Physical Therapy Commons^™

Different Biomechanical Variables Explain Within-Subjects Versus Between-Subjects Variance In Step Length Asymmetry Post-Stroke, Natalia Sánchez, Nicolas Schweighofer, James M. Finley

Physical Therapy Faculty Articles and Research

Step length asymmetry (SLA) is common in most stroke survivors. Several studies have shown that factors such as paretic propulsion can explain between-subjects differences in SLA. However, whether the factors that account for between-subjects variance in SLA are consistent with those that account for within subjects, stride-by-stride variance in SLA has not been determined. SLA direction is heterogeneous, and different impairments likely contribute to differences in SLA direction. Here, we identified common predictors between-subjects that explain within-subjects variance in SLA using sparse partial least squares regression (sPLSR). We determined whether the SLA predictors differ based on SLA direction and whether …

Using Biofeedback To Reduce Spatiotemporal Asymmetry Impairs Dynamic Balance In People Post-Stroke, Sungwoo Park, Chang Liu, Natalia Sánchez, Julie K. Tilson, Sara J. Mulroy, James M. Finley

Physical Therapy Faculty Articles and Research

Background. People poststroke often walk with a spatiotemporally asymmetric gait, due in part to sensorimotor impairments in the paretic lower extremity. Although reducing asymmetry is a common objective of rehabilitation, the effects of improving symmetry on balance are yet to be determined. Objective. We established the concurrent validity of whole-body angular momentum as a measure of balance, and we determined if reducing step length asymmetry would improve balance by decreasing whole-body angular momentum. Methods. We performed clinical balance assessments and measured wholebody angular momentum during walking using a full-body marker set in a sample of 36 people with …

Lost In Translation: Simple Steps In Experimental Design Of Neurorehabilitation-Based Research Interventions To Promote Motor Recovery Post-Stroke, Natalia Sánchez, Carolee J. Winstein

Physical Therapy Faculty Articles and Research

Stroke continues to be a leading cause of disability. Basic neurorehabilitation research is necessary to inform the neuropathophysiology of impaired motor control, and to develop targeted interventions with potential to remediate disability post-stroke. Despite knowledge gained from basic research studies, the effectiveness of researchbased interventions for reducing motor impairment has been no greater than standard of practice interventions. In this perspective, we offer suggestions for overcoming translational barriers integral to experimental design, to augment traditional protocols, and re-route the rehabilitation trajectory toward recovery and away from compensation. First, we suggest that researchers consider modifying task practice schedules to focus on …

Neural Constraints Affect The Ability To Generate Hip Abduction Torques When Combined With Hip Extension Or Ankle Plantarflexion In Chronic Hemiparetic Stroke, Natalia Sánchez, Ana M. Acosta, Roberto López-Rosado, Julius P. A. Dewald

Physical Therapy Faculty Articles and Research

Stroke lesions interrupt descending corticofugal fibers that provide the volitional control of the upper and lower extremities. Despite the evident manifestation of movement impairments post-stroke during standing and gait, neural constraints in the ability to generate joint torque combinations in the lower extremities are not yet well determined. Twelve chronic hemiparetic participants and 8 age-matched control individuals participated in the present study. In an isometric setup, participants were instructed to combine submaximal hip extension or ankle plantarflexion torques with maximal hip abduction torques. Statistical analyses were run using linear mixed effects models. Results for the protocol combining hip extension and …

Cortical Contribution To Linear, Non-Linear And Frequency Components Of Motor Variability Control During Standing, Niklas König Ignasiak

Physical Therapy Faculty Articles and Research

Motor variability is an inherent feature of all human movements and reflects the quality of functional task performance. Depending on the requirements of the motor task, the human sensory-motor system is thought to be able to flexibly govern the appropriate level of variability. However, it remains unclear which neurophysiological structures are responsible for the control of motor variability. In this study, we tested the contribution of cortical cognitive resources on the control of motor variability (in this case postural sway) using a dual-task paradigm and furthermore observed potential changes in control strategy by evaluating Ia-afferent integration (H-reflex). Twenty healthy subjects …

Lower Extremity Motor Impairments In Ambulatory Chronic Hemiparetic Stroke: Evidence For Lower Extremity Weakness And Abnormal Muscle And Joint Torque Coupling Patterns, Natalia Sánchez, Ana Maria Acosta, Roberto Lopez-Rosado, Arno H. A. Stienen, Julius P. A. Dewald

Physical Therapy Faculty Articles and Research

Although global movement abnormalities in the lower extremity poststroke have been studied, the expression of specific motor impairments such as weakness and abnormal muscle and joint torque coupling patterns have received less attention. We characterized changes in strength, muscle coactivation and associated joint torque couples in the paretic and nonparetic extremity of 15 participants with chronic poststroke hemiparesis (age 59.6 ± 15.2 years) compared with 8 age-matched controls. Participants performed isometric maximum torques in hip abduction, adduction, flexion and extension, knee flexion and extension, ankle dorsi- and plantarflexion and submaximal torques in hip extension and ankle plantarflexion. Surface electromyograms (EMGs) …

The Motor Cortical Representation Of A Muscle Is Not Homogeneous In Brain Connectivity, Jo Armour Smith, Alaa Albishi, Sarine Babikian, Skulpan Asavasopon, Beth E. Fisher, Jason Kutch

Physical Therapy Faculty Articles and Research

Functional connectivity patterns of the motor cortical representational area of single muscles have not been extensively mapped in humans, particularly for the axial musculature. Functional connectivity may provide a neural substrate for adaptation of muscle activity in axial muscles that have both voluntary and postural functions. The purpose of this study was to combine brain stimulation and neuroimaging to both map the cortical representation of the external oblique (EO) in primary motor cortex (M1) and supplementary motor area (SMA), and to establish the resting-state functional connectivity associated with this representation. Motor evoked potentials were elicited from the EO muscle in …

Role Of Corpus Callosum Integrity In Arm Function Differs Based On Motor Severity After Stroke, Jill Campbell Stewart, Pritha Dewanjee, George Tran, Erin Burke Quinlan, Lucy Dodakian, Alison Mckenzie, Jill See, Steven C. Cramer

Physical Therapy Faculty Articles and Research

While the corpus callosum (CC) is important to normal sensorimotor function, its role in motor function after stroke is less well understood. This study examined the relationship between structural integrity of the motor and sensory sections of the CC, as reflected by fractional anisotropy (FA), and motor function in individuals with a range of motor impairment level due to stroke. Fifty-five individuals with chronic stroke (Fugl-Meyer motor score range 14 to 61) and 18 healthy controls underwent diffusion tensor imaging and a set of motor behavior tests. Mean FA from the motor and sensory regions of the CC and from …

What Is The Contribution Of Ia-Afference For Regulating Motor Output Variability During Standing?, Niklas König Ignasiak

Physical Therapy Faculty Articles and Research

Motor variability is an inherent feature of all human movements, and describes the system‘s stability and rigidity during the performance of functional motor tasks such as balancing. In order to ensure successful task execution, the nervous system is thought to be able to flexibly select the appropriate level of variability. However, it remains unknown which neurophysiological pathways are utilized for the control of motor output variability. In responding to natural variability (in this example sway), it is plausible that the neuro-physiological response to muscular elongation contributes to restoring a balanced upright posture. In this study, the postural sway of 18 …

Can Gait Signatures Provide Quantitative Measures For Aiding Clinical Decision-Making? A Systematic Meta-Analysis Of Gait Variability Behavior In Patients With Parkinson’S Disease, Niklas König Ignasiak

Physical Therapy Faculty Articles and Research

A disturbed, inconsistent walking pattern is a common feature of patients with Parkinson's disease (PwPD). Such extreme variability in both temporal and spatial parameters of gait has been associated with unstable walking and an elevated prevalence of falls. However, despite their ability to discretise healthy from pathological function, normative variability values for key gait parameters are still missing. Furthermore, an understanding of each parameter's response to pathology, as well as the inter-parameter relationships, has received little attention. The aim of this systematic literature review and meta-analysis was therefore to define threshold levels for pathological gait variability as well as to …

Revealing The Quality Of Movement: A Meta-Analysis Review To Quantify The Thresholds To Pathological Variability During Standing And Walking, Niklas König Ignasiak

Physical Therapy Faculty Articles and Research

Neuromotor processes are inherently noisy, which results in variability during movement and fluctu-ations in motor control. Although controversial, low levels of variability are traditionally considered healthy, while increased levels are thought to be pathological. This systematic review and meta-analysisof the literature investigates the thresholds between healthy and pathological task variability.

After examining 13,195 publications, 109 studies were included. Results from over 3000 healthy sub-jects and 2775 patients revealed an overall positive effect size of pathology on variability of 0.59 forwalking and 0.80 for sway. For the coefficient of variation of stride time (ST) and sway area (SA), upperthresholds of 2.6% …

Effects Of Pelvis Impact Angle And Hip Muscle Forces On Hip Fracture Risk During A Fall Using An Advanced Hip Impact Simulator, Woochol J. Choi, Stephen N. Robinovitch

Physical Therapy Faculty Articles and Research

"Over 90% of hip fractures in older adults are caused by falls [1]. Whether a given fall will cause hip fracture depends on bone strength, and on the impact force and stress applied to the bone during impact [2]. Improved understanding is required on how peak bone stresses during a fall depend on the mechanics of a fall, and on the state of contraction at the moment of impact of the muscles spanning the hip. Recently, Choi et al showed that, for lateral impact to the hip, peak stresses decrease with increases in hip abductor muscle force [3]. In the …

Influence Of Pelvis Impact Angle During A Fall: On The Protective Benefit Of Hip Protectors, Woochol J. Choi, Stephen N. Robinovitch

Physical Therapy Faculty Articles and Research

"Over 90% of hip fractures are due to falls [1]. Laboratory measures have shown that wearable hip protectors reduce impact forces to the proximal femur during a simulated sideways fall on the hip [2, 3]. However, clinical evidence suggests that hip fractures still occur when hip protectors are worn [4]. Furthermore, while falls in real life result in a variety of impact configurations, biomechanical tests to date have focused only on lateral impact to the pelvis. In the current study, we examined how the force reduction provided by wearable hip protectors is affected by pelvis impact configuration during simulated sideways …

Pressure Distribution Over The Palm Region During Forward Falls On The Outstretched Hands, Woochol J. Choi, Stephen N. Robinovitch

Physical Therapy Faculty Articles and Research

Falls on the outstretched hands are the cause of over 90% of wrist fractures, yet little is known about bone loading during this event. We tested how the magnitude and distribution of pressure over the palm region during a forward fall is affected by foam padding (simulating a glove) and arm configuration, and by the faller’s body mass index (BMI) and thickness of soft tissues over the palm region.

Thirteen young women with high (n=7) or low (n=6) BMI participated in a “torso release experiment” that simulated falling on both outstretched hands with the arm inclined either at 20° or …

Pressure Distribution Over The Palm During Falls On The Outstretched Hands, Woochol J. Choi, Stephen N. Robinovitch

Physical Therapy Faculty Articles and Research

"Over 90% of wrist fractures are caused by falls on the outstretched hands (Palvanen et al., Osteoporos Int, 2000). Along with bone strength, fracture risk depends on the magnitude and distribution of force to soft and hard tissues during impact. In the current study, we examined how pressure distribution over the palm during a fall is affected by impact configuration, body mass index (BMI), palmer soft tissue thickness, and a 5 mm thick foam pad (simulating a protective glove)."

Performance Of A Hip Protector Depends On Its Position During A Fall, Woochol J. Choi, Joaquin A. Hoffer, Stephen N. Robinovitch

Physical Therapy Faculty Articles and Research

"Hip protectors are designed to attenuate and redistribute the force applied to the hip region during a fall, and thereby reduce risk for hip fracture [1]. However, little information exists on the effectiveness of hip protectors in achieving these goals, and how this is altered by displacement of the hip protector relative to the greater trochanter (GT). In the current study, we tested these issues."