1,721,073 research outputs found
Human locomotion: right/left symmetry in 3D trajectory of the body centre of mass
No full textSUMMARY
A mathematical 3D representation of displacement of centre of mass of human body (BCOM) during locomotion on treadmill has been used to assess, in each movement direction (forward, vertical and lateral), the symmetry of BCOM trajectory between the two stride phases (steps).
CONCLUSIONS
Differently from what expected, healthy human locomotion is rather asymmetrical. The illustrated methodology, by analysing even subtle changes in 3D BCOM trajectory, quantitatively describes the individual gait signature and represents the basis for evaluation of gait anomaly/pathology.
INTRODUCTION
Current literature lacks an accepted method globally describing the displacement pattern of BCOM during locomotion. The main purpose of this study was: to apply a mathematical function representing the 3D displacement of BCOM over time domain [1], identify and clarify its symmetry, and build up a comprehensive database of equations coefficients, designed to be the reference for healthy locomotion.
PATIENTS/MATERIALS AND METHODS
Seventy healthy subjects (35 men and 35 women) were recruited according to 7 different age groups (from 6 to 65 years). Each subject was requested to walk and run on treadmill at different speeds (0.83-1.94 m.s-1 for walking and 1.94-3.06 m.s-1 for running) on level. Each data capture lasted 1’. A motion capture system with 8 infrared cameras recorded kinematic data of relevant joints of body at 100 Hz. From them, 3D displacement of BCOM was calculated [2] and Fourier Series (1 coefficient amplitude and 1 phase per each harmonic, per 3 spatial coordinates, per 6 harmonics) and Lissajous contours graphically defined the Digital Locomotory Signature (DLS; see figure), a global index of BCOM dynamics. Harmonic coefficients were used to calculate the Symmetry Index (SI, 0: no symmetry, 1: complete symmetry), namely representing the spatial differences, in BCOM trajectory, between two steps. Differences between age groups (over speed) and between speeds (over age) were assessed by using t-tests.
RESULTS
No significant differences were found in SI between males and females. In each movement direction, SI was lower in young children (6-13 yrs; 0.79±0.03, in walking; and 0.75±0.03, in running; p<0.01) and in elderly adults (56-65 yrs; 0.82±0.04, in walking; and 0.80±0.03, in running; p<0.05) than in all the other age groups (pooled 14 to 55 yrs; 0.84±0.01, in walking; and 0.82±0.01, in running). Walking forward and vertical SI, in each age group, increased in the speed range 0.83-1.67 m.s-1 (p<0.001); medial/lateral direction SI slightly decreased (p<0.05). Running forward SI increased with speed (p<0.001).
DISCUSSION
Although no gender differences were found, human ‘healthy’ gait is rather asymmetrical. It is interesting to note that, in each testing condition, right and left steps are mostly symmetrical in the medial/lateral direction. Also, global asymmetry is more pronounced at extreme ages: while at early stages of lifespan this result could be ascribed to the process of gait development, old age asymmetries are probably due to structural wearing of musculo-skeletal system.
REFERENCES
[1] Minetti A. E. (2006) IMEC, Banff.
[2] Minetti A. E. et al. (1993) J. Physiol. 471: 725-735
Epicuro ed Ermarco: due statue-ritratto romane da Sarteano
No full textCaratterizzazione di due statue raffiguranti i filosofi greci Epicuro e Ermarco, provenienti da una villa romana nella Toscana meridionale e conservate nella Villa Corsini a Firenze
Functional study of residual iCre activity relevant for split-Cre applications
Full text linkCre-lox system is a major tool in mouse molecular genetics instrumental in promoting somatic recombination to spatiotemporally control transcriptional activation/inhibition in subsets of cells or tissues in vivo. A critical factor behind this system may be represented by the availability of a specific promoter driving Cre expression in the cell subset of interest. Split-Cre recombinase system represents an evolution that circumvents this limitation using split N- and C-terminal domains of Cre recombinase placed under the control of two distinct promoters defining an intersectional domain where functional complementation of Cre protein fragments is obtained. This system is a valuable tool for controlling Cre recombinase activity in a spatially and temporally defined manner based on the assumption that neither N- or C-terminal Cre fragments alone have recombinase activity. However, residual recombinase activity of one of the two fragments can occur leading to confounding experimental results. In this work, we delve into characterizing functional activity of different N-terminal deleted codon-optimized Cre (iCre) isoforms to refine Split-Cre-based technologies, aiming to avoid uncontrolled recombinase events. Given the presence of several methionine residues in the amino acidic iCre sequence, we explored whether these residues could serve as potential translation start sites, resulting in truncated isoforms that might retain recombinase activity. To address this question, we tested in HEK293T cells whether site-specific recombination was retained in progressively amino-terminal deleted iCre isoforms. Our results reveal residual enzymatic activity of most amino-terminal deleted isoforms of iCre whose ATG start codon is located downstream of the commonly used split site. This insight holds significance for future refinements of the widely used Split-Cre system, providing information to avoid false positive results stemming from unwanted activity
The transmission efficiency of backward walking at different gradients
No full textThe specialized design of the bipedal system towards forward locomotion has been assessed by measuring the metabolic cost and the mechanical work of both forward and backward walking on a treadmill at seven gradients from 0 to +32%. With respect to forward locomotion, backward walking implies: (1) a higher metabolic cost particularly at level gradient, while at steeper inclines the difference decreases, (2) the same mechanical internal work despite an increased stride frequency, (3) higher mechanical external work within a gradient range from 0 to +15%, (4) lower "energy recovery", i.e. the ability to save mechanical energy by moving as an inverted pendulum, mainly in level walking, and (5) as a consequence of the above results, a decrease of the efficiency of locomotion particularly at the 0% gradient. The transmission efficiency of backward walking, relative to the forward progression, was found to be about 65% in level locomotion, while at higher gradients it increased to and was maintained at a value of about 93%. The poorer economy of level backward walking could also be explained by an impaired elastic contribution in the last part of the double contact phase, while the similarity of the two gaits on higher gradients is caused by disruption of the pendulum-like paradigm due to the trajectory geometry of the body's centre of mass progressively losing its downward portion
New technologies in the evaluation of the elderly: a computational model predicting the dynamics of drop landing
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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