Browsing by Author "Barbosa, Tiago M."
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- Assessment of passive drag in swimming by numerical simulation and analytical procedurePublication . Barbosa, Tiago M.; Ramos, Rui; Silva, António; Marinho, DanielThe 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 characteristics.
- Association Between Force-Time Curve Characteristics and Vertical Jump Performance in Trained AthletesPublication . Marques, MC; Izquierdo, Mikel; Marinho, Daniel; Barbosa, Tiago M.; Ferraz, Ricardo; González-Badillo, Juan JoséCountermovement jump (CMJ) has been extensively used in training; yet, limited and contradictory kinematic data are available for trained subjects. To our best knowledge, no other studies have evaluated the associations between force-time curve characteristics and CMJ in a large sample of trained athletes using a linear transducer. Thus, the aim of this study was to determine the association between force-time measures and CMJ performance collected with a linear transducer. Thirty-five trained athletes were asked to perform 3 maximal weighted CMJ using a linear transducer attached to a barbell (17 kg). The data indicated that the maximal rate of force development (RFD(max)) was strongly related to CMJ displacement (r = 0.809/0.807, p < 0.001) and also to the percentage of peak force (r = -0.823/-0.809, p < 0.001) at RFD(max). Velocity and displacement at RFD(max) were not correlated to CMJ height. It was therefore concluded that the percentage of PF applied at RFD(max) and RFD(max) were the best predictive variables for CMJ performance in this study.
- Can 8-weeks of Training Affect Active Drag in Young Swimmers?Publication . Marinho, Daniel; Barbosa, Tiago M.; Costa, Mário Jorge; Figueiredo, Catarina; Reis, Victor M.; Silva, António; Marques, Mário CThe aim of this study was to assess the effects of 8-weeks of training on active drag in young swimmers of both genders. Eight girls and twelve boys' belonging to the same swimming team and with regular competitive participation in national and regional events for the previous two seasons participated in this study. Active drag measurements were conducted in two different evaluation moments: at the beginning of the season and after 8 weeks of training (6.0 ± 0.15 training units per week, 21.00 ± 3.23 km per week and 3.50 ± 0.23 km per training unit). The maximal swimming velocity at the distance of 13 m, active drag and drag coefficient were measured on both trials by the method of small perturbations with the help of an additional hydrodynamic body. After 8 weeks of training, mean active drag (drag force and drag coefficient) decreased in girls and boys, although no significant differences were found between the two trials. It seems that 8 weeks of swimming training were not sufficient to allow significant improvements on swimming technique. Key pointsThe velocity perturbation method seems to be a good, simple and reliable approach to assess active drag in young swimmers.Eight weeks of swimming training were not sufficient to allow significant improvements on swimming hydrodynamics.There were no differences between boys and girls concerning active drag. A possible explanation may be related to the similar values of body mass and height in boys and girls found in this study.Specific training sets concerning technique correction and improvement in young swimmers might be a main aim during training planning.
- Can concurrent teaching promote equal biomechanical adaptations at front crawl and backstroke swimming?Publication . Costa, Mário Jorge; Barbosa, Tiago M.; Morais, Jorge; Miranda, Sérgio; Marinho, DanielThe biomechanical adaptations in front crawl and backstroke swimming, as influenced by the implementation of a concurrent teaching programme were analysed. 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.
- Changes of the energetic profile in masters' swimmers over a seasonPublication . Ferreira, M I; Barbosa, Tiago M.; Neiva, Henrique; Alves, J Vilaça; Costa, M J; Marinho, DanielThe aim of this study was to track and compare the changes of performance and energetic profile of male and female masters swimmers during a season. Eleven female (age: 34.7±7.3-y) and fourteen male (age: 35.6±7.4-y) with 4.2±3.7-y and 3.9±1.6-y of experience in masters, respectively, performed an all-out 200 m freestyle to evaluate total energy expenditure (Etot), aerobic (Aer), anaerobic lactic (AnL) and alactic (AnAl) contributions. The oxygen uptake (VO2) was measured immediately after the 200 m trial and the VO2 reached during the trial was estimated through the backward extrapolation of the O2 recovery curve. Fingertip capillary blood samples were collected before the 200 m trial and 3, 5, and 7 minutes after its end. Significant differences were observed between male (TP1:177.50±30.96s; TP2:174.79±29.08s; TP3:171.21±22.38s) and female (TP1:205.18±24.47s; TP2: 197.45±20.97s; TP3: 193.45±18.12s) for 200 m freestyle performance at the three time periods (TPs). Male presented higher Etot in all TPs (TP1:230.40±48.40kJ; TP2:242.49±37.91kJ; TP3:257.94±46.32kJ) compared with that found for female swimmers (TP1:188.51±35.13kJ; TP2:193.18±20.98kJ; TP3:199.77±25.94kJ). Male presented higher AnL (TP1:33.42±6.82kJ; TP2:30.97±8.73kJ; TP3:30.66±8.27kJ) and AnAl (TP1:30.61±3.48kJ; TP2:30.61±3.48kJ; TP3:30.60±3.48kJ) than female (TP1:18.83±8.45kJ; TP2:14.98±4.17kJ; TP3:18.33±8.66kJ) and (TP1:24.32±2.22kJ; TP2:24.31±2.23kJ; TP3: 24.31±2.23kJ). Aerobic metabolism is the major contributor for Etot both in male (TP1:71.63±4.99%; TP2:74.05±5.03%; TP3:76.14±4.46%) and female swimmers (TP1:76.87±3.86%; TP2:79.40±3.63%; TP3:78.40±5.54%). The better performance obtained by male compared to female swimmers may be due to the different contributions of the energetic pathways. Aerobic metabolism was the major contributor to Etot in a 200 m race, in both genders. Partial aerobic contribution was higher in female, while partial anaerobic contribution was greater in male.
- Characterization of speed fluctuation and drag force in young swimmers: A gender comparisonPublication . Barbosa, Tiago M.; Costa, Mário Jorge; Morais, Jorge; Morouço, Pedro; Moreira, Marc; Garrido, Nuno; Marinho, Daniel; Silva, AntónioThe aim of this study was to compare the speed fluctuation and the drag force in young swimmers between genders. Twenty-three young pubertal swimmers (12 boys and 11 girls) volunteered as subjects. Speed fluctuation was measured using a kinematical mechanical method (i.e., speedo-meter) during a maximal 25-m front crawl bout. Active drag, active drag coefficient and power needed to overcome drag were measured with the velocity perturbation method for another two maximal 25m front crawl bouts with and without the perturbation device. Passive drag and the passive drag coefficient were estimated using the gliding decay velocity method after a maximal push-off from the wall while being fully immersed. The technique drag index was also assessed as a ratio between active and passive drag. Boys presented meaningfully higher speed fluctuation, active drag, power needed to overcome drag and technique drag index than the girls. There were no significant gender differences for active drag coefficient, passive drag and passive drag coefficient. There were positive and moderate-strong associations between active drag and speed fluctuation when controlling the effects of swim velocity. So, increasing speed fluctuation leads to higher drag force values and those are even higher for boys than for girls.
- Cluster Stability as a New Method to Assess Changes in Performance and its Determinant Factors Over a Season in Young SwimmersPublication . Morais, Jorge; Silva, António; Marinho, Daniel; Seifert, Ludovic; Barbosa, Tiago M.To apply a new method to identify, classify, and follow up young swimmers based on their performance and its determinant factors over a season and analyze the swimmers' stability over a competitive season with that method. Fifteen boys and 18 girls (11.8±0.7 y) part of a national talent-identification scheme were evaluated at 3 different moments of a competitive season. Performance (ie, official 100-m freestyle race time), arm span, chest perimeter, stroke length, swimming velocity, speed fluctuation, coefficient of active drag, propelling efficiency, and stroke index were selected as variables. Hierarchical and k-means cluster analysis were computed. Data suggested a 3-cluster solution, splitting the swimmers according to their performance in all 3 moments. Cluster 1 was related to better performances (talented swimmers), cluster 2 to poor performances (nonproficient swimmers), and cluster 3 to average performance (proficient swimmers) in all moments. Stepwise discriminant analysis revealed that 100%, 94%, and 85% of original groups were correctly classified for the 1st, 2nd, and 3rd evaluation moments, respectively (0.11≤Λ≤0.80; 5.64≤χ2≤63.40; 0.001
- A Comparison of Experimental and Analytical Procedures to Measure Passive Drag in Human SwimmingPublication . Barbosa, Tiago M.; Morais, Jorge; Forte, Pedro; Neiva, Henrique; Garrido, Nuno; Marinho, DanielThe aim of this study was to compare the swimming hydrodynamics assessed with experimental and analytical procedures, as well as, to learn about the relative contributions of the friction drag and pressure drag to total passive drag. Sixty young talented swimmers (30 boys and 30 girls with 13.59±0.77 and 12.61±0.07 years-old, respectively) were assessed. Passive drag was assessed with inverse dynamics of the gliding decay speed. The theoretical modeling included a set of analytical procedures based on naval architecture adapted to human swimming. Linear regression models between experimental and analytical procedures showed a high correlation for both passive drag (Dp = 0.777*Df+pr; R2 = 0.90; R2a = 0.90; SEE = 8.528; P<0.001) and passive drag coefficient (CDp = 1.918*CDf+pr; R2 = 0.96; R2a = 0.96; SEE = 0.029; P<0.001). On average the difference between methods was -7.002N (95%CI: -40.480; 26.475) for the passive drag and 0.127 (95%CI: 0.007; 0.247) for the passive drag coefficient. The partial contribution of friction drag and pressure drag to total passive drag was 14.12±9.33% and 85.88±9.33%, respectively. As a conclusion, there is a strong relationship between the passive drag and passive drag coefficient assessed with experimental and analytical procedures. The analytical method is a novel, feasible and valid way to gather insight about one's passive drag during training and competition. Analytical methods can be selected not only to perform race analysis during official competitions but also to monitor the swimmer's status on regular basis during training sessions without disrupting or time-consuming procedures.
- Complementing Warm-up with Stretching Routines: Effects in Sprint PerformancePublication . Marinho, Daniel; Gil, Maria Helena; Marques, MC; Barbosa, Tiago M.; Neiva, HenriqueThe present study aimed to examine the effects of using static or dynamic stretching added to the common warm-up routine for short sprint distances and to repeated sprint performance. In 3 different sessions, 16 college-age men (n = 10) and women (n = 6) performed one of 3 warm-ups followed by a 2 × 60 m dash sprint time trial (5 min of rest) in a counterbalanced design. The control warm-up consisted of 10 min of light-intensity running, and the 2 experimental warm-ups included a static or dynamic stretching routine (5 exercises) in the control warm-up. Performance (time) and physiological variables (tympanic temperature, heart rate) were monitored. In the first 60 m time trial, there were no differences between the 3 warmups tested (F = 0.21, p = 0.73; ηp 2 = 0.01), as opposed to that observed in the second (F = 7.04, p < 0.01; ηp 2 = 0.32). The participants were 1.7 % faster after the static stretching warm-up compared with the control warm-up. The sum of the time performed in the 2 sprints emphasizes these results, with better performances after the static stretching warm-up than the control (1 %) or dynamic stretching warm-up (0.7 %). These results suggest that including a set of static or dynamic stretching exercises may enhance sprinting performance. The better performance in the second trial after the warm-up including static stretching suggests that this type of stretching may positively influence repeated sprint performance ( < 10 s sprint).
- Deep and Shallow Water Effects on Developing Preschoolers’ Aquatic SkillsPublication . Costa, Aldo M.; Marinho, Daniel; Rocha, Helena Isabel Amaral; Silva, António; Barbosa, Tiago M.; Ferreira, Sandra S.; Martins, MartaThe aim of the study was to assess deep and shallow water teaching methods in swimming lessons for preschool children and identify variations in the basic aquatic skills acquired. The study sample included 32 swimming instructors (16 from deep water programs and 16 from shallow water programs) and 98 preschool children (50 from deep water swimming pool and 48 from shallow water swimming pool). The children were also studied regarding their previous experience in swimming (6, 12 and 18 months or practice). Chi-Square test and Fisher’s exact test were used to compare the teaching methodology. A discriminant analysis was conducted with Λ wilk’s method to predict under what conditions students are better or worse (aquatic competence). Results suggest that regardless of the non-significant variations found in teaching methods, the water depth can affect aquatic skill acquisition - shallow water lessons seem to impose greater water competence particularly after 6 months of practice. The discriminant function revealed a significant association between groups and all predictors for 6 months of swimming practice (p<0.001). Body position in gliding and leg displacements were the main predictors. For 12 and 18 months of practice, the discriminant function do not revealed any significant association between groups. As a conclusion, it seems that the teaching methodology of aquatic readiness based on deep and shallow water programs for preschoolers is not significantly different. However, shallow water lessons could be preferable for the development of basic aquatic skills.