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Background: Evidence suggests that participation in physical activity may support young people's current and future mental health. Although previous reviews have examined the relationship between physical activity and a range of mental health outcomes in children and adolescents, due to the large increase in published studies there is a need for an update and quantitative synthesis of effects. Objectives: The objectives of this study were to determine the effect of physical activity interventions on mental health outcomes by conducting a systematic review and meta-analysis, and to systematically synthesize the observational evidence (both longitudinal and cross-sectional studies) regarding the associations between physical activity and sedentary behavior and mental health in preschoolers (2–5 years of age), children (6–11 years of age) and adolescents (12–18 years of age). Methods: A systematic search of the PubMed and Web of Science electronic databases was performed from January 2013 to April 2018, by two independent researchers. Meta-analyses were performed to examine the effect of physical activity on mental health outcomes in randomized controlled trials (RCTs) and non-RCTs (i.e. quasi-experimental studies). A narrative synthesis of observational studies was conducted. Studies were included if they included physical activity or sedentary behavior data and at least one psychological ill-being (i.e. depression, anxiety, stress or negative affect) or psychological well-being (i.e. self-esteem, self-concept, self-efficacy, self-image, positive affect, optimism, happiness and satisfaction with life) outcome in preschoolers, children or adolescents. Results: A total of 114 original articles met all the eligibility criteria and were included in the review (4 RCTs, 14 non-RCTs, 28 prospective longitudinal studies and 68 cross-sectional studies). Of the 18 intervention studies, 12 (3 RCTs and 9 non-RCTs) were included in the meta-analysis. There was a small but significant overall effect of physical activity on mental health in children and adolescents aged 6–18 years (effect size 0.173, 95% confidence interval 0.106–0.239, p < 0.001, percentage of total variability attributed to between-study heterogeneity [I2] = 11.3%). When the analyses were performed separately for children and adolescents, the results were significant for adolescents but not for children. Longitudinal and cross-sectional studies demonstrated significant associations between physical activity and lower levels of psychological ill-being (i.e. depression, stress, negative affect, and total psychological distress) and greater psychological well-being (i.e. self-image, satisfaction with life and happiness, and psychological well-being). Furthermore, significant associations were found between greater amounts of sedentary behavior and both increased psychological ill-being (i.e. depression) and lower psychological well-being (i.e. satisfaction with life and happiness) in children and adolescents. Evidence on preschoolers was nearly non-existent. Conclusions: Findings from the meta-analysis suggest that physical activity interventions can improve adolescents' mental health, but additional studies are needed to confirm the effects of physical activity on children's mental health. Findings from observational studies suggest that promoting physical activity and decreasing sedentary behavior might protect mental health in children and adolescents. PROSPERO Registration Number: CRD42017060373. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine spatiotemporal characteristics and joint angles during forward and backward walking in water at low and high stride frequency. Eight healthy adults (22.1 ± 1.1 years) walked forward and backward underwater at low (50 pulses) and high frequency (80 pulses) at the xiphoid process level with arms crossed at the chest. The main differences observed were that the participants presented a greater speed (0.58 vs. 0.85 m/s) and more asymmetry of the step length (1.24 vs. 1.48) at high frequency whilst the stride and step length (0.84 vs. 0.7 m and 0.43 vs. 0.35 m, respectively) were lower compared to low frequency (P < 0.05). Support phase duration was higher at forward walking than backward walking (61.2 vs. 59.0%). At initial contact, we showed that during forward walking, the ankle and hip presented more flexion than during backward walking (ankle: 84.0 vs. 91.8º and hip: 22.8 vs. 8.0º;P < 0.001). At final stance, the knee and hip were more flexed at low frequency than at high frequency (knee: 150.0 vs. 157.0º and hip: −12.2 vs. –14.5º;P < 0.001). The knee angle showed more flexion at forward walking (134.0º) than backward walking (173.1º) (P < 0.001). In conclusion, these results show how forward and backward walking in water at different frequencies differ and contribute to a better understanding of this activity in training and rehabilitation. [ABSTRACT FROM AUTHOR]

Background: Physical fitness is a powerful health marker in childhood and adolescence, and it is reasonable to think that it might be just as important in younger children, i.e. preschoolers. At the moment, researchers, clinicians and sport practitioners do not have enough information about which fitness tests are more reliable, valid and informative from the health point of view to be implemented in preschool children. Objective: Our aim was to systematically review the studies conducted in preschool children using field-based fitness tests, and examine their (1) reliability, (2) validity, and (3) relationship with health outcomes. Our ultimate goal was to propose a field-based physical fitness-test battery to be used in preschool children. Data Sources: PubMed and Web of Science. Study Eligibility Criteria: Studies conducted in healthy preschool children that included field-based fitness tests. Study Appraisal and Synthesis Methods: When using PubMed, we included Medical Subject Heading (MeSH) terms to enhance the power of the search. A set of fitness-related terms were combined with 'child, preschool' [MeSH]. The same strategy and terms were used for Web of Science (except for the MeSH option). Since no previous reviews with a similar aim were identified, we searched for all articles published up to 1 April 2014 (no starting date). A total of 2,109 articles were identified, of which 22 articles were finally selected for this review. Results: Most studies focused on reliability of the fitness tests ( n = 21, 96 %), while very few focused on validity (0 criterion-related validity and 4 (18 %) convergent validity) or relationship with health outcomes (0 longitudinal and 1 (5 %) cross-sectional study). Motor fitness, particularly balance, was the most studied fitness component, while cardiorespiratory fitness was the least studied. After analyzing the information retrieved in the current systematic review about fitness testing in preschool children, we propose the PREFIT battery, field-based FITness testing in PREschool children. The PREFIT battery is composed of the following tests: the 20 m shuttle-run test for assessing cardiorespiratory fitness, the handgrip-strength and the standing long-jump tests for assessing musculoskeletal fitness, and the 4 × 10 m shuttle run and the one-leg-stance tests for assessing motor fitness, i.e. speed/agility and balance, respectively. The rationale for the selection of each of the tests included in the PREFIT battery is provided in this review, as well as directions for future research. Limitations: Levels of evidence based on quality assessment of selected studies could not be constructed due to the limited number of studies identified for each test. Conclusions: The present systematic review has identified a need for further research on the validity of fitness tests in preschool children, as well as on their relationship with health. Due to this limited information, the PREFIT battery hereby proposed is based on the output of the current systematic review in preschool children, together with existing evidence in older children and adolescents. While we wait for more evidence to be accumulated in preschool children, the PREFIT battery hereby proposed is a useful tool for assessing physical fitness in children aged 3-5 years. [ABSTRACT FROM AUTHOR]