pagina emcitacoes indiretas (parafrase) embora facultativa, recomenda-se sempreidentificar a pagina para evitar problemas posteriores; uso de um unico autor em determinado item e,pior ainda, durante varias paginas consecutivas.EXEMPLO:Important considerations when studying the impact of physical education on health in youthLaura Canadas,Oscar L Veiga andDavid Martinez-GomezEmail authorBMC Pediatrics201414:75DOI: 10.1186/1471-2431-14-75 Canadas et al.; licensee BioMed Central Ltd. 2014Received: 10 October 2013Accepted: 10 March 2014Published: 15 April 2014Open Peer Review reportsAbstractKlakk et al. conducted an intervention study by increasing the frequency of physical education lessons in children aged 8 to 13 years, and they examined its effect on body fat during two school years. Physical education has potential to provide health in childhood and adolescence. For achieving these benefits, one of the most relevant aspects that need to be addressed during physical education classes is to provide students with high levels of physical activity. A well-recognized recommendation suggests that students should engage in moderate to vigorous physical activity for at least 50% of the time they spend in physical education classes. Therefore, it would be crucial to know what is happening during physical education classes before increasing their frequency. On the other hand, it seems that the main concern of health-related researchers is provide evidence on the impact of physical education on physical health outcomes (e.g. obesity), whereas other dimensions of health such as social, emotional, intellectual, and spiritual health are understudied. New evidence on the role of physical education on other health outcomes beyond physical health would also be important for the recognition of this curricular subject.KeywordsPhysical education Health Physical activity YouthCommentaryWe have read with interest the recent study by Klakk and colleagues entitled Effect of four additional physical education lessons on body composition in children aged 813 years a prospective school study during two school years [1]. Their main findings indicate that four additional lessons of physical education slightly decreased the prevalence of overweight and obesity in youth. Also, they found that the intervention had a greater effect in decreasing body fat among overweight and obese children at baseline. The study by Klakk et al. has important strengths (e.g. sample size, long-term intervention, imaging technics for measuring body fat), but some issues must be taken into consideration when interpreting its results as well as for designing future studies aimed to examine the impact of physical education on health.As described by the authors, the single intervention was to increase the number of physical education lessons. In this study, the authors are based on the premise that a substantial increase in the frequency of physical education classes is a good opportunity to accumulate more physical activity at recommend levels (i.e. 60 minutes per day at moderate to vigorous intensity) and in turn, it will have benefits on health. However, we cannot assume that all physical educators have similar qualifications and skills to provide students with high levels of physical activity during their lessons. The main indicator of physical education quality in health-related physical education is guaranteeing that students are physically active in terms of duration and intensity in each lesson. The operational goal for this