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Purpose: To assess the efficacy of a supervised in-school combined resistance and aerobic training program in adolescent girls and investigate whether responses differ according to birthweight. Methods: Participants (girls aged 13–17 y) were randomized either to an intervention replacing physical education (PE) classes with 2 × 60-minute training sessions per week (n = 58) or to a control group that continued to attend 2 × 60 minutes per week of curriculum PE (n = 41). We measured muscular fitness (handgrip, standing long jump, and sit-ups), cardiorespiratory fitness (20-m shuttle run), skinfolds, and lean body mass preintervention and postintervention and determined effect size (Hedge’s g) differences between changes in these measures. We also compared changes within lower (<3000 g) and normal birthweight intervention and PE control subgroups. Results: The intervention group showed greater improvements in all the fitness measures and lean body mass (g = 0.22–0.48) and lower skinfold increases (g = 0.41) than PE controls. Within the intervention group, improvements in all fitness measures were larger in lower birthweight (g = 0.53–0.94) than in normal birthweight girls (g = 0.02–0.39). Conclusion: Replacing curriculum PE with supervised training improved muscular and cardiorespiratory fitness and body composition outcomes in adolescent females. Our findings suggest an enhanced adaptive response to training in participants with lower birthweight which warrants further investigation.

Purpose: The study analyzed the influence of exercise on hypoglycemia episodes postexercise and in the subsequent 24 hours in children and adolescents with type 1 diabetes. Methods: Thirty young people performed the same protocol of physical exercises for 1 hour (Ex1h) and 2 hours (Ex2h) after the administration of insulin. They performed 30 minutes of exercise on a cycle ergometer with a load of 60% of maximal oxygen uptake, interspersed with maximum intensity sprints lasting 10 seconds every 5 minutes. Results: Regarding the occurrence of hypoglycemia, in the 8 hours following the exercises, there was no occurrence in Ex1h (χ ² = 0.001; P = .0001) and a greater proportion for Ex2h (n = 71 episodes, 53.8%), while Ex1h had a higher number of nocturnal hypoglycemic episodes (n = 60, 71.4%) compared with Ex2h (n = 31, 23.1%, χ ² = 49.521, P = .0001), Ex1h triggered a lower number of hypoglycemia (n = 84) than Ex2h (n = 134, χ ² = 11.504, P = .001). There was a greater reduction in the average amount of fast-acting insulin administered the day after Ex1h compared with Ex2h (P = .031). Conclusions: Intermittent exercise performed 1 hour after insulin administration shows a lower risk of hypoglycemia within 8 hours after exercise, as well as a reduction in insulin the following day.

Purpose: Using wearable monitoring devices is increasingly ubiquitous, including among young people. However, there is limited evidence of the validity of devices which are aimed at children and adolescents. The purpose of this study was to evaluate the validity of Fitbit Ace and Moki monitors in healthy young adolescents. Methods: This cross-sectional study included 17 young adolescents (ages 11–13 y) ambulating between 3 different walking conditions (incidental [∼6 min], controlled, and treadmill [each 3 min], while wearing wrist-worn devices [Fitbit Ace, Moki] on each wrist [left and right, respectively]). Data from the devices were compared with observer counts (criterion). Bland–Altman plots and mean absolute percentage errors were computed. Results: Analyses identified that the Fitbit Ace showed higher levels of bias across conditions compared with the Moki device: (mean difference [SD]; Fitbit Ace: 30.0 [38.0], 3.0 [13.0], and 13.0 [23.0] steps and Moki: 1.0 [19.0], 4.0 [16.0], and 6.0 [14.0] steps, incidental, controlled, and treadmill, respectively). Mean absolute percentage errors ranged from 3.1% to 9.5% for the Fitbit Ace and 3.0% to 4.0% for the Moki device. Conclusion: The Fitbit Ace and Moki devices might not provide acceptable validity under all walking conditions, but the Moki provides more accurate estimates of incidental walking and might therefore be a good choice for free-living research or school-based interventions.

Purpose: To determine the effect of a 12-week fundamental motor skill (FMS) program on FMS and physical activity (PA) on preschool-aged children. Method: A cluster randomized controlled trial. The intervention (PhysicaL ActivitY and Fundamental Motor Skills in Pre-schoolers [PLAYFun] Program) was a 12-week games-based program, delivered directly to the children in childcare centers by exercise physiologists. Children in the control arm received the usual preschool curriculum. Outcomes included FMS competence (Test of Gross Motor Development-2) and PA (accelerometer) assessed at baseline, 12 weeks, and 24 weeks (12-wk postintervention). Results: Fifty children (mean age = 4.0 [0.6] y; 54% male) were recruited from 4 childcare centers. Two centers were randomized to PLAYFun and 2 centers were randomized to the waitlist control group. Children attended on average 2.0 (1.0) 40-minute sessions per week. The PLAYFun participants demonstrated significant increases in object control (P < .001) and total FMS (P = .010) competence at week 12, compared with controls in a group × time interaction. Girls, but not boys, in PLAYFun significantly increased moderate to vigorous PA after the intervention (P = .004). These increases were not maintained 12-week postcompletion of PLAYFun. Conclusions: The PLAYFun Program is effective at improving FMS competence in boys and girls and increasing PA in girls. However, improvements are not maintained when opportunities to practice are not sustained.

Purpose: To systematically review the literature on the relationship between physical activity and the effect of physical training on brain-derived neurotrophic factor (BDNF) concentrations in children and adolescents. Methods: The searches were conducted in the databases: PubMed, ScienceDirect, Web of Science, Scopus, SPORTDiscus, Latin American and Caribbean Center for Science Information of Health, and SciELO. All original studies that analyzed the relationship between the practice of physical activity and the effect of physical training on plasma and serum BDNF concentrations in children and adolescents were included. The standardized mean difference (SMD), correlation coefficient (r), and 95% confidence interval were calculated. Results: Eleven studies were selected, totaling 1424 children and adolescents. Cross-sectional studies indicated a significant inverse relationship between physical activity and BDNF concentrations in boys (r = −.117 [−.222, −.009]; P = .033), but not in girls (P = .230). Adolescent athletes tend to have lower serum, but higher plasma BDNF concentrations than sedentary ones (SMD = −0.677 [0.188]; P < .001). An increase in serum BDNF was observed after physical training (SMD = 0.437 [0.183]; P = .017), with no effect in the control group (SMD = 0.235 [0.193]; P = .225). Conclusions: Adolescent athletes tend to show lower serum, but higher plasma BDNF concentrations compared with sedentary individuals. Furthermore, physical training seems to increase serum BDNF concentrations in sedentary adolescents to a small extent.

Purpose: To examine differences in resistance exercise-induced hormonal responses among young athletes according to their maturity levels. Materials and Methods: A total of 12 collegiate and 32 junior high school male athletes were enrolled. The junior high school participants were divided into pre–peak height velocity (PHV) and post-PHV groups, according to their PHV ages. The salivary testosterone, cortisol, and human growth hormone levels were analyzed before (pre), immediately after (post), and at 15 minutes after performing body weight resistance exercise. Results: The testosterone levels were higher in the collegiate than in the junior high school group (P < .01) and increased after 15 minutes of exercise (P < .01). A significant decrease in the cortisol levels postexercise in the junior high school groups (P < .01) and an increase in the human growth hormone levels at 15 minutes after exercise in the post-PHV group were observed (P < .01). In the collegiate and post-PHV groups, the testosterone-to-cortisol ratio increased post and at 15 minutes after exercise (P < .01). The testosterone-to-cortisol ratio values were higher in the collegiate than in the post-PHV (at preexercise and at 15 min after [P < .01]) and pre-PHV groups (at all times [P < .01]). Conclusion: Exercise-induced acute hormonal responses to resistance exercise may depend on individuals’ maturity levels, even in those having the same age.

Introduction: Gender differences in neurocognitive function have been reported over the past few decades. However, multiple studies that report gender differences in Immediate Post-Concussion Assessment and Cognitive Tests composite scores ignore potential confounders which may lead to inaccurate results. Methods: A total of 4829 male and 2477 female baseline Immediate Post-Concussion Assessment and Cognitive Tests from 2009 to 2019 of subjects ages 12–18 years were used to evaluate gender differences in baseline neurocognitive scores and symptom severity ratings. Regression analyses were used to assess the effects of gender on neurocognitive performance at baseline while controlling for a number of potential confounders including symptom burden at the time of testing. Results: Differences in 3 of 5 composite scores as well as severity rating scores were maintained in multivariate analysis. Females had increased Post-Concussion Symptom Scale (β = 3.54, 95% confidence interval, 2.91 to 4.16, P < .0001) along with higher verbal memory (β = 1.82, 95% confidence interval, 1.15 to 2.50, P < .0001) and visual motor (β = 1.29, 95% confidence interval, 0.85–1.72, P < .0001) scores. Conclusions: Statistically significant gender differences were found in baseline neurocognitive function. This study clarifies for the first time that gender differences in these neurocognitive domains are not simply an artifact of differences in symptom burden. However, the small effect sizes call into question the clinical relevance of these differences.