Predicting the intra-cyclic variation of the velocity of the centre of mass from segmental velocities in butterfly stroke: a pilot study

The purpose of this study was to analyze the relationship between the intra-cycle variation of the horizontal velocity of displacement of the center of mass (dV), the hand’s and feet’s velocity, as well as, to identify the variables that most predict the dV’s, in butterfly stroke. The study was divided in two parts. The aim of Part I was to investigate the behavior of variables in study at slow swimming velocities and the purpose of Part II was the same but at high swimming velocities. 3 male Portuguese swimmers and 1 female swimmer, of international level were studied in Part I. The swimmers were submitted to an incremental set of 200 m butterfly swims. In the Part II, 7 Portuguese male swimmers of national and international level were studied. Each swimmer performed two maximal 25 m butterfly swims. Both protocols were recorded from four different plans, allowing a 3D analysis. It was calculated the dV, the 3D components (Vx, Vy, Vz) of the hand’s velocity and the 2D components (Vx, Vy) of the feet’s velocity. Several variables presented significant correlation coefficients with dV at all selected velocities (high velocity ranged from r = 0.58 for Vx-out to r = 0.82 for Vy-1dwn; slow velocity ranged from r = -0.45 for Vx-1dwn to r=0.73 for Vx-ups; overall velocity ranged from r= 0.34 for Vz-ent to r = 0.82 for Vx-ins). It was also computed a regression model to predict dV. For high velocity (up to 1.75 ± 0.09 m.s-1), the variables that best predict dV were Vy during the first downbeat, Vx and Vy during the arm’s insweep (r2 = 0.93). At slow velocity (up to 1.48 m.s-1), the variables included in the forward step-bystep regression model were Vx during upsweep, Vy and Vx during insweep (r2 = 0.69). For overall velocity, the variables that most fit the regression model were Vx during upsweep, Vy during second downbeat and Vz during entry (r2= 0.94). In order to reduce dV, butterfliers should increase hand’s velocity in all orthogonal components at the end of the underwater path, should increase the vertical velocity durin

Social-Cognitive Theories to Explain Physical Activity

Despite the widely recognized health benefits of physical activity, participation in regular physical activity falls far short of the Global Action Plan on Physical Activity 2018–2030. More than half of the population does not reach current recommendations, and around one-fourth is not sufficiently active at all. Understanding social-cognitive theories may aid in the creation of interventions to improve long-term physical activity maintenance. The current work covers theory and research on physical activity patterns. It specifically provides an overview of contemporary conceptualizations of motivational and cognitive theories, as well as reviews recent perspectives on how physical activity can be adopted and maintained. Key questions, such as whether physical activity can be executed purely based on cognitive functions, are also addressed. Furthermore, this review identifies possible and effective intervention strategies to promote physical activity.info:eu-repo/semantics/publishedVersio

Fabrication of Poly(Glycerol Sebacate)-Poly(ε-Caprolactone) Extrusion-Based Scaffolds for Cartilage Regeneration

Acknowledgements: This research was supported by the European Regional Development Fund (FEDER), through COMPETE2020 under the PT2020 program (POCI-01-0145-FEDER-023423), by the Portuguese Foundation for Science and Technology (UID/Multi/04044/2013) and Centro2020 PAMI - ROTEIRO/0328/2013 (Nº 022158).Cartilage related diseases are on the top list concerns of the World Health Organization, being the prevention of articular cartilage degeneration a major health matter for which there are few effective solutions. Using an extrusion-based approach and a polyester elastomer it was aimed to produce 3D structures with controlled architecture and with closer mimicry to cartilage native tissue. The obtained constructs demonstrated high reliability, being the addition of poly (glycerol sebacate) a procedure to enhance the properties of the constructs.info:eu-repo/semantics/publishedVersio

CFD comparison of friction and pressure drag between road and time trial helmets for wheelchair racing

Computer Fluid Dynamics (CFD) has been used by sports scientists aiming to improve the athlete’s performance in sprinting events. In wheelchair sprinting velocity can reach 7m/s. Sports garment such helmets may reduce aerodynamic drag by 10%. The aim of this study was to compare the friction and pressure drag between a road and time trial helmet.info:eu-repo/semantics/publishedVersio

The variations on the aerodynamics of a world-ranked wheelchair sprinter in the key-moments of the stroke cycle: a numerical simulation analysis

Biomechanics plays an important role helping Paralympic sprinters to excel, having the aerodynamic drag a significant impact on the athlete's performance. The aim of this study was to assess the aerodynamics in different key-moments of the stroke cycle by Computational Fluid Dynamics. A world-ranked wheelchair sprinter was scanned on the racing wheelchair wearing his competition gear and helmet. The sprinter was scanned in three different positions: (i) catch (hands in the 12h position on the hand-rim); (ii) the release (hands in the 18h position on the hand-rim) and; (iii) recovery phase (hands do not touch the hand-rim and are hyperextended backwards). The simulations were performed at 2.0, 3.5, 5.0 and 6.5 m/s. The mean viscous and pressure drag components, total drag force and effective area were retrieved after running the numerical simulations. The viscous drag ranged from 3.35 N to 2.94 N, pressure drag from 0.38 N to 5.51 N, total drag force from 0.72 N to 8.45 N and effective area from 0.24 to 0.41 m2. The results pointed out that the sprinter was submitted to less drag in the recovery phase, and higher drag in the catch. These findings suggest the importance of keeping an adequate body alignment to avoid an increase in the drag force.This project was supported by the National Funds through FCT - Portuguese Foundation for Science and Technology (UID/DTP/ 04045/2013) - and the European Fund for regional development (FEDER) allocated by European Union through the COMPETE 2020 Programme (POCI- 01-0145-FEDER-006969). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.info:eu-repo/semantics/publishedVersio

Aerodynamic drag on helmet use in wheelchair racing

Nas provas de velocidade em cadeira de rodas os atletas paralímpicos recorrem à utilização de capacetesIn wheelchair racing sprinting events, Paralympics use helmets. During the strokes, athletes tend to oscillate the head with helmet use looking down and forward in only one stroke.info:eu-repo/semantics/publishedVersio

Estimation of an elite road cyclist performance in different positions based on numerical simulations and analytical procedures

The aim of this study was to use numerical simulations and analytical procedures to compare a cyclist's performance in three different cycling positions. An elite level road cyclist competing at a national level was recruited for this research. The bicycle was 7 kg and the cyclist 55 kg. A 3D scan was taken of the subject on the competition bicycle, wearing race gear and helmet in the upright position, in the handlebar drops (dropped position) and leaning on the elbows (elbows position). Numerical simulations by computer fluid dynamics in Fluent CFD code assessed the coefficient of drag at 11.11 m/s. Following that, a set of assumptions were employed to assess cycling performance from 1 to 22 m/s. Drag values ranged between 0.16 and 99.51 N across the different speeds and positions. The cyclist mechanical power in the elbows position differed from the upright position between 0 and 23% and from the dropped position from 0 to 21%. The cyclist's energy cost in the upright position differed 2 to 16% in comparison to the elbows position and the elbows position had less 2 to 14% energy cost in comparison to the dropped position. The estimated time of arrival was computed for a 220,000 m distance and it varied between 7,715.03 s (2 h:8 min:24 s) and 220,000 s (61 h:6 min:40 s) across the different speeds and positions. In the elbows position, is expected that a cyclist may improve the winning time up to 23% in comparison to he upright and dropped position across the studied speedsFunding. This work is supported by national funding through the Portuguese Foundation for Science and Technology, I.P., under project UIDB/04045/2020info:eu-repo/semantics/publishedVersio

A Novel Biomanufacturing System to Produce Multi-Material Scaffolds for Tissue Engineering: Concept and Preliminary Results

This research work aims to validate a new system that enables the fabrication of multimaterial 3D structures using poly(e-caprolactone) and sodium alginate for potential use in Tissue Engineering applications. To produce multi-material scaffolds for Tissue Engineering, accurate techniques are needed to obtain three-dimensional constructs with clinically appropriate size and structural integrity. This paper presents a novel biomanufacturing system which can fabricate 3D scaffolds with precise shape and porosity, through the control of all fabrication modules by an integrated computational platform. The incorporation of a clean flow unit and a camera makes it possible to produce scaffolds in a clean environment and provides a monitoring tool to analyse constructs during the production, respectively.info:eu-repo/semantics/publishedVersio

Estimation of mechanical power and energy cost in elite wheelchair racing by analytical procedures and numerical simulations

The aim was to compare the mechanical power and energy cost of an elite wheelchair sprinter in the key-moments of the stroke cycle. The wheelchair-athlete system was 3D scanned and then computational fluid dynamics was used to estimate the drag force. Mechanical power and energy cost were derived from a set of formulae. The effective area in the catch, release and recovery phases were 0.41m(2), 0.33m(2) and 0.24m(2), respectively. Drag increased with speed and varied across the key-moments. The catch required the highest total power (range: 62.76-423.46W), followed-up by the release (61.50-407.85W) and the recovery (60.09-363.89W).This project was supported by the National Funds [FCT - Portuguese Foundation for Science and Technology (UID/ DTP/04045/2013)] and the European Fund for regional development (FEDER) allocated by European Union through the COMPETE 2020 Programmeinfo:eu-repo/semantics/publishedVersio

Aerodynamics of a wheelchair sprinter racing at the 100m world record pace by CFD

The aim of this study was to analyze aerodynamics in a racing position of a wheelchair-racing sprinter, at the world record speed. The athlete and wheelchair were scanned at the beginning of the propulsive phase position (hands near the handrims at 12h) for the 3D model acquisition. Numerical simulation was run on Fluent, having as output the pressure, viscosity and total drag force, and respective coefficients of drag at the world record speed in T-52 category. Total drag was 7.56N and coefficient of drag was 1.65. This work helped on getting a deeper insight about the aerodynamic profile of a wheelchair-racing athlete, at a 100m world record speed.info:eu-repo/semantics/publishedVersio