The aim of this article was to identify differences in the anthropometric and physiological characteristics of first team and reserve young soccer players (10-14 years old) at both the beginning and end of the soccer season. Body composition was calculated by measuring weight, height, skinfold, limb circumference, and joint diameter. Vo2max was estimated by Astrand's test. Sprint and jump tests were also performed. In general, first team players (FTPs) were taller and leaner. However, the most relevant difference that we found at the beginning of the season was that FTPs had shorter sprint times than reserves in the 30-m test (both flat and with 10 cones). Moreover, these differences in sprint time were more marked at the end of the season. In addition, jump test performance by the reserves declined from the beginning to the end of the season. These results indicate that sprint time is an important factor associated with selection as an FTP between the ages of 10 and 14 years. The progression of the FTPs during the course of the season is better than that of the reserves and is associated with a different degree of growth and maturity. These findings should be taken into account by trainers and coaches to avoid a bias against late maturing or younger soccer players.
During a national championship, the anthropometric, physiological, and maturation characteristics of 13- to 14-year-old players of elite basketball teams and their association with sport performance were analyzed. Body parameters (weight, height, skinfold thicknesses, and lengths) were measured and physiological capacities assessed by sprint (20 m) and jump tests (i.e., countermovement jump with arm swing). Chronological age (CA) and maturity offset (years from age at peak height velocity; YAPHV) were calculated, and then predicted age at peak height velocity, as the difference between CA and YAPHV. Game performance was assessed with point averages and the performance index rating (PIR). The birth-date distribution of players was biased, those born early in the selection year outnumbering those born later. Anthropometric analysis indicated that players who performed better had longer body lengths. Physiological testing showed that semi-finalists had better sprint performance than quarter-finalists and those players with greater jump capacity scored more points. Early maturation and advanced maturity status were also associated with better PIR and scored points per game. Multiple blockwise regression analysis showed that, among the factors analyzed, YAPHV was the best predictor of basketball performance. In conclusion, around puberty, physical and physiological parameters associated with maturity and CA are important in determining the success of elite basketball players. Consequently, boys who are born in the second half of the year and/or late maturing tend to be marginalized or totally excluded, and not given the chance to play under equal conditions; their careers may then be held back by the relative disadvantage associated with inexperience.
The endogenous opioid system has been reported to have important functions in human reproduction. Practically all the components of this peptide system have been discovered in human sperm cells, but their functions in these cells are far from being well understood. In the present work, we report the effects of opioid agonism and antagonism on human sperm motility, a parameter which is crucially associated with male fertility. Morphine (10(-7) M), a μ- opioid receptor agonist, decreased both the percentage of motile progressive sperm and three measured velocities without altering the linearity, straightness or vigour of sperm cells. This effect was reversed by naloxone. Higher doses of morphine did not have further effects on the measured parameters. The incubation of sperm cells with the δ-opioid receptor agonist D-penicillamine (2,5)-enkephalin did not affect sperm cell motility. However, naltrindole, a specific δ-receptor antagonist, reduced the linear and curvilinear velocities, as well as linearity, straightness and the amplitude of head displacement, and beat frequency. In summary, our results indicate that the endogenous opioid system may regulate opioid motility in vitro. These finding suggest that the endogenous opioid system could be useful as a biochemical tool for the diagnosis and treatment of male infertility.
Abstract:The purpose of this study was to evaluate whether the "date of birth" influences the process of gaining access to university. To this end, we considered the distribution of the birth dates during the year, the qualifications required to enter the University of the Basque Country and the selected degree of 32,740 students who had entered the University from 1999 to 2004. Correlation analysis demonstrated that there is a small (r=-0.015) but significant (p=0.011) relationship between date of birth (January 1 st =1; December 31 st = 365) and the average grade students obtained in their university admittance exams. Moreover, this difference is more marked in certain degrees such as Medicine, Audiovisual Communication, Psychology, Engineering, Fine Arts or Physical Education. The effect may be due to a different degree of maturity between the adolescents born in January and those born in December. Thus, the former may be more mature and obtain better qualifications in secondary school. In conclusion, the data suggest that the "date of birth" factor influences the process of gaining access to university. Therefore special attention should be made to avoid the potential disadvantages associated with being born late in the year.
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