Effect of Rule Modifications on Kinematic Parameters Using Maturity Stage as a Moderating Variable in U-10 Football Players.

The aim of the present study was to analyse the effects of regulatory modifications in competitive situations on cinematic variables, considering maturity stage as a moderating factor, in youth football players. A quasi-experimental study was conducted in which 45 players with a mean age of 9.47 ± 0.

Effect of changes in the net height, court size, and serve limitations on technical-tactical, physical, and psychological aspects of U-14 female volleyball matches.

Introduction: The objective was to analyze the effect of a reduction of the net height and the court size and serve limitations on the technical-tactical actions, physical actions, and psychological aspects in youth volleyball players.

Methods: The sample was 29 under-14 female volleyball players (three regional club teams). A quasi-experimental design was implemented to assess the effect of modification in three tournaments.

Reliability of a Qualitative Instrument to Assess High-Risk Mechanisms during a 90° Change of Direction in Female Football Players.

Sidestep cuts between 60° and 180° and one-leg landings have been identified as the main mechanisms of ACL injuries in several sports. This study sought to determine intra- and inter-rater reliability of a qualitative tool to assess high-risk movements in a 90° change of direction when the test is applied in a real framework of sport practice. Female footballers from two teams ( = 38) participated in this study and were asked to perform 90° cutting trials to each side, which were simultaneously filmed from a frontal and a sagittal view.

Effect of scaling basket height for young basketball players during the competition: seeking out positive sport experiences.

Proper scaling of sports equipment is necessary to ensure an optimal teaching-learning process . This study aimed to analyse the effect of reducing basket height on the technical-tactical actions, physical participation, self-efficacy, cooperation and enjoyment of young basketball players in the competition. 51 under-14 male basketball players from four teams were chosen as the sample.

Three-qubit refrigerator with two-body interactions.

We propose a three-qubit setup for the implementation of a variety of quantum thermal machines where all heat fluxes and work production can be controlled. An important configuration that can be designed is that of an absorption refrigerator, extracting heat from the coldest reservoir without the need of external work supply. Remarkably, we achieve this regime by using only two-body interactions instead of the widely employed three-body interactions.

Effect of Modification Rules in Competition on Technical-Tactical Action in Young Tennis Players (Under-10).

Adapting competitions to young players' characteristics is an important pillar in the optimal teaching-learning process. The objective of the present study is to analyze the effect of modifying net height (from 0.91 to 0.

Effect of the Modification of the Number of Players, the Size of the Goal, and the Size of the Field in Competition on the Play Actions in U-12 Male Football.

A player's sports development involves a long process. The modification of rules for youth players seeks to adapt the sport to the child and his/her development. The manipulation of rules affects the technical and tactical skills demonstrated by players and, therefore, their development.

Jump Performance During Official Matches in Elite Volleyball Players: A Pilot Study.

The purpose of this pilot study was to assess the types and intensity of the jumps that professional male volleyball players executed. Seven male elite volleyball players participated in this study. The sample was composed of 1599 jumps performed in 15 sets of five official matches of the regular season of a professional team.

Classical emulation of quantum-coherent thermal machines.

The performance enhancements observed in various models of continuous quantum thermal machines have been linked to the buildup of coherences in a preferred basis. But is this connection always an evidence of "quantum-thermodynamic supremacy"? By force of example, we show that this is not the case. In particular, we compare a power-driven three-level continuous quantum refrigerator with a four-level combined cycle, partly driven by power and partly by heat.

Design, Validation, and Reliability of an Observation Instrument for Technical and Tactical Actions of the Offense Phase in Soccer.

The use of observational methodology in the sports context provides coaches and other sports professionals with flexible tools that adapt to their needs. In collective sports, the use of these instruments is common for the technical and tactical analysis of the game. Based on the importance of data quality in these instruments, the purpose was to design, validate, and test the reliability of a mixed observational instrument of field formats and category systems to analyze technical and tactical actions in the offense phase in soccer.

Daily and weekly training load and wellness status in preparatory, regular and congested weeks: a season-long study in elite volleyball players.

The study aimed to assess the changes in the perceived internal load and wellness status of volleyball players in preparatory, regular (i.e. uncongested), and congested weeks during a full season.

Seasonal player wellness and its longitudinal association with internal training load: study in elite volleyball.

Background: Monitoring training load is critical to minimize the risk of overreaching, injury or illness. The purpose of this study was to assess the relationships and variance between perceived internal load and wellness status of elite male volleyball.

Methods: Thirteen elite volleyball players were studied during a full competitive season (nine months, 237 training sessions and 37 official matches).

Effect of eight weeks of upper-body plyometric training during the competitive season on professional female volleyball players.

Background: The purpose of this study was to assess the effect of incorporating specific upper-body plyometric training for the spike into the competitive season of a women's professional volleyball team.

Methods: A professional team from the Spanish first division participated in the study. An A-B-A' quasi-experimental design with experimental and control groups was used.

Evolution of Game Demands From Young to Elite Players in Men's Volleyball.

Purpose: To assess the evolution of the volleyball's game demands throughout players' development in men's volleyball.

Methods: A total of 150 sets and 6.671 rallies were analyzed.

Effect of Age Group on Technical-Tactical Performance Profile of the Serve in Men's Volleyball.

The aim of this study was to analyze the technical-tactical performance profile of the serve for various age groups and categories of competition in men's volleyball. The sample comprised 13,262 serves performed by 986 players in 299 sets observed in various categories of competition (U-14, U-16, U-19, national senior, and international senior). An observational design was used.

Internal dissipation and heat leaks in quantum thermodynamic cycles.

The direction of the steady-state heat currents across a generic quantum system connected to multiple baths may be engineered to realize virtually any thermodynamic cycle. In spite of their versatility, such continuous energy-conversion systems are generally unable to operate at maximum efficiency due to non-negligible sources of irreversible entropy production. In this paper we introduce a minimal model of irreversible absorption chiller.

Anthropometric, physical, and age differences by the player position and the performance level in volleyball.

The purpose of this paper was to study the ranges in height, weight, age, spike reach, and block reach of volleyball players in relation to the player position and the level of their respective teams in peak performance. The analysed sample included 1454 male and 1452 female players who participated in the volleyball competitions of the Olympic Games and World Championships in the 2000-2012 period. A descriptive, correlational, and longitudinal design was used.

Optimal performance of endoreversible quantum refrigerators.

The derivation of general performance benchmarks is important in the design of highly optimized heat engines and refrigerators. To obtain them, one may model phenomenologically the leading sources of irreversibility ending up with results that are model independent, but limited in scope. Alternatively, one can take a simple physical system realizing a thermodynamic cycle and assess its optimal operation from a complete microscopic description.

Collegiate coaches' knowledge of the female athlete triad in relation to sport type.

Background: The purpose of this study was to determine what coaches of female athletes know about the three components of the female athlete triad with regard to type of sport coached and the characteristics of the coach.

Methods: The sample consisted of 309 NCAA Division I coaches of female athletes in the sports of: sports with subjective scoring of performance (gymnastics and diving), low body weight sports (cross country and rowing), revealing or fitted clothing (volleyball and swimming), and other (soccer and basketball). An original, self-report questionnaire, and a 4-point Likert scale to measure confidence in answer was used.

Quantum-enhanced absorption refrigerators.

Thermodynamics is a branch of science blessed by an unparalleled combination of generality of scope and formal simplicity. Based on few natural assumptions together with the four laws, it sets the boundaries between possible and impossible in macroscopic aggregates of matter. This triggered groundbreaking achievements in physics, chemistry and engineering over the last two centuries.

Performance bound for quantum absorption refrigerators.

An implementation of quantum absorption chillers with three qubits has been recently proposed that is ideally able to reach the Carnot performance regime. Here we study the working efficiency of such self-contained refrigerators, adopting a consistent treatment of dissipation effects. We demonstrate that the coefficient of performance at maximum cooling power is upper bounded by 3/4 of the Carnot performance.

Match Duration and Number of Rallies in Men's and Women's 2000-2010 FIVB World Tour Beach Volleyball.

After the 2000 Olympic Games, the Fédération Internationale de Volleyball (FIVB) modified the scoring system used in beach volleyball from side-out to a rally point system. The goal was to facilitate the comprehension of the game and to stabilize match duration. The purpose of this study was to assess the duration and number of rallies in men's and women's beach volleyball matches (2000-2010 FIVB World Tour).

Effects of classical nonlinear resonances in grazing diatom-surface collisions.

Energy transfer between vibrational, rotational, and translational degrees of freedom of a molecule during a collision process is enhanced when the classical frequencies associated with the initial state are in the proximity of nonlinear resonance conditions. We present an analysis of the classical resonant effects in the collisions of light diatoms with periodic surfaces, and discuss the initial conditions in which these effects can be observed. In particular, we find that for grazing incidence and resonant initial values of the classical frequencies, corresponding to specific vibro-rotational molecular states and translational energies, an efficient energy transfer between the intramolecular vibro-rotational degrees of freedom and the translational degree of freedom along a symmetry direction on the surface can be found.