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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 …

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, …

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 …

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 …

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 …