Gait variablility is altered in older adults when listening to auditory stimuli with differing temporal structures

Gait variability in the context of a deterministic dynamical system may be quantified using nonlinear time series analyses that characterize the complexity of the system. Pathological gait exhibits altered gait variability. It can be either too periodic and predictable, or too random and disordered, as it is the case with aging. While gait therapies often focus on restoration of linear measures such as gait speed or stride length, we propose that the goal of gait therapy should be to restore optimal gait variability, which exhibits chaotic fluctuations and is the balance between predictability and complexity. In this context, our purpose was to investigate how listening to different auditory stimuli affects gait variability. Twenty-seven young and 27 elderly subjects walked on a treadmill for 5 minutes while listening to white noise, a chaotic rhythm, a metronome, and with no auditory stimulus. Stride length, step width, and stride intervals were calculated for all conditions. Detrended Fluctuation Analysis was then performed on these time series. A quadratic trend analysis determined that an idealized inverted-U shape described the relationship between gait variability and the structure of the auditory stimuli for the elderly group, but not for the young group. This proof-of-concept study shows that the gait of older adults may be manipulated using auditory stimuli. Future work will investigate which structures of auditory stimuli lead to improvements in functional status in older adults

Gait Variability Measures Reveal Differences between Multiple Sclerosis Patients and Healthy Controls

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 \u3c .001) and step width (p \u3c .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

The Appropriate Use of Approximate Entropy and Sample Entropy with Short Data Sets

Approximate entropy (ApEn) and sample entropy (SampEn) are mathematical algorithms created to measure the repeatability or predictability within a time series. Both algorithms are extremely sensitive to their input parameters: m (length of the data segment being compared), r (similarity criterion), and N (length of data). There is no established consensus on parameter selection in short data sets, especially for biological data. Therefore, the purpose of this research was to examine the robustness of these two entropy algorithms by exploring the effect of changing parameter values on short data sets. Data with known theoretical entropy qualities as well as experimental data from both healthy young and older adults was utilized. Our results demonstrate that both ApEn and SampEn are extremely sensitive to parameter choices, especially for very short data sets, N ≤ 200. We suggest using N larger than 200, an m of 2 and examine several r values before selecting your parameters. Extreme caution should be used when choosing parameters for experimental studies with both algorithms. Based on our current findings, it appears that SampEn is more reliable for short data sets. SampEn was less sensitive to changes in data length and demonstrated fewer problems with relative consistency

Walking Before and During a Sea Voyage

In this article More Share Options Abstract Stationary and moving surfaces impose different constraints on walking. In this study we investigated within-participants differences between walking on a ship before (at the dock) and during (at sea) a sea voyage. Four individuals participated in the study. While on the ship they wore a tri-axial accelerometer (ActiGraph GT3X+; ActiGraph LLC, Pensacola, FL) on their waists. Activity data were sampled at 30 Hz. Data were collected on the day before the voyage began and on several days at sea. The number of steps per day was greater at the dock than at sea. The net resultant force per day also was greater at the dock than at sea. However, resultant force per step was greater at sea (79.97 ± 8.50 vector magnitude counts/step) than on land (62.94 ± 10.03 vector magnitude counts/step). In addition, we observed variations in resultant force per step across days at sea. Ship motion decreased overall activity but increased the force per step

Persistent fluctuations in stride intervals under fractal auditory stimulation

Copyright @ 2014 Marmelat et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Stride sequences of healthy gait are characterized by persistent long-range correlations, which become anti-persistent in the presence of an isochronous metronome. The latter phenomenon is of particular interest because auditory cueing is generally considered to reduce stride variability and may hence be beneficial for stabilizing gait. Complex systems tend to match their correlation structure when synchronizing. In gait training, can one capitalize on this tendency by using a fractal metronome rather than an isochronous one? We examined whether auditory cues with fractal variations in inter-beat intervals yield similar fractal inter-stride interval variability as isochronous auditory cueing in two complementary experiments. In Experiment 1, participants walked on a treadmill while being paced by either an isochronous or a fractal metronome with different variation strengths between beats in order to test whether participants managed to synchronize with a fractal metronome and to determine the necessary amount of variability for participants to switch from anti-persistent to persistent inter-stride intervals. Participants did synchronize with the metronome despite its fractal randomness. The corresponding coefficient of variation of inter-beat intervals was fixed in Experiment 2, in which participants walked on a treadmill while being paced by non-isochronous metronomes with different scaling exponents. As expected, inter-stride intervals showed persistent correlations similar to self-paced walking only when cueing contained persistent correlations. Our results open up a new window to optimize rhythmic auditory cueing for gait stabilization by integrating fractal fluctuations in the inter-beat intervals.Commission of the European Community and the Netherlands Organisation for Scientific Research

Total Worker Health on Occupational Injury among Male and Female, Career and Volunteer Firefighters

There are more than 1 million firefighters in the US, of which 70% are career, 30% are volunteer, and 5% of the entire fire service is female. Physical characteristics, health behaviors, and psychosocial factors have been explored in association with on-duty injury among male career firefighters, but never in volunteer firefighters or female firefighters. The aim of this study was to explore the role of obesity on the association between on-duty injury and physical characteristics, health behaviors, and psychosocial factors in male and female, career and volunteer firefighters. Data for this cross-sectional study came from the Firefighter Injury and Risk Evaluation Study (2008-2010), the Fuel 2 Fight study (2010-2013), The First Twenty for Volunteer Firefighters study (2014-2017), and The Health of Women Firefighters study (2013-2014). Male career (n=1,419), male volunteer (n=533), and female career (n=1,817) firefighters were examined separately. On-duty injury was the dependent variable, obesity was the effect modifier among the male firefighters, and the following factors were explored as independent variables: sleep, total work hours, physical activity, depression, job stress, job satisfaction, anxiety, rank, and age. Mixed effect multivariable logistic regression models stratified by obesity with a group level factor of department were conducted among male career and volunteer firefighters. A multivariable logistic regression model was conducted among female career firefighters since there was no department selection factor to consider. Potential confounders were evaluated using backward elimination approach and the change in estimate of 10% applied to determine model efficiency. The odds ratios, stratified odds ratio, 95% CI, and p-value (p\u3c0.05) were used to evaluate results for significance and model fit was explored for models in each of the analyses. Female career firefighters had the highest prevalence of on-duty injury, followed by male career firefighters, and male volunteer firefighters. Male volunteer firefighters had the highest prevalence of obesity compared to male career firefighters and female career firefighters. Obesity modified the association between on-duty injury and sleep, physical activity, depression, and job stress among male career firefighters. Among male volunteer firefighters, obesity modified the association between on-duty injury and total work hours, sleep, and depression. Depression and job stress were found to be significantly associated with on-duty injury among female firefighters. The results of the study as a whole suggest the risk profile for on-duty injury is different among non-obese and obese male firefighters, and different from the risk profile for female firefighters likely due to the lower prevalence of obesity among females. Body composition should be examined as an effect modifier between on-duty injury and its predictors among male firefighters. Findings from this study highlight the need to address obesity, depression, job stress, sleep, and fitness to reduce the disproportionate burden of on-duty injuries in the fire service

Diet, supplement use, and hypertension in firefighters

Dietary intake and supplement use among US firefighters has never been described. Diet is an important risk factor for hypertension and cardiovascular disease, both highly prevalent among firefighters. The intake of calcium, magnesium, sodium, and potassium from food and dietary supplements (both over the counter and prescribed) is associated with hypertension in clinical and observational studies. Secondary data from the Fuel 2 Fight study was used to determine the type and prevalence of dietary supplement consumption among US male, career firefighters in 2011-2012. The Fuel 2 Fight cohort is compromised of career firefighters across the United States. The average age of the cohort is 39 years old and over 80% are overweight or obese. Mean mineral intakes and the proportion of firefighters who met USDA dietary guidelines for the intake of sodium, potassium, calcium and magnesium in supplement nonusers and users, using diet only and diet combined with supplements, respectively, was calculated. The association between systolic blood pressure and intake of calcium, magnesium, sodium, and potassium, each, from diet and supplements was calculated using a multivariable linear regression. The prevalence of taking at least one dietary supplement among male firefighters was 55.2%. The most commonly used dietary supplements were bodybuilding and multivitamin-mineral supplements. More than half of firefighters had diets not meeting the USDA recommended intakes for the selected minerals. Dietary supplement users consumed significantly more calcium and magnesium from food alone than non-dietary supplement users. In addition, dietary supplement users consumed significantly more calcium, magnesium and potassium from food plus supplements than non-supplement users. Significantly more dietary supplement users diets met the USDA recommended daily allowance from food alone for calcium and food plus supplements for calcium and magnesium than non-dietary supplement users. However, more non-dietary supplement users achieved a diet low in sodium than did dietary supplement users. After adjusting for energy intake, age, race, BMI, and antihypertensive medication use, systolic blood pressure was not linearly associated with calcium, magnesium, sodium, nor potassium from diet only or diet plus supplements in either supplement users or nonusers. Results from this study suggest calcium, magnesium, sodium, and potassium may not be as important to systolic blood pressure regulation in firefighters as once thought

Simulating Prism Adaptation In Virtual Reality To Determine Efficacy for Future Intervention Use

A common impairment following stroke is called unilateral spatial neglect, which is an attentional deficit that significantly reduces quality of life. Symptoms include the inability to process and respond to stimuli toward the side opposite of the individual’s stroke. One successful form of treatment, called prism adaptation, involves the individual interacting with their surroundings while wearing prism goggles that shift their visual environment to one side. This study is working to validate a VR environment that simulates this standard treatment protocol with twenty healthy participants. The VR environment instructs the user to point directly to targets before, during, and after simulating a 10˚ sideways shift and records the position of the hand along the entire reach to then calculate how much the individual errored. We hypothesize that individuals will have negligible error before, a rightward error during, and a leftward error after the shift. Preliminary results show that the simulated prism adaptation protocol, along with simulated hand occlusion during the first part of reaching, results in a statistically significant difference between the errors during and after the prism shift. Additionally, average error during prism shift is more rightward than before, and the average error after the prism shift is more leftward than before, as hypothesized. Validations of these hypotheses provide support for future studies to use the simulation with individuals who have neglect, an alternative to the standard prism adaptation treatment. This facilitates greater visual complexity, as well as the ability to quantify performance and progress

Developing an Immersive Environment for Visual Scanning Assessment and Training of Unilateral Spatial Neglect After Stroke and Healthy Baseline Assessment

Spatial neglect is a common outcome after stroke that often manifests in symptoms such as bumping into objects on one side, looking to the side of someone’s face during conversation, or neglecting to groom a certain side of one’s face. One common way to assess and treat spatial neglect is with visual scanning (identifying objects in one’s surroundings). However, this approach can require traveling to places with different environments or a clinician performing lengthy setup work, reducing intervention time. Additionally, the approach is conversation-based, and performance is subjective. Virtual reality is an emerging approach in spatial neglect research because it allows for supporting complex virtual spaces, measuring things quantitatively, and setting up and cleaning up the space quickly. We developed a virtual reality game for assessing and treating spatial neglect with visual scanning, and we did an alpha test of the game with five participants to test its assessment mode in four different virtual spaces. When finding items in a room, a spatial neglect patient will often take longer to find items in one direction. For a healthy individual, you would expect them to be able to find items in a room equally well between left, right, up, and down directions, which is what we found in our alpha test. Additionally, we found that the time to find items increases from a simple room to a visually complex room. Our software provides a foundation for this impactful new modality in spatial neglect therapy and assessment

COMPARISON OF BRAIN ACTIVATION AND FUNCTIONAL OUTCOMES BETWEEN MANUAL AND VIRTUAL REALITY MODALITIES: A CASE STUDY

Virtual reality (VR) as a neuro-rehabilitation tool has been reported to increase functional task performance for individuals with stroke1,2. Functional near-infrared spectroscopy (fNIRS) is a brain imaging technique that detects changes in cortical blood oxygenation and can be used to measure functional task improvements. Functional improvements can also be measured using the Box and Blocks test (BBT), which is a clinical measure of total upper extremity dexterity. The purpose of this study was to compare motor cortex activation and functional outcomes between VR and manual BBT. We hypothesized that there would be no difference in BBT score or motor cortex activation between VR and manual conditions. A case study was performed with a participant with chronic stroke (age: 55years, affected hand: left) who performed the BBT manually using their less-affected and affected hands for three trials each. The BBT was then repeated in VR using each hand while under observation with fNIRS. Four pair-tests were calculated comparing the manual to VR BBT conditions for each hand using brain activation data and BBT scores. The participant exhibited no statistically significant difference in motor cortex activation between the VR and manual BBT conditions for both the affected (p=0.2925) and less-affected (p=0.2155). There was also no significant difference in BBT scores between the VR and manual BBT conditions for the affected (difference: 0 blocks) and less-affected (difference: 2 blocks) hands. These results indicate that VR may provide a comparable neuromotor response to a physical-space task. REFERENCES Yin CW, et al. Clin Rehabil. 28, 1107-1114, 2014. Cameirao MS et al. Stroke. 43, 2720-2728, 2016