffrey P. Kaipust, Denise Mcgrath, Mukul Mukherjee, Nikolaos Stergiou

Journal Articles

Gait variability in the context of a deterministic dynamical system may be quantified using nonlinear time series analyses that characterize the complexity of the system. Pathological gait exhibits altered gait variability. It can be either too periodic and predictable, or too random and disordered, as it is the case with aging. While gait therapies often focus on restoration of linear measures such as gait speed or stride length, we propose that the goal of gait therapy should be to restore optimal gait variability, which exhibits chaotic fluctuations and is the balance between predictability and complexity. In this context, our purpose …

Vascular Occlusion Affects Gait Variability Patterns Of Healthy Younger And Older Individuals, Sara A. Myers, Jason Johanning, Iraklis Pipinos, Kendra K. Schmid, Nikolaos Stergiou

Journal Articles

Insufficient blood flow is one possible mechanism contributing to altered gait patterns in lower extremity peripheral arterial disease (PAD). Previously, our laboratory found that induced occlusion alters gait variability patterns in healthy young individuals. However the effect of age was not explored. The purpose of this study was to account for age by investigating gait variability following induced vascular occlusion in healthy older individuals and to identify amount of change from baseline to post vascular occlusion between younger and older individuals. Thirty healthy younger individuals and 30 healthy older individuals walked on a treadmill during baseline and post vascular occlusion …

Executive Function Orchestrates Regulation Of Task-Relevant Gait Fluctuations, Leslie M. Decker, Fabien Cignetti, Nikolaos Stergiou

Journal Articles

Humans apply a minimum intervention principle to regulate treadmill walking, rapidly correcting fluctuations in the task-relevant variable (step speed: SS) while ignoring fluctuations in the task-irrelevant variables (step time: ST; step length: SL). We examined whether the regulation of fluctuations in SS and not in ST and SL depends on high-level, executive function, processes. Young adults walked on a treadmill without a cognitive requirement and while performing the cognitive task of dichotic listening. SS fluctuations became less anti-persistent when performing dichotic listening, meaning that taxing executive function impaired the ability to rapidly correct speed deviations on subsequent steps. Conversely, performing …

Gait Mechanics Are Different Between Healthy Controls And Patients With Multiple Sclerosis, Jessie M. Huisinga, Kendra K. Schmid, Mary Filipi, Nikolaos Stergiou

Journal Articles

Multiple sclerosis (MS) causes severe gait problems in relatively young individuals, yet there have been limited studies to quantitatively identify the specific gait parameters that are affected. The purpose of this study was to define any differences in biomechanical gait parameters between patients with MS and healthy controls. A total of 31 MS patients and 31 healthy controls were evaluated: joint torques and joint powers were calculated at the ankle, knee, and hip during the stance phase of gait. The self-selected walking velocity was used as a covariate in the analysis to ensure that group differences were not due to …

Temporal Structure Of Variability Reveals Similar Control Mechanisms During Lateral Stepping And Forward Walking, Shane R. Wurdeman, Nikolaos Stergiou

Journal Articles

Previous research exploring a lateral stepping gait utilized amount of variability (i.e. coefficient of variation) in the medial-lateral (ML) and anterior-posterior (AP) direction to propose that the central nervous system’s active control over gait in any direction is dependent on the direction of progression. This study sought to further explore this notion through the study of the temporal structure of variability which is reflective of the neuromuscular system’s organization of the movement over time. The largest Lyapunov exponent (LyE) of the reconstructed attractors for the foot’s movement in the AP and ML was calculated. Results revealed that despite the obvious …

Early Complexity Supports Development Of Motor Behaviors In The First Months Of Life, Stacey C. Dusing, Leroy R. Thacker, Nikolaos Stergiou, James C. Galloway

Journal Articles

Complexity in motor behavior is a hallmark of healthy systems. The purpose of this study was to investigate postural complexity during development of early motor behaviors and under two conditions. Twenty-two infants participated from 1 to 6 months of age. Linear and nonlinear measures of displacement of the center of pressure at the base of support were used to quantify magnitude and temporal structure of postural control. Behavioral coding was used to quantify the emergence of midline head control and early reaching. Results suggest that infants have complexity in postural control strategies early in development. This complexity decreases as infants …

A Home-Based Exercise Program For The Foot And Ankle To Improve Balance, Muscle Performance And Flexibility In Community Dwelling Older Adults: A Pilot Study, Laurel Long, Kurt Jackson, Lloyd L. Laubach

Physical Therapy Faculty Publications

Background and purpose: Strength and range of motion of the foot and ankle have been shown to be related to measures of balance and fall risk in older adults. The primary purpose of this pilot investigation was to evaluate the feasibility of a 6-week home-based exercise program focusing on the foot and ankle and any associated changes in balance, muscle performance and range of motion in older adults. Methods: This single-group repeated measures study involved a convenience sample of 21 healthy communitydwelling older adults age 60-90. Nineteen participants completed all phases of the testing and training. The intervention was a …

New Perspectives In Human Movement Variability, Thurmon Lockhart, Nikolaos Stergiou

Journal Articles

Movement variability is defined as the normal variations that occur in motor performance across multiple repetitions of a task.2 Bernstein1 described movement variability quite eloquently as ‘‘repetition without repetition.’’ Traditionally, movement variability has been linked to noise and error, being considered to be random and independent. This theoretical approach blends well with traditional statistical and assessment methods of movement variability that assume randomness and independence of observations. However, numerous studies have indicated that when movement is observed over time variations are closely related with each other neither being random nor independent. Practically, traditional methods can mask the temporal structure of …

Sitting Postural Control In Infants With Typical Development, Motor Delay, Or Cerebral Palsy, Anastasia Kyvelidou, Regina T. Harbourne, Sandra L. Willett, Nikolaos Stergiou

Journal Articles

Purpose: To determine whether infants born full-term, infants born preterm with motor delays, and infants born preterm who have a diagnosis of cerebral palsy (CP) differed in postural control at the emergence of early sitting.

Methods: Thirty infants born at term who were developing typically, 6 infants born preterm who were later diagnosed with CP, and 5 infants born preterm who were delayed in motor development participated in this study. Center-of-pressure data from unsupported sitting were recorded and analyzed using measures of both amount and temporal organization of center-of-pressure variability.

Results: Infants born full-term, infants born preterm …

Transtibial Amputee Joint Motion Has Increased Attractor Divergence During Walking Compared To Non-Amputee Gait, Shane R. Wurdeman, Sara A. Myers, Nikolaos Stergiou

Journal Articles

The amputation and subsequent prosthetic rehabilitation of a lower leg affects gait. Dynamical systems theory would predict the use of a prosthetic device should alter the functional attractor dynamics to which the system self-organizes. Therefore, the purpose of this study was to compare the largest Lyapunov exponent (a nonlinear tool for assessing attractor dynamics) for amputee gait compared to healthy non-amputee individuals. Fourteen unilateral, transtibial amputees and fourteen healthy, non-amputee individuals ambulated on a treadmill at preferred, self-selected walking speed. Our results showed that the sound hip (p = 0.013), sound knee (p = 0.05), and prosthetic ankle …

Enhancing Fundamental Robot-Assisted Surgical Proficiency By Using A Portable Virtual Simulator, Jung Hung Chien, I. H. Suh, Shi-Huyn Park, Mukul Mukherjee, D. Oleynikov, Ka-Chun Siu

Journal Articles

Background. The development of a virtual reality (VR) training platform provides an affordable interface. The learning effect of VR and the capability of skill transfer from the VR environment to clinical tasks require more investigation.

Methods. Here, 14 medical students performed 2 fundamental surgical tasks—bimanual carrying (BC) and peg transfer (PT)—in actual and virtual environments. Participants in the VR group received VR training, whereas participants in the control group played a 3D game. The learning effect was examined by comparing kinematics between pretraining and posttraining in the da Vinci Surgical System. Differences between VR and playing the 3D game were …

Motor Control Of The Lower Extremity Musculature In Children With Cerebral Palsy, David J. Arpin, Wayne A. Stuberg, Nick Stergiou, Max J. Kurz

Journal Articles

The aim of this investigation was to quantify the differences in torque steadiness and variability of the muscular control in children with cerebral palsy (CP) and typically developing (TD) children. Fifteen children with CP (age = 14.2 ± 0.7 years) that had a Gross Motor Function Classification System (GMFCS) score of I-III and 15 age and gender matched TD children (age = 14.1 ± 0.7 years) participated in this investigation. The participants performed submaximal steady-state isometric contractions with the ankle, knee, and hip while surface electromyography (sEMG) was recorded. An isokinetic dynamometer was used to measure the steady-state isometric torques …

An Informational Algorithm As The Basis For Perception-Action Control Of The Instantaneous Axes Of The Knee, Wangdo Kim, Margarida M. Espanha, António P. Veloso, Duarte Araújo, Filipa João, Luis Carrão, Sean S. Kohles

Mechanical and Materials Engineering Faculty Publications and Presentations

Traditional locomotion studies emphasize an optimization of the desired movement trajectories while ignoring sensory feedback. We propose an information based theory that locomotion is neither triggered nor commanded but controlled. The basis for this control is the information derived from perceiving oneself in the world. Control therefore lies in the human-environment system. In order to test this hypothesis, we derived a mathematical foundation characterizing the energy that is required to perform a rotational twist, with small amplitude, of the instantaneous axes of the knee (IAK). We have found that the joint’s perception of the ground reaction force may be replaced …

A Simple Exoskeleton That Assists Plantarflexion Can Reduce The Metabolic Cost Of Human Walking, Philippe Malcolm, Wim Derave, Samuel Galle, Dirk De Clercq

Journal Articles

Background

Even though walking can be sustained for great distances, considerable energy is required for plantarflexion around the instant of opposite leg heel contact. Different groups attempted to reduce metabolic cost with exoskeletons but none could achieve a reduction beyond the level of walking without exoskeleton, possibly because there is no consensus on the optimal actuation timing. The main research question of our study was whether it is possible to obtain a higher reduction in metabolic cost by tuning the actuation timing.

Methodology/Principal Findings

We measured metabolic cost by means of respiratory gas analysis. Test subjects walked with a simple …

A Comparison Of Upper Extremity Function Between Female Breast Cancer Survivors And Healthy Controls: Typical Self-Report Of Function, Motion, Strength, And Muscular Endurance, Mary Insana Fisher

Physical Therapy Faculty Publications

Many women who have experienced breast cancer (BC) report continued impairments in upper extremity (UE) function beyond the time required for normal healing after surgical treatment. Most research supporting this has not made comparisons between survivors of breast cancer (BCS) to a sample of healthy women. This lack of comparison to a healthy cohort prevents an understanding of whether continued deficits in UE function are due to normal aging or the BC treatment.

The purpose of this research was to compare quality of life (QOL) and UE function among long term breast cancer survivors and similar aged women without cancer. …

Temporal Structure Of Variability Decreases In Upper Extremity Movements Post Stroke, Amit Sethi, Tara Patterson, Theresa Mcguirk, Carolynn Patten, Lorie G. Richards, Nikolaos Stergiou

Journal Articles

Methods: Sixteen participants with chronic stroke and nine age-matched controls performed three trials of functional reach-to-grasp. The amount of variability was quantified by computing the standard deviation of shoulder, elbow, wrist and index finger flexion/extension joint angles. The temporal structure of variability was determined by calculating approximate entropy in shoulder, elbow, wrist and index finger flexion/extension joint angles.

Findings: Individuals with stroke demonstrated greater standard deviations and significantly reduced approximate entropy values as compared to controls. Furthermore, motor impairments and kinematics demonstrated moderate to strong correlations with temporal structure of variability.

Interpretation: Changes in the temporal structure of variability in …

Stroke Survivors Control The Temporal Structure Of Variability During Reaching In Dynamic Environments, Mukul Mukherjee, Panagiotis Koutakis, K.-C. Siu, Pierre B. Fayad, Nikolaos Stergiou

Journal Articles

Learning to control forces is known to reduce the amount of movement variability (e.g., standard deviation; SD) while also altering the temporal structure of movement variability (e.g., approximate entropy; ApEn). Such variability control has not been explored in stroke survivors during reaching movements in dynamic environments. Whether augmented feedback affects such variability control, is also unknown. Chronic stroke survivors, assigned randomly to a control/experimental group, learned reaching movements in a dynamically changing environment while receiving either true feedback of their movement (control) or augmented visual feedback (experimental). Hand movement variability was analyzed using SD and ApEn. A significant change in …

The Appropriate Use Of Approximate Entropy And Sample Entropy With Short Data Sets, Jenna M. Yentes, Nathaniel Hunt, Kendra K. Schmid, Jeffrey P. Kaipust, Denise Mcgrath, Nikolaos Stergiou

Journal Articles

Approximate entropy (ApEn) and sample entropy (SampEn) are mathematical algorithms created to measure the repeatability or predictability within a time series. Both algorithms are extremely sensitive to their input parameters: m (length of the data segment being compared), r (similarity criterion), and N (length of data). There is no established consensus on parameter selection in short data sets, especially for biological data. Therefore, the purpose of this research was to examine the robustness of these two entropy algorithms by exploring the effect of changing parameter values on short data sets. Data with known theoretical entropy qualities as well as experimental …

Changes In The Activation And Function Of The Ankle Plantar Flexor Muscles Due To Gait Retraining In Chronic Stroke Survivors, Brian A. Knarr, Trisha M. Kesar, Darcy S. Reiman, Stuart A. Binder-Macleod

Journal Articles

Background

A common goal of persons post-stroke is to regain community ambulation. The plantar flexor muscles play an important role in propulsion generation and swing initiation as previous musculoskeletal simulations have shown. The purpose of this study was to demonstrate that simulation results quantifying changes in plantar flexor activation and function in individuals post-stroke were consistent with (1) the purpose of an intervention designed to enhance plantar flexor function and (2) expected muscle function during gait based on previous literature.

Methods

Three-dimensional, forward dynamic simulations were created to determine the changes in model activation and function of the paretic ankle …

Role Of Satellite Cells In Long Term Fiber Type Shifts, Honglu Liu

Lewis Honors College Capstone Collection

Muscle fiber type shifts in respect to satellite cells, muscle stem cells, are not well understood currently. The Peterson Lab has generated a mouse model (PAX7-DTA) that ablates satellite cells to determine if these muscle stem cells contribute to mouse muscle fiber type changes over an eight week period. In the study, control and satellite-cell-ablated mouse groups were split into control and overload groups (via synergist ablation surgery) and placed under similar environmental conditions. Eight weeks post-experiment, muscles were dissected to obtain the plantaris muscles of animals from all groups. Muscle cross-sections obtained were immunohistochemically stained, imaged, quantified by fiber …