Respective Coefficient Of Variation Research Articles

An intensive exercise-based training program reduces prefrontal activity during usual walking in patients with Parkinson’s disease

IntroductionParkinson’s disease (PD) leads to a progressive loss of locomotor automaticity. Consequently, PD patients rely more on executive resources for the control of gait, resulting in increased prefrontal activity while walking. Exercise-based training programs may improve automaticity of walking and reduce prefrontal activity in this population. This study aimed to assess the effect of an intensive multidisciplinary exercise-based training program on prefrontal activity and gait performance during usual walking in PD patients. MethodFourteen patients (mean age: 67 ± 9; disease duration: 6 ± 5 years; Hoehn and Yahr score: 1.9 ± 0.6) were included in this study. They were assessed in ON stage at three different times at 5-week intervals: two times before the training program (T0 and T1) and once after the training program (T2). Gait performance (stride time, speed, stride length, cadence, and their respective coefficient of variation) and cortical activity in the dorsolateral prefrontal cortex (DLPFC) using functional near infrared spectroscopy (fNIRS) were measured during usual walking. ResultsPatients had reduced cortical activity of the DLPFC at T2 compared to T1 (p = 0.003). Patients had shorter stride time at T2 compared to T1 (p = 0.025) and tended to have longer stride length at T2 than at T1 (p = 0.056). ConclusionThe training program led to positive effects on prefrontal activity and gait performance. Reduced prefrontal activity during usual walking after training program suggests that patients may have a greater reserve capacity to face more challenging walking conditions. Further studies will investigate the effect of this training on cortical activity during dual-task walking..

Measuring the Cognitive Workload During Dual-Task Walking in Young Adults: A Combination of Neurophysiological and Subjective Measures.

Background: Walking while performing a secondary task (dual-task (DT) walking) increases cognitive workload in young adults. To date, few studies have used neurophysiological measures in combination to subjective measures to assess cognitive workload during a walking task. This combined approach can provide more insights into the amount of cognitive resources in relation with the perceived mental effort involving in a walking task.Research Question: The objective was to examine cognitive workload in young adults during walking conditions varying in complexity.Methods: Twenty-five young adults (mean = 24.4 ± 5.4) performed four conditions: (1) usual walking, (2) simple DT walking, (3) complex DT walking and (4) standing while subtracting. During the walking task, mean speed, cadence, stride time, stride length, and their respective coefficient of variation (CV) were recorded. Cognitive workload will be measured through changes in oxy- and deoxy-hemoglobin (ΔHbO2 and ΔHbR) during walking in the dorsolateral prefrontal cortex (DLPFC) and perceived mental demand score from NASA-TLX questionnaire.Results: In young adults, ΔHbO2 in the DLPFC increased from usual walking to both DT walking conditions and standing while subtracting condition. ΔHbO2 did not differ between the simple and complex DT and between the complex DT and standing while subtracting condition. Perceived mental demand gradually increased with walking task complexity. As expected, all mean values of gait parameters were altered according to task complexity. CV of speed, cadence and stride time were significantly higher during DT walking conditions than during usual walking whereas CV of stride length was only higher during complex DT walking than during usual walking.Significance: Young adults had greater cognitive workload in the two DT walking conditions compared to usual walking. However, only the mental demand score from NASA-TLX questionnaire discriminated simple from complex DT walking. Subjective measure provides complementary information to objective one on changes in cognitive workload during challenging walking tasks in young adults. These results may be useful to improve our understanding of cognitive workload during walking.

Multivariate Prediction Model of Strength and Acoustic Emission Energy considering Parameter Correlation of Coal or Rock

Due to the heterogeneity of the internal structure and the different external loading conditions, the mechanical and acoustic emission (AE) characteristic parameters of coal and rock are discrete in the process of loading until failure, and many repeated and destructive tests need to be completed to obtain the performance parameters. It is of theoretical significance to explore the correlation of various parameters and to establish multiparameter regression models of coal rock strength and AE characteristics for predicting the strength and acoustic emission characteristic parameters of coal rock and reducing the repeated tests. For the coal sample from a coal seam of Longde Coal Mine in China, the mass density of coal samples and the acoustic velocity in the samples before loading are measured at first, and their respective coefficient of variation is analyzed. Then, the stress-strain curve and the time history curve of AE characteristic parameters are obtained by the uniaxial compression AE test of each coal sample according to the different loading rates. The influence of loading rate, mass density, and acoustic velocity on the mechanical and AE energy parameters of coal sample is analyzed by the section morphology of the coal sample after failure, the three-dimensional location map of AE, and the scanning micrograph of the electron microscope. Based on the least-square method, the multiple regression models of compressive strength, elastic modulus, and the maximum AE energy are established by mass density, acoustic velocity, and loading rate of coal samples. The results indicate that, for the coal samples from the same geological source, the obtained regression models can, respectively, predict the uniaxial compressive strength, elastic modulus, and the maximum AE energy according to the predesigned loading rate, the acoustic velocity, and mass density of coal samples measured before loading, without too many repeated loading failure tests.

Striatal Dopamine Denervation Impairs Gait Automaticity in Drug-Naïve Parkinson's Disease Patients.

Gait automaticity, which is impaired in patients with Parkinson's disease (PD), can be quantified by gait variability analysis. Among the 3 regions of the striatum (sensorimotor, executive, and limbic), the sensorimotor region may play a crucial role in motor automaticity in healthy individuals. However, neural correlates of impaired gait automaticity are poorly investigated in PD. We aimed to examine the relationship between gait automaticity and striatal dopaminergic depletion in drug-naïve PD patients. A total of 21 drug-naïve PD patients and 12 healthy controls were enrolled. Gait parameters were measured via wearable inertial sensors under fast-paced gait or cognitive dual-task conditions, and their respective coefficient of variation (CV) and dual-task cost were calculated. The extent of striatal dopaminergic depletion was evaluated by dopamine transporter (DAT) imaging with single-photon emission computed tomography using N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-[123 I]iodophenyl)nortropane. Correlation between DAT uptake and gait variables was analyzed using the region-of-interest analysis for the 3 right or left striatal regions and voxel-based analysis. PD had higher mean bilateral CV and dual-task cost of stride length than healthy controls. The mean bilateral CV of stride length was negatively correlated with DAT uptake in the bilateral executive regions of the striatum. Voxel-based analysis revealed a negative correlation between the mean bilateral CV of stride length and DAT uptake in the anteromedial striatum. Dopaminergic denervation in the anteromedial striatum, a part of the executive region, is associated with impaired gait automaticity in drug-naïve PD patients. This region may compensate for the posterior sensorimotor striatum, maintaining gait automaticity. © 2020 International Parkinson and Movement Disorder Society.

Comparison of physical behavior estimates from three different thigh-worn accelerometers brands: a proof-of-concept for the Prospective Physical Activity, Sitting, and Sleep consortium (ProPASS)

BackgroundPooling data from thigh-worn accelerometers across multiple studies has great potential to advance evidence on the health benefits of physical activity. This requires harmonization of information on body postures, physical activity types, volumes and time patterns across different brands of devices. The aim of this study is to compare the physical behavior estimates provided by three different brands of thigh-worn accelerometers.MethodsTwenty participants volunteered for a 7-day free-living measurement. Three accelerometers - ActiGraph GT3X+, Axivity AX3 and ActivPAL Micro4 - were randomly placed in a vertical line on the midsection of the right thigh. Raw data from each accelerometer was processed and classified into 8 physical activities and postures using the Acti4 software. Absolute differences between estimates and the respective coefficient of variation (CV) were calculated.ResultsWe observed very minor differences between physical behavior estimates from three different accelerometer brands. When averaged over 24 h (1,440 min), the absolute difference (CV) between accelerometers were: 1.2 mins (0.001) for lying/sitting, 3.4 mins (0.02) for standing, 3.5 mins (0.06) for moving, 1.9 mins (0.03) for walking, 0.1 mins (0.19) for running, 1.2 mins (0.19) for stair climbing, 1.9 mins (0.07) for cycling. Moreover, there was an average absolute difference of 282 steps (0.03) per 24 h.ConclusionsPhysical behaviors were classified with negligible difference between the accelerometer brands. These results support harmonization of data from different thigh-worn accelerometers across multiple cohorts when analyzed in an identical manner.

Effects of variable practice on the motor learning outcomes in manual wheelchair propulsion.

BackgroundHandrim wheelchair propulsion is a cyclic skill that needs to be learned during rehabilitation. It has been suggested that more variability in propulsion technique benefits the motor learning process of wheelchair propulsion.The purpose of this study was to determine the influence of variable practice on the motor learning outcomes of wheelchair propulsion in able-bodied participants. Variable practice was introduced in the form of wheelchair basketball practice and wheelchair-skill practice. Motor learning was operationalized as improvements in mechanical efficiency and propulsion technique.MethodsEleven Participants in the variable practice group and 12 participants in the control group performed an identical pre-test and a post-test. Pre- and post-test were performed in a wheelchair on a motor-driven treadmill (1.11 m/s) at a relative power output of 0.23 W/kg. Energy consumption and the propulsion technique variables with their respective coefficient of variation were calculated. Between the pre- and the post-test the variable practice group received 7 practice sessions. During the practice sessions participants performed one-hour of variable practice, consisting of five wheelchair-skill tasks and a 30 min wheelchair basketball game. The control group did not receive any practice between the pre- and the post-test.ResultsComparison of the pre- and the post-test showed that the variable practice group significantly improved the mechanical efficiency (4.5 ± 0.6% → 5.7 ± 0.7%) in contrast to the control group (4.5 ± 0.6% → 4.4 ± 0.5%) (group x time interaction effect p < 0.001).With regard to propulsion technique, both groups significantly reduced the push frequency and increased the contact angle of the hand with the handrim (within group, time effect). No significant group × time interaction effects were found for propulsion technique. With regard to propulsion variability, the variable practice group increased variability when compared to the control group (interaction effect p < 0.001).ConclusionsCompared to a control, variable practice, resulted in an increase in mechanical efficiency and increased variability. Interestingly, the large relative improvement in mechanical efficiency was concomitant with only moderate improvements in the propulsion technique, which were similar in the control group, suggesting that other factors besides propulsion technique contributed to the lower energy expenditure.Electronic supplementary materialThe online version of this article (doi:10.1186/s12984-016-0209-7) contains supplementary material, which is available to authorized users.

Effects of visual feedback-induced variability on motor learning of handrim wheelchair propulsion.

BackgroundIt has been suggested that a higher intra-individual variability benefits the motor learning of wheelchair propulsion. The present study evaluated whether feedback-induced variability on wheelchair propulsion technique variables would also enhance the motor learning process. Learning was operationalized as an improvement in mechanical efficiency and propulsion technique, which are thought to be closely related during the learning process.Methods17 Participants received visual feedback-based practice (feedback group) and 15 participants received regular practice (natural learning group). Both groups received equal practice dose of 80 min, over 3 weeks, at 0.24 W/kg at a treadmill speed of 1.11 m/s. To compare both groups the pre- and post-test were performed without feedback. The feedback group received real-time visual feedback on seven propulsion variables with instruction to manipulate the presented variable to achieve the highest possible variability (1st 4-min block) and optimize it in the prescribed direction (2nd 4-min block). To increase motor exploration the participants were unaware of the exact variable they received feedback on. Energy consumption and the propulsion technique variables with their respective coefficient of variation were calculated to evaluate the amount of intra-individual variability.ResultsThe feedback group, which practiced with higher intra-individual variability, improved the propulsion technique between pre- and post-test to the same extent as the natural learning group. Mechanical efficiency improved between pre- and post-test in the natural learning group but remained unchanged in the feedback group.ConclusionThese results suggest that feedback-induced variability inhibited the improvement in mechanical efficiency. Moreover, since both groups improved propulsion technique but only the natural learning group improved mechanical efficiency, it can be concluded that the improvement in mechanical efficiency and propulsion technique do not always appear simultaneously during the motor learning process. Their relationship is most likely modified by other factors such as the amount of the intra-individual variability.

The Efficacy of Standardized Electronic Insulin Orders In Controlling Blood Glucose Levels In Internal Medicine Departments

Background: Hyperglycemia in hospitalized patients is found to be associated with increased risk of complications, systemic infections and mortality. Thus, managing and controlling glucose blood levels in these patients are essential. The aim of the present retrospective study was to evaluate the efficacy of standardized electronic insulin orders, using a computerized physician order entry (CPOE), in controlling blood glucose levels, preventing hypoglycemic events and reducing the variability of daily blood glucose levels during hospitalization of patients with diabetes mellitus in internal medicine departments. Methods: Data were obtained from an internal medicine unit that used the standardized electronic insulin orders (Department 7) and compared to data from 6 other internal medicine departments in which the standardized electronic insulin orders was not used (Departments 1-6). The variability of daily changes in blood glucose levels was determined by the standard deviation of the daily changes and respective coefficient of variation. Results: 130,078 point-of-care bedside glucose tests were recorded from 13,577 hyperglycemic patients. The average daily mean blood glucose levels were significantly lower in patients from Department 7 than from Departments 1-6. The rate of patients achieving average daily mean blood glucose levels ≤ 180 mg/dL was higher in Department 7 than Departments 1-6. The percent of patient days with hypoglycemia and the variability of daily changes in blood glucose levels were significantly lower in Department 7 than Departments 1-6. Conclusions: A standardized electronic insulin orders of basal/bolus regimen improves glucose control in hospitalized patients.

English

Body weight and twelve body measurements taken on fifteen ewes and five rams of the Zambian indigenous Fat-tailed were analysed. The sheep were extensively managed in the Southern and driest part of Zambia. The aim of the study was to achieve a preliminary assessment of type and function of the breed based on zoometrical indices produced from combinations of different morphometric values obtained from the field. The body measurements used were body length, cannon perimeter, chest depth, head width and length, heart (thoracic) girth, hip length and width, rump height, head width and lenght, and withers height. From these linear measurements there were derived eleven indices: Body, cephalic, cranial, dactyl–thoracic, depth, foreleg length, height, height slope, pelvic, relative cannonthickness, rump-length and weight indexes. The tested indices showed that Zambian indigenous Fattailed sheep are mildly productive meat animals. The respective coefficient of variation between breeds (flocks/herds) indicates the amount of opportunity available for improving the breed through selection. The need for further investigations is presented but as a matter of fact a separation of Zambian fattailed sheep breed from the others could be suspected.

Probiotics for broiler chickens in Brazil: systematic review and meta-analysis

This study evaluated the efficacy of probiotic utilization as growth promoters in broiler chicken feeding using systematic literature review and meta-analysis. Thirty-five studies were recovered by the systematic review, 27 of which met the following criteria to be included in the meta-analysis: (1) Brazilian studies published between 1995 and 2005; (2) probiotics administered in the diet without growth promoter; (3) results included performance data with the respective coefficient of variation. Meta-analysis have shown that the probiotics promoted better weight gain and feed conversion than the negative control (no antimicrobial) in the initial phase (1 to 20-28 days); nevertheless, results were similar in the total period (1 to 35-48 days). Weight gain and feed conversion were similar between probiotics and the positive control (with antimicrobial) both in the initial and in the total periods. Viability in the total period improved with the use of probiotics in comparison to the negative or positive controls. Sensitivity analysis showed that the results of meta-analysis were coherent. The funnel plots and the Egger regression method evidenced that the studies published in Brazil do not present biased results. It is possible to conclude that the probiotics are a technically viable alternative to antimicrobial growth promoters in broiler feeding. Nevertheless, further studies are necessary to identify eventual differences among the probiotics commercially available in Brazil.

Doppler Investigation of Within-Session Reproducibility in a Visual Stimulation Task to Assess the Volunteer-Dependent Variation

Objective: In functional magnetic resonance imaging (MRI) studies in humans the tightness of activity-flow coupling was questioned due to a notable within-session variability of the signals obtained. To differentiate between moments of volunteer-dependent or technique-inherent variation in hemodynamic MRI measurements a method with a low technique-inherent variation is needed. Therefore, and because temporal features might also be of some relevance, we used the transcranial Doppler method. Methods: In 22 healthy volunteers the flow-velocity response to a visual stimulation task was evaluated. Conditions of 20 s of eye closure were altered with 40 s of silent reading, repeated 10 times. Averaged individual flow-velocity responses were evaluated from conditions of 40 s of stimulation and a 5-second time interval prior to the beginning of stimulation. The averaged data were subtracted from each single recording to calculate the mean squared differences (MSD). Statistical evaluation was performed according to a two-way ANOVA for repeated measures. To obtain additional qualitative data of the flow response, the individual flow curves were evaluated according to a control system approach specifying a second-order linear model. Results: The coefficient of variation (COV) of the within-session MSD was 7% for the stimulation phase and 2.9% for the resting phase, whereas the respective COVs were 15 and 8.1% for the interindividual MSDs. The interindividual COVs of control system parameters ranged from 3.6 to 7.6%. The ANOVA resulted in a significant (p < 0.003) difference for the MSD values between stimulation conditions, whereas the test repetition (p = 0.55) and the test for an interaction of repetition and stimulation condition (p = 0.54) revealed no significance. Discussion: Confirming the notion of a tight coupling between cortical activity and cerebral blood flow and being indicative of a low technique-inherent variation, we found a high within-session reproducibility in a functional Doppler test.

Estimates of variances due to sire × herd interactions and environmental covariances between paternal half-sibs for first lactation dairy production

The concepts of a sire × herd interaction and of an environmental covariance, common to all daughters of the sire in a herd, are statistically equivalent. Estimates of the variance due to interaction reflect both interactions and common environmental effects and vice versa. Hence, environmental covariances were estimated as the variance due to a sire × herd (or herd-year-season) effect and c 2 effects were defined as the proportion of the phenotypic variance due to this interaction. Estimates were obtained for milk, fat and protein yield and fat and protein content. Data consisted of lactation records of 391 156 British Friesian-Holstein heifers, calving between November 1981 and October 1983. Analyses were carried out considering records from pedigree, non-pedigree and “mixed” herds, separately. Effects of transforming data to logarithmic scale and of standardizing records in each herd according to the pooled within-herd-year-season variance or respective coefficient of variation were investigated. Interaction components of variance amounted on average to half of the respective sire components. Estimates of c 2 were higher for yields (2.1–4.3%) than for contents (1.7–2.9%) and higher fitting a sire × herd-year-season than a sire × herd interaction. Values were considerably lower for non-pedigree than for other herds. Transforming or standardizing records reduced c 2 throughout, indicating that estimates may have been inflated by differences in variability between herds. Variances between sires and heritabilities were markedly higher for pedigree data, differences could only partially be explained by scale effects or differing selection intensities. Sire evaluation procedures should account for c 2 effects to minimize bias due to “preferential treatment” and to avoid overestimates of the accuracy of sire proofs, in particular for limited herd-use sires.