The effects of maturation on jumping ability and sprint adaptations to plyometric training in youth soccer players

The aim of this study was to investigate the effects of maturation on power and sprint performance adaptations following 6 weeks of plyometric training in youth soccer players during pre-season. Sixty male soccer players were categorized into 3 maturity groups (Pre, Mid and Post peak height velocity [PHV]) and then randomly assigned to plyometric group and control group. Vertical jump, standing long jump, and 20-m sprint (with and without ball) tests were collected before- and after-intervention. After the intervention, the Pre, Mid and Post-PHV groups showed significant (P ≤ 0.05) and small to moderate effect size (ES) improvement in vertical jump (ES = 0.48; 0.57; 0.73), peak power output (E = 0.60; 0.64; 0.76), standing long jump (ES = 0.62; 0.65; 0.7), 20-m sprint (ES = ?0.58; ?0.66), and 20-m sprint with ball (ES = ?0.44; ?0.8; ?0.55) performances. The Post-PHV soccer players indicated greater gains than Pre-PHV in vertical jump and sprint performance after training (P ≤ 0.05). Short-term plyometric training had positive effects on sprinting and jumping-power which are important determinants of match-winning actions in soccer. These results indicate that a sixty foot contact, twice per week program, seems effective in improving power and sprint performance in youth soccer players.     

Burning a Candle in a Vessel, a Simple Experiment with a Long History

The experiment in which a candle is burned inside an inverted vessel partially immersed in water has a history of more than 2,200 years, but even nowadays it is common that students and teachers relate the change in volume of the enclosed air to its oxygen content. Contrary to what many people think, Lavoisier concluded that any change in volume in this experiment is negligible; moreover, the explanation relating oxygen consumption in the air with its change in volume is known to be wrong. In this work we briefly review the history behind the candle experiment and its relationship with some typical erroneous explanations. One of the key factors behind Lavoisier’s success was the use of experiments carefully designed to test different hypotheses. Following these steps, we performed several closed volume experiments where the candle wick was replaced by a capillary stainless steel cylinder supported and heated by a nichrome filament connected to an external power supply. Our recorded experiments are displayed as web pages, designed with the purpose that the reader can easily visualize and analyze modern versions of Lavoisier’s experiments. These experiments clearly show an initial phase of complete combustion, followed by a phase of incomplete combustion with elemental carbon or soot rising to the top of the vessel, and a final phase where the hot artificial wick only evaporates a white steam of wax that cannot ignite because no oxygen is left in the closed atmosphere. After either a complete or incomplete combustion of the oxygen, our experiments show that the final gas volume is nearly equal to the initial air volume.     

The influence of the family educational scenario on internet use of primary and secondary school children / La influencia del escenario educativo familiar en el uso de internet en los niños de primaria y secundaria

Abstract

With the aim of studying the impact of the internet in the home, this paper analyses how the physical component (where and with whom) and attitudinal component (who decides what the child is to see on the internet and motivations for internet use) of the family educational scenario influence the frequency of internet use and diversity of uses, as reported by parents. The participants included 711 parents of children in primary and secondary school. Results showed that being in secondary school, using the internet in privacy at home, without company, internet content under the child’s control, and parental motivations based on the internet being used as a means for the child to relax, predicted higher frequency of internet use. Some of these factors, as well as the presence of peers and new parental attitudes related to the use of the internet for social and learning purposes, predicted a greater variety of uses, suggesting a more appropriate family scenario. The practical implications for parental education on this matter are described.     

Perspectives on the Origins of Life in Science Textbooks from a Christian Publisher: Implications for Teaching Science

This study analyzes six seventh grade Israeli mathematics textbooks, examining (1) the extent to which students are required to justify and explain their mathematical work, and (2) whether students are asked to justify a mathematical claim that is stated by the textbook or a mathematical claim that they themselves generated when solving a problem. Two different units of analysis were used to analyze two central topics in the seventh grade curriculum as follows: (1) equation solving in algebra and (2) triangle properties in geometry. The findings indicate that all six textbooks had considerably larger percentages of geometric tasks than algebraic tasks, which required students to justify or explain their mathematical work. Moreover, considerable differences were found among the six textbooks regarding the percentages of tasks that required students to justify and explain in both topics, but more so with the algebraic topic. Analysis of whether the textbook tasks required students to justify a mathematical claim that is stated by the textbook or a mathematical claim that the students themselves generated also revealed substantial differences among the textbooks. These findings are discussed, as well as the research methods used, in light of relevant literature.     

Mexican Educators Survey on Anatomical Sciences Education and a Review of World Tendencies

Anatomical sciences curricula have been under constant reform over the years, with many countries having to reduce course hours while trying to preserve laboratory time. In Mexico, schools have historically been autonomous and unregulated, and data regarding structure and methods are still lacking. A national survey was sent by the Mexican Society of Anatomy to 110 anatomical sciences educators. The questionnaire consisted of 50 items (open and multiple choice) for gross anatomy, microscopic anatomy, neuroanatomy, and embryology courses in medical schools across Mexico. A clinical approach was the most common course approach in all disciplines. Contact course hours and laboratory hours were higher in Mexican anatomy education compared to other countries, with the highest reported contact hours for embryology (133.4 ± 44.1) and histology (125 ± 33.2). There were similar contact hours to other countries for gross anatomy (228.5 ± 60.5). Neuroanatomy course hours (43.9 ± 13.1) were less than reported by the United States and similar to Saudi Arabia and higher than the United Kingdom. Dissection and microscopy with histological slides predominate as the most common laboratory activities. Traditional methods prevail in most of the courses in Mexico and only a few educators have implemented innovative and technological tools. Implementation of new methods, approaches, and curricular changes are needed to enhance anatomical sciences education in Mexico.     

Kinetics and kinematics analysis of incremental cycling to exhaustion

Technique changes in cyclists are not well described during exhaustive exercise. Therefore the aim of the present study was to analyze pedaling technique during an incremental cycling test to exhaustion. Eleven cyclists performed an incremental cycling test to exhaustion. Pedal force and joint kinematics were acquired during the last three stages of the test (75%, 90% and 100% of the maximal power output). Inverse dynamics was conducted to calculate the net joint moments at the hip, knee and ankle joints. Knee joint had an increased contribution to the total net joint moments with the increase of workload (5-8% increase, p < 0.01). Total average absolute joint moment and knee joint moment increased during the test (25% and 39%, for p < 0.01, respectively). Increases in plantar flexor moment (32%, p < 0.01), knee (54%, p < 0.01) and hip flexor moments (42%, p = 0.02) were found. Higher dorsiflexion (2%, for p = 0.03) and increased range of motion (19%, for p = 0.02) were observed for the ankle joint. The hip joint had an increased flexion angle (2%, for p < 0.01) and a reduced range of motion (3%, for p = 0.04) with the increase of workload. Differences in joint kinetics and kinematics indicate that pedaling technique was affected by the combined fatigue and workload effects.     

The sensitivity of the alternative maximal accumulated oxygen deficit method to discriminate training status

The purpose of the study was to investigate the sensitivity of an alternative maximal accumulated oxygen deficit (MAOD_ALT) method to discriminate the “anaerobic” capacity while comparing: least trained (LT) participants (n = 12), moderately trained (MT) participants (n = 12), endurance trained (ET) participants (n = 16), and rugby (RG) players (n = 11). Participants underwent a graded exercise test on a treadmill and a supramaximal effort for assessing MAOD_ALT. MAOD_ALT was calculated as the sum of oxygen equivalents from the phosphagen and glycolytic metabolic pathways. MAOD_ALT was significantly higher (P < 0.05) in RG (64.4 ± 12.1 mL · kg^?1) than in ET (56.8 ± 5.4 mL · kg^?1; effect size [ES] = 0.77; +13.5%), MT (53.8 ± 5.3 mL · kg^?1; ES = 1.08; +19.8%), and LT (49.9 ± 4.5 mL · kg^?1; ES = 1.50; +36.4%). In addition, the magnitude-based inference analysis revealed that MAOD_ALT was likely (LT vs. MT), very likely (MT vs. RG, and ET vs. RG) and most likely (LT vs. ET, and LT vs. RG) different between all groups, except for MT and ET, which presented an unclear difference. In conclusion, MAOD_ALT was sensitive enough to distinguish the “anaerobic” capacity in individuals with different training status, especially for RG players compared with LT participants and MT participants.     

IQ vs phonological recoding skill in explaining differences between poor readers and normal readers in word recognition: Evidence from a naming task

The aim of this study was to investigate whether differences inreading performance between poor readers and normal readers could bebetter explained by phonological recoding deficiences than IQ. A sampleof 132 Spanish children was classified into four groups according to IQ(<80; 81--90; 91--109; 110--140) and into two groups based on readingskills (poor readers vs normal readers). A word naming task was alsoadministered. We manipulated the word parameters (length, positionalsyllable frequency, and word frequency) and nonword parameters (lengthand positional syllable frequency) to find out whether students withreading disabilities would have more difficulties than normal readers innaming words under conditions that require extensive phonologicalcomputation. The results demonstrated that there were differencesbetween Spanish children who were normal readers and those who were poorreaders, independent of their IQs.     

Muscle activity and pedal force profile of triathletes during cycling to exhaustion

The purpose of this study was to analyze pedaling cadence, pedal forces, and muscle activation of triathletes during cycling to exhaustion. Fourteen triathletes were assessed at the power output level relative to their maximal oxygen uptake (355 +/- 23 W). Cadence, pedal forces, and muscle activation were analyzed during start, middle, and end test stages. Normal and tangential forces increased from the start to the end of the test (-288 +/- 33 to -352 +/- 42 N and -79 +/- 45 to -124 +/- 68 N, respectively) accompanied by a decrease in cadence (96 +/- 5 to 86 +/- 6 rpm). Muscle activation increased from the start to the middle and the end in the gluteus maximus (27 +/- 5.5% and 76 +/- 9.3%) and in the vastus lateralis (13 +/- 3.5% and 27 +/- 4.4%), similar increase was observed from the start to the end in the rectus femoris and the vastus medialis (50 +/- 9.3% and 20 +/- 5.7%, respectively). Greater normal force along with enhanced activation of knee and hip extensor muscles is linked with fatigue and declines in cadence of triathletes during cycling to exhaustion.