Lack of physical activity is a global public health problem causing not only morbidity and premature mortality, but it is also a major economic burden worldwide. One of the cornerstones of a physically active lifestyle is Motor Competence (MC). MC is a complex biocultural attribute and therefore, its study requires a multi-sectoral, multi-, inter- and transdisciplinary approach. MC is a growing area of research, especially in children and adolescents due to its positive association with a plethora of health and developmental outcomes. Many questions, however, remain to be answered in this field of research, with regard to: (i) Health and Developmental-related Associations of MC; (ii) Assessment of MC; (iii) Prevalence and Trends of MC; (iv) Correlates and Determinants of MC; (v) MC Interventions, and (vi) Translating MC Research into Practice and Policy. This paper presents a narrative review of the literature, summarizing current knowledge, identifying key research gaps and presenting questions for future investigation on MC in children and adolescents. This is a collaborative effort from the International Motor Competence Network (IMCNetwork) a network of academics and researchers aiming to promote international collaborative research and knowledge translation in the expansive field of MC. The knowledge and deliverables generated by addressing and answering the aforementioned research questions on MC presented in this review have the potential to shape the ways in which researchers and practitioners promote MC and physical activity in children and adolescents across the world.

Adolescents' physical fitness levels are an important indicator of their lifestyle and seem to have positive consequences in health-related quality of life (HRQoL). The purpose of this study is to analyse the combined associations of cardiorespiratory fitness and muscular fitness with HRQoL and to assess the differences between HRQoL scores across groups of cardiorespiratory fitness and muscular fitness in Portuguese adolescents. This is a cross-sectional analysis with 567 Portuguese adolescents aged 12-18 years-old. HRQoL was measured using the Kidscreen-10 questionnaire. Cardiorespiratory fitness was estimated with the 20-m shuttle-run test. Muscular fitness was evaluated using the handgrip and the standing long jump tests and a muscular fitness index was computed by means of standardized measures of both tests. Socioeconomic status was assessed using the Family Affluence Scale. Body composition (body mass and height) was measured according to standard protocols. Accelerometers were used to obtain objective physical activity time. Pubertal stage was assessed using Tanner stages. Adherence to the Mediterranean diet was assessed using the KIDMED index. Participants were divided into four groups based on low or high values of both cardiorespiratory and muscular fitness. Regression analysis, mediation analysis and ANCOVA were performed. HRQoL was positively associated with cardiorespiratory fitness (B = 0.112; p < 0.05) and muscular fitness score (B = 0.328 p < 0.05), after controlling for potential confounders. However, when both fitness variables were entered in the same model only cardiorespiratory fitness remained significantly associated with HRQoL (B = 0.093 p < 0.05). Cardiorespiratory fitness acted as a full mediator variable on the relationship between muscular fitness and HRQoL in adolescents (p < 0.05). ANCOVA showed that adolescents with high cardiorespiratory fitness/high muscular fitness exhibit better HRQoL scores when compared to those with low muscular fitness/low cardiorespiratory fitness and with those with low muscular fitness/high cardiorespiratory fitness (p < 0.05). In adolescents, the combination of high cardiorespiratory fitness and high muscular fitness was positively associated with a better HRQoL.

Normal-weight obesity (NWO) has been shown to be associated with cardiometabolic dysfunction. However, little is known regarding this potential relationship in early adulthood. The aim of this study was to investigate the associations between NWO and cardiometabolic risk factors in a large population of Colombian young adults. A cross-sectional study was conducted on 1354 subjects (61% women), aged from 18 to 30. Anthropometric data, including body mass index (BMI) and waist circumference (WC), were estimated, and the percentage of fat mass was measured through bioelectrical impedance analysis (BIA). Muscular fitness was determined by using a handgrip strength test and normalized grip strength (NGS = handgrip (kg)/body mass (kg)). A cardiometabolic risk Z-score was derived by assessing WC, triglycerides, high-density lipoprotein cholesterol (HDL-C) cholesterol, fasting glucose, and systolic blood pressure. NWO was defined by the combination of excess %BF (over 25.5% for men and 38.9% for women) and a BMI < 25 kg/m². The overall prevalence of NWO was 29.1%. Subjects with NWO have an increased risk of cardiometabolic risk compared to the normal-weight lean group (OR = 3.10). Moreover, NWO was associated with an increased risk of presenting low HDL-C (OR = 2.34), high abdominal obesity (OR = 7.27), and low NGS (OR = 3.30), p < 0.001. There is a high prevalence of NWO in American Latin young adults and this condition is associated with an increased cardiovascular risk, high blood pressure, low HDL-C, high abdominal obesity, and low muscular strength early in life. Screening for adiposity in subjects with a normal BMI could help to identify young adults at a high risk of cardiometabolic abnormalities.

Dual-energy X-ray absorptiometry (DXA) has been considered a reference method for measuring body fat percentage (BF%) in children and adolescents with an excess of adiposity. However, given that the DXA technique is impractical for routine field use, there is a need to investigate other methods that can accurately determine BF%. We studied the accuracy of bioelectrical impedance analysis (BIA) technology, including foot-to-foot and hand-to-foot impedance, and Slaughter skinfold-thickness equations in the measurement of BF%, compared with DXA, in a population of Latin American children and adolescents with an excess of adiposity. A total of 127 children and adolescents (11–17 years of age; 70% girls) from the HEPAFIT (Exercise Training and Hepatic Metabolism in Overweight/Obese Adolescent) study were included in the present work. BF% was measured on the same day using two BIA analysers (Seca^® 206, Allers Hamburg, Germany and Model Tanita^® BC-418^®, TANITA Corporation, Sportlife Tokyo, Japan), skinfold measurements (Slaughter equation), and DXA (Hologic Horizon DXA System^®, Quirugil, Bogotá, Columbia). Agreement between measurements was analysed using t-tests, Bland–Altman plots, and Lin’s concordance correlation coefficient (ρc). There was a significant correlation between DXA and the other BF% measurement methods (r > 0.430). According to paired t-tests, in both sexes, BF% assessed by BIA analysers or Slaughter equations differ from BF% assessed by DXA (p < 0.001). The lower and upper limits of the differences compared with DXA were 6.3–22.9, 2.2–2.8, and −3.2–21.3 (95% CI) in boys and 2.3–14.8, 2.4–20.1, and 3.9–18.3 (95% CI) in girls for Seca^® mBCA, Tanita^® BC 420MA, and Slaughter equations, respectively. Concordance was poor between DXA and the other methods of measuring BF% (ρc < 0.5). BIA analysers and Slaughter equations underestimated BF% measurements compared to DXA, so they are not interchangeable methods for assessing BF% in Latin American children and adolescents with excess of adiposity.

Health-related quality of life is among global health goals not only in adulthood but also in childhood and adolescence. Being a multi-component construct, health-related quality of life covers various domains, such as physical and psychological wellbeing and social and environmental areas. Bullying might significantly influence those domains especially in adolescence, a period of life when numerous personal and interpersonal transformations are experienced. Therefore, the aim of the current systematic review was to provide a comprehensive overview of the relationship of bullying with the health-related quality of adolescents’ lives. An electronic literature search was performed using PubMed, Embase, and Cochrane Library, and 3621 full-text articles were identified. After a selection process, 12 studies covering diagnosis, prevention and treatment for each of the three sections “adolescents”, “health related quality of life” and “bullying” were reviewed. An overall reduction in health-related quality of life in regard to bullying appeared from the studies analyzed, as well as a decline in adolescent mental health. Different bullying types were identified as causing harm to various adolescents‘ health-related quality of life domains. These findings may contribute to effective bullying management in schools and/or societal settings, and inform intervention strategies for maintaining the quality of life of adolescents being bullied.