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Purpose: We assessed maintenance of skeletal advantages 3 years after completion of a 2-year, school-based, controlled exercise trial in adolescent girls. Method: Middle-school girls participated in a resistance training program embedded in physical education classes. Effort groups (low-effort group [LO] and high-effort group [HI]) were identified; the control group (CON) participated in standard physical education at a separate school. Baseline and follow-up (FU) assessments at 6, 18, and 54 (FU3) months included densitometry, anthropometry, and questionnaires assessing physical maturity and nonintervention organized physical activity. Linear mixed effects models were fit to evaluate bone outcomes across all FU time points for CON versus LO/HI. Results: Sixty-eight girls (23 CON/25 HI/20 LO) were 11.6 (0.3) years at baseline. Bone parameters did not differ at baseline, except femoral neck bone mineral density (LO < HI/CON, P < .05). Forty-seven participants provided FU3 assessment: 17 CON/16 HI/14 LO. After adjusting for height, gynecologic age, baseline bone, and organized physical activity, bone gains across all time points were greater for HI versus CON for legs bone mineral content, femoral neck bone mineral content/bone mineral density, and third lumbar vertebra bone mineral content/bone mineral density (P ≤ .05). At FU3, bone values were greater for HI versus CON at subhead, legs, femoral neck, and third lumbar vertebra (P < .03). Conclusion: Adolescent girls who exerted high effort in a school-based resistance training program demonstrated significant skeletal benefits 3 years after program completion.

Purpose: To identify associations between amount of school recess provision and children’s physical activity (PA), weight status, adiposity, cardiorespiratory endurance, muscular strength, and muscular endurance. Method: Data from 6- to 11-year-old participants (n = 499) in the 2012 National Youth Fitness Survey were analyzed. Parents/guardians reported children’s PA levels and recess provision, categorized as no/minimal (9.0%), low (26.1%), medium (46.0%), or high (18.9%). Children wore a wrist-worn accelerometer for 7 days and completed anthropometric measurements. Fitness was assessed using grip strength and treadmill, pull-up, and plank tests. Cross-sectional linear and logistic regression compared outcomes across levels of recess provision adjusting for the survey’s complex sampling design. Results: Children with high provision of recess were 2.31 times more likely to meet PA guidelines according to parent report than those with no/minimal recess. Accelerometer-measured PA followed a more U-shaped pattern, wherein PA was higher in children with high, compared to low, recess provision but comparable to those with no/minimal recess provision. There were no associations with weight status, adiposity, or fitness. Conclusion: Current recess recommendations (20 min·d⁻¹) may be insufficient as 30 minutes per day of recess was associated with a 2-fold greater likelihood of achieving recommended PA levels. Additional research on recess quantity and quality is needed.

Purpose: To summarize the evidence on associations of adiposity and cardiorespiratory fitness (CRF) with arterial structure and function in nonclinical children and adolescents. Methods: Two researchers conducted a search in 5 electronic databases in April 2022 to find studies in nonclinical youth (age 5–17.9 y) reporting multivariable associations. Studies were eligible if adiposity and/or CRF were used as the predictor and arterial structure and/or function was the outcome. The Quality Assessment Tool for Quantitative Studies was used to assess methodological quality for experimental studies, and a modified version was used for observational studies. Results: Ninety-nine studies (72.7% cross-sectional) were included. Ninety-four assessed associations between adiposity and arterial outcomes, most using overall body proportion (n = 71), abdominal (n = 52), or whole-body adiposity (n = 40). Most evidence was inconsistent or nonsignificant, but 59 studies suggested higher abdominal adiposity and worse body proportion were associated with adverse arterial outcomes. Twenty-one assessed associations between CRF and arterial outcomes, with findings inconsistent. Most evidence was rated weak in quality. Conclusion: While high adiposity may contribute to poor arterial outcomes, evidence is limited regarding CRF. Future studies should disentangle these associations by studying youth with healthy adiposity but poor CRF, or vice versa, using longitudinal or experimental study designs.

Purpose: To assess conventional assumptions that underpin the percentage of mature height index as the simple ratio of screening height (numerator) divided by actual or predicted adult height (denominator). Methods: We examined cross-sectional data from 99 academy youth soccer players (chronological age range, 11.5 to 17.7 y) skeletally immature at the screening time and with adult height measurements available at follow-up. Results: The y-intercept value of −60 cm (95% confidence interval, −115 to −6 cm) from linear regression between screening height and adult height indicated the failure to meet the zero y-intercept assumption. The correlation coefficient between present height and adult height of .64 (95% confidence interval, .50 to .74) was not equal to the ratio of coefficient of variations between these variables (CV _x /CV _y  = 0.46) suggesting Tanner’s special circumstance was violated. The non-zero correlation between the ratio and the denominator of .21 (95% confidence interval, .01 to .39) indicated that the percentage of mature height was biased low for players with generally shorter adult height, and vice versa. Conclusion: For the first time, we have demonstrated that the percentage of mature height is an inconsistent statistic for determining the extent of completed growth, leading to potentially biased inferences for research and applied purposes.

Purpose: Understanding which physical activity (PA) and sedentary behavior correlates cluster in children is important, particularly in the home, where children spend significant time. Therefore, this study aimed to assess clustering of physical and social activity-related factors at home, and whether these clusters are related to home-based sitting and PA in children. A secondary aim was to explore whether the clusters were associated with child, parent, and family characteristics. Methods: Altogether, 235 children (55% girls, mean age = 10.2 [0.7] y) and their parents took part. Physical (eg, PA and electronic media equipment, house and garden size, layout) and social (eg, activity preferences, priorities, parental rules) home environmental factors were obtained via the HomeSPACE-II audit and self-report, respectively. Principal component analysis was used to identify clusters of physical and social environmental factors. Backward regression analysis and partial correlations were used to examine relationships between clusters, children’s device-measured home-based activity behaviors, and background characteristics. Results: The findings show that physical and social environment activity-related factors at home cluster. The clusters were associated with several background characteristics, with socioeconomic factors appearing to be particularly influential. The clusters were also associated with home-based activity behaviors in the hypothesized directions. Conclusion: Interventions which target clusters of social and physical factors at home, especially among low-socioeconomic status families, are warranted.

Background: Sickle cell disease is the most common genetic hemoglobinopathy globally and systemically affects body functioning, decreasing exercise capacity. Objective: To assess exercise capacity through the 6-minute walk test (6MWT) and biomarkers in children and adolescents with sickle cell disease. Materials and Methods: Cross-sectional study involving 20 children and adolescents from Brazil. Demographic and socioeconomic data were obtained. Baseline measurements included biomarkers (red blood cells, hemoglobin, hematocrit, white blood cells, platelets, reticulocytes, lactate dehydrogenase, creatine phosphokinase, C-reactive protein, interleukin 6, and fetal hemoglobin). The following data were obtained before, during, and after the 6MWT: heart rate, blood pressure, and peripheral oxygen saturation. Results: Eighteen children and adolescents ages 5–14 years old were analyzed, 61.1% boys, 100% black or brown, and 61.1% in primary education, with low household income. The average distance walked in 6MWT was 463.8 (137.7) m, significantly less than the predicted value (P < .001). The distance of 6MWT was associated positively with age (P = .042) and inversely with reticulocyte count (P = .42) and interleukin 6 (P = .00). Age modified the effect of interleukin 6 in younger children (P = .038). Conclusion: Our findings suggest increased baseline levels of biomarkers of hemolysis and inflammation impact on 6MWT performance.

Purpose: This study investigated the associations between physical activity (PA), sedentary behavior, and executive function in preadolescents. Methods: One hundred and twenty preadolescents were recruited from 2 Hong Kong primary schools. PA and sedentary behavior were recorded for 7 consecutive days by accelerometer. Executive function performance, including inhibition (Stroop task and Flanker task) and working memory (Sternberg paradigm task), were measured. Body mass index and cardiorespiratory fitness (multistage fitness test) were tested. Latent profile analysis explored the profiles of PA and sedentary behavior in preadolescents. Results: Three distinct profiles were identified: low activity, average activity, and high activity. Participants in low activity performed worse in the accuracy of Stroop task (vs average activity, P = .03; vs high activity, P < .01), Flanker task (vs average activity, P = .02; vs high activity, P < .001), and Sternberg paradigm task (vs average activity, P < .01; vs high activity, P < .01). No significant difference was observed between participants with average and high activities. No significant association was observed for profiles on body mass index and cardiorespiratory fitness. Conclusion: Supplementing the consensus of the literature that moderate to vigorous PA benefits cognition, the authors conclude that light PA may also enhance preadolescents’ executive functioning.