Changes in classical kinematics and non‐linear parameters after a maximal 100‐m front‐crawl bout

In a linear system there is proportionality between input and output. Under this framework it is expected that the amount of change in sports performance must be proportional to variations in the inputs.info:eu-repo/semantics/publishedVersio

Changes in classical kinematics and non-linear parameters after a maximal 100-m front-crawl bout

In a linear system there is proportionality between input and output. Under this framework it is expected that the amount of change in sports performance must be proportional to variations in the inputs. However, as far as elite performance goes, this is not a straightforward assumption. Sometimes the variables selected are not sensitive enough. Hence, there is the need of having non-linear concepts underpinning such analysis. The aim was to compare classical kinematics and non-linear parameters after a maximal 100-m front-crawl bout. Twenty-four subjects (12 males and 12 females; 22.38±1.68-y) were invited to perform a 100-m freestyle race at maximal pace. Before (pre-test, i.e. rested) and immediately after (post-test, i.e. under fatigue) the maximal bout, they performed two maximal 25m swims at freestyle with push-off start. A speedo-meter cord (Swim speedo-meter, Swimsportec, Hildesheim, Germany) was attached to the swimmer’s hip (Barbosa et al., 2015) in the two 25m trials collecting the instantaneous speed. It was computed the speed fluctuation (dv; Barbosa et al., 2015), approximate entropy (ApEn; Barbosa et al., 2015) and fractal dimension (FD; Higuchi, 1988). Repeated measures ANOVAs (pre-test vs. post-test; P≤0.05), effect sizes (eta squared) and 95% of confidence intervals (95CI) were computed. The speed was 1.44±0.24 and 1.28±0.23m/s in the pre- and post/test, respectively (F=55.136, P<0.001)info:eu-repo/semantics/publishedVersio

Efeitos de um programa de 12 semanas de Hidroginástica na postura corporal de mulheres de meia-idade

À medida que a população mundial envelhece, sérias preocupações são levantadas sobre o efeito do exercício físico e de aptidão física para a saúde pública, especialmente na meia e terceira idade (Cruz-Ferreira et al., 2011). Os programas de exercícios aquáticos ganharam popularidade devido à diminuição de hipotéticos pacientes (i.e. ajudam na prevenção de patologias), e até mesmo entre indivíduos saudáveis (Costa et al., 2011). Ambos os programas, terrestres e aquáticos, baseiam-se no objetivo de alcançar e manter um nível adequado de aptidão física (incluindo a postura corporal) e, portanto, melhorar a qualidade de vida. A postura corporal tem em consideração a oscilação e/ou o alinhamento do corpo. O alinhamento do corpo representa a posição do corpo e a relação espacial entre os seus segmentos anatómicos para manter o equilíbrio, em condições estáticas ou dinâmicas, de acordo com os requisitos do ambiente e da tarefa motora. Um alinhamento adequado do corpo envolve o menor esforço (i.e. gasto energético) e sobrecarga mecânica, para otimizar a eficiência do sistema biológico. Uma postura corporal incorreta pode estar relacionada com alguma desordem a nível ortopédico (Kristensen, Bandholm, Holm, Ekdahl, & Kehlet, 2009), músculo-esquelético (Oyarzo, Villagrán, Silvestre, Carpintero, & Berral, 2013) ou neurológico (Busse, Zimdars, Zalewski, & Steffen, 2005), mas também associada com uma maior probabilidade de quedas (Sakamoto et al., 2006).info:eu-repo/semantics/publishedVersio

Variation of linear and nonlinear parameters in the swim strokes according to the level of expertise

The aim was to examine the variation of linear and nonlinear proprieties of the behavior in participants with different levels of swimming expertise among the four swim strokes. Seventy-five swimmers were split into three groups (highly qualified experts, experts and nonexperts) and performed a maximal 25m trial for each of the four competitive swim strokes. A speed-meter cable was attached to the swimmer's hip to measure hip speed; from which speed fluctuation (dv), approximate entropy (ApEn) and fractal dimension (D) variables were derived. Although simple main effects of expertise and swim stroke were obtained for dv and D, no significant interaction of expertise and stroke were found except in ApEn. The ApEn and D were prone to decrease with increasing expertise. As a conclusion, swimming does exhibit nonlinear properties but its magnitude differs according to the swim stroke and level of expertise of the performer.info:eu-repo/semantics/publishedVersio

Comparison of the fractal dimension among swimmers with different levels of expertise

It is known that performance is strongly related to proportional changes in the inputs. The “marginal gains theory” in sports performance gained popularity a few years ago. It encompasses the assumption that small changes in the input (or the sum of several changes) may have a significant effect on the output.info:eu-repo/semantics/publishedVersio

Skillful swimming in age-groups is determined by anthropometrics, biomechanics and energetics

This work was supported by the national funding through the Portuguese Foundation for Science and Technology, I.P., under the project UID/DTP/04045/2019, and European Regional Development Fund (FEDER) under the COMPETE 2020 Programme for Competitiveness and Internationalization (POCI) (POCI-01-0145-FEDER-006969). RB is an FCT-Ph.D. scholar (SFRH/BD/142009/2018).The aim was to compare the anthropometrics, biomechanics and energetics in young swimmers of different competitive levels. Seventy-five boys aged between 11 and 13 years-old with a broad range of performances were ranked based on their personal best time in the men’s 100m freestyle event and then split-up into three tiers (Tier-1, i.e., top-tier, best performers; Tier-2, mid-tier; Tier-3, lower-tier). A set of anthropometric features was measured (height, body mass, arm span and trunk transverse surface area). Stroke kinematics (speed, stroke length, stroke frequency) was assessed by a Speedo-meter. Swim efficiency was then estimated (stroke index, speed fluctuation, Froude efficiency). Hydrodynamics assessment encompassed the estimation of active drag and drag coefficient by velocity perturbation method and a set of dimensionless numbers (Froude, hull speed, Reynolds). Mechanical power (to overcome drag, transfer of kinetic energy to water, external power) and power input were derived. There was a significant variation with moderate effect sizes in all anthropometric features but the trunk transverse surface area. Tier-1 swimmers were taller, heavier and with longer limbs than remaining counterparts. There were also significant variations in the stroke kinematics with moderate-large effect sizes. Tier-1 swimmers showed higher stroke frequency, stroke length, speed, stroke index and propelling efficiency but lower speed fluctuations. Reynold number, Froude number and hull speed were significantly higher in Tier-1 swimmers, denoting large effect sizes. The mechanical power and power input delivered were significantly higher in tier-1 swimmers, showing moderate effect sizes. As a conclusion, it was noted significant variations, with moderate-large effect sizes, among the three tiers, for the vast majority of the selected variables. The better performances by tier-1 swimmers were related to their anthropometrics, biomechanics and energetics.info:eu-repo/semantics/publishedVersio

The changes in classical and nonlinear parameters after a maximal bout to elicit fatigue in competitive swimming

The aim was to assess the effect of fatigue on linear and nonlinear parameters in swimming. Twenty-four fitness-oriented swimmers performed a maximal bout of 100m at front-crawl to elicit fatigue. Before (pre-) and immediately after (post-test) the bout, participants swam an allout 25m to derive the speed fluctuation (dv), approximate entropy (ApEn) and fractal dimension (FD) from the speed-time series collected by a speedo-meter. Swim speed was 10.85% slower in the post-test than in the pre-test (p < .001, η2=0.72). There was an effect of the fatigue on the dv with a moderate effect size. The dv increased shifting the 95CI band from 0.116–0.134 to 0.140–0.161. The ApEn showed non-significant variations between the pre- and post-test having the 95CI of pre- and post-test overlapped (pre: 0.659–0.700; post: 0.641–0.682). The FD showed as well a significant variation (the 95CI moved from 1.954–1.965 to 1.933–1.951). It can be concluded that in swimming there are changes in classical and nonlinear parameters under fatigue.This research was funded by the NIE AcRF grant (RI 11/13 TB)info:eu-repo/semantics/acceptedVersio

Can concurrent teaching promote equal biomechanical adaptations at front crawl and backstroke swimming?

The biomechanical adaptations in front crawl and backstroke swimming, as influenced by the implementation of a concurrent teaching programme were analysed. Methods: Sixteen participants (19.75 ± 1.13 years) underwent a 30 weeks intervention characterized by an increasing complexity to accomplish motor skills in the following order: (i) lower limbs propulsion; (ii) lower limbs propulsion synchronized with breathing cycle; (iii) lower limbs propulsion synchronized with one upper limb action; (iv) lower limbs propulsion synchronized with both breathing cycle and one upper limb action; (v) full swimming stroke; (vi) motor trajectory of the arms stroke. Performance and biomechanics were measured at front crawl and backstroke during three time points throughout the programme. There were improvements in performance over time at front crawl (21.49 s to 19.99 s, p < 0.01) and backstroke (27.15 s to 24.60 s, p = 0.01). Significant improvements were found for velocity at front crawl (1.13 m/s to 1.22 m/s, p < 0.01) and backstroke (0.92 m/s to 1.00 m/s, p < 0.01). Stroke frequency increased at backstroke (0.64 to 0.73 Hz, p = 0.01), while the intra-cyclic variation of the velocity decreased at front crawl (0.13 to 0.12%, p = 0.02). There was also a moderate-high inter-subject variability in response to the programme. These findings prove that a programme of 30 weeks teaching concurrently front crawl and backstroke is effective to promote similar biomechanical adaptations in low-tier swimmers. However, each subject shows an individual response to better adapt the biomechanical actions and to reach a higher level of expertise.info:eu-repo/semantics/publishedVersio

Fractal analysis of human aquatic locomotion: an exploratory and descriptive study

Fractal analysis has recently been applied to study a wide range of objects/systems in Biology and Medicine to assess non-linear phenomena. Human swimming is a non-linear behavior and as much as we are aware, no fractal research was conducted in such locomotion technique.info:eu-repo/semantics/publishedVersio

Editorial: Building Mathematical Models for Multicriteria and Multiobjective Applications

In our daily lives or professional settings, there are many decision problems involving multiple criteria, which may be conflicting and incommensurable. The complexity of real-world decision and the plethora of factors involved necessitate the implementation of sound theoretical frameworks for structuring decision-making processes. Multicriteria Decision Making/Aid (MCDM/A) and multiobjective methods can be highly useful for decision makers (DMs) in such tasks. Multicriteria and multiobjective approaches provide a wide variety of methodological tools for supporting the DMs when facing real-world decision problems when designing and analyzing mathematical models, representing both the preferences of decision makers and the various characteristics of the decision problems at hand in a number of areas