Life Sciences Commons^™

Original Investigation Correlated Joint Fluctuations Can Influence The Selection Of Steady State Gait Patterns In The Elderly, Max J. Kurz, Nikolaos Stergiou

Journal Articles

This investigation utilized a Markov model to investigate the relationship of correlated lower extremity joint fluctuations and the selection of a steady state gait pattern in the young and elderly. Our model simulated the neuromuscular system by predicting the behavior of the joints for the next gait cycle based on the behavior exhibited in the preceding gait cycles. Such dependencies in the joint fluctuations have been noted previously in the literature. We speculated that compared to the young model, the characteristics of the correlated fluctuations in the elderly model would result in the selection of a different steady state gait …

The Locomotor Kinematics Of Asian And African Elephants: Changes With Speed And Size, John R. Hutchinson, Delf Schwerda, Daniel J. Famini, Robert H.I. Dale, Martin S. Fischer, Rodger Kram

Scholarship and Professional Work - LAS

For centuries, elephant locomotion has been a contentious and confusing challenge for locomotion scientists to understand, not only because of technical difficulties but also because elephant locomotion is in some ways atypical of more familiar quadrupedal gaits. We analyzed the locomotor kinematics of over 2400 strides from 14 African and 48 Asian elephant individuals (body mass 116-4632 kg) freely moving over ground at a 17-fold range of speeds, from slow walking at 0.40 m s^-1 to the fastest reliably recorded speed for elephants, 6.8 m s^-1. These data reveal that African and Asian elephants have some subtle …

In Situ Muscle Power Differs Without Varying In Vitro Mechanical Properties In Two Insect Leg Muscles Innervated By The Same Motor Neuron, Anna N. Ahn, Kenneth Meijer, Robert J. Full

All HMC Faculty Publications and Research

The mechanical behavior of muscle during locomotion is often predicted by its anatomy, kinematics, activation pattern and contractile properties. The neuromuscular design of the cockroach leg provides a model system to examine these assumptions, because a single motor neuron innervates two extensor muscles operating at a single joint. Comparisons of the in situ measurements under in vivo running conditions of muscle 178 to a previously examined muscle (179) demonstrate that the same inputs (e.g. neural signal and kinematics) can result in different mechanical outputs. The same neural signal and kinematics, as determined during running, can result in different mechanical functions, …

Optimal Movement Variability: A New Theoretical Perspective For Neurologic Physical Therapy, Nikolaos Stergiou, Regina T. Harbourne, James T. Cavanaugh

Journal Articles

Variability is a natural and important feature of human movement. Using existing theoretical frameworks as a foundation, we propose a new model to explain movement variability as it relates to motor learning and health. We contend that mature motor skills and healthy states are associated with an optimal amount of movement variability. This variability also has form and is characterized by a chaotic structure. Less than optimal movement variability characterizes biological systems that are overly rigid and unchanging, whereas greater than optimal variability characterizes systems that are noisy and unstable. Both situations characterize systems that are less adaptable to perturbations, …

Statistical Approach To Background Subtraction For Production Of High-Quality Silhouettes For Human Gait Recognition, Jennifer J. Samler

Theses and Dissertations

This thesis uses a background subtraction to produce high-quality silhouettes for use in human identification by human gait recognition, an identification method which does not require contact with an individual and which can be done from a distance. A statistical method which reduces the noise level is employed resulting in cleaner silhouettes which facilitate identification. The thesis starts with gathering video data of individuals walking normally across a background scene. From there the video is converted into a sequence of images that are stored as joint photographic experts group (jpeg) files. The background is subtracted from each image using a …

Robotic Surgery And Training: Electromyographic Correlates Of Robotic Laparoscopic Training, Timothy N. Judkins, D. Oleynikov, N. Karazaki, Nikolaos Stergiou

Journal Articles

Background: Robotic laparoscopic surgery has been shown to decrease task completion time, reduce errors, and decrease training time when compared to manual laparoscopic surgery. However, current literature has not addressed physiological effects, in particular muscle responses, to training with a robotic surgical system. We seek to determine the frequency response of electromyographic (EMG) signals of specific arm and hand muscles with training using the da Vinci Surgical System (dVSS).

Methods: Seven right-handed medical students were trained in three tasks with da Vinci Surgical System over four weeks. These subjects, along with eight controls, were tested before and after …

Hper Biomechanics Laboratory 2005 Annual Report, Issue 4, Nebraska Biomechanics Core Facility

Biomechanics Annual Report

This issue features Dr. Stergiou Receives a K25 Award from the National Institutes of Health, Training Methods to Improve Robotic Laparoscopic Surgery, Progress Update for Federal Grant: The Development of Sitting Posture in Children with Cerebral Palsy, Pioneering Gait Analysis Research, Collaboration with UNMC Department of Surgery and VA Hospital: The Effects of Peripheral Arterial Disease on Gait, Sabbatical Strengthened Collaborations in Orthopedics, Computer Modeling with Dynamic Toys Reveals Human Gait Patterns, Prestigious Awards to Dr. Stergiou, Teachers Enriched During Final Year of Banneker 2000, New Staff Joins the HPER Biomechanics Laboratory, Noteworthy Events, Internationally Recognized Bioengineer Visited HPER Biomechanics …

Follow-Up Evaluation 2 Years After Acl Reconstruction With Bone–Patellar Tendon–Bone Graft Shows That Excessive Tibial Rotation Persists, Stavros Ristanis, Nikolaos Stergiou, Kostas Patras, Elias Tsepis, Constantina O. Moraiti, Anastasios D. Georgoulis

Journal Articles

Objective: To investigate in vivo if the increased tibial rotation found in anterior cruciate ligament (ACL)-deficient patients before surgery is restored 2 years after the reconstruction, during 2 high-demanding activities.

Design: Prospective follow-up study.

Setting: A gait analysis laboratory.

Participants: Nine subjects with unilateral ACL rupture, reconstructed with a bone–patellar tendon–bone (BPTB) graft, and 10 healthy control subjects.

Interventions: All the ACL-deficient patients underwent a unilateral ACL reconstruction after prereconstruction data acquisition.

Main Outcome Measurements: Using a 6-camera motion analysis system, kinematics were collected as subjects (1) descended from a stair and, after foot …

A Novel Approach To Measure Variability In The Anterior Cruciate Ligament Deficient Knee During Walking: The Use Of The Approximate Entropy In Orthopaedics, Anastasios D. Georgoulis, Constantina O. Moraiti, Stavros Ristanis, Nikolaos Stergiou

Journal Articles

Objective. The evaluation of variability of biological rhythmic activities through measures such as Approximate Entropy (ApEn) has provided important information regarding pathology in disciplines such as cardiology and neurology. This research lead to the “loss of complexity hypothesis” where decreased variability is associated with loss of healthy flexibility rendering the system more rigid and unable to adapt to stresses. ApEn as a measure of variability and complexity, correlates well with pathology while, in some cases, it is predictive of subsequent clinical changes. The study of human gait could benefit from the application of ApEn since it is also a …

The Effect Of Leg Muscle Activation State And Localized Muscle Fatigue On Tibial Response During Impact, Adriana M. Holmes, David M. Andrews

Human Kinetics Publications

The purpose of this research was to examine the effects of voluntarily manipulating muscle activation and localized muscle fatigue on tibial response parameters, including peak tibial acceleration, time to peak tibial acceleration, and the acceleration slope, measured at the knee during unshod heel impacts. A human pendulum delivered consistent impacts to 15 female and 15 male subjects. The tibialis anterior and lateral gastrocnemius were examined using electromyography, thus allowing voluntary contraction to various activation states (baseline, 15%, 30%, 45%, and 60% of the maximum activation state) and assessing localized muscle fatigue. A skin-mounted uniaxial accelerometer, preloaded medial to the tibial …

Recovery Of Postural Control After Cerebral Concussion: New Insights Using Approximate Entropy, James T. Cavanaugh, Kevin M. Guskiewicz, Carol Giuliani, Stephen Marshall, Vicki S. Mercer, Nikolaos Stergiou

Journal Articles

Context: The return-to-play decision after sport-related cerebral concussion depends in part on knowing when an athlete has fully recovered postural control after injury.

Objective: To describe the postconcussion recovery of postural control using approximate entropy (ApEn), a regularity statistic from nonlinear dynamics.

Design: Retrospective case series analysis.

Setting: Sports medicine research laboratory.

Patients or Other Participants: Collegiate athletes from whom center-of-pressure and symptom data were collected at preseason, less than 48 hours after injury, and 48 to 96 hours after injury.

Main Outcome Measure(s): Approximate entropy values reflecting the amount of randomness contained in center-of-pressure oscillations were calculated for anterior-posterior …

Sight-Reading Versus Repertoire Performance On The Piano: A Case Study Using High-Speed Motion Analysis, Brenda Wristen, Sharon Evans, Nikolaos Stergiou

Journal Articles

The purpose of the study was to examine whether differences exist in the motions employed by pianists when they are sight-reading versus performing repertoire and determine whether these differences could be quantified using high speed motion capture technology. A secondary question of interest was whether or not an improvement in the efficiency of motion could be observed between two sight-reading trials of the same musical excerpt. This case study employed a six digital infrared camera system (Motion Analysis, Inc.) to capture the motion of pianists playing two trials of a repertoire piece and two trials of a sight-reading excerpt. Angular …

An Improved Surrogate Method For Detecting The Presence Of Chaos In Gait, David J. Miller, Nikolaos Stergiou, Max J. Kurz

Journal Articles

It has been suggested that the intercycle variability present in the time series of biomechanical gait data is of chaotic nature. However, the proper methodology for the correct determination of whether intercycle fluctuations in the data are deterministic chaos or random noise has not been identified. Our goal was to evaluate the pseudoperiodic surrogation (PPS) [Small et al., 2001. Surrogate test for pseudoperiodic time series data. Physical Review Letters 87(18), 188,101–188,104], and the surrogation algorithms of Theiler et al. [1992. Testing for nonlinearity in time series: the method of surrogate data. Physica D 58(1–4), 77–94] and of Theiler and Rapp …