Are the new starting block facilities beneficial for backstroke start performance?

We aimed to analyse the handgrip positioning and the wedge effects on the backstroke start performance and technique. Ten swimmers completed randomly eight 15 m backstroke starts (four with hands on highest horizontal and four on vertical handgrip) performed with and without wedge. One surface and one underwater camera recorded kinematic data. Standardised mean difference (SMD) and 95% confidence intervals (CI) were used. Handgrip positioning did not affect kinematics with and without wedge use. Handgrips horizontally positioned and feet over wedge displayed greater knee angular velocity than without it (SMD = ?0.82; 95% CI: ?1.56, ?0.08). Hands vertically positioned and feet over wedge presented greater take-off angle (SMD = ?0.81; 95% CI: ?1.55, ?0.07), centre of mass (CM) vertical positioning at first water contact (SMD = ?0.97; 95% CI: ?1.87, ?0.07) and CM vertical velocity at CM immersion (SMD = 1.03; 95% CI: 0.08, 1.98) when comparing without wedge use. Swimmers extended the hip previous to the knee and ankle joints, except for the variant with hands vertically positioned without wedge (SMD = 0.75; 95% CI: ?0.03, 1.53). Swimmers should preserve biomechanical advantages achieved during flight with variant with hands vertically positioned and wedge throughout entry and underwater phase.     

Educational Neuromyths Among Teachers in Latin America

Neuroscientific knowledge has undeniably gained interest among educators worldwide. However, not all “brain facts” believed by teachers are supported by science. This study sought to evaluate the belief in these so‐called neuromyths among 3,451 Latin American teachers. We found that, consistent with prior research among teachers in other geographic areas, teachers in Latin America hold major misconceptions about neuroscience, especially as it relates to factual information about its structure and functioning. Differences across South American nations were observed with moderate and slight effect sizes for general knowledge of the brain and neuromyths, respectively. Teachers working in higher education had slightly superior performance. Teachers at all levels who reported knowing more about the brain, however, were more likely to believe invalid assertions known as neuromyths. These results shed light on trends in the field of education, hoping to encourage the development of strategies aimed at correcting the use of science as it relates to education. The implications regarding teaching practice, policy, and teacher training are discussed.     

An assessment of a social–cognitive model of academic performance in mathematics in Argentinean middle school students

This study tested a set of hypotheses derived from the model of academic achievement in mathematics of the Social Cognitive Career Theory in a sample of Argentinean middle school students. To this aim, 277 students (male and female; age: 13–15 years) were assessed using the following instruments: logical–mathematical self-efficacy scale, mathematics outcome expectations, mathematics performance goals, and mathematics ability test. All of these instruments had been adapted for use in Argentinean students. Academic achievement in mathematics (i.e., grades obtained on regular school exams) was the variable to be modeled through the path analysis technique. The analysis allowed identification of interrelations among the variables and identification of direct and indirect effects. Academic achievement in mathematics was partially explained by the model. Overall, the results support the theoretical postulates of Social Cognitive Career Theory.     

Biomechanical analyses of synchronised swimming standard and contra-standard sculling

Synchronised swimming involves a variety of sculling movements essential for body support and propulsion but its study is scarce. We aimed to biomechanically compare standard and contra-standard sculling techniques, and to observe the relationship between measures. Six synchronised swimmers performed two, 30 s maximal intensity, fully tethered standard and contra-standard sculling motions. Kinetic and kinematic data were obtained using a load-cell and underwater cameras, respectively. Force decreased along both techniques’ bouts, but no differences in-between techniques were noted for any kinetic variables. Standard sculling presented a higher cycle rate and a lower elbow mean angle than the contra-standard sculling (2.4 ± 0.3 vs. 2.0 ± 0.2 cycles/s and 134.1 ± 5.8 and 141.5 ± 4.7°, p < 0.05). In the standard sculling, by removing and maintaining the variation between participants (r _w and r, respectively), the absolute mean force was directly related with cycle rate (r _w  = 0.60) and wrist angular velocity during flexion (r = 0.82), while in the contra-standard condition the force was inversely associated with wrist mean angle (r = ?0.95) and directly with hand speed (r _w  = 0.76), and elbow angular velocity (r _w  ≈ 0.60). Therefore, technique learning and training require different attention by coaches and swimmers.     

Validity of a portable force platform for assessing biomechanical parameters in three different tasks

The aim of this study was to determine the precision and accuracy of the vertical and anterior–posterior force components of the portable PASCO PS-2142 force plate. Impulse, peak force, and time to peak force were assessed and compared to a gold standard force plate in three different tasks: vertical jump, forward jump, and sprint start. Two healthy male participants performed ten trials for each task, resulting in 60 trials. Data analyses revealed good precision and accuracy for the vertical component of the portable force plate, with relative bias and root mean square (RMS) error values nearly the same in all tasks for the impulse, time to peak force, and peak force parameters. Precision and accuracy of the anterior–posterior component were lower for the impulse and time to peak force, with relative bias and RMS error values nearly the same between tasks. Despite the lower precision and accuracy of the anterior–posterior component of the portable force plate, these errors were systematic, reflecting a good repeatability of the measure. In addition, all variables presented good agreement between the portable and gold standard platforms. Our results provide a good perspective for using the aforementioned portable force plate in sports and clinical biomechanics.     

The geometric curvature of the spine during the sirshasana,the yoga’s headstand

This study analysed the behaviour of the geometric curvature of the spine during sirshasana. The position of dorsal retroreflective markers was computed via stereophotogrammetric analysis in six males and five females (29.4 ± 8.8 years, 63.0 ± 11.4 kg, 1.66 ± 0.08 m [average ± standard deviation]). The spinal points were projected onto the sagittal and frontal planes of the trunk, a polynomial was fitted to the data and the two-dimensional geometric curvature was quantified. The inferior lumbar lordosis decreased compared to the orthostatic position and gait, which may favour the posterior protrusion of the lumbar spinal nucleus pulposus in people with posterior herniation. The lateral deviation at the middle of the thoracic spine increases during sirshasana, which may reflect increased difficulties for postural control and spinal loads. It could be useful for promoting positive spinal structural and functional chronic adaptations for healthy participants, if the yoga programme is carefully planned and the spinal alignment is carefully monitored during a headstand. However, it may aggravate some spinal diseases, especially scoliosis.     

Impact sports and bone fractures among adolescents

The objective of the present study was to investigate the effects of different sports on stress fractures among adolescents during a 9-month follow-up period. The sample was composed of 184 adolescents divided into three groups (impact sports [n = 102]; swimming [n = 35]; non-sports [n = 47]). The occurrence of stress fracture was reported by participants and coaches. As potential confounders we considered age, sex, resistance training, body composition variables and age at peak of height velocity. There were 13 adolescents who reported fractures during the 9-month period. Bone mineral density values were higher in adolescents engaged in impact sports (P-value = 0.002). Independently of confounders, the risk of stress fracture was lower in adolescents engaged in impact sports than in non-active adolescents (hazard ratio [HR] = 0.23 [95% confidence interval (CI) = 0.05 to 0.98]), while swimming practice was not associated to lower risk of fracture (HR = 0.49 [95% CI = 0.09 to 2.55]). In conclusion, the findings from this study indicate the importance of sports participation among adolescents in the reduction of stress fracture risk, especially with impact sports. More importantly, these results could be relevant for recognising adolescents in danger of not reaching their potential for peak bone mass and later an increased risk of fractures.     

Scholarly Communities at the Crossroads: Internationalizing Sociological Networks in Valparaíso,Chile (2003–2019)

Minerva - Achievements and tensions derived from the internationalization of national scholarly communities have attracted extensive attention. However, very little is hitherto known about the...     

Adding Compression to Block Addressing Inverted Indexes

Inverted index compression, block addressing and sequential search on compressed text are three techniques that have been separately developed for efficient, low-overhead text retrieval. Modern text compression techniques can reduce the text to less than 30% of its size and allow searching it directly and faster than the uncompressed text. Inverted index compression obtains significant reduction of its original size at the same processing speed. Block addressing makes the inverted lists point to text blocks instead of exact positions and pay the reduction in space with some sequential text scanning.In this work we combine the three ideas in a single scheme. We present a compressed inverted file that indexes compressed text and uses block addressing. We consider different techniques to compress the index and study their performance with respect to the block size. We compare the index against three separate techniques for varying block sizes, showing that our index is superior to each isolated approach. For instance, with just 4% of extra space overhead the index has to scan less than 12% of the text for exact searches and about 20% allowing one error in the matches.