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Pedro Figueiredo, Ana Silva, António Sampaio, João Paulo Vilas-Boas, and Ricardo J. Fernandes

The aim of this study was to evaluate the determinants of front crawl sprint performance of young swimmers using a cluster analysis. 103 swimmers, aged 11- to 13-years old, performed 25-m front crawl swimming at 50-m pace, recorded by two underwater cameras. Swimmers analysis included biomechanics, energetics, coordinative, and anthropometric characteristics. The organization of subjects in meaningful clusters, originated three groups (1.52 ± 0.16, 1.47 ± 0.17 and 1.40 ± 0.15 m/s, for Clusters 1, 2 and 3, respectively) with differences in velocity between Cluster 1 and 2 compared with Cluster 3 (p = .003). Anthropometric variables were the most determinants for clusters solution. Stroke length and stroke index were also considered relevant. In addition, differences between Cluster 1 and the others were also found for critical velocity, stroke rate and intracycle velocity variation (p < .05). It can be concluded that anthropometrics, technique and energetics (swimming efficiency) are determinant domains to young swimmers sprint performance.

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Fernando Santos, Martin Camiré, Dany J. MacDonald, Henrique Campos, Manuel Conceição, and Ana Silva

Coach education courses can be designed to help youth sport coaches improve their ability to foster positive youth development (PYD). To date, few studies have investigated coaches’ perspectives on their participation in PYD-focused coach education courses, and even less have observed coaches in the act of coaching before, during, and after course delivery to assess the extent to which they are implementing course material. The purpose of the present study was to conduct a process and outcome evaluation of a PYD-focused coach education course that was delivered online. Participants were seven Portuguese youth sport coaches who coached athletes between 10 and 18 years of age. Data were collected through non-participant qualitative observations, field notes, semi-structured interviews, and reflective journals. Process evaluation findings indicated that the coaches felt the course was well structured and appropriately delivered, yet limited in its ability to effect change due to the absence of a practical component. Outcome evaluation findings showed how coaches made efforts to implement the course material in their coaching practice, but their implementation efforts were met with limited success. Overall, the findings suggest that although online coach education courses are of interest to coaches due to their flexibility, they could be supplemented by practical components to enhance coaches’ ability to implement course content.

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Ana Silva, Pedro Figueiredo, Susana Soares, Ludovic Seifert, João Paulo Vilas-Boas, and Ricardo J. Fernandes

Our aim was to characterize front crawl swimming performed at very high intensity by young practitioners. 114 swimmers 11–13 years old performed 25 m front crawl swimming at 50 m pace. Two underwater cameras was used to assess general biomechanical parameters (velocity, stroke rate, stroke length and stroke index) and interarm coordination (Index of Coordination), being also identified each front crawl stroke phase. Swimmers presented lower values in all biomechanical parameters than data presented in studies conducted with older swimmers, having the postpubertal group closest values to adult literature due to their superior anthropometric and maturational characteristics. Boys showed higher velocity and stroke index than girls (as reported for elite swimmers), but higher stroke rate than girls (in opposition to what is described for adults). In addition, when considering the total sample, a higher relationship was observed between velocity and stroke length (than with stroke rate), indicating that improving stroke length is a fundamental skill to develop in these ages. Furthermore, only catch-up coordination mode was adopted (being evident a lag time between propulsion of the arms), and the catch and the pull phases presented the highest and smallest durations, respectively.

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Ana F. Silva, Pedro Figueiredo, Sara Morais, João P. Vilas-Boas, Ricardo J. Fernandes, and Ludovic Seifert

This study aimed to examine young swimmers’ behavioral flexibility when facing different task constraints, such as swimming speed and stroke frequency. Eighteen (five boys and 13 girls) 13- to 15-year-old swimmers performed a 15 × 50-m front crawl with five trials, at 100%, 90%, and 70% each of their 50 m maximal swimming speed and randomly at 90%, 95%, 100%, 105%, and 110% of their preferred stroke frequency. Seven aerial and six underwater cameras were used to assess kinematics (one cycle), with upper-limb coordination computed through a continuous relative phase and index of coordination. A cluster analysis identified six patterns of coordination used by swimmers when facing various speed and stroke frequency constraints. The patterns’ nature and the way the swimmers shifted between them are more important than getting the highest number of patterns (range of repertoire), that is, a change in the motor pattern in order to adapt correctly is more important than being able to execute a great number of patterns.

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Matheus Barbalho, Ana Francisca Rozin Kleiner, Bianca Callegari, Ramon Costa de Lima, Givago da Silva Souza, Anselmo de Athayde Costa e Silva, and Victor Silveira Coswig

Background: Jumps are important evaluation tools for muscle strength and power and for interlimb asymmetries. Different jump tests are well related to athletic performance, prediction of injury risk, and common motor gestures of several sports such as soccer. Low-cost mobile applications (apps) have gained popularity for this measure. The authors hypothesized that the My Jump 2 app would be a valid tool to assess drop-jump performance and interlimb asymmetry in soccer players. Methods: Eleven male soccer players took part in this study (18.2 [1.3] y, 69.9 [9.5] kg, 174 [6.6] cm). The athletes performed each test twice on a force plate (gold-standard method), while the jumps were recorded through the mobile app. Measures with the My Jump 2 app were applied by 2 evaluators, independently and in duplicate (interrater and intrarater reliability). The agreement analysis between both evaluations was done using an intraclass correlation coefficient and Bland–Altman plots. Results: Compared with the force platform, the app tested showed excellent reliability for the drop jump’s flight time and interlimb asymmetry (intraclass correlation coefficient > .98). For interlimb contact-time asymmetry, the values were 18.4 (9.9) and 19.1 (9.9) milliseconds for the My Jump 2 app and the force platform, respectively (P = .88). For flight-time asymmetries, the values were 389.7 (114.3) and 396.8 (112.5) milliseconds for the My Jump 2 app and the force platform, respectively (P = .88). Conclusion: The My Jump 2 app is a valid tool to assess drop-jump and interlimb asymmetry in soccer players.

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Henrique Nascimento, Ana Inês Alves, Ana Filipa Medeiros, Susana Coimbra, Cristina Catarino, Elsa Bronze-da-Rocha, Elísio Costa, Petronila Rocha-Pereira, Gustavo Silva, Luísa Aires, André Seabra, Jorge Mota, Helena Ferreira Mansilha, Carla Rêgo, Alice Santos-Silva, and Luis Belo


There are few reliable studies assessing the effect of physical exercise (PE) on adipokines levels at young ages. Our objective was to study the effects of regular PE on plasma adipokines in pediatric overweight and obesity.


117 overweight and obese children and adolescents (47% females; 10.2 years) participated in an 8-month longitudinal study divided in two groups: PE group (n = 80), engaged in an after-school PE program; control group (n = 37), with no PE program. Plasma lipids, C-reactive protein (CRP), adiponectin, resistin, leptin, IL-6, IL-1beta, TNF-alpha, insulin and glucose levels were determined.


contrarily to the control group, the PE group presented reductions in body mass index z-score (BMIzsc) and body fat percentage that were accompanied by an improvement in lipid profile and insulin resistance, a reduction in CRP and TNF-alpha and an increase in adiponectin levels. The reductions in BMIzsc were inversely correlated with changes in adiponectin (r=−0.329, p = .003) and positively correlated with changes in percentage body fat (r = .262, p = .032), triglycerides (r = .228, p = .042) and leptin (r = .285, p = .010).


Moderate reductions in adiposity improve proinflammatory status in obese children and adolescents. A more substantial reduction in BMIzsc was associated with a greater increment in adiponectin and reduction in leptin.

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Ana C. Santos-Mariano, Fabiano Tomazini, Cintia Rodacki, Romulo Bertuzzi, Fernando De-Oliveira, and Adriano E. Lima-Silva

Purpose: To investigate the effects of caffeine (CAF) on performance during high- and long-jump competitions. Methods: Using a crossover and double-blind design, 6 well-trained high jumpers and 6 well-trained long jumpers performed a simulation of a high- and long-jump competition 60 minutes after ingesting a capsule containing either 5 mg·kg−1 body mass of anhydrous CAF or a placebo. The high jumps were video recorded for kinematic analysis. The velocity during the approach run of the long jump was also monitored using photocells. Results: CAF improved jump performance (ie, the highest bar height overlap increased by 5.1% [2.3%], P = .008), as well as enhancing the height displacement of the central body mass (+1.3% [1.7%], P = .004) compared with the placebo. CAF had no ergogenic effect on jump distance (P = .722); however, CAF increased the velocity during the last 10 m of the long jump (P = .019), and the percentage of “foul jumps” was higher than that expected by chance in the CAF group (80.5% [12.5%], χ2 = 13.44, P < .001) but not in the cellulose condition (58.3% [22.9%], χ2 = 1.48, P = .224). Conclusion: CAF ingestion (5 mg·kg−1 body mass) improves high-jump performance but seems to negatively influence technical aspects during the approach run of the long jump, resulting in no improvement in long-jump performance. Thus, CAF can be useful for jumpers, but the specificity of the jump competition must be taken into account.

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Filipe M. Clemente, Ana F. Silva, Cain C.T. Clark, Daniele Conte, João Ribeiro, Bruno Mendes, and Ricardo Lima

Purpose: The purposes of this study were to (1) analyze the variations of acute and chronic training load and well-being measures during 3 periods of the season (early, mid, and end) and (2) test the associations between weekly training load and well-being measures during different periods of the season. Methods: Thirteen professional volleyball players from a team competing in the Portuguese Volleyball First Division (age 31.0 [5.0] y) were monitored during an entire season. Weekly acute (wAL) and chronic load (wCL), acute to chronic workload ratio (wACWL), and training monotony (wTM) were calculated during all weeks of the season. The weekly values of muscle soreness (wDOMS), stress (wStress), fatigue (wFatigue), sleep (wSleep), and Hooper index (wHI) were also obtained across the season. Results: The midseason had meaningfully low values of wAL (−26.9%; effect size [ES]: −1.12) and wCL (−28.0%; ES: −2.81), and greater values of wACWL (+38.9%; ES: 2.81) compared with early season. The wCL (+10.6%; ES: 0.99), wStress (44.6%; ES: 0.87), and wHI (29.0%; ES: 0.62) were meaningfully greater during the end of season than in midseason. Overall, wAL presented very large correlations with wDOMS (r = .80), wSleep (r = .72), and wFatigue (r = .82). Conclusions: The results of this study suggest that the load was meaningfully higher during early season; however, stress was higher during the final stages of the season. Overall, it was also found that the acute load is more highly correlated with well-being status and its variations than chronic load or training monotony.

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Ana F. Silva, Pedro Figueiredo, João Ribeiro, Francisco Alves, João Paulo Vilas-Boas, Ludovic Seifert, and Ricardo J. Fernandes

To analyze young swimmers’ performance regarding sex and skill level, 23 boys and 26 girls (15.7 ± 0.8 and 14.5 ± 0.8 years old, respectively) were assessed for anthropometry, flexibility, strength, drag, coordination, and biomechanical variables. During a 50-m maximal front-crawl bout, seven aerial and six underwater Qualisys cameras assessed kinematics, and a load cell was used to measure drag (Tedea, United Kingdom) and tethered swimming force. A multivariate analysis of variance test (p < .05) enabled us to observe differences between skill levels in speed, stroke frequency, stroke index, and intracyclic velocity variations, but most relevant differences were noticed when comparing sexes, particularly for anthropometrics, shoulder flexibility, speed, stroke frequency, stroke length, drag, mechanical power, power per stroke, and maximal and mean force. Considering the included variables, only male swimmers’ performance could be predicted through multiple linear regression, with stroke index, left shoulder flexion, and intracycle velocity variations showing great importance in achieving better results.

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Ana Carina Naldino Cassou, Rogerio Fermino, Ciro Romélio Rodriguez Añez, Mariana Silva Santos, Marlos R. Domingues, and Rodrigo S. Reis


The aim of this study was to identify barriers to physical activity among elderly Brazilian women of different socioeconomic status (SES).


A focus-group approach was employed. Subjects were aged, on average, 69.9 years (±6.9; n = 25). SES was measured based on a structured interview and women were grouped according to SES classification. Content analysis was used to categorize mentions of barriers to physical activities followed by descriptive analysis of absolute and relative frequencies of similar reports.


Most common barriers among high-SES elderly women were those within “psychological, cognitive, and emotional” dimensions (33.8%) and “environmental” (29.2%). Among women from lower SES, barriers were inversely ranked, the highest prevalence was verified for environmental (33.8%) and “psychological, cognitive, and emotional” dimensions (25%).


The results highlight that barriers perception varies according to women’s SES, indicating that physical activity promotion strategies must address such differences.