Biomechanics Commons^™

On The Choice Of Multiscale Entropy Algorithm For Quantification Of Complexity In Gait Data, Peter C. Raffalt, William Denton, Jennifer M. Yentes

Journal Articles

The present study aimed at identifying a suitable multiscale entropy (MSE) algorithm for assessment of complexity in a stride-to-stride time interval time series. Five different algorithms were included (the original MSE, refine composite multiscale entropy (RCMSE), multiscale fuzzy entropy, generalized multiscale entropy and intrinsic mode entropy) and applied to twenty iterations of white noise, pink noise, or a sine wave with added white noise. Based on their ability to differentiate the level of complexity in the three different generated signal types, and their sensitivity and parameter consistency, MSE and RCMSE were deemed most appropriate. These two algorithms were applied to …

Reliability Of Center Of Pressure Measures For Assessing The Development Of Sitting Postural Control Through The Stages Of Sitting, Jordan Wickstrom, Nicholas Stergiou, Anastasia Kyvelidou

Journal Articles

Cerebral palsy (CP) impairs an individual’s ability to move and control one’s posture. Unfortunately, the signs and symptoms of CP may not be apparent before age two. Evaluating sitting posture is a potential way to assess the developing mechanisms that contribute to CP. The purpose of this project was to determine the reliability of linear and nonlinear measures, including inter- and intrastage reliability, when used to analyze the center of pressure (COP) time series during the stages of sitting development in children with typical development (TD) and with/at-risk for cerebral palsy (CP). We hypothesized that nonlinear tools would be more …

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 …

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 …

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 …

Prosthesis Preference Is Related To Stride-To-Stride Fluctuations At The Prosthetic Ankle, Shane R. Wurdeman, Sara A. Myers, Adam L. Jacobsen, Nikolaos Stergiou

Journal Articles

The purpose of this study was to determine the relationship between stride-to-stride fluctuations and prosthesis preference. Thirteen individuals with unilateral, transtibial amputation consented to participate. Individuals walked on a treadmill for 3 min with their prescribed and an alternate prosthesis. Stride-to-stride fluctuations were quantified with the largest Lyapunov exponent (LyE) of each joint flexion/extension time series. The change in the LyE was calculated for each major lower-limb joint for both conditions. Participants indicated preference between the prostheses on a continuous visual analog scale. The change in the LyE was correlated with the degree of preference between the two prostheses at …

Gait Variability Measures Reveal Differences Between Multiple Sclerosis Patients And Healthy Controls, Jeffrey P. Kaipust, Jessie M. Huisinga, Mary Filipi, Nikolaos Stergiou

Journal Articles

The purpose of this study was to determine the differences in gait variability between patients with multiple sclerosis (MS) and healthy controls during walking at a self-selected pace. Methods: Kinematics were collected during three minutes of treadmill walking for 10 patients with MS and 10 healthy controls. The Coefficient of Variation (CoV), the Approximate Entropy (ApEn) and the Detrended Fluctuation Analysis (DFA) were used to investigate the fluctuations present in stride length and step width from continuous strides. Results: ApEn revealed that patients with MS had significantly lower values than healthy controls for stride length (p < .001) and step width (p < .001). Conclusions: ApEn results revealed that the natural fluctuations present during gait in the stride length and step width time series are more regular and repeatable in patients with MS. These changes implied that patients with MS may exhibit reduced capacity to adapt and respond to perturbations during gait.

Reliability Of Center Of Pressure Measures For Assessing The Development Of Sitting Postural Control In Infants With Or At Risk Of Cerebral Palsy, Anastasia Kyvelidou, Regina T. Harbourne, Valerie K. Shostrom, Nikolaos Stergiou

Journal Articles

Objective

To establish the test-retest reliability of linear and nonlinear measures, including intra- and intersession reliability, when used to analyze the center of pressure (COP) time series during the development of infant sitting postural control in infants with or at risk for cerebral palsy (CP).

Design

Longitudinal study.

Setting

University hospital laboratory.

Participants

Infants with or at risk for CP (N=18; mean age ± SD at entry into the study, 13.7±3.6mo).

Interventions

Not applicable.

Main Outcome Measures

Infant sitting COP data were recorded for 3 trials at each session (2 sessions for each month within 1 week) for 4 consecutive …

Reliability Of Center Of Pressure Measures For Assessing The Development Of Sitting Postural Control, Anastasia Kyvelidou, Regina T. Harbourne, Wayne A. Stuberg, Junfeng Sun, Nikolaos Stergiou

Journal Articles

Objectives: To determine the reliability of linear and nonlinear tools, including intrasession and intersession reliability, when used to analyze the center of pressure (COP) time series during the development of infant sitting postural control.

Design: Longitudinal study.

Setting: University hospital laboratory.

Participants: Typically developing infants (N33; mean SD age at entry in the study, 152.417.6d).

Interventions: Not applicable.

Main Outcome Measures: Infants were tested twice in 1 week at each of the 4 months of the study. Sitting COP data were recorded for 3 trials at each session (2 each month within 1 week). …

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 Aging Human Neuromuscular System Expresses Less Certainty For Selecting Joint Kinematics During Gait, Max J. Kurz, Nikolaos Stergiou

Journal Articles

This investigation quantitatively characterized the certainty of the aging neuromuscular system in selecting a joint range of motion during gait based on the statistical concept of entropy. Elderly and young control groups walked on a treadmill at a self-selected pace. Joint angles were calculated for the ankle, knee and hip. We hypothesized that the aging group would exhibit less certainty in selecting a joint range of motion during gait. Our results supported this hypothesis, and indicated that aged individuals demonstrated statistically less certainty for the knee (16.8%) and hip (24.6%). We suggest that neurophysiological changes associated with aging may result …

Nonlinear Dynamics Indicates Aging Affects Variability During Gait, Ugo H. Buzzi, Nikolaos Stergiou, Max J. Kurz, Patricia A. Hageman, Jack Heidel

Journal Articles

Objective. To investigate the nature of variability present in time series generated from gait parameters of two different age groups via a nonlinear analysis.

Design. Measures of nonlinear dynamics were used to compare kinematic parameters between elderly and young females.

Background. Aging may lead to changes in motor variability during walking, which may explain the large incidence of falls in the elderly.

Methods. Twenty females, 10 younger (20–37 yr) and 10 older (71–79 yr) walked on a treadmill for 30 consecutive gait cycles. Time series from selected kinematic parameters of the right lower extremity were analyzed using nonlinear dynamics. The …