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Deforche B.,Vrije Universiteit Brussel | Deforche B.,Fund for Scientific Research Flanders FWO | Deforche B.,Ghent University | Haerens L.,Fund for Scientific Research Flanders FWO | And 2 more authors.
International Journal of Pediatric Obesity | Year: 2011

As regular physical activity of high enough intensity is essential in the management of overweight, efforts should be made to increase physical activity adherence in overweight children. To make overweight children exercise and follow the recommendations, it is essential to have insight into determinants of exercise initiation and adherence. According to the Self-determination Theory, creating opportunities to satisfy the need for autonomy (i.e., having choices), competence (i.e., feeling effective) and relatedness (i.e., being socially connected) might increase autonomous motivation for physical activity in overweight children and promote a long-lasting active lifestyle. To increase feelings of autonomy in overweight children, exercise programs could be delivered in an autonomy-supportive manner by providing choices, supporting the child's initiatives, avoiding use of external rewards, offering relevant information and rationale for changing behaviour, making a decisional balance and using autonomy supportive language, while minimizing pressure and control. Perceived competence in physical activities could be increased by offering activities tailored to the capabilities of the overweight child, helping the children set realistic goals, learning the children self-management skills, providing the children with appropriate feedback and organizing separate exercise sessions for overweight children. Feelings of relatedness in overweight children might increase by adopting an empathic approach, showing interest in the child's well-being and problems, showing enjoyment and enthusiasm, knowing the names of the children, talking to the children as equals, offering group sessions and talks, encouraging club participation and having a sports partner and encouraging parental support. © 2011 Informa Healthcare.

Tonoli C.,Vrije Universiteit Brussel | Heyman E.,UDSL | Roelands B.,Vrije Universiteit Brussel | Roelands B.,Fund for Scientific Research Flanders FWO | And 4 more authors.
Sports Medicine | Year: 2012

Objective: Exercise has been accepted and generally recommended for the management of type 1 diabetes mellitus (T1D) and for improving the overall quality of life in affected individuals. This meta-analysis was conducted to determine the overall effects of exercise (acute bouts of exercise and chronic exercise [or training]) on acute and chronic glycaemic control in patients with T1D, the effects of different types of exercise on glycaemic control and which conditions are required to obtain these positive effects. Methods: PubMed, ISI Web of Knowledge and SPORTDiscus were consulted to identify studies on T1D and exercise. Cohen's d statistics were used for calculating mean effect sizes (ES) as follows: small d = 0.3, medium d = 0.5 and large d = 0.8. Ninety-five percent confidence intervals (95% CIs) were used to establish the significance of our findings. Results: From a total of 937 studies, 33 that met the inclusion criteria were selected. Nine studies were used to calculate the ES of a single bout of aerobic exercise; 13 studies to calculate the ES of aerobic training; 2 studies to calculate the ES of strength training; 4 studies to calculate the ES of combined (aerobic and strength) training and 6 studies to calculate the ES of highintensity exercise (HIE) and training. ES for exercise on acute glycaemic control were large, while they were small for chronic glycaemic control. Aerobic exercise, resistance exercise, mixed exercise (aerobic combined with resistance training) and HIE acutely decreased blood glucose levels. To prevent late-onset hypoglycaemic episodes, the use of single bouts of sprints into an aerobic exercise can be recommended. This meta-analysis also showed that a regular exercise training programme has a significant effect on acute and chronic glycaemic control, although not all exercise forms showed significant results. Specifically, aerobic training is a favourable tool for decreasing chronic glycaemic control, while resistance training, mixed and HIE did not significantly improve chronic glycaemic control. Although, this meta-analysis showed there was a tendency for improvement in glycaemic control due to resistance training or resistance training combined with endurance training, there were not enough studies and/or subjects to confirm this statistically. Conclusions: Based on this meta-analysis, we can conclude that the addition of brief bouts of high-intensity, sprint-type exercise to aerobic exercise can minimize the risk of sustaining a hypoglycaemic episode. We can also conclude that only regular aerobic training will improve the glycated haemoglobin level of a patient with T1D. © 2012 Springer International Publishing AG. All rights reserved.

Roelands B.,Vrije Universiteit Brussel | Roelands B.,Fund for Scientific Research Flanders FWO | De Koning J.,VU University Amsterdam | De Koning J.,University of Wisconsin-La Crosse | And 4 more authors.
Sports Medicine | Year: 2013

Fatigue during prolonged exercise is often described as an acute impairment of exercise performance that leads to an inability to produce or maintain a desired power output. In the past few decades, interest in how athletes experience fatigue during competition has grown enormously. Research has evolved from a dominant focus on peripheral causes of fatigue towards a complex interplay between peripheral and central limitations of performance. Apparently, both feedforward and feedback mechanisms, based on the principle of teleoanticipation, regulate power output (e.g. speed) during a performance. This concept is called 'pacing' and represents the use of energetic resources during exercise, in a way such that all energy stores are used before finishing a race, but not so far from the end of a race that a meaningful slowdown can occur. It is believed that the pacing selected by athletes is largely dependent on the anticipated exercise duration and on the presence of an experientially developed performance template. Most studies investigating pacing during prolonged exercise in ambient temperatures, have observed a fast start, followed by an even pace strategy in the middle of the event with an end sprint in the final minutes of the race. A reduction in pace observed at commencement of the event is often more evident during exercise in hot environmental conditions. Further, reductions in power output and muscle activation occur before critical core temperatures are reached, indicating that subjects can anticipate the exercise intensity and heat stress they will be exposed to, resulting in a tactical adjustment of the power output. Recent research has shown that not only climatic stress but also pharmacological manipulation of the central nervous system has the ability to cause changes in endurance performance. Subjects seem to adapt their strategy specifically in the early phases of an exercise task. In high-ambient temperatures, dopaminergic manipulations clearly improve performance. The distribution of the power output reveals that after dopamine reuptake inhibition, subjects are able to maintain a higher power output compared with placebo. Manipulations of serotonin and, especially, noradrenaline, have the opposite effect and force subjects to decrease power output early in the time trial. Interestingly, after manipulation of brain serotonin, subjects are often unable to perform an end sprint, indicating an absence of a reserve capacity or motivation to increase power output. Taken together, it appears that many factors, such as ambient conditions and manipulation of brain neurotransmitters, have the potential to influence power output during exercise, and might thus be involved as regulatory mechanisms in the complex skill of pacing. © Springer International Publishing Switzerland 2013.

Vanoverberghe D.,Fund for Scientific Research Flanders FWO
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

Given a program and an assertion in that program, determining if the assertion can fail is one of the key applications of program analysis. Symbolic execution is a well-known technique for finding such assertion violations that can enjoy the following two interesting properties. First, symbolic execution can be precise: if it reports that an assertion can fail, then there is an execution of the program that will make the assertion fail. Second, it can be progressing: if there is an execution that makes the assertion fail, it will eventually be found. A symbolic execution algorithm that is both precise and progressing is a semi-decision procedure. Recently, compositional symbolic execution has been proposed. It improves scalability by analyzing each execution path of each method only once. However, proving precision and progress is more challenging for these compositional algorithms. This paper investigates under what conditions a compositional algorithm is precise and progressing (and hence a semi-decision procedure). © 2011 Springer-Verlag.

Gillis J.,Catholic University of Leuven | Diehl M.,Fund for Scientific Research Flanders FWO
Proceedings of the IEEE Conference on Decision and Control | Year: 2013

Periodic Lyapunov differential equations can be used to formulate robust optimal periodic control problems for nonlinear systems. Typically, the added Lyapunov states are discretized in the same manner as the original states. This straightforward technique fails to guarantee conservation of positive-semidefiniteness of the Lyapunov matrix under discretization. This paper describes a discretization method, coined PDPLD, that does come with such a guarantee. The applicability is demonstrated at hand of a tutorial example, and is specifically suited for direct collocation methods. Keywords : optimal control, Lyapunov differential equation, robustification, collocation. © 2013 IEEE.

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