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Purpose: To assess the quality of the available evidence on the effect of exercise for the improvement of lung function in healthy children and adolescents. Method: We performed a systematic review and meta-analysis of intervention studies examining the effects of regular exercise on spirometric parameters of healthy children and adolescents aged ≤18 years. Results: Within the exercise groups, there were significant improvements in forced vital capacity (mean difference: 0.17 L; 95% confidence interval, 0.07 to 0.26; P < .05) and forced expiratory volume in the first second (mean difference: 0.14 L; 95% confidence interval, 0.06 to 0.22; P < .05). Results were consistent across different age groups and duration of interventions. In the between-group analysis, forced vital capacity, forced expiratory volume in the first second, and peak expiratory flow were higher in the exercise group compared with the nonexercise group, but the differences did not reach statistical relevance. There was significant statistical heterogeneity between studies. Conclusion: Regular exercise has the potential to improve lung function parameters in healthy children and adolescents; however, the small number of studies and the heterogeneity between them raise concern about the quality of the currently available evidence. These findings bring to attention the need for well-designed trials addressing this important public health issue.

Purpose: To determine whether a 12-week, lower body-targeted aqua-plyometric (AquaPlyo) exercise program could improve muscle strength, bone mineral properties, and physical fitness in patients with juvenile idiopathic arthritis. Methods: A randomized controlled trial was adopted and included 48 patients with polyarticular juvenile idiopathic arthritis (age: 12–18 y). Patients were assigned to undergo either AquaPlyo exercises (AquaPlyo group, n = 24) or standard exercises (control group, n = 24). The outcome measures were assessed pretreatment and posttreatment and included concentric quadriceps peak torque, bone mineral properties (areal bone mineral density [BMD], volumetric BMD, bone mineral content, and BMD Z score), and physical fitness. Results: A significant posttreatment increase in the concentric quadriceps peak torque was detected in the AquaPlyo group compared with the control group (either at an angular velocity of 90°/s [right side: P = .016, left side: P = .025] or 180°/s [right side: P = .007, left side: P = .029]). Besides, a considerably greater improvement in the areal BMD (P = .0006), volumetric BMD (P = .027), bone mineral content (P = .002), and BMD Z score (P = .0004) was observed in the AquaPlyo group. Moreover, a remarkably greater rise in the physical fitness (P < .001) was revealed in the AquaPlyo group. Conclusion: AquaPlyo training can efficiently enhance muscle strength, improve bone mineral properties, and boost physical fitness in patients with juvenile idiopathic arthritis.

Purpose: This study examined metabolic flexibility with respect to fat metabolism during exercise in children who are lean (n=11; 10.9[0.9] y) and overweight/obese (OW/OB; n=9; 10.3[1.2] y). Method: Participants were grouped based on body mass index percentiles for age and sex. Groups were mixed in age and sex. Participants completed two 20-minute exercise bouts on a cycle ergometer, separated by a 10-minute rest. Bout 1 consisted of 10 minutes at 50% VO₂peak and 10 minutes at 75% VO₂peak. Bout 2 was 20 minutes at 50% VO₂peak. Absolute fat oxidation rate (FOR), FOR relative to body mass, FOR relative to fat-free mass, and proportional fat use were measured at 10 minutes of bout 1 and 5, 10, 15, and 20 minutes of bout 2. Results: Absolute FOR was higher in the OW/OB group (range: 117.8 [55.1]–206.2 [48.3] mg·min⁻¹) than in the lean group (81.1 [32.2]–152.2 [38.2] mg·min⁻¹); however, there were no significant main effects for group or significant interactions for proportional fat use, FOR relative to body mass, or FOR relative to fat-free mass. Conclusion: Children in this age range who are overweight/obese do not display impaired metabolic flexibility with respect to fat metabolism during exercise.

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.