Educational performance and conduct problem trajectories from childhood to adolescence: Observational and genetic associations in a Brazilian birth cohort.

Background: Educational difficulties are an important potential influence on both the onset and course of children's conduct problems. This study evaluated the association between school failure and children's conduct problems in Brazil, a context with high rates of both conditions, using both observational and genetic approaches.

Methods: Prospective, population-based, birth cohort study in Pelotas city, Brazil.

Cross-sectional and prospective associations between physical activity, body mass index and waist circumference in children and adolescents.

Objective: To study the cross-sectional and prospective associations between physical activity (PA) of different intensities, body mass index (BMI) and waist circumference (WC) in children and adolescents using isotemporal substitution modelling.

Methods: Physical activity (accelerometry), BMI and WC were assessed in 6- ( = 970), 9- ( = 2,423) and 15-year-olds ( = 1,544) in 2005/2006 and 2011/2012. Participants aged 9 years in 2005/2006 were followed prospectively to 2011/12 (age 15).

Sport-Specific Capacity to Use Elastic Energy in the Patellar and Achilles Tendons of Elite Athletes.

During running and jumping activities, elastic energy is utilized to enhance muscle mechanical output and efficiency. However, training-induced variations in tendon spring-like properties remain under-investigated. The present work extends earlier findings on sport-specific profiles of tendon stiffness and cross-sectional area to examine whether years of distinct loading patterns are reflected by tendons' ability to store and return energy.

Exhaustion Experiences in Junior Athletes: The Importance of Motivation and Self-Control Competencies.

Quality of motivation, self-control competencies, as well as past performance experience influence sport participation outcomes in developing athletes. Studies have shown that junior athletes high in self-determined motivation are less prone to experience burnout, while self-control competencies help developing athletes to be conscious and deliberate in their self-regulatory efforts toward elite sport performances and avoid negative sport participation outcomes. Combining the self-determination theory framework and psychosocial theories of self-regulation, the aim of this cross-sectional study was to examine how various types of motivation and self-control competencies together are associated with the development of burnout symptoms in junior athletes.

Changes in Balance Strategy and Neuromuscular Control during a Fatiguing Balance Task-A Study in Perturbed Unilateral Stance.

Fatigue impairs sensorimotor performance, reduces spinal reflexes and affects the interaction of antagonistic muscles in complex motor tasks. Although there is literature dealing with the interference of fatigue and postural control, the interpretation is confounded by the variety of paradigms used to study it. This study aimed to evaluate the effects of postural fatigue on balance control and strategy, as well as on neuromuscular modulation, in response to postural perturbation (PERT) during a fatiguing balance task.

Voluntary Movement Frequencies in Submaximal One- and Two-Legged Knee Extension Exercise and Pedaling.

Understanding of behavior and control of human voluntary rhythmic stereotyped leg movements is useful in work to improve performance, function, and rehabilitation of exercising, healthy, and injured humans. The present study aimed at adding to the existing understanding within this field. To pursue the aim, correlations between freely chosen movement frequencies in relatively simple, single-joint, one- and two-legged knee extension exercise were investigated.

Foundations of Intervention Research in Instrumental Practice.

The goals of the present study are to evaluate, implement, and adapt psychological skills used in the realm of sports into music performance. This research project also aims to build foundations on how to implement future interventions to guide music students on how to optimize practice toward performance. A 2-month psychological skills intervention was provided to two students from the national music academy's bachelor program in music performance to better understand how to adapt and construct psychological skills training programs for performing music students.

Regional differences of [(18)F]-FDG uptake within the brain during fatiguing muscle contractions.

Background And Purpose: Many studies have shown that a position task is more difficult than a force task although both are performed at a similar net muscle force. Thus, the time to task failure is consistently shown to be briefer during the position task. The contributions of the central nervous system to these two types of fatiguing contractions are not completely understood.

Exercise economy in skiing and running.

Substantial inter-individual variations in exercise economy exist even in highly trained endurance athletes. The variation is believed to be determined partly by intrinsic factors. Therefore, in the present study, we compared exercise economy in V2-skating, double poling, and uphill running.

Influence of loading rate on patellar tendon mechanical properties in vivo.

Background: Rate-dependent properties of tendons have consistently been observed in vitro but in vivo studies comparing the effects of loading duration on this feature remain conflicting. The main purpose of the present study was to evaluate whether tendon loading rate per se would affect in vivo tendon mechanical properties.

Methods: Twenty-two physically active male subjects were recruited.

The role of skeletal muscle glycogen breakdown for regulation of insulin sensitivity by exercise.

Glycogen is the storage form of carbohydrates in mammals. In humans the majority of glycogen is stored in skeletal muscles (∼500 g) and the liver (∼100 g). Food is supplied in larger meals, but the blood glucose concentration has to be kept within narrow limits to survive and stay healthy.

An intermittent running test to estimate maximal oxygen uptake: the Andersen test.

Aim: Monitoring of height and weight in children in schools has been discussed to get data on trends in obesity. Physical fitness may be just as important to monitor and a simple reliable test will therefore be important. The aim of this paper was to analyze the association between VO2max measured during maximal work on a treadmill and running distance in an intermittent running test.