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Purpose: To investigate the association between muscular strength and metabolic syndrome (MetS), with a specific focus on the role of weight status, using a nationally representative sample of US youth. Methods: The analysis included 409 boys and 415 girls from the 2011 to 2014 National Health and Nutrition Examination Survey between 12 and 18 years of age. The prevalence of MetS was defined using age- and sex-specific criteria for abdominal obesity, elevated triglycerides, blood pressure, fasting glucose, and low high-density lipoprotein (HDL) cholesterol. Strength was assessed via handgrip dynamometer and expressed as age- and sex-specific z scores of relative strength. Low strength was defined as a relative strength below the 25th percentile. Analyses controlled for age, sex, race/ethnicity, physical activity, and weight status. Results: The sample prevalence of MetS was approximately 5.3%. However, MetS prevalence was 18.5% in overweight/obese youth with low strength. The adjusted odds of MetS were 3.1 (95% confidence interval, 1.5–6.3, P < .001) times higher for overweight/obese youth with low strength versus sufficient strength. Conclusion: Muscular strength is predictive of adolescent MetS, specifically in those with unhealthy weight status. Approximately one in 5 overweight/obese youth with low strength had MetS. These findings highlight the relevance of muscular strength in youth cardiometabolic morbidities.

Purpose: This study examined the physiological, perceptual, and performance effects of a 6% carbohydrate (CHO) drink during variable-intensity exercise (VIE) and a postexercise test in premenarchal girls. Methods: A total of 10 girls (10.4 [0.7] y) participated in the study. VO₂peak was assessed, and the girls were familiarized with VIE and performance during the first visit. The trial order (CHO and placebo) was randomly assigned for subsequent visits. The drinks were given before VIE bouts and 1-minute performance (9 mL/kg total). Two 15-minute bouts of VIE were completed (10 repeated sequences of 20%, 55%, and 95% power at VO₂peak and maximal sprints) before a 1-minute performance sprint. Results: The mean power, peak power, heart rate (HR), %HR_peak, and rating of perceived exertion during VIE did not differ between trials. However, the peak power decreased, and the rating of perceived exertion increased from the first to the second bout. During the 1-minute performance, there were no differences between the trial (CHO vs placebo) for HR (190 [9] vs 189 [9] bpm), %HR_peak (97.0% [3.2%] vs 96.6% [3.0%]), rating of perceived exertion (7.8 [2.3] vs 8.1 [1.9]), peak power (238 [70] vs 235 [60] W), fatigue index (54.7% [10.0%] vs 55.9% [12.8%]), or total work (9.4 [2.6] vs 9.4 [2.1] kJ). Conclusion: CHO supplementation did not alter physiological, perceptual, or performance responses during 30 minutes of VIE or postexercise sprint performance in premenarchal girls.

Purpose:To examine (1) associations between body fat percent (BF) and lifestyle behaviors in children aged 9–11 years and (2) the consistency of these associations over a 10-year period. Methods: In this repeat, cross-sectional study, 15,977 children aged 9–11 years completed an anthropometric assessment and the SportsLinx Lifestyle survey between 2004 and 2013. Body fat was estimated according to the sum of the triceps and subscapular skinfold measurements. Multilevel models were utilized to examine associations between BF and responses to the lifestyle survey while controlling for known covariates. Results: Lifestyle behaviors explained 8.6% of the total variance in body fat. Specifically, negative associations were found between BF and active transport to school ( β = −0.99 [0.19], P < .001), full-fat milk (−0.07 [0.15], P < .001), and sweetened beverage consumption (−0.40 [0.15], P = .007). Relative to the reference group of ≤8:00 PM, later bedtime was positively associated with BF: 8:00 to 8:59 PM ( β = 1.60 [0.26], P < .001); 9:00 to 10:00 PM ( β = 1.04 [0.24], P < .001); ≥10:00 PM ( β = 1.18 [0.30], P < .001). Two-way interactions revealed opposing associations between BF and the consumption of low-calorie beverages for boys ( β = 0.95 [0.25], P < .001) and girls ( β = −0.85 [0.37], P = .021). There was no significant change in these associations over a 10-year period. Conclusions: In this population-level study covering a decade of data collection, lifestyle behaviors were associated with BF. Policies and interventions targeting population-level behavior change, such as active transport to school, sleep time, and consumption of full-fat milk, may offer an opportunity for improvements in BF.

Purpose: Atherosclerosis is a complex multifactorial disease whose first steps can be initiated from childhood. Therefore, we examined the effects of 2 training models on salusins levels, inflammatory markers, and lipid profile in boys with overweight/obesity. Method: Forty-five boys with overweight/obesity with the mean age of 11.06 (1.0) years were randomly divided into three groups of 15: a high-intensity interval training (HIIT) group (100%–110% of maximum aerobic speed); an aerobic training group (40%–70% of heart rate reserve); and a control group. The intervention included 3 sessions per week for 12 weeks. Results: Findings showed significant improvements in serum levels of salusins, salusins ratio, interleukin-6 (IL-6), and total cholesterol (TC) in both training groups (P < .001). Also, the serum levels of C-reactive protein (CRP), triglycerides (TG), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), atherogenic index of plasma (AIP), and cholesterol index improved significantly (P < .01). Except for the TG, HIIT caused higher improvements than aerobic training (P < .001 for salusin-α, salusins ratio, IL-6, CRP, TC, HDL, AIP, and cholesterol index; and P < .01 for salusin-β and LDL). Conclusion: The present study shows that HIIT has more positive effects than aerobic exercise on the atherosclerotic and inflammatory factors, as well as lipid profile variables in children with overweight/obesity.

Purpose: To appraise the effects of incremental aerobic training (IAT) on systemic inflammatory mediators, cardiorespiratory indices, and functional capacity in obese children with bronchial asthma. Methods: This study included 30 children with asthma (age = 8–16 y) allocated randomly into either the control group (n = 15; received the traditional pulmonary rehabilitation program) or IAT group (n = 15; engaged in 8 weeks of IAT in addition to the traditional pulmonary rehabilitation program). The systemic inflammatory mediators (high-sensitivity C-reactive protein and interleukin-6), cardiorespiratory indices (peak oxygen uptake, minute ventilation, maximum heart rate, heart rate recovery at 1 min after exercises, and oxygen pulse), and functional capacity (represented by 6-min walk test) were analyzed pretreatment and posttreatment. Results: A significant reduction in the level of high-sensitivity C-reactive protein and interleukin-6 and increase in peak oxygen uptake, minute ventilation, maximum heart rate, and heart rate recovery at 1 minute after exercises was observed among the IAT group as compared with the control group. In addition, the IAT group covered a longer distance in the 6-minute walk test than the control group, suggesting favorable functional capacity. Conclusion: The study results imply that IAT has the potential to improve the inflammatory profile, cardiorespiratory fitness, and functional capacity of obese children with bronchial asthma.

Purpose: To examine the influence of growth and maturation in the trajectory of stretch-shortening cycle capability. Method: Using a mixed-longitudinal design, absolute and relative leg stiffness and reactive strength index (RSI) were measured 3 times over a 3-year period in 44 youth team-sport players. Maturation was determined as maturity offset and included within the Bayesian inference analysis as a covariate alongside chronological age. Results: Irrespective of age and maturation, there was no change in absolute leg stiffness, however relative leg stiffness decreased over time. Maturation and age reduced this decline, but the decline remained significant (Bayesian factor [10] = 5097, model averaged R ² = .61). The RSI increased over time and more so in older more mature youth players (Bayesian factor [10] = 9.29e ⁸, model averaged R ² = .657). Conclusion: In youth players who are at/post peak height velocity, relative leg stiffness appears to decline, which could have an impact on both performance and injury risk. However, RSI increases during this period, and these data reinforce that leg stiffness and RSI reflect different components of stretch-shortening cycle capability. Practitioners should consider these differences when planning training to maximize stretch-shortening cycle capability during growth and maturation in athletes on the developmental performance pathway.

Background: To examine substrate oxidation in prepubertal and early pubertal children as a function of body weight, body composition, and sex during an exhaustive cycling test. Methods: This study included 320 children in prepubertal and early puberty (Tanner stage 1 or 2; n = 188 males) who completed a minimum of 4 stages (2–5 min/stage) of an adapted version of the McMaster exhaustive exercise protocol on an upright cycle ergometer. Substrate utilization, relative to individual VO₂peak, was determined using VO₂ and VCO₂ data, obtained with breath-by-breath gas analysis during exercise. Results: Both peak (mg/kg lean body mass·min) and submaximal lipid oxidation (mg/kg lean body mass·min) were highest (P < .01) in children with healthy weight (HW), then overweight, and lowest in obese (OB). Both females with HW (compared with males with HW) and females with OB (compared with males with OB) had higher (P < .01) peak and submaximal lipid oxidation. In children with OB, fat-free mass correlated positively (P < .01) with submaximal lipid oxidation (r = .50). In contrast, in children with HW and overweight, fat-free mass correlated positively (P < .01) with carbohydrate oxidation (r = .52 and r = .47, respectively). Conclusion: Obesity during childhood may alter substrate oxidation during exercise. These results may have implications in the implementation of exercise programs in prepubertal or early puberty to control adiposity.

The majority of studies examining children’s responses to high-intensity interval exercise primarily utilized running; however, this modality does not require/include other important aspects of physical activity including muscular fitness. Purpose: To compare acute responses between a body weight resistance exercise circuit (CIRC) and treadmill-based (TM) high-intensity interval exercise. Method: A total of 17 boys (age = 9.7 [1.3] y) completed a graded exercise test to determine peak heart rate, peak oxygen uptake (VO₂peak), and maximal aerobic speed. Sessions were randomized and counterbalanced. CIRC required 2 sets of 30-second maximal repetitions of 4 exercises. TM included eight 30-second bouts of running at 100% maximal aerobic speed. Both included 30-second active recovery between bouts. Blood lactate concentration was measured preexercise and postexercise. Rating of perceived exertion, affective valence, and enjoyment were recorded preexercise, after intervals 3 and 6, and postexercise. Results: Participants attained 88% (5%) peak heart rate and 74% (9%) VO₂peak for CIRC and 89% (4%) peak heart rate and 81% (6%) VO₂peak for TM, with a significant difference in percentage of VO₂peak (P = .003) between protocols. Postexercise blood lactate concentration was higher following CIRC (5.0 [0.7] mM) versus TM (2.0 [0.3] mM) (P < .001). Rating of perceived exertion, affective valence, and enjoyment responses did not differ between protocols (P > .05). Conclusion: HR responses were near maximal during CIRC, supporting that this body-weight circuit is representative of high-intensity interval exercise.