Teun Remmers

General discussion | 189 researchers tend to account for these errors in the buffer size, misclassifications still cannot be avoided. Consequently, although the direction and strength of investigated determinants may be comparable between studies, specific effect sizes may be difficult to compare and generalize to other contexts. This makes it challenging to evaluate the impact of attributes of the physical environment on PA behavior in children, and ultimately to assess the impact of PA on children's health. Recommendations for practice The following is recommended for health promotors and policy makers:  Promotion of regular PA and limiting sedentary time should remain a primary target in the prevention of overweight and obesity, especially in heavier boys and girls (chapter 2), next to other known behavioral determinants of weight gain such as dietary behavior and sleep. Health promotors are also encouraged to emphasize the emerging short-term benefits of increased PA on children's cognitive, social and emotional well-being.  Schools and playgrounds in the school environment play an important role in the promotion of PA (chapters 7 and 9) (47, 85, 86, 102, 103). As schools are evaluated primarily on children's cognitive performance, health promotion is sometimes perceived as a secondary objective. However, recent findings suggesting associations between PA and improved cognitive performance, may help to integrate PA into daily school curricula (104, 105). In addition, high- quality physical education may enhance children's PA, well-being and competency, and related physical literacy (106-108). Previously developed school-based PA interventions indicate the potential of multi-setting and bottom- up approaches in improving children's PA levels (e.g. schools, communities, and parents), while acknowledging the local school-context (96, 109-111).  Individual-level determinants of PA in children are part of a multidimensional construct involving, for example, enjoyment, quality of motivation, fundamental movement skills, general self-concept and self-efficacy (chapter 3) (106, 107, 112). Interventions targeting individual-level determinants should take into account the interactive contribution of each of these factors, and that these may depend on the context of PA (e.g. organized sports participation versus physical education).  Improving young children's outside play require interventions involving their parents, as they act as gatekeepers in providing their child with opportunities for outside play (chapters 4 and 5). This is in line with previous research focusing on children's active transport and free play (76, 113-115). These interventions may, for example, involve awareness of accessibility to PA facilities (chapter 5) or safety issues (116).  Environmental determinants of PA are highly context-specific (chapters 7, 8 and 9). Critical consideration of time- and place-specificity, as well as the influence of weather elements is therefore recommended (chapters 6 and 7). Evidence on the influence of specific environmental determinants on PA is currently still