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Special Cycle-Ergometer to Optimize the Rider Position through Force Measurement
No full textThis paper presents an original 7-degrees of freedom device to analyze, test and optimize different positions of a bicycle rider. The system allows data acquisitions of forces, angles and velocities during cycling performance. An overall of eight forces and three angles are simultaneously measured.
An efficient position enables the rider to reduce the muscular effort for a given power produced. Basically good bike position presents three general parameters: saddle height, saddle-to-bar distance, and fore/aft saddle position. Determining the correct horizontal saddle position is of relevant importance in finding the correct fit for a road cyclist and the optimal frame geometry.
Moreover saddle position determines seat tube angle as well as the top tube/stem length dimension. The traditional method consists of positioning the rider's saddle so that the knee (the tibial tuberosity) is over the pedal spindle with the crank in horizontal position. This method considers only partially the relation between the positions of arms and torso for different physiques. This special device, adjusted through hydraulic cylinder actuators, allows to achieve optimum horizontal saddle position by measuring horizontal forces on saddle and handlebar. The aim of the research is to determine a quantitative method to establish the optimum rider position in order to minimize the muscular efforts in aerobic phase. Moreover special pedals, developed both for cycling sport performances and for clinical analysis, equipped with three-axial load cells, measure the effective pedalling force exerted by the rider in three orthogonal directions. In particular the lateral force components on the pedals, perpendicular to the para-sagittal plane are measured. Notwithstanding literature usually neglects the lateral components in pathological and non pathological subjects, these components provide meaningful information in rehabilitation treatment of pathological subjects and moreover the biomechanical analysis of pedalling through three-axial force measurements over each pedal allows to improve efficiency during cycling performance
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
A study on the biomechanical efficiency of different cycling positions
No full textIt is well known that several are the "biomechanical" parameters (e.g. the pedalling frequency, the crank-arm length, the saddle height, the seat tube angle, etc only to name a few) that could affect cycling performance. Even if the optimal values and the sensitivity of each parameter would differ whether the efficiency or the power output have to be maximized, the variations in the positioning of the athlete are found to be, in either case, of particular importance. The biomechanical analysis of bicycle pedalling through experimental devices designed to evaluate the muscular efficiency of the lower limbs is an important asset in sport medicine. In this field, one of the main effort is focused to improve athlete’s performance through special positions that may influence the muscular coordination and the pedalling technique [1] [2].. For these reasons, in the last decades many researches has been carried out in sport medicine making use of both mechanical and medical techniques. The biomechanical analysis of pedalling requires a theoretical model together with a proper experimental device, suitably equipped to detect the parameters involved by the model in order to obtain a fully determined activity monitoring [3]. Then by a mathematical model of the two human body structures, the skeleton and the muscular apparatus, the kinematics and dynamics of the system of lower limbs and crank can be obtained. The medical techniques mainly consist of estimating the muscle metabolism based on measurements of heart rate, lactate production, oxygen uptake and determination of the ventilatory threshold [4] while mechanical-engineering devices are developed to detect the kinematical and dynamical parameters [5].
In order to study the improvement in the cycling performance due to variations in the position, a systematic series of tests on an actuated and instrumented bicycle prototype were performed in this research. In particular the relationship between the mechanical and the physiological parameters are taken into account with particular concern to the maximal O2 consumption (Vo2max) and the lactate production registered with different values of the seat tube angle (STA) and the frame geometry. Ten semi-professional road male cyclist volunteers participated in the experiments. In the first step the tests were performed in two different sessions (separated at the most by one week) at approximately the same hour of the day. The special prototype adopted allows to detect the external mechanical power, the pedalling frequency, the force exerted on each pedal in three main directions, the angle of oscillation of each pedal during revolution and the forces exerted on the saddle and the handlebar. By “link-segment modeling” and considering the kinematical parameters, by means of an inverse dynamic procedure it is possible to calculate the internal actions and in particular the moments acting on each link segment with free-body diagram method. The bidimensional five-bar linkage model has been previously and successfully applied in many researches [6].
The athletes were equipped with a portable system (Cosmed quark b2) to measure pulmonary ventilation (VE, [lmin-1]), HR [bpm], carbon dioxide output (VCO2, [lmin-1]) and oxygen uptake (VO2; [lmin-1]) on time basis. In the first session, performed with the ergometer in a configuration reproducing the position of each subject usual bicycle frame, the athletes were monitored passing from a resting state reproducing their natural metabolic rate and gradually increasing the external mechanical power by 50 W every 5 min. The subjects were requested to maintain the 90 rpm pedalling cadence at each load rate. In this way the anaerobic threshold with V-slope method was determined for each subject and the power rate for the second session was determined.
In the second experimental session the subjects were requested to repeat the test with the fixed power and pedalling rate while the STA was changed from 70° to 75° with an interval of 1 degree every 5 min. The tests performed with a rigid protocol shows an interesting relationship between the trend of the coefficient of variation of O2 consumption (respiratory dynamics) and the forces measured on saddle and handlebar. The stabilization of the respiratory dynamics registered for a particular position could be considered as a first step of O2 consumption physiologic adaptation.
On the basis of this results a second step was carried out to analyze the long term adaptation concerning other metabolic parameters i.e. lactate involved in the process. A professional road male cyclist performed the same two previous experimental sessions, with the same accurate protocol, and then was requested to train for 8 weeks with a frame bicycle that reproduced the equilibrium force position between the horizontal component of the force on the saddle and on the handlebar registered with the prototype ergometer. The test seems to confirm the presence of a stabilization of the respiratory dynamics in case of equilibrium between the force on saddle and handlebar for a particular position and suggests the possibility to identify an optimization of the O2 consumption
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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