Jorge del Rosario Fernández-Santos

Objectively measured physical activity has a negative but weak association with academic performance in children and adolescents

There is an emerging body of evidence on the potential effects of regular physical activity on academic performance. The aim of this study was to add to the debate, by examining the association between objectively measured physical activity and academic performance in a relatively large sample of children and adolescents.

Reliability and Validity of Tests to Assess Lower-Body Muscular Power in Children.

Abstract Fernandez-Santos, JR, Ruiz, JR, Cohen, DD, Gonzalez-Montesinos, JL, and Castro-Piñero, J. Reliability and validity of tests to assess lower body muscular power in children. J Strength Cond Res 29(8): 2277–2285, 2015—The purpose of this study was to analyze the reliability and the criterion-related validity of several lower-body muscular power tests (i.e., standing long jump [SLJ], squat jump, countermovement jump, and Abalakov jump) in children aged 6–12 years. Three hundred sixty three healthy children (168 girls) agreed to participate in this study. All the lower-body muscular power tests were performed twice (7 days apart), whereas the 1 repetition maximum (1RM) leg extension test was performed 2 days after the first session of testing. All the tests showed a high reliability (intertrial difference close to 0 and no significant differences between trials, all p > 0.05). The association between the lower-body muscular power tests and 1RM leg extension test was high (all p < 0.001). The SLJ and the Abalakov jump tests showed the highest association with 1RM leg extension test (R 2 = 0.700, test result, weight, height, sex, and age were added in the model). The SLJ test can be a useful tool to assess lower-body muscular power in children when laboratory methods are not feasible because it is practical, time efficient, and low in cost and equipment requirements.

Convergent validation of a questionnaire to assess the mode and frequency of commuting to and from school

Aims: The purposes of this research were to study the convergent validity of the Mode and Frequency of Commuting To and From School Questionnaire using objectively assessed steps and time spent in different physical activity intensities and to compare the self-reported versus objective journey time in Spanish youths. Methods: Three hundred and eighty-nine Spanish youth aged 7–19 years were asked to complete the questionnaire and wore an accelerometer for five days. The objective commuting distance and time from home to school were estimated using Google MapsTM. Results: There were significant differences between passive and walking participants on step numbers, sedentary time and physical activity levels (except for vigorous physical activity in children). For children, a mean difference of −4.03 minutes between objective measured and self-reported journey time was found (95% limits of agreement were 13.55 and −21.60 minutes). For adolescents, the mean difference was −1.39 minutes (95% limits of agreement were 15.23 and −18.02 minutes). Conclusions: The findings indicated that the Mode of Commuting To and From School Questionnaire showed a convergent validity to assess this behaviour in Spanish youths. Self-reported journey time for walking is comparable to Google MapsTM in adolescents but not in children.

Inflammatory biomarkers and academic performance in youth. The UP & DOWN Study.

Inflammation influences cognitive development in infants and older adults, however, how inflammation may affect academic development during childhood and adolescence remains to be elucidated. This study aimed to examine the association between inflammatory biomarkers and academic performance in children and adolescents. A total of 494 youth (238 girls) aged 10.6 ± 3.4 years participated in the study. Four inflammatory biomarkers were selected: C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and white blood cell (WBC) count. An inflammatory index was created using the above mentioned biomarkers. Academic performance was assessed through schools records. Results showed that three of the four inflammatory biomarkers (CRP, IL-6 and WBC) and the inflammatory index were negatively associated with all academic indicators (β values ranging from -0.094 to -0.217, all P<0.05) independent of confounders including body fat percentage. Indeed, youth in the highest tertile of the inflammatory index had significantly lower scores in all academic indicators compared with youth in the middle tertile (scores ranging from -0.578 to -0.344) and in the lowest tertile (scores ranging from -0.678 to -0.381). In conclusion, inflammation may impair academic performance independently of body fat levels in youth. Our results are of importance because the consequences of childhood and adolescence inflammation tend to continue into adulthood. Lifestyle interventions in youth may be promising in reducing levels of inflammation beyond the reduction in body fat in order to achieve cognitive benefits.

Muscle strength is associated with lower diastolic blood pressure in schoolchildren

Cardiorespiratory fitness (CRF) provides protection against the elevated blood pressure in overweight youth. Less is known regarding any similar protective effect of muscular fitness. We investigated how handgrip strength, an easy to implement measure of muscular strength, interacted with CRF and BMI to determine blood pressure in youth. We measured systolic (SBP) and diastolic (DBP) blood pressure, handgrip strength (HG), CRF and body mass index (BMI) in n=7329 10-16year-olds (47% girls). We defined elevated blood pressure as >91st percentile and Good HG as >33rd percentile. Participants were classified as Fit or Unfit and as Normal or Overweight/Obese based on international standards. The prevalence of elevated SBP was 23%, and 44% of participants had elevated DBP. In unfit participants Good HG was associated with lower SBP (z=0.41 (95%CI: 0.20-0.61) and DBP (z=0.29 (95%CI: 0.12-0.47). In Overweight/Obese participants, DBP was z=0.24 (95%CI: 0.14-0.34) lower in the Good (versus Low) HG group. Overweight/Obese participants with Good HG also had a 32% lower risk of elevated DBP (OR: 0.68, 95%CI: 0.57-0.82). This association was attenuated but remained important after adjusting for BMI (20% risk reduction, OR: 0.80, 95%CI: 0.63-1.01). Muscular fitness appears to play some protective role against the risk of elevated blood pressure; particularly for the more prevalent measure: elevated DBP (44%). Effects may be restricted to Overweight / Obese or unfit youth, who have an increased risk of elevated BP and also may be less likely to engage in traditional cardiorespiratory fitness training. Research to determine the effects of muscular fitness training on blood pressure is warranted in these subgroups.

Physical Activity Coparticipation and Independent Mobility as Correlates of Objectively Measured Nonschool Physical Activity in Different School Grades. The UP&DOWN Study.

BACKGROUND The aim was to investigate the association of (i) parental, sibling, and friend coparticipation in physical activity (PA); and (ii) independent mobility (IM) for walking, cycling, and taking public transport with objectively measured nonschool PA on week- and weekend days in different school grades. METHODS A total of 1376 Spanish youngsters (50.8% boys; mean age 11.96 ± 2.48 years) participated in the study. Participants reported the frequency of their parental, sibling, and best friend coparticipation in PA with them and their IM for walking, cycling, and taking public transport. PA was objectively measured by accelerometry. RESULTS Coparticipation in PA and IM were more frequently related to nonschool PA among adolescents than among children. Friend coparticipation in PA was positively associated with higher levels of nonschool PA in adolescents. IM for walking and IM for cycling in adolescents were related to nonschool PA on weekdays. CONCLUSIONS Our results highlight the need for age-focused interventions and the integration of family and friends to promote PA in youth.

The Role of Adiposity in the Association between Muscular Fitness and Cardiovascular Disease

Objectives To test the associations of muscular fitness and body mass index (BMI), individually and combined, with clustered cardiovascular disease risk factors in children and adolescents and to analyze the mediator role of BMI in the association between muscular fitness and clustered cardiovascular disease risk factors. Study design In total, 239 children (113 girls) and 270 adolescents (128 girls) participated in this cross‐sectional study. Height and weight were assessed, and BMI was calculated. A cardiovascular disease risk factors index (CVDRF‐I) was created from the combination of the following variables: waist circumference, systolic blood pressure, triglycerides, high‐density lipoprotein cholesterol, and glucose. Handgrip strength/weight and standing long jump tests were used to assess muscular fitness. A muscular fitness index was computed from the combination of both tests. Results Muscular fitness index was associated with CVDRF‐I in children of both sexes and adolescent boys; however, these associations disappeared after accounting for BMI. BMI was associated with CVDRF‐I in both children and adolescents, even after adjusting for muscular fitness (all P < .001). In male and female children and in adolescent boys, the association between muscular fitness and CVDRF‐I was mediated by BMI (all P < .001). Because there was no association between muscular fitness and CVDRF‐I in adolescent girls, the mediation hypothesis was discarded. Conclusions BMI is an independent predictor of CVDRF‐I in children and adolescents of both sexes. Conversely, the effect of muscular fitness on CVDRF‐I seems to be fully mediated by BMI levels in male and female children and in adolescent boys.

Kinematic analysis of the standing long jump in children 6- to 12-years-old

ABSTRACT The purpose of this study was to analyze the kinematic variables that determine the performance of the standing long jump in children 6- to 12-years-old. There were 121 healthy children (58 girls) recorded while they performed the standing long jump test. All kinematic variables showed a significant correlation with calculated jump distance and measured jump distance, except for the knee joint angle at maximum shoulder extension angle, ankle joint angle at maximum shoulder extension angle, and shoulder joint angle at maximum knee flexion angle. Stepwise multiple regression analysis showed that sex, age, and body mass index accounted for 51.1% of the jump distance variance. Among all the kinematic variables, take-off distance and take-off speed were accounted for the most of the variation in the jump distance. Physical education teachers and coaches should consider special attention to these anthropometrics and kinematic aspects in improving the standing long jump performance in children.

Physical fitness reference standards for preschool children: The PREFIT project

OBJECTIVES Reference values are necessary for classifying children, for health screening, and for early prevention as many non-communicable diseases aggravate during growth and development. While physical fitness reference standards are available in children aged 6 and older, such information is lacking in preschool children. Therefore, the purposes of this study were (1) to provide sex-and age-specific physical fitness reference standards for Spanish preschool children; and (2) to study sex differences across this age period and to characterise fitness performance throughout the preschool period. DESIGN Cross-sectional. METHODS A total of 3179 preschool children (1678 boys) aged 2.8-6.4 years old from Spain were included in the present study. Physical fitness was measured using the PREFIT battery. RESULTS Age- and sex-specific percentiles for the physical fitness components are provided. Boys performed better than girls in the cardiorespiratory fitness, muscular strength, and speed-agility tests over the whole preschool period studied and for the different percentiles. In contrast, girls performed slightly better than boys in the balance test. Older children had better performance in all fitness tests than their younger counterparts. CONCLUSIONS Our study provides age- and sex-specific physical fitness reference standards in preschool children allowing interpretation of fitness assessment. Sexual dimorphism in fitness tests exists already at preschool age, and these differences become larger with age. These findings will help health, sport, and school professionals to identify preschool children with a high/very low fitness level, to examine changes in fitness over time, and to analyse those changes obtained due to intervention effects.