Effects of Parkinson’s disease on motor asymmetry

Introduction: Persons with Parkinson’s disease (PD) experience changes cortically, subcortically and behaviorally. This dissertation examines the asymmetry of motor behavior to explore the role of asymmetry in persons with PD and its connection to clinical symptoms. Purpose: Project 1: To assess the hand asymmetry difference in young adults versus older adults. Project 2: To investigate the difference in hand asymmetry in older adults and persons with PD. Project 3: To explore the correlation between function and clinical symptoms of persons with PD. Methods: 55 right-handed participants [Young Adults (YA) = 20, Female = 10; Older Adults (OA) = 20, Female = 10; Persons with PD = 15, Female = 5] were recruited and performed motor tasks: Purdue Pegboard test, grip strength test, response task, thumb opposition task, tapping task, three variations of timed-up-and-go test (TUG), single leg stance task (SLS), Weight Distribution test and Limits of Stability test. The two-way ANOVA was conducted to examine a variance between YA and OA. A separate two-way ANOVA was conducted comparing variance between OA and persons with PD. The purpose was to explore asymmetries, characterized by a significant difference between groups’ left and right sides. Pearson’s correlation was implemented to examine connection of clinical symptoms and motor behavior. Statistics: IBM SPSS 24 software was used. Two 2-way ANOVAs with the between group factor of group (Young vs. Older in Project 1; Older vs. PD in project 2), and within group factor of hand (Right vs. Left in Study 1 & Study 2) were used to examine if age (or PD) changes hand asymmetry. Pearson’s correlation coefficient was used to determine correlations between Unified Parkinson’s Disease Rating Scale (UPDRS) and motor tasks in PD patients (Study 3). Results: Project 1: Results indicate asymmetry reduces with age in fine motor tasks containing speed, dexterity and strength components. Project 2: The basal ganglia dysfunction does not overall further exacerbate the reduced asymmetry with age. Project 3: Clinical symptoms of PD measured by the UPDRS are generally not associated with fine motor tasks of this study

Does practice of multi-directional stepping with auditory stimulation improve movement performance in patients with Parkinson\u27s disease

Parkinson’s disease (PD) is a debilitating neurodegenerative disorder causing many physical limitations. Rhythmic auditory stimulation (RAS) influences motor complications not alleviated by medicine and has been used to modify straight line walking in this population. However, motor complications are exacerbated during more complex movements including those involving direction changes. Thus immediate RAS effects on direction switch duration (DSD) and other kinematic measures during a multi-directional step task were investigated in PD patients. Long term RAS application was also explored by evaluating functional gait and balance and kinematic step measures before and after 6 weeks of multi-directional stepping either with (Cue, C group) or without (No cue, NC group) RAS use. Evaluations were also administered 1, 4 and 8 weeks after training termination. Kinematic measures were collected during stepping without, then with RAS for the C group and without RAS for the NC group. Step testing/training was performed at slow, normal and fast speeds in forward, back and side directions. Participants with PD switched step direction during the stepping task faster with RAS use before training. Like straight line walking RAS application influenced the more complex task of direction switching and counteracted the well-known bradykinesia in PD. After training both groups improved their functional gait and balance measures and maintained balance improvements for at least 8 weeks. Only the C group retained gait improvements for at least 8 weeks after training termination. Adding RAS resulted in functional benefits not observed in training without it. Kinematic measures compared before and after step training clarified the underlying contributors to functional performances. Both groups reduced the variability of DSD. The C group participants maintained this alteration longer. DSD reduction also occurred after training and was retained for at least 8 weeks for this group. These outcomes further support the advantages of adding RAS to training regiments for those with PD. The current results indicate that RAS effects are not limited to simple activities like straight line walking. Moreover, RAS can be used for improving and maintaining improvements longer in activities involving various forms of transition which present most difficulties for those with PD

A life course approach to balance ability

Balance ability is a crucial component of everyday life, underlying physical movement at all stages in life. Despite this, balance is an overlooked aspect of physical health and ageing, with minimal evidence of how factors throughout life are associated with balance ability. This PhD thesis used a life course approach to investigate how factors across life contribute to standing balance in mid and later life, and to examine associations between balance ability and subsequent falls risk. Data from the MRC National Survey of Health and Development (NSHD) were used. NSHD is a nationally representative sample of 5362 males and females, born in England, Scotland and Wales in March 1946 and followed up to 24 times across life. One-legged balance time with eyes closed was assessed at ages 53, 60-64 and 69 (n=3111 individuals with a balance time at one or more age). Analytical methods included multilevel models, structural equation models, linear and logistic regressions and receiver-operating characteristic analyses. In adulthood, disadvantaged socioeconomic position, poor health and adverse health related behaviours were associated with poorer balance ability (Chapter 3). In childhood, disadvantaged socioeconomic position, lower cognitive ability, slower coordination and early or late attainment of motor milestones were associated with poorer balance ability (Chapter 3, 4). Across several domains, higher cognitive ability in midlife was associated with better balance ability (Chapter 5). The association between verbal memory and subsequent balance ability was unidirectional, with some evidence of more complex bidirectional associations with search speed (Chapter 6). Most factors across life demonstrated changing patterns of association with balance with age. Finally, balance ability was associated with subsequent falls, although the one-legged stand did not appear to be a sensitive prognostic indicator of fall risk (Chapter 7). Better understanding of the socioeconomic, cognitive, behavioural and health pathways across life which relate to subsequent balance ability, identified in this thesis, provides an opportunity to intervene earlier in life to minimise, prevent or delay balance impairment or decline

Within-subject variation in the Cognitive Timed Up and Go test as an explanatory variable in fall risk in patients with Parkinson’s disease

Objective: To explore the use of within-subject variation in the Cognitive Timed Up and Go test (Cognitive TUGwsv) as an explanatory variable in fall risk in the Parkinson’s disease population. Design: Cross-sectional study. Methods: Fifty-three patients with Parkinson’s disease completed 3 trials of the Cognitive TUGwsv. Within-subject variation was calculated using the standard deviation of an individual’s repeated measurements, and compared on the basis of the fall history reported in the previous 6 months. Participants who reported < 2 falls were classified as “non-recurrent fallers” (n = 31) and those who reported ≥ 2 falls were classified as “recurrent fallers” (n = 22). Univariate and a multivariate logistic regression were used to investigate the statistical impact of the Cognitive TUGwsv as an explanatory variable in fall risk. Discriminative ability and cut-off score were determined based on receiver operating characteristic analysis. Results: There was a significant difference between groups in the Cognitive TUGwsv (p = 0.002). Univariate logistic regression indicated a significant association between Cognitive TUGwsv and fall risk (χ2=12.365, p < 0.001), with an odds ratio of 2.5 (95% confidence interval (95% CI) = 1.34–4.65). Multivariate logistic regression showed that body mass index (BMI), Falls Efficacy Scale-International (FES-I), Cognitive TUGwsv, and the mean velocity of the centre of foot pressure (Closed Eyes) (Velocity COP (CE)) were significant explanatory variables in fall risk. Cognitive TUGwsv was the most important independent variable. Receiver operating characteristic analysis revealed an acceptable discriminative power (area under the curve (AUC) = 0.757, 95% CI = 0.619–0.864, p < 0.001) and a cut-off point of 1.53 s. Conclusion: A higher Cognitive TUGwsv correlated with higher fall risk. Thus, diagnostic tests and exercise programmes could consider Cognitive TUGwsv when assessing fall risk in the Parkinson’s disease population.Sergio Sebastiá-Amat participated in this study supported by a pre-doctoral grant (ACIF/2018/209) from the Generalitat Valenciana, Spain

Mechanisms of Slowed Foot Tap Speed in Older Adults

Rapid repetitive tapping, like the Foot Tap Test (FTT), slows with age, but the underlying mechanisms are unknown. Purpose: 1. Test the hypotheses that greater performance variability, increased muscle coactivation, and slowed muscle contractile speeds are related to lower foot tap count (FTC) in older adults; 2. Examine the relationship between FTC and physical function in older adults, using the advanced SPPB-A. Methods: 18 (25.0±3.1years, 9F, mean±SD), and 28 (73.4±4.9, 14F) adults were recruited; the later were divided into Higher (HFO) and Lower (LFO) Functioning based on SPPB-A score. Participants performed 10s of rapid tapping (FTT) while seated. A MATLAB program was used to calculate FTC and variability of the intertap-interval (COV-ITI). Contractile speed (rates of force development and relaxation, RFD and RFR) of the dorsiflexor muscles were determined using ballistic contractions. Electromyography was recorded on the tibialis anterior, soleus, and coactivation was calculated based on their agreement. Results: LFO had a lower FTC than Young and HFO (45.9±7.0taps, 54.4±7.5, 53.1±5.7, respectively; p=0.003), and lower COV-ITI than Young (12.3±5.9%, 20.5±8.1, respectively, p=0.009). No associations were found between COV-ITI and FTC. Coactivation was higher in Young than HFO (0.568±0.209, 0.321±0.129) and was negatively related to FTC in older (r2=0.274, p=0.005). The LFO had a slower RFD than Young and FTC was positively related to maximal RFD (r2=0.345, p=0.001) and RFR (r2=0.162, p=0.038) in older adults. In older, FTC was related to SPPB-A (r2=0.329, p=0.001). Conclusions: Greater coactivation during the FTT and slower force development may negatively affect FTC in older adults

The effect of simple and complex dual-tasks on ambulation in individuals with Alzheimer's disease and healthy older adults: the role of divided attention and other higher brain functions in gait dual-task performance

Research using gait-dual task methodology suggests that the ability to divide attention during walking appears to be particularly vulnerable to the effects of Alzheimer’s disease (AD), even in the earliest stages of the illness. However, these previous studies are limited by the variability in the types of gait-dual tasks employed, as well as by the inclusion of heterogeneous groups of patients at different stages of disease severity. Study 1 aimed to address these methodological concerns by examining the effects of a simple and complex counting task on gait speed in healthy older adults and individuals with early stage AD. In contrast to previous findings reported in the literature, Study 1 found that when compared to an age appropriate control group individuals with early stage AD were not differentially impaired by a gait dual-task, regardless of the level of task complexity. Study 2 was designed to be a replication and extension of Study 1. In Study 2, sixteen individuals diagnosed with amnestic Mild Cognitive Impairment (aMCI; Petersen, 1999; 2001), 15 individuals with early-stage AD, 17 individuals with moderate stage AD, and 27 healthy older adults performed a timed walking task and simple and complex verbal counting tasks in single and dual-task combinations. In keeping with the results of Study 1, there were no significant differences among the early stage AD group, aMCI group, and healthy older adults on the gait dual-task, regardless of task complexity. However, significant differences were detected between the moderate AD group and the healthy normal control group on the complex dual-task. Study 3 examined the relationship between other higher brain functions and gait speed, with and without interference, in the same group of participants as Study 2. Neuropsychological test scores were used to create theoretically derived cognitive composite scores (i.e., Executive Functioning/Attention/Speed; Episodic Memory; Language) that were used as predictors of gait speed, with and without interference. As expected, The Executive Functioning/Attention/Speed composite was the most potent predictor of gait speed across conditions; however this relationship varied as a function of task complexity and all three factors predicted gait interference in the complex condition, even after controlling for disease severity. In contrast to previous gait dual-task studies, the current research suggests that aMCI and early stage AD are not associated with impaired gait dual-task performance. Rather, these results suggest that when overall degree of dementia severity is controlled for by subdividing patients based on diagnostic criteria, the specific deficit in attention appears later in the progression of AD than previously theorized. Furthermore, these results provide evidence that the relationship between cognition and gait is likely built upon components of cognitive, physical and task prioritization processes that appear to be modulated by task complexity and disease severity

Factors Contributing to Ladder Falls and Broader Impacts on Safety and Biomechanics

Ladder falls cause disabling injury and death in the workplace and at home. Numerous scenarios lead to ladder falls given the variation in ladder types and how they are used. Of the potential factors influencing ladder fall risk under these different scenarios, many have yet to be investigated. This dissertation used a multifaceted approach to determine ladder fall risk factors. Specifically, this dissertation tested younger and older adults, designed occupational and domestic based ladder experiments, and investigated factors that precede and follow a ladder falling event. Aim 1 of this dissertation identified individual factors associated with safe and effective domestic ladder use among older adults. Balance measured with clinical assessments was a primary predictor of safe and effective ladder use. Aim 2 of this dissertation determined individual, environmental and biomechanical factors that aid in arresting a falling event from a ladder. Ascending climbs, males, greater upper body strength, higher hand placement during recovery and reestablishing at least one foot back onto the ladder during recovery were associated with reduced ladder fall severity (i.e. better recovery). Surprisingly, glove condition was not found to contribute to ladder fall severity. Hand-rung forces were correlated with the severity of the falling event and not an individual’s ability to generate force, suggesting that these forces are dependent on the circumstances of the perturbation. Findings from this dissertation may guide fall interventions (e.g. screenings, improvements in safety standards, perturbation response training, ladder re-design). Therefore, this work is expected to have impact on the safety field by reducing ladder fall injuries. Furthermore, this work contributes new knowledge to the biomechanics of ladder use and fall recovery. As part of a larger strategy to improve safety for all populations, increased diversity is needed in the Science, Technology, Engineering, and Mathematics (STEM) fields. Aim 3 of this dissertation utilized biomechanics as a link to develop a student-interest based pedagogy to improve engagement of underrepresented groups in the STEM fields. This work found lectures tailored to student interests to increase student engagement. Long-term effects from this work can increase diversity in the STEM fields including safety

Catch the ruler: concurrent validity and test–retest reliability of the ReacStick measures of reaction time and inhibitory executive function in older people

Background: Reduced cognitive function, particularly executive function (EF), is associated with an increased risk of falling in older people. We evaluated the utility of the ReacStick test, a clinical test of reaction time, and inhibitory EF developed, for young athletes, for fall-risk assessment in older people. Aims: To evaluate the psychometric properties of ReacStick measures of reaction time and executive functioning in healthy community-dwelling older people. Methods: 140 participants (aged 77 ± 5 years) underwent testing. Two test conditions—simple and inhibitory go/no-go—provided measures of reaction time, recognition load (difference in reaction time between conditions), and go/no-go accuracy. Concurrent validity was evaluated against the conventional tests of reaction time and EF (simple hand reaction time, trail-making test, and Stroop colour test). Discriminant ability was determined for fall-risk factors (age, gender, physiological profile assessment, and fall history). Test–retest reliability after 1 week was evaluated in 30 participants. Results: ReacStick reaction time correlated with tests of reaction time and EF, recognition load correlated with inhibitory EF, and go accuracy correlated with reaction time and inhibitory EF. No-go accuracy was not significantly correlated with any of the reaction time and EF tests. Test–retest reliability was good-to-excellent (ICC > 0.6) for all the outcomes. ReacStick reaction time discriminated between groups based on age, recognition load between genders, and no-go accuracy between retrospective fallers and non-fallers. Discussion: An unavoidable time pressure may result in complementary information to the traditional measures. Conclusions: The ReacStick is a reliable test of reaction time and inhibitory EF in older people and could have value for fall-risk assessment

Age-Related Differences in Motor Performance

The purpose of this work was to study the age effects on average performance and variability of movement responses in children, young adults, and older adults across multiple motor tasks. Optimal motor performance is observed in healthy young adults with declines observed at either end of the lifespan. This pattern has been represented as a U-shaped/inverted U-shaped curve. Little is known about if this pattern persists in chewing dynamics. While chewing has been found to improve aspects of attention, a cognitive function, research is limited on the relationship between chewing and other motor tasks. The first aim of this research was to conduct a scoping systematic review to identify what measures of variability are reported for preferred performance of chewing and walking in children, young adults, and older adults and the age-related differences across these age groups. The available research was insufficient across these groups and does not support the perspective that children and older adults are more variable than young adults. The second aim was to examine age-related differences in averages and variability of chewing, reaction time, balance, and walking responses across children, young adults, and older adults. A U-shaped curve was revealed for reaction time and postural sway with the young adults producing faster reaction times and decreased postural sway than the children and older adults. Chewing rates followed a similar curve but with children chewing at faster rates than young and older adults. No age-related differences were observed for normalized gait speed. The final aim was to examine dual task relationships between chewing and secondary motor tasks in children. Sixteen healthy children completed finger tapping, reaction time, and walking while chewing at different speeds. Chewing rates varied when produced with a secondary motor task and the secondary motor tasks were differentially influenced by chewing. Reaction times slowed during chewing while walking rates increased/decreased with changes in chewing rates. This relationship was not as strong as previous reports in adults. Overall, the anticipated patterns across the age groups were only partially revealed within this work. Understanding normal movement patterns is the foundation to identifying variations in atypical populations