Chris J Hass

Chris J Hass
University of Florida | UF · Department of Applied Physiology and Kinesiology

About

240
Publications
30,595
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7,003
Citations
Additional affiliations
August 2006 - February 2020
University of Florida
Position
  • Researcher

Publications

Publications (240)
Article
Nearly 75% of older adults in the US report balance problems. Although it is known that aging results in widespread brain atrophy, less is known about how brain structure relates to balance in aging. We collected T 1- and diffusion-weighted MRI scans and measured postural sway of 36 young (18-34 years) and 22 older (66-84 years) adults during eyes...
Article
It is not well understood how older adults meet the combined locomotor demands of obstacle avoidance at fast speeds as compared to obstacle avoidance under cognitive loads. The purpose of this study was to quantify changes in locomotor stability (margin of stability, MOS) from walking to crossing obstacles at fast speeds versus with added cognitive...
Preprint
Nearly 75% of older adults in the United States report balance problems. Balance difficulties are more pronounced during sensory feedback perturbation (e.g., standing with the eyes closed or on foam). Although it is known that aging results in widespread brain atrophy, less is known about how brain structure relates to balance performance under var...
Article
Introduction Although there is growing literature supporting the implementation of backward walking as a potential rehabilitation tool, moving backwards may precipitate falls for persons with Parkinson's disease. We sought to better understand interlimb coordination during backward walking in comparison to forward walking in persons with Parkinson'...
Article
Introduction Gait termination (GT) is a challenging transitory task involving converting from a dynamic state of motion to a static state. These transitional locomotor tasks are particularly troublesome for populations with postural deficits, i.e., Parkinson’s disease (PD) and Essential Tremor (ET). They demand greater postural control and intricat...
Preprint
Full-text available
Almost 25% of all older adults experience difficulty walking. Mobility difficulties for older adults are more pronounced when performing a simultaneous cognitive task while walking (i.e., dual task walking). Although it is known that aging results in widespread brain atrophy, few studies have integrated across more than one neuroimaging modality to...
Article
Full-text available
The split-belt treadmill has been used to examine the adaptation of spatial and temporal gait parameters. Historically, similar studies have focused on anterior-posterior (AP) spatiotemporal gait parameters because this paradigm is primarily a perturbation in the AP direction, but it is important to understand whether and how medial-lateral (ML) co...
Article
Split-belt treadmills have become an increasingly popular means of quantifying ambulation adaptability. Multiple sensory feedback mechanisms, including vision, contribute to task execution and adaptation success. No studies have yet explored visual feedback effects on locomotor adaptability across a spectrum of available visual information. In this...
Article
Background Although human gait is typically studied in a laboratory environment, the findings of laboratory-based gait assessments are often applied to daily life scenarios. Assessing gait in varied conditions may offer a better understanding of the influence of environment on gait performance. Research questions How do spatiotemporal gait measure...
Preprint
Full-text available
The split-belt treadmill (SBT) has been used to examine the adaptation of spatial and temporal gait parameters. Historically, SBT studies have focused on anterior-posterior (AP) spatiotemporal gait parameters because SBT is primarily a perturbation in the anterior-posterior direction, but it is important to understand whether and how ML control ada...
Article
Background The ability to walk at various speeds is essential to independence for older adults. Maintaining fast walking requires changes in spatial-temporal measures, increasing step length and/or decreasing step time. It is unknown how mobility affects the parameters that change between preferred and fast walking. Research Question How does pref...
Article
We sought to determine how people with Parkinson disease (PD) perform the sit to stand task (STS). After measuring kinetic and kinematic data our results suggest that people with PD perform the STS task by redistributing their joint torques but is accompanied with postural instability.
Article
Older adults walk with greater metabolic energy consumption than younger for reasons that are not well understood. We suspect that a distal-to-proximal redistribution of leg muscle demand, from muscles spanning the ankle to those spanning the hip, contributes to greater metabolic energy costs. Recently, we found that when younger adults using biofe...
Article
Background Entrainment of walking with rhythmic auditory cues (e.g., metronome or music) induces gait improvements in people with Parkinson’s disease (PD). However, evidence regarding acute impacts of music cues on parkinsonian gait is lacking. Findings in healthy adults imply that familiarity with music cues modulates stride amplitude and stride-t...
Article
Motor responses are more efficient when there is a match (or congruency) between the motivational properties of an emotional state and the distance altering characteristics of the movement being executed to the emotion-eliciting stimulus. However, the role of spatial context in shaping motivational orientations to approach and avoid, particularly d...
Article
Full-text available
Background: Treating medication-refractory freezing of gait (FoG) in Parkinson’s disease (PD) remains challenging despite several trials reporting improvements in motor symptoms using subthalamic nucleus or globus pallidus internus (GPi) deep brain stimulation (DBS). Pedunculopontine nucleus (PPN) region DBS has been used for medication-refractory...
Article
Parkinson’s disease symptoms impair gait, limit mobility and reduce independence. Levodopa improves muscle activation, strength, and coordination; thus, facilitates increased step length, but few studies have evaluated the underlying forces associated with medication-induced gait improvements. Here, we assess the effects of levodopa on gait kinetic...
Article
Gait adaptation is crucial for adults at risk for mobility disability, and executive function and physical function may be important for adaptation performance. Gait adaptation can be measured using a treadmill with two belts, known as a split-belt treadmill. Increasing evidence supports that gait adaptability, executive function, and physical func...
Article
Entrainment of walking to rhythmic auditory cues (e.g., metronome and/or music) improves gait in people with Parkinson's disease (PD). Studies on healthy individuals indicate that entrainment to pleasant musical rhythm can be more beneficial for gait facilitation than entrainment to isochronous rhythm, potentially as a function of emotional/motivat...
Article
Background: The impact of concurrent osteoarthritis on mobility and mortality in individuals with Parkinson's disease is unknown. Objective: We sought to understand to what extent osteoarthritis severity influenced mobility across time and how osteoarthritis severity could affect mortality in individuals with Parkinson's disease. Methods: In a...
Article
Background Emerging research has proposed a growing reliance on visual processing during motor performance in individuals following anterior cruciate ligament reconstruction. Reconstructed individuals display increased activation of visual processing areas during task execution and exhibit dramatic performance decrements when vision is completely r...
Article
Objectives: The relationship between elevated inflammatory cytokine levels and peak pain intensity following acute musculoskeletal injury has not been fully elucidated in high risk subgroups. Identifying the role that these cytokines have on pain responses may help with developing tailored therapeutic approaches. Methods: Data were collected fro...
Article
Full-text available
This study aimed to characterize the neurophysiological correlates of gait in the human pedunculopontine nucleus (PPN) region and the globus pallidus internus (GPi) in Parkinson’s disease (PD) cohort. Though much is known about the PPN region through animal studies, there are limited physiological recordings from ambulatory humans. The PPN has rece...
Article
Full-text available
Gait impairment and increased gait variability are common among individuals with Parkinson’s disease (PD) and have been associated with increased risk for falls. The development of composite scores has gained interest to aggregate multiple aspects of gait into a single metric. The Enhanced Gait Variability Index (EGVI) was developed to compare an i...
Article
Introduction: Orthostatic tremor (OT) patients frequently report gait unsteadiness with the advancement of disease; however, there is little understanding of its physiology. We sought to examine in OT, the spatial and temporal characteristics of gait, and the relationship with tremor physiology. Methods: Gait parameters for OT (n = 16) were reco...
Article
Full-text available
Age-related brain changes likely contribute to mobility impairments, but the specific mechanisms are poorly understood. Current brain measurement approaches (e.g., functional magnetic resonance imaging (fMRI), functional near infrared spectroscopy (fNIRS), PET) are limited by inability to measure activity from the whole brain during walking. The Mi...
Article
Full-text available
Background Conventional Parkinson’s disease (PD) deep brain stimulation (DBS) utilizes a pulse with an active phase and a passive charge-balancing phase. A pulse-shaping strategy that eliminates the passive phase may be a promising approach to addressing movement disorders.Objectives The current study assessed the safety and tolerability of square...
Article
Background: Turning is an activity of daily living known to elicit falls in older adults and particularly in persons with movement disorders. Specifically, those with Parkinson's disease have marked impairments in forward walking and turning. Although recent work has identified gait impairment in those with Essential tremor, turning has not been e...
Article
Background: Essential tremor (ET) is a common movement disorder characterized by kinetic and postural tremor in the upper extremities and frequently in the midline. Persons with ET often also exhibit gait ataxia. Previous studies have observed associations between midline tremor severity and gait ataxia in persons with ET, suggesting a common path...
Article
Essential tremor (ET) is a common movement disorder that causes motor deficits similar to those seen in cerebellar disorders. These include kinetic tremor, gait ataxia, and impaired motor adaptation. Previous studies of motor adaptation in ET have focused on reaching while the effects of ET on gait adaptation are currently unknown. The purpose of t...
Article
Background: Persons with Parkinson's disease exhibit gait deficits during comfortable-pace overground walking and data from pressure sensitive mats have been used to quantify gait performance. The Primary Gait Screen is a new assessment which includes gait initiation, overground walking, turning, and gait termination. Although overground assessmen...
Article
Full-text available
The role of exercise in Parkinson's Disease (PD) has been studied extensively in the last decade. Recent evidence shows physical activity partially improves the motor and non-motor symptoms of the disease. In this new era of personalized medicine, it is crucial to better characterize the benefits of exercise in PD. In the present review, we discuss...
Article
Purpose Individuals with Parkinson's disease (PD) demonstrate language- and emotion-related impairments; however, emotional language production has received little attention within the literature despite the fact that deficits could significantly impact one's daily interactions with loved ones and others. Multitasking (i.e., dual tasking), specific...
Article
Background: Essential Tremor is characterized by an action tremor of the upper extremities, which may or may not be accompanied by a head, voice, leg or trunk tremor. Problems with gait and balance have also been identified in persons with Essential Tremor. Therefore, understanding gait performance is an important area of focus for clinicians and...
Article
Background: Community ambulation requires the ability to adapt walking patterns to task demands. For example, complex walking tasks, such as obstacle crossing (OBS) and backwards walking (BW), require modification of gait kinematics to complete the task, maintain stability and prevent falling. More women than men fall each year, but few studies ha...
Article
Music elicits a wide range of human emotions, which influence human movement. We sought to determine how emotional states impact forward gait during music listening, and whether the emotional effects of music on gait differ as a function of familiarity with music. Twenty-four healthy young adults completed walking trials while listening to four typ...
Article
Objective To investigate the effects of unilateral thalamic deep brain stimulation (DBS) on walking in persons with medication-refractory essential tremor (ET). Methods We performed laboratory-based gait analyses on 24 persons with medication-refractory ET before and after unilateral thalamic DBS implantation. Normal and tandem walking parameters...
Article
Aberrant loading is a mechanism by which individuals with chronic ankle instability (CAI) may negatively impact cartilage health and therefore long-term health outcomes. We aimed to quantify walking vertical ground reaction force (vGRF) component differences between those with and without CAI. Participants (n = 36) walked barefoot overground at a s...
Article
Full-text available
Abstract: A growing body of literature has reported the effects of dual tasks on gait performance in people with Parkinson's disease (PD). The purpose of this meta-analysis was to synthesize the existing literature and quantify the overall influence of dual tasks on gait performance in PD. A thorough literature search was conducted, and 19 studies...
Article
Clinical locomotor research seeks to facilitate adaptation or retention of new walking patterns by providing feedback. Within a split-belt treadmill paradigm, sagittal plane feedback improves adaptation but does not affect retention. Representation of error in this manner is cognitively demanding. However, it is unknown in this paradigm how frontal...
Article
Context: Following a lateral ankle sprain, approximately 40% of individuals develop chronic ankle instability (CAI), characterized by recurrent injury and sensations of giving way. Deafferentation due to mechanoreceptor damage post-injury is suggested to contribute to arthrogenic muscle inhibition (AMI). Whole-body vibration (WBV) has the potentia...
Conference Paper
Neurologic music therapy (NMT) has demonstrated clinical benefits in patients with Parkinson’s disease (PD), especially improvement in gait disturbance. Most NMTs use an isochronous metronome pulse called rhythmic auditory stimulation (RAS) which ignores emotional and motivational benefits of music. Given that musical pleasure is associated with ac...
Article
Background: Persons with anterior cruciate ligament reconstruction (ACLR) show deficits in gait and neuromuscular control following rehabilitation. This altered behavior extends to locomotor adaptation and learning, however the contributing factors to this observed behavior have yet to be investigated. Objective: The purpose of this study was to...
Conference Paper
Research Objectives: To investigate 1) emotional impacts of music on cycle ergometer performance in persons with Parkinson’s disease (PD), and 2) whether familiarity with music differentially impacts emotional reactions and ensuing cycling performance. Design: Participants were asked to initiate and continue pedaling on a cycle ergometer while expe...
Article
Background: Conventional deep brain stimulation (DBS) utilizes regular, high frequency pulses to treat medication-refractory symptoms in essential tremor (ET). Modifications of DBS pulse shape to achieve improved effectiveness is a promising approach. Objectives: The current study assessed the safety, tolerability and effectiveness of square bip...
Conference Paper
Freezing-of-Gait (FoG) is a syndrome of Parkinson's disease defined by episodes when patients show a complete inability to take a step or continue with their locomotion. In order to develop closed-loop therapeutic strategies, including deep brain stimulation, a reliable means of detecting freezing episodes is required. By using wearable acceleromet...
Article
Bradykinesia is a prominent problem for persons with Parkinson’s disease (PD) and has been studied extensively with upper extremity tasks; however there is a lack of research examining bradykinesia in targeted lower extremity tasks related to mobility. Navigating steps and curbs are challenging tasks for older adults and neurologically impaired and...
Article
Persons with Parkinson’s disease (PD) are typically more susceptible than healthy adults to impaired performance when two tasks (dual task interference) are performed simultaneously. This limitation has by many experts been attributed to limitations in cognitive resources. Nearly all studies of dual task performance in PD employ walking or balance-...
Article
This study compared how wheelchair propulsion styles affect changes in percentage of time spent in extreme wrist orientations, which have been associated with median nerve injury, after a fatiguing bout of propulsion. Twenty novice, non-disabled adult males learned arcing (ARC) and semicircular (SEMI) propulsion styles and utilized each to perform...
Article
Background: Dystonia often has inconsistent benefits and requires more energy-demanding DBS settings. Studies suggest that squared biphasic pulses could provide significant clinical benefit; however, dystonia patients have not been explored. Objectives: To assess safety and tolerability of square biphasic DBS in dystonia patients. Methods: Thi...
Article
Interventions that manipulate gait speed may also affect the control of frontal plane mechanics. Expanding the current knowledge of frontal plane adaptations during split-belt treadmill walking could advance our understanding of the influence of asymmetries in gait speed on frontal plane mechanics and provide insight into the breadth of adaptations...
Chapter
Parkinson disease (PD) is a neurodegenerative disorder that not only impacts motor function but also severely impacts cognition, which often precedes PD diagnosis. Cognitive problems for those with PD include difficulty with psychomotor and cognitive slowing, set-shifting and multitasking, working memory, and forgetfulness, attributed to deregulati...
Article
Background: Changes in the quantity, quality and integration of sensory information are thought to persist long after anterior cruciate ligament reconstruction and completion of physical therapy. Our purpose was to investigate the ability of individuals with anterior cruciate ligament reconstruction to perceive imposed asymmetry and symmetry while...
Article
Objectives: Parkinson's disease (PD) results in a range of non-motor deficits that can affect mood, cognition, and language, and many of these issues are unresponsive to pharmacological intervention. Aerobic exercise can improve mood and cognition in healthy older adults, although only a few studies have examined exercise effects on these domains...
Article
Full-text available
Computational walking simulations could facilitate the development of improved treatments for clinical conditions affecting walking ability. Since an effective treatment is likely to change a patient's foot-ground contact pattern and timing, such simulations should ideally utilize deformable foot-ground contact models tailored to the patient's foot...
Article
Background: Wheelchair propulsion has been linked to overuse injuries regardless of propulsion style. Many aspects of the arcing (ARC) and semicircular (SEMI) propulsion styles have been compared, but differences in intracycle movement variability, which have been linked to overuse injuries, have not been examined. Objective: To explore how ARC...
Article
Impairments in acoustically cued repetitive finger movement often emerge at rates near to and above 2Hz in persons with Parkinson's Disease (PD) in which some patients move faster (hastening) and others move slower (bradykinetic). The clinical features impacting this differential performance of repetitive finger movement remain unknown. The purpose...
Article
Full-text available
In Parkinson's disease (PD), slow gait speed is significantly related to clinical ratings of disease severity, impaired performance of daily activities, as well as increased overall disability. Conducting a meta-analysis on gait speed is an objective and quantitative technique to summarize the effectiveness of DBS and to determine the effect sizes...
Article
Background: Natural aging and disease processes such as Parkinson's disease often lead to gait impairment. This impairment often manifests as changes in symmetry, complexity, and variability of lower limb joint movements during gait as compared to young healthy adults. Current gait assessment tools primarily focus on discrete events during gait or...
Article
Full-text available
Background: Despite the strong implications for rehabilitation design, the capability of individuals with anterior cruciate ligament reconstruction (ACLR) to adapt and store novel gait patterns have not been well studied. Purpose: To investigate how reconstructive surgery may affect the ability to adapt and store novel gait patterns in persons with...
Article
Introduction: A broad range of subjective and objective assessments have been used to assess balance confidence and balance control in persons with Parkinson's disease (PD). However, little is known about the relationship between self-perceived balance confidence and actual balance control in PD. The purpose of this investigation was to determine...
Article
Full-text available
Parkinson's disease (PD) patients have an increased risk of falls resulting in important social and economical consequences. Risk factors for falls include the use of psychotropic drugs, which are used for the treatment of PD neuropsychiatric symptoms. We aimed to determine the association between psychotropic drug use and falls in a PD cohort. A c...
Article
Full-text available
Exercise "stress tests" are widely used to assess cardiovascular function and to detect abnormalities. In line with the view of exercise as a stressor, the present study examined the relationship between cognitive function and cardiovascular activity before and after light physical exercise in a sample of 84 non-demented community-dwelling older ad...
Article
Full-text available
Differentiating movement disorders is critical for appropriate treatment, prognosis, and for clinical trials. In clinical trials this is especially important as effects can be diluted by inclusion of inappropriately diagnosed participants. In early disease duration phases, disorders often have overlapping clinical features, such as impairments in r...
Article
Quantitative gait assessment is important in diagnosis and management of Parkinson's disease (PD); however, gait characteristics of a cohort are dispersed by patient physical properties including age, height, body mass, and gender, as well as walking speed, which may limit capacity to discern some pathological features. The aim of this study was tw...