Variables Of Foot Research Articles

Increased foot strike variability in Parkinson's disease patients with freezing of gait

IntroductionFreezing of gait (FOG) is a debilitating, late motor complication of Parkinson's disease (PD) that occurs in 50–80% of patients. Gait freezing significantly worsens quality of life by decreasing mobility and increasing falls. Studies have shown that patients with episodic freezing episodes also have deficits in continuous gait. We evaluated whether there was an objective gait correlate to the increased stumbling reported by many patients with gait freezing. MethodsPD subjects and healthy controls (HC) were enrolled after IRB approval. Subjects with more than 1 fall/day or a Montreal Cognitive Assessment score <10 were excluded. Subjects walked at their normal pace, 8 lengths of a 20 × 4 foot pressure-sensor mat. Data was collected and analyzed using PKMAS software (Protokinetics) and statistical analysis performed using SPSS 22 (IBM). Results72 age matched subjects (22 PD FOG, 27 PD no-FOG, and 23 HC) were enrolled. Disease duration and Hoehn & Yahr scores were not significantly different between the PD groups. Mean dimensions of foot strike were not significantly different between groups, but PD FOG subjects had increased step-to-step variability in foot strike as measured by the percent coefficient of variation (%CV) in foot strike length compared to PD no-FOG and HC, independent of stride velocity. In PD no-FOG subjects, fallers also had higher variability in foot strike length compared to non-fallers. ConclusionPD subjects with FOG had increased variability in foot strike suggesting that in addition to stride length variability, foot strike variability could contribute to imbalance leading to falls.

Evaluating variability in foot to pedal movements using functional principal components analysis

There are reasons why the driver’s foot may not be applied to the correct pedal while driving and this can lead to unintended consequences. In this study, we seek to capture common and unique patterns of variations in drivers’ foot movements using functional principal components analysis (FPCA). This analysis technique was used to analyze three categories of pedal response types (direct hits, corrected trajectories, and pedal errors) based on the various foot to pedal trajectories. Data from a driving simulator study with video data of foot movements for 45 drivers was used for analyses. Most foot movements show common patterns associated with direct hits and corrected trajectories with some level of variation. However, those foot movements associated with unique patterns might be early indicators of pedal errors. The findings of this study can be used with collision mitigation systems to provide early detection of foot trajectories that are more likely to result in a pedal error.

Sources of variability in foot and mouth disease vaccine potency estimates based on serum neutralizing antibody assay

Some vaccines can be assayed for potency by measuring the serum antibody response they produce in vaccinated test animals. Using data obtained from potency assays on batches of foot and mouth disease vaccine, the sources of variability in such a method were examined. A linear model is proposed for the analysis of replicate serum neutralizing antibody assays, which represents an improvement on the usual approach of working with only a mean serum assay value for each test animal. Components of variance were calculated, allowing the relative importance of the numbers of test animals, or the numbers of serum assays per test animal, to be estimated in terms of the variability of the overall group mean antibody response. A method is described for calculating fiducial intervals for the serological potency estimates, and it is shown that these intervals are no larger than, and are in fact probably smaller than, those obtained from quantal challenge tests. The results have important implications for the design and analysis of similar biological tests used for other products.