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Purpose: We examined fluid intake, the relation between body mass (BM) loss and performance, and core temperature in young triathletes during a competition in tropical climate. Methods: Fluid intake and pre and post BM were measured in 35 adolescent athletes, and core temperature was measured in one female and one male. Results: Mean urine specific gravity (1.024 [0.007]) indicated that athletes were in suboptimal state of hydration upon waking. Race time was 73.2 (8.0) minutes. BM decreased by 0.6 (0.3) kg (P < .05). Fluid intake (528.5 [221.6] mL) replaced 47% of the fluid loss (1184.9 [256.4] mL) and was higher during run (11.5 [6.6] mL·min⁻¹) compared to bike (7.3 [3.1] mL·min⁻¹), P < .01. Loss in BM was ≥1.0% in 66% and ≥1.5% in 29% of the athletes. Males showed a moderate association between percentage loss in BM and finishing time (r = −.52), higher sweat rates (1.0 [0.3] L·h⁻¹), and faster times (69.4 [7.5] min; P < .05). Core temperature rose to 40.1 °C in the female and 39.6 °C in the male. Conclusion: Young triathletes competing in a hot/humid climate became mildly to moderately dehydrated and hyperthermic even when water and sports drinks were available but did not show symptoms of heat illness.

Purpose: Previous literature has demonstrated the mediating role of adiposity in the association between cardiorespiratory fitness (CRF) and cardiometabolic risk as well as the potential role of CRF in attenuating the adverse consequences associated with excess weight. This study aimed to evaluate the mediating role of CRF and adiposity in the possible association with cardiometabolic risk. Method: Observational 3-year longitudinal study that included 420 children and adolescents (10.50 [2.05] y of age at baseline; 56.2% girls). Body mass index (BMI) was calculated, and CRF was evaluated using field assessments. A clustered cardiometabolic risk score (cMetS) was calculated from glucose, systolic blood pressure, total cholesterol/high-density lipoprotein cholesterol ratio, and triglycerides z scores. Analyses evaluated the mediating role of BMI in the association between CRF and cMetS as well as whether CRF mediated the association between BMI and cMetS. Results: BMI at baseline was directly associated with the cMetS at follow-up (0.102; 95% confidence interval, 0.020 to 0.181), independently of CRF, whereas CRF was only indirectly associated with cMetS at follow-up through BMI (−0.036; 95% confidence interval, −0.070 to −0.009), meaning that the association between CRF and cMetS was explained via the mediation role of BMI. Conclusions: BMI presented direct association with cMetS, whereas CRF exhibited indirect association with cMetS mediated via BMI.

Purpose: This 2-year longitudinal study examined the development of upper-extremity bone mineral density (BMD), bone mineral content (BMC), and lean mass (LM) asymmetry magnitudes in male and female youth tennis players. Methods: Dominant and nondominant upper-extremity BMD, BMC, and LM values of 49 male and 31 female players were measured yearly using dual X-ray absorptiometry. From these values, asymmetry magnitudes were calculated and expressed as a percentage. Maturity offset was estimated using anthropometric measurements. Linear mixed effect models examined the development of BMD, BMC, and LM asymmetry magnitudes according to players’ maturity offset, sex, and training volume. Results: Adjusted for sex and training volume, a 1-year increment in maturity offset was associated with a significant increase in BMD (1.3% [2.2%]; P < .001) and BMC (0.6% [2.4%]; P = .011) asymmetry magnitudes. Male players displayed significantly higher LM asymmetry magnitudes (Δ3.2% [8.4%]; P = .002) compared with their female counterparts. Training volume was not significantly associated with asymmetry magnitude development. Conclusion: In contrast to LM, male and female youth tennis players’ upper-extremity bones are still responsive to mechanical loading with a significant increase in BMD and BMC asymmetry magnitudes according to maturity offset.

The present study aimed to clarify the development of motor unit (MU) firing properties and the association between those neural properties and force steadiness (FS)/neurological tests in 6- to 12-year-old children. Fifty-eight school-aged children performed maximal voluntary knee extension contraction, a submaximal FS test at 10% of maximal voluntary knee extension contraction, knee extension reaction time to light stimulus test, and single-leg standing test, and data from 38 children who passed the criteria were subject to analysis. During the FS test, high-density surface electromyography was recorded from the vastus lateralis muscle to identify individual MU firing activity. FS was improved with an increase in age (r = −.540, P < .001). The MU firing rate (MUFR) was significantly decreased with an increase in age (r = −.343, P = .035). MUFR variability was not associated with age. Although there was no significant correlation between FS and MUFR, FS was significantly correlated with MUFR variability even after adjustment for the effect of age (r = .551, P = .002). Neither the reaction time nor the single-leg standing test was correlated with any MU firing properties. These findings suggest that MUFR variability makes an important contribution to precise force control in children but does not naturally develop with age.

Background: Inflammatory bowel disease (IBD) is a chronic, systemic condition affecting the gastrointestinal tract. IBD can be severe and are associated with impairment in growth, school absences, abdominal pain, and fatigue. Physical activity (PA) could have an anti-inflammatory effect in addition to other benefits. It is important to address the possible risks, physiological effects of PA, and potential barriers, and facilitators for PA participation in pediatric IBD. However, potential barriers and facilitators to PA have yet to be adequately described. Methods: We conducted a scoping review to map and describe the current literature on PA in pediatric IBD populations between 1980 and April 2022 using Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines for Scoping reviews. Results: Nineteen articles were identified including 10 descriptive, 6 interventional, and 3 physiological responses to PA studies. Patients and healthy controls demonstrated similar responses to exercise. Barriers to participation were low self-esteem, body image, and active IBD symptoms. Facilitators included personal interest, activity with friends, and support from family. Conclusion: This review highlighted that PA participation may reduce in children with IBD-related symptoms. Short- and medium-term impacts of PA on immune modulation require further study; it is possible that regular PA does not negatively affect biomarkers of disease activity.

Background: Children with inflammatory bowel disease (IBD) experience extraintestinal side effects including altered body composition, impaired muscle strength, and aerobic capacity. Exercise training may remedy these issues. Purpose: To assess the feasibility, safety, participant satisfaction, and efficacy of a training program for youth with IBD. Methods: Children with IBD completed 16 weeks of training (2 supervised + 1 home sessions per week). Feasibility was assessed by tracking recruitment, adherence, and compliance rates. Safety was assessed by tracking symptoms and adverse events. Posttraining interviews gauged satisfaction. Circulating inflammatory markers, body composition, muscle strength, aerobic fitness, and habitual physical activity were measured at baseline, midtraining (8 wk), and posttraining. Results: Eleven youth were recruited and 10 completed the study. Participants adhered to 28 (1) of 32 prescribed supervised sessions and 8 (4) of 16 prescribed home sessions. There were no adverse events, and overall feedback on training was positive. Posttraining, we observed an increase in lean mass (+2.4 [1.1] kg), bone density (+0.0124 [0.015] g·cm⁻²), aerobic fitness (+2.8 [5.7] mL·kg LM⁻¹· min⁻¹), and vigorous physical activity levels (+13.09 [8.95] min·h⁻¹) but no change in inflammation or muscle strength. Conclusion: Supervised exercise training is feasible, safe, and effective for youth with IBD and should be encouraged.