Repositório Colecção:
http://hdl.handle.net/10198/114
2017-12-17T06:11:32ZAssessment of passive drag in swimming by numerical simulation and analytical procedure
http://hdl.handle.net/10198/14735
Título: Assessment of passive drag in swimming by numerical simulation and analytical procedure
Autor: Barbosa, Tiago M.; Ramos, Rui; Silva, A.J.; Marinho, D.A.
Resumo: The aim was to compare the passive drag-gliding underwater by a numerical simulation and an analytical procedure. An Olympic swimmer was scanned by computer tomography and modelled gliding at a 0.75-m depth in the streamlined position. Steady-state computer fluid dynamics (CFD) analyses were performed on Fluent. A set of analytical procedures was selected concurrently. Friction drag (Df), pressure drag (Dpr), total passive drag force (Df +pr) and drag coefficient (CD) were computed between 1.3 and 2.5 m · s−1 by both techniques. Df +pr ranged from 45.44 to 144.06 N with CFD, from 46.03 to 167.06 N with the analytical procedure (differences: from 1.28% to 13.77%). CD ranged between 0.698 and 0.622 by CFD, 0.657 and 0.644 by analytical procedures (differences: 0.40–6.30%). Linear regression models showed a very high association for Df +pr plotted in absolute values (R2 = 0.98) and after log–log transformation (R2 = 0.99). The CD also obtained a very high adjustment for both absolute (R2 = 0.97) and log–log plots (R2 = 0.97). The bias for the Df +pr was 8.37 N and 0.076 N after logarithmic transformation. Df represented between 15.97% and 18.82% of the Df +pr by the CFD, 14.66% and 16.21% by the analytical procedures. Therefore, despite the bias, analytical procedures offer a feasible way of gathering insight on one’s hydrodynamics characteristic2017-01-01T00:00:00ZLinear and nonlinear relationships between body mass index and physical fitness in Brazilian children and adolescents
http://hdl.handle.net/10198/14731
Título: Linear and nonlinear relationships between body mass index and physical fitness in Brazilian children and adolescents
Autor: Lopes, Vítor P.; Cossio-Bolaños, Marco; Gómez-Campos, Rossana; Arruda, Miguel; Hespanhol, Jefferson Eduardo; Rodrigues, Luis Paulo
Resumo: The purpose of this study was to evaluate the linear and curvilinear relationship
between body mass index (BMI) and physical fitness in children and
adolescents.
Participants were 4567 (2505 girls) children aged 6–16 years. Weight and
height were measured and BMI was calculated and adjusted for age and sex using
WHO z-scores. Physical fitness was evaluated with the following tests: Yo-Yo test,
standing long jump, seated 2-kg medicine ball throw, and 20-m dash. Participants
were grouped into two groups according to their maturity status, estimated as years
from peak height velocity. Associations were determined with linear and nonlinear
quadratic regression models.
The nonlinear quadratic regression coefficient was significant for the 20-m
dash among girls of both maturity status levels, and in maturity status level 1 boys;
for the standing long jump among boys of both maturity status levels, and in maturity
status level 1 girls. The Yo-Yo test was only significant for maturity status level 1
boys. For the medicine ball throw, the linear regression coefficient was significant for
both maturity status levels in both sexes. Almost all physical fitness items were
observed to have meaningfully large nonlinear relationships with BMIz, but they
were not all significant due to the small sample size, especially in maturity status
level 2.
Conclusion: The association between BMI and physical fitness is nonlinear in the
majority of its components, and those with lower and higher BMI had poorer fitness.2017-01-01T00:00:00ZEffectiveness of physical education to promote motor competence in primary school children
http://hdl.handle.net/10198/14490
Título: Effectiveness of physical education to promote motor competence in primary school children
Autor: Lopes, Vítor P.; Stodden, David F.; Rodrigues, Luis Paulo
Resumo: Motor skill (MS) competence is an important contributing factor for healthy development. The goal was to test the effectiveness of primary school physical education (PE) on MS and physical fitness (PF) development.
Three classes (n = 60, aged 9.0 ± 0.9) were randomly assigned to three diverse conditions during a school year: two PE lessons/week (PE-2), three PE lessons/week (PE-3), and no PE lessons control group (CG). BMI, skinfolds, PF (9-min run/walk, sit-up, modified pull-ups), gymnastics, soccer, handball, basketball and track-and-field skills were evaluated. Effect sizes (d) were reported as magnitude of change.
Skinfolds significantly increased only in CG (d = 1.21). PF composite z-scores improved in PE-3 (d = 0.61), but decreased in PE-2 (d = 0.57), and had no changes in CG. Statistically significant improvement was verified in gymnastics and handball skills in both experimental groups (gymnastic: d = 2.95 and d = 2.61 for PE-3 and PE-2, respectively; handball: d = 1.87 and d = 0.57 for PE-3 and PE-2, respectively), and no changes were seen in CG. In soccer, there were improvements only in the PE-3 (d = 0.55), and in basketball only in PE-2 (d = 0.46). There were no changes in any group for track-and-field skills. PE programs can effectively promote PF and MS development.2017-01-01T00:00:00ZMonitoring the biomechanics of a wheelchair sprinter racing the 100m final at the 2016 Paralympic Games
http://hdl.handle.net/10198/14414
Título: Monitoring the biomechanics of a wheelchair sprinter racing the 100m final at the 2016 Paralympic Games
Autor: Barbosa, Tiago M.; Coelho, Eduarda
Resumo: The aim was to run a case study of the biomechanics of a wheelchair sprinter racing the 100 m final at the 2016 Paralympic Games. Stroke kinematics was measured by video analysis in each 20 m split. Race kinetics was estimated by employing an analytical model that encompasses the computation of the rolling friction, drag, energy output and energy input. A maximal average speed of 6.97 m s(-1) was reached in the last split. It was estimated that the contributions of the rolling friction and drag force would account for 54% and 46% of the total resistance at maximal speed, respectively. Energy input and output increased over the event. However, we failed to note a steady state or any impairment of the energy input and output in the last few metres of the race. Data suggest that the 100 m is too short an event for the sprinter to be able to achieve his maximal power in such a distance.2017-01-01T00:00:00Z