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Slower Speed (slower + speed)
Selected AbstractsSubventricular zone-derived neuroblast migration to the olfactory bulb is modulated by matrix remodellingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2007Serena Bovetti Abstract In the rodent brain neural progenitor cells are born in the subventricular zone and migrate along a pathway called the rostral migratory stream (RMS) into the olfactory bulb where they differentiate into several classes of interneurones. In the adult, tangential migration in the RMS takes place in ,chains' of cells contained within glial tubes. In contrast, neonatal neuroblasts along the RMS lack these defined glial tubes and chains, migrating instead as individual cells. Time-lapse confocal microscopy of neuroblasts at each of these ages shows that individual cells migrate in a saltatory manner with bursts of high speed followed by periods of slower speed. Tangential migration within a glial tube is 20% faster than migration as individual cells. Neuroblasts may also interact and modify the extracellular matrix during migration through expression of a family of proteins, the matrix metalloproteinases (MMPs). MMPs are present and active along the subventricular zone,olfactory bulb pathway. In the presence of inhibitors of MMPs, neuroblast migration rates were reduced only when cells migrate individually. Chain migration in the adult was unaffected by MMP inhibitors. Taken together, these data suggest that MMPs only influence migration as individual cells and not as chains. [source] Stair Performance in People Aged 75 and OlderJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 4 2004Kathryn A. Hamel PhD Objectives: To examine specific behaviors used by older adults while ascending and descending stairs and to assess the relationships between confidence and stair performance. Design: Cross-sectional. Setting: Center for Locomotion Studies, The Pennsylvania State University. Participants: Sixteen male (mean age=82.7, range= 77,89) and 16 female (mean age=82.2, range=77,87) community-dwelling adults. Measurements: A stair self-efficacy (SSE) test was created to assess individuals' confidence in their safety on stairs. Observational stair performance measures, measures of walking speed on stairs, and the total SSE score were examined for differences due to sex, and the relationships between SSE and specific stair behaviors were assessed. Results: There was a significant relationship between SSE and the safety precautions taken during stair negotiation. Those with lower SSE were more likely to ascend and descend the stairs at a slower speed, use the handrail to a greater extent, and position themselves closer to the rail. The women had lower domain-specific SSE and tended to use the handrail to a greater extent than men even though there were no sex differences in self-reported functional ability or general falls and mobility confidence. A small group of subjects exhibited characteristics of instability, particularly during stair descent, yet most of this group had high SSE scores and failed to use the handrail. Conclusion: It appears that confidence related to stair negotiation plays a major role in determining risk-taking propensity during stair use in older adults. [source] Reliability of measurement of angular movements of the pelvis and lumbar spine during treadmill walkingPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 4 2001Nicholas Taylor Abstract Background and Purpose Angular movements of the pelvis and lumbar spine are thought to play an important role in walking. However, little is known about the amount of unpredictable variability in measurement of these movements during human walking. The aim of the present study was to determine the retest reliability of measuring the angular movements of the pelvis and lumbar spine during unimpaired familiarized treadmill walking. Method Retest reliability for 26 subjects without pathology was determined over a one-week interval. Subjects walked on a treadmill at self-selected or a slower speed while measurements of the three-dimensional angular movements were taken with a computer-based video analysis system. Results The frontal plane movements of pelvic list and lumbar lateral flexion (relative to the pelvis) could be measured with high retest reliability at both self-selected and slow walking speeds (intraclass coefficient (ICC) (2,1) , 0.81). In contrast, transverse and sagittal plane movements demonstrated moderate reliability at both speeds (0.37 , ICC (2,1) , 0.76). Averaging the measurement over six strides resulted in increased observed reliability (self-selected walking speed summary Pearson's r = 0.71, slow walking speed summary Pearson's r = 0.79) compared to taking the measurement based on a single stride (self-selected walking speed summary Pearson's r = 0.63, slow walking speed summary Pearson's r = 0.67). Unlike pelvic and lumbar movements (relative to the pelvis), the measurement of lumbar movements (relative to the global reference frame) appeared to depend on whether subjects were walking at self-selected or slow speeds. Conclusions Measurement of pelvic list and lumbar lateral flexion (relative to the pelvis) could be applied with confidence to hypothesis testing about individuals or groups. Movements in the transverse and sagittal planes are unlikely to be appropriate in hypothesis testing about individuals and hence clinical practice, but may still have experimental applications in hypothesis testing about groups. Copyright © 2001 Whurr Publishers Ltd. [source] Not so fast: Speed effects on forelimb kinematics in cercopithecine monkeys and implications for digitigrade postures in primatesAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2009Biren A. Patel Abstract Terrestrial mammals are characterized by their digitigrade limb postures, which are proposed to increase effective limb length (ELL) to achieve preferred or higher locomotor speeds more efficiently. Accordingly, digitigrade postures are associated with cursorial locomotion. Unlike most medium- to large-sized terrestrial mammals, terrestrial cercopithecine monkeys lack most cursorial adaptations, but still adopt digitigrade hand postures. This study investigates when and why terrestrial cercopithecine monkeys adopt digitigrade hand postures during quadrupedal locomotion. Three cercopithecine species (Papio anubis, Macaca mulatta, Erythrocebus patas) were videotaped moving unrestrained along a horizontal runway at a range of speeds (0.4,3.4 m/s). Three-dimensional forelimb kinematic data were recorded during forelimb support. Hand posture was measured as the angle between the metacarpal segments and the ground (MGA). As predicted, a larger MGA was correlated with a longer ELL. At slower speeds, subjects used digitigrade postures (larger MGA), however, contrary to expectations, all subjects used more palmigrade hand postures (smaller MGA) at faster speeds. Digitigrade postures at slower speeds may lower cost of transport by increasing ELL and step lengths. At higher speeds, palmigrade postures may be better suited to spread out high ground reaction forces across a larger portion of the hand thereby potentially decreasing stresses in hand bones. It is concluded that a digitigrade forelimb posture in primates is not an adaptation for high speed locomotion. Accordingly, digitigrady may have evolved for different reasons in primates compared to other mammalian lineages. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source] | |||||||||||||