Biomechanics Commons^™

Joint Kinetics Of The Ankle And Knee When Running Over Obstacles, Alan Hreljac, Nikolaos Stergiou, Shane D. Scholten

Journal Articles

When running over obstacles of increasing height, heelstrike runners switch to a forefoot landing pattern once a critical obstacle height is reached. The primary purpose of this study was to determine whether ankle or knee joint kinetic variables trigger the gait change from a heelstrike to a forefoot striking pattern as obstacle height increases. Ten subjects were filmed from the sagittal plane as they ran at their preferred running speed over a force platform during six obstacle height conditions ranging from 10% to 22.5% of standing height, as well as an additional baseline condition with no obstacle (0%). An inverse …

A Nonlinear Dynamic Approach For Evaluating Postural Control, James T. Cavanaugh, Kevin M. Guskiewicz, Nikolaos Stergiou

Journal Articles

Recent research suggests that traditional biomechanical models of postural stability do not fully characterise the nonlinear properties of postural control. In sports medicine, this limitation is manifest in the postural steadiness assessment approach, which may not be sufficient for detecting the presence of subtle physiological change after injury. The limitation is especially relevant given that return-to-play decisions are being made based on assessment results. This update first reviews the theoretical foundation and limitations of the traditional postural stability paradigm. It then offers, using the clinical example of athletes recovering from cerebral concussion, an alternative theoretical proposition for measuring changes in …

Excessive Tibial Rotation During High-Demand Activities Is Not Restored By Anterior Cruciate Ligament Reconstruction, Stavros Ristanis, Nikolaos Stergiou, Kostas Patras, Haris S. Vasiliadis, Giannis Giakas, Anastasios D. Georgoulis

Journal Articles

Purpose: Recent in vitro research has suggested that anterior cruciate ligament (ACL) reconstruction does not restore control of tibial rotation. The purpose of this study was to explore these findings in vivo and investigate rotational knee stability during landing and subsequent pivoting. Such an activity places higher demands on the knee, almost similar to those found during high-level sports.

Type of Study: Case control series study.

Methods: We assessed 11 patients who had undergone ACL reconstruction with the same arthroscopic technique using a bone–patellar tendon–bone graft, 11 ACL-deficient subjects who had sustained the injury more than 1 year prior to …

Functional Electric Stimulation Cycle Ergometry Training Effect On Lower Limb Muscles In Acute Sci Individuals, Timothy J. Demchak, Jon K. Linderman, W. Jerry Mysiw, Rebecca Jackson, Jihong Sunn, Steven T. Devor

Health and Sport Science Faculty Publications

The purpose of this study was to compare three different intervals for a between sets rest period during a common isokinetic knee extension strength-testing protocol of twenty older Brazilian men (66.30 ± 3.92 yrs). The volunteers underwent unilateral knee extension (Biodex System 3) testing to determine their individual isokinetic peak torque at 60, 90, and 120° ·s-1. The contraction speeds and the rest periods between sets (30, 60 and 90 s) were randomly performed in three different days with a minimum rest period of 48 hours. Significant differences between and within sets were analyzed using a One Way Analysis of …

An Artificial Neural Network That Utilizes Hip Joint Actuations To Control Bifurcations And Chaos In A Passive Dynamic Bipedal Walking Model, Max J. Kurz, Nikolaos Stergiou

Journal Articles

Chaos is a central feature of human locomotion and has been suggested to be a window to the control mechanisms of locomotion. In this investigation, we explored how the principles of chaos can be used to control locomotion with a passive dynamic bipedal walking model that has a chaotic gait pattern. Our control scheme was based on the scientific evidence that slight perturbations to the unstable manifolds of points in a chaotic system will promote the transition to new stable behaviors embedded in the rich chaotic attractor. Here we demonstrate that hip joint actuations during the swing phase can provide …

Electromechanical Delay Of The Knee Extensor Muscles Is Not Altered After Harvesting The Patellar Tendon As A Graft For Acl Reconstruction: Implications For Sports Performance, Anastasios D. Georgoulis, Stavros Ristanis, Anastasios Papadonikolakis, Elias Tsepis, U. Moebius

Journal Articles

Although the scar tissue, which heals the donor site defect, has different elasticity from the neighbouring patellar tissue, it remains unclear if this scar tissue can lead to the changes of the electromechanical delay (EMD) of the knee extensor muscles. If such changes do exist, they can possibly affect both the utilization of the stored energy in the series elastic component, as well as the optimal performance of the knee joint movement. The purpose of this study was to investigate the influence of harvesting the patellar tendon during anterior cruciate ligament (ACL) reconstruction and the associated patellar tendon scar tissue …

Anterior Cruciate Ligament Reconstruction With A Quadrupled Hamstring Autograft Does Not Restore Tibial Rotation, Anastasios D. Georgoulis, Stavros Ristanis, Vasilis Chouliaras, Constantina O. Moraiti, Nikolaos Stergiou

Journal Articles

As a result of the morbidity associated with anterior cruciate ligament (ACL) reconstruction with a bone–patellar–tendon– bone graft, many orthopaedic surgeons prefer hamstrings as the graft for ACL reconstruction. However, this selection is not based on solid scientific evidence. In vitro research shows that this graft cannot restore control of tibial rotation. Our recent in vivo research work has also demonstrated the same result. In particular, patients undergoing ACL repair who were reconstructed with a quadrupled hamstring tendon graft showed excessive tibial rotation during a dynamic activity when compared with healthy control subjects. Although the hamstring tendon graft has a …

Using Three Dimensional Motion Capture Technology To Describe And Assess Piano Technique: A Case Study, Brenda Wristen, Nikolaos Stergiou, Sharon Evans

Health and Kinesiology Faculty Proceedings & Presentations

The purpose of the study was to examine any differences that exist in the quality of motions employed by pianists when they are sight-reading versus performing repertoire. 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. While data analysis for the full study is ongoing, the following results from a case study are illustrative.

The Influence Of Landing Technique Versus Technique And Strength Training On Valgus Knee Deformity In Females, Kirsten R. Holmes

Masters Theses

The purpose of this study was to evaluate the effectiveness of landing technique training versus landing technique and plyometric/strength training program on knee valgus during landing in females. Subjects participated in a 6-week training program. A 2 X 3 repeated measures ANOVA with two within subjects’ factors Test and Group was used to test for differences in the knee valgus angle in the landing condition and the five jump condition. A 2 x 2 repeated measures ANOVA with two within subjects’ factors, was used to test for difference in knee extension strength and knee flexion strength. Pre-test knee-valgus 4.76 ± …

Using Three Dimensional Motion Capture Technology To Describe And Assess Piano Technique: A Case Study, Brenda Wristen, Nikolaos Stergiou, Sharon Evans

Journal Articles

The purpose of the study was to examine any differences that exist in the quality of motions employed by pianists when they are sight-reading versus performing repertoire. 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. While data analysis for the full study is ongoing, the following results from a case study are illustrative.

The Effect Of Anterior Cruciate Ligament Recontruction On Lower Extremity Relative Phase Dynamics During Walking And Running, Max J. Kurz, Nikolaos Stergiou, Ugo H. Buzzi, Anastasios D. Georgoulis

Journal Articles

The purpose of this investigation was to use relative phase dynamics to evaluate gait in individuals with a reconstructed anterior cruciate ligament (ACL) during walking and running. Relative phase dynamics can describe the coordination strategies between the interacting segments at the lower extremity. Ten subjects who had undergone ACL reconstruction using the central third of their patellar tendon and ten healthy controls walked and ran on a treadmill at a self-selected pace. Relative phase dynamics were calculated for the foot–shank and shank–thigh coordinative relation- ships. Statistical differences between the groups were noted for the foot– shank relationship (p<0.05) during both walking and running and for the shank–thigh relationship (p<0.05) during walking. Our results indicate that current ACL reconstructive techniques may result in altered relative phase dynamics. These changes in relative phase dynamics could be related to a loss of sensory information about joint position and velocity that is typically provided by the intact ACL. Additionally, relative phase adaptations could be a learned response from the early stages of postsurgical rehabilitation. Relative phase dynamics provide quantitative information about the dynamic status of the ACL-reconstructed knee that cannot be gained from the conventional time-series evaluation of gait analysis data. Relative phase dynamics measures should supplement the conventional gait analysis measures that are used today for the clinical evaluation of the functional dynamic stability of the reconstructed knee. The examination of relative phase dynamics could be clinically important for the quantification of new ACL surgical interventions and of patient performance at various stages of rehabilitation. Further research should incorporate relative phase dynamics to understand the influence of ACL reconstruction on coordination and functional patient outcomes.

Hper Biomechanics Laboratory 2004 Annual Report: A Surveillance Of The Neuromuscular System, Issue 3, Nebraska Biomechanics Core Facility

Biomechanics Annual Report

This issue features 2004 - A Great Year for External Funding: Three Grants Awarded to Dr. Stergiou, Robotic Surgery Research is Funded by the Nebraska Research Initiative, Federal Grant is Awarded for the Study of the Development of Posture in Children with Cerebral Palsy, The Nebraska Research Initiative funds our Innovative Research in Gait Analysis, Collaboration with the Department of Surgery of the University of Nebraska Medical Center on the Effects of Peripheral Arterial Disease on Gait, Omaha Media Features Nicholas Stergiou, Dr. Stergiou participates in an NIH Review Panel, Prestigious Teaching Award for Dr. Stergiou, NASA Visits HPER Biomechanics …

Baseline Measures Are Altered In Biomechanical Studies, Nikolaos Stergiou, Melissa Scott

Journal Articles

The purpose of this investigation was to examine if baseline measures are altered between conditions in biomechanical studies and to determine the need for baseline measurements in biomechanics. Ten runners were asked to run at varying speeds and obstacle heights. Baseline measures were acquired between all conditions. Right lower extremity kinematic and kinetic data were collected for all baseline trials and evaluated by both a group and a single subject analysis. The group analysis revealed significant differences between baselines only for the obstacle perturbation. The single subject analysis indicated that baseline measures are altered in a greater degree for kinematics …

Detecting Altered Postural Control After Cerebral Concussion In Athletes With Normal Postural Stability, James T. Cavanaugh, Kevin M. Guskiewicz, Carol Giuliani, Stephen Marshall, Vicki S. Mercer, Nikolaos Stergiou

Journal Articles

Objective: To determine if approximate entropy (ApEn), a regularity statistic from non-linear dynamics, could detect changes in postural control during quiet standing in athletes with normal postural stability after cerebral concussion.

Methods: The study was a retrospective, case series analysis of centre of pressure (COP) data collected during the Sensory Organization Test (SOT) from NCAA Division I (USA) athletes prior to and within 48 h after injury. Subjects were 21 male and six female athletes from a variety of sports who sustained a cerebral concussion between 1997 and 2003. After injury, athletes displayed normal postural stability equivalent to preseason levels. …

Robotic Surgery Training And Performance, Kenji Narazaki, D. Oleynikov, Nikolaos Stergiou

Journal Articles

Background: To understand the process of skill acquisition in robotic surgery and to allow useful real-time feedback to surgeons and trainees in future generations of robotic surgical systems, robotic surgical skills should be determined with objective variables. The aim of this study was to assess skill acquisition through a training protocol, and to identify variables for the quantification of proficiency.

Methods: Seven novice users of the da Vinci Surgical System engaged in 4 weeks of training that involved practicing three bimanual tasks with the system. Seven variables were determined for assessing speed of performance, bimanual coordination, and muscular activation. These …

A Template For The Exploration Of Chaotic Locomotive Patterns, Max J. Kurz, Nikolaos Stergiou, Jack Heidel, E. Terry Foster

Journal Articles

Inverted pendulum and spring-mass models have been successfully used to explore the dynamics of the lower extremity for animal and human locomotion. These models have been classified as templates that describe the biomechanics of locomotion. A template is a simple model with all the joint complexities, muscles and neurons of the locomotor system removed. Such templates relate well to the observed locomotive patterns and provide reference points for the development of more elaborate dynamical systems. In this investigation, we explored if a passive dynamic double pendulum walking model, that walks down a slightly sloped surface (γγ was increased, …

Mechanical Properties Of The Integument Of The Common Gartersnake, Thamnophis Sirtalis (Serpentes: Colubridae), Gabriel Rivera, Alan H. Savitzky, Jeffrey A. Hinkley

Biological Sciences Faculty Publications

The evolution of the ophidian feeding mechanism has involved substantial morphological restructuring associated with the ability to ingest relatively large prey. Previous studies examining the morphological consequences of macrophagy have concentrated on modifications of the skull and cephalic musculature. Although it is evident that macrophagy requires highly compliant skin, the mechanical properties of the ophidian integument have received limited attention, particularly in the context of feeding. We examined mechanical properties of skin along the body axis in Thamnophis sirtalis (Colubridae). Data were collected from tensile tests and were analyzed using a multivariate analysis of variance (MANOVA) and post-hoc multiple comparison …

Body-Induced Vortical Flows: A Common Mechanism For Self-Corrective Trimming Control In Boxfishes, Ian K. Bartol, Morteza Gharib, Paul W. Webb, Daniel Weihs, Malcolm S. Gordon

Biological Sciences Faculty Publications

Boxfishes (Teleostei: Ostraciidae) are marine fishes having rigid carapaces that vary significantly among taxa in their shapes and structural ornamentation. We showed previously that the keels of the carapace of one species of tropical boxfish, the smooth trunkfish, produce leading edge vortices (LEVs) capable of generating self-correcting trimming forces during swimming. In this paper we show that other tropical boxfishes with different carapace shapes have similar capabilities. We conducted a quantitative study of flows around the carapaces of three morphologically distinct boxfishes (spotted boxfish, scrawled cowfish and buffalo trunkfish) using stereolithographic models and three separate but interrelated analytical …

Medicine Meets Virtual Reality 14, James D. Westwood, Timothy N. Judkins, D. Oleynikov, Nikolaos Stergiou

Faculty Books and Monographs

Chapter, Real-Time Augmented Feedback Benefits Robotic Laparoscopic Training, co-authored by Nicholas Steriou, UNO faculty member.

Machine intelligence will eclipse human intelligence within the next few decades - extrapolating from Moore’s Law - and our world will enjoy limitless computational power and ubiquitous data networks. Today’s iPod® devices portend an era when biology and information technology will fuse to create a human experience radically different from our own. Already, our healthcare system now appears on the verge of crisis; accelerating change is part of the problem. Each technological upgrade demands an investment of education and money, and a costly infrastructure more …

Three-Dimensional Kinematics Of The Tibiofemoral Joint In Acl-Deficient And Reconstructed Patients Shows Increased Tibial Rotation, Anastasios D. Georgoulis, Stavros Ristanis, Constantina O. Moraiti, Argyris Mitsou, Manfred Bernard, Nikolaos Stergiou

Journal Articles

The study of the altered knee joint movement patterns that follow anterior cruciate ligament (ACL) rupture can be very insightful in the development of prevention and therapeutic strategies concerning this injury. This can be achieved through three-dimensional kinematic analysis, because it provides an objective evaluation in vivo of the knee joint function. It has been demonstrated that ACL-deficient patients develop functional adaptations (ie, quadriceps avoidance gait) and walk with the knee in a more extended position to compensate for the ACL loss. Furthermore, it has been shown that ACL rupture results in anterior tibial translation and excessive tibial rotation while …