Effects of resistance training and aerobic exercise on insulin sensitivity in overweight korean adolescents: a controlled randomized trial

Effect of high-intensity interval training and moderate-intensity continuous training on cardiovascular risk factors in adolescents: Systematic review and meta-analysis of randomized controlled trials

BACKGROUND

In recent years, cardiovascular diseases in adolescents have become more serious. High intensity interval training (HIIT) and moderate intensity continuous training (MICT) have been shown to improve cardiovascular diseases in adolescents. Meta-analysis was conducted to compare the effects of HIIT and MICT on cardiovascular risk factors in adolescents.

METHODS

Randomised controlled trials of HIIT and MICT for cardiovascular risk factors in adolescents up to January 2023 were searched using authoritative databases such as CNKI, Web of Science, PubMed, and EBSCO. Data analysis was performed using Review Manage 5.4 and Stata 14.0.

RESULTS

A total of 12 studies involving 468 participants, mean age 15.19±4.35, were included in the study. The findings showed that compared with MICT, HIIT reduced adolescents' body weight (SMD=-0.18, 95 %CI=-0.58, 0.21) and increased maximal oxygen uptake (SMD=0.56, 95 %CI=0.20, 0.93) and high-density lipoprotein (SMD=-0.47, 95 % CI=-1.11, 0.17), and improved systolic blood pressure (SMD=-0.35, 95 %CI=-0.78, 0.09), glucose (SMD=-1.53, 95 %CI=-2.93, -0.13), and insulin (SMD=-0.66, 95 % CI=-1.73, 0.41), p<0.05. HIIT and MICT improved BMI, fat mass, diastolic blood pressure, triglycerides, total cholesterol, and LDL, with no significant difference between these training types.

CONCLUSION

HIIT was better than MICT for improving cardiovascular health in adolescents, with better effects on body weight, BMI, fat mass, systolic blood pressure, diastolic blood pressure, maximal oxygen uptake, triglyceride, total cholesterol, LDL, HDL, glucose, and insulin levels.

Effects and dose-response relationships of exercise intervention on weight loss in overweight and obese children: a meta-regression and system review

The aim of this study was to determine the effect of different exercise doses on weight loss in obese/overweight children. PubMed, Embase, SPORTDiscus, and the Cochrane library were searched from inception to November 2020 for randomized controlled trials. Fourty six trials involving 2,599 obese/overweight children were finally included. Different exercise dose interventions had different impacts. Exercise intervention reduce body weight (BW) by 1.46 kg (95% CI, -2.35 to -0.56, p=0.001), body fat percentage (BF%) by 2.24 (95% CI, -2.63 to -1.84, p<0.001) and body mass index (BMI) by 1.09 kg/m² (95% CI, -1.45 to -0.73, p<0.001). Each MET-h/week was association with 0.147 kg (95% CI, -0.287 to -0.007, p=0.039) decrease in BW, 0.060 (95% CI, -0.118 to -0.002, p=0.042) decrease in BF%, and 0.069 kg/m² (95% CI, -0.125 to -0.014, p=0.015) decrease in BMI. The findings suggest that there is a positive liner between exercise dose and weight loss, each MET-h/week associated with 0.147 kg, 0.060 and 0.069 kg/m² decrease in body weight, BF%, BMI, respectively.

The Benefits of Resistance Training in Obese Adolescents: A Systematic Review and Meta-analysis

BACKGROUND

Physical activity is essential in acquiring healthy lifestyle behaviors in the early years of maturational development and preventing various diseases. Resistance training (RT) is fundamental for improving body composition and is increasingly recommended for obese adolescents. A systematic review and meta-analysis were performed to synthesize and analyze data on the effects of RT programs in this population, seeking to develop useful recommendations for health and sports professionals.

METHODS

A search was performed using four databases (Web of Science, Scopus, PubMed, and ScienceDirect). According to specific inclusion criteria, twenty-one studies were selected to evaluate the impact of RT on body mass index (BMI), body fat, waist circumference, muscle strength, insulin sensitivity, lean mass and cardiorespiratory fitness.

RESULTS

After the RT programs, the adolescents improved their muscle strength (SMD, 1.44; 95% CI: 0.76-2.12), cardiorespiratory fitness (SMD, 1.09; 95% CI: 0.15-2.04), BMI (SMD, 0.21; 95% CI: 0.07-0.35), waist circumference (SMD, 0.27; 95% CI: 0.06-0.47) and body fat (SMD, 0.20; 95% CI: 0.05-0.34). However, insulin sensitivity (SMD, 0.32; 95% CI: - 0.47 to 1.10) and lean mass (SMD, 0.12; 95% CI: - 0.06 to 0.31) did not reveal any changes. Different RT programs were used but it seems that 2-3 times/week ∼60 min/session of RT for 12 weeks should be recommended for positive changes.

CONCLUSIONS

RT seems to be effective when the objective is to improve muscle strength, cardiorespiratory fitness and can be an efficient strategy to reduce obesity in adolescents by reducing body fat, waist circumference and body mass index. PROSPERO Registration number: CRD42022333411.

Exercise and Nutrition Strategies for Combating Sarcopenia and Type 2 Diabetes Mellitus in Older Adults

Medical and technology development have drastically the improved quality of life and, consequently, life expectancy. Nevertheless, the more people who enter the third-age, the more geriatric syndromes expand in the elderly. Sarcopenia and Type 2 diabetes mellitus (T2DM) are common diseases among the elderly and the literature has extensively studied these two diseases separately. Recent evidence, however, revealed that there is a bidirectional relationship between sarcopenia and T2DM. The aims of the present review were: (1) to present diet and exercise interventions for the management of sarcopenia and T2DM and (2) identify which diet and exercise interventions can be used simultaneously in order to effectively deal with these two disorders. Exercise and a balanced diet are used as effective countermeasures for combating sarcopenia and T2DM in older adults based on their bidirectional relationship. Lifestyle changes such as exercise and a balanced diet seem to play an important role in the remission of the diseases. Results showed that chronic exercise can help towards glycemic regulation as well as decrease the incidence rate of muscle degradation, while diet interventions which focus on protein or amino acids seem to successfully treat both disorders. Despite the fact that there are limited studies that deal with both disorders, it seems that a combined exercise regime (aerobic and resistance) along with protein intake > 1gr/kg/d is the safest strategy to follow in order to manage sarcopenia and T2DM concurrently.

Effect of resistance training with and without caloric restriction on visceral fat: A systemic review and meta-analysis

We performed a systematic review and meta-analysis to investigate the effect of resistance training (RT) with and without caloric restriction (CR) on visceral fat (VF). PubMed and Scopus were searched to identify original articles published through December 2020. Standardized mean differences and 95% confidence intervals (95% CIs) were determined, and separate analyses were conducted for RT versus control, and RT plus CR versus CR only. Thirty-four studies including 38 intervention arms and involving 2285 were included in the meta-analysis. RT effectively reduced VF [-24 (95% CI -0.34 to -0.13), p < 0.001; I²  = 4.17%, p = 0.40; 24 intervention arms] when compared with control. Based on subgroup analyses, reduction in VF was significant for individual with (p = 0.04) and without (p < 0.001) obesity as well as across medium-term (p = 0.001) and long-term (p = 0.002) interventions. Reduction in VF was significant for both middle-age (p = 0.03) and elderly (p = 0.001) adults but was not significant for pediatric (p = 0.08) participants. However, RT plus CR did not indicate superiority effect on VF [0.23 95% CI -0.04 to 0.51, p = 0.09; I²  = 58.76%, p = 0.003; 14 intervention arms] when compared with CR only. Our results confirm that RT may be effective for reducing VF, but adding RT with CR was not associated with a greater effect for reducing VF.

Role of exercise on insulin sensitivity and beta-cell function: is exercise sufficient for the prevention of youth-onset type 2 diabetes?

Parallel with the current pediatric obesity epidemic, the escalating rates of youthonset type 2 diabetes mellitus (T2DM) have become a major public health burden. Although lifestyle modification can be the first-line prevention for T2DM in youths, there is a lack of evidence to establish optimal specific exercise strategies for obese youths at high risk for T2DM. The purpose of this narrative review is to summarize the potential impact of exercise on 2 key pathophysiological risk factors for T2DM, insulin sensitivity and β-cell function, among obese youths. The studies cited are grouped by use of metabolic tests, i.e., direct and indirect measures of insulin sensitivity and β-cell function. In general, there are an increasing number of studies that demonstrate positive effects of aerobic exercise, resistance exercise, and the 2 combined on insulin sensitivity. However, a lack of evidence exists for the effect of any exercise modality on β-cell functional improvement. We also suggest a future direction for research into exercise medical prevention of youth-onset T2DM. These suggestions focus on the effects of exercise modalities on emerging biomarkers of T2DM risk.

What Is the Role of Resistance Exercise in Improving the Cardiometabolic Health of Adolescents with Obesity?

Traditionally, individuals with obesity have been encouraged to participate in aerobic exercise for long-term weight management and improved obesity-related health outcomes. Recently, resistance exercise has become a popular mode of exercise among youth with obesity. However, to date, the literature is mixed as to whether resistance exercise training alone improves body weight, fat free mass, body composition, cardiovascular risk factors, or atherogenic lipoprotein profiles. The limited research in this area suggests potential sex differences in response to resistance training in youth. The literature is more consistent in demonstrating improvements in muscular fitness and insulin resistance independent of caloric restriction and weight loss. Although major health organizations recommend combining aerobic and resistance training, little research has examined the effects of their combination versus their individual effects, thus it is unclear whether their combination is associated with benefits that extend beyond those of either exercise modality alone. The purpose of this review is to examine the effects of resistance exercise on body composition and the health risk factors associated with cardiovascular disease and type 2 diabetes in youth with obesity.

Effects of HIIT and MICT on cardiovascular risk factors in adults with overweight and/or obesity: A meta-analysis

Objective

The purpose of this study was to evaluate the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on cardiovascular disease (CVD) risk factors in adults with overweight and obesity.

Methods

Twenty-two articles were included by searching six databases, the total number of subjects was 620 in these articles. Outcomes were synthesised using a random-effects meta-analysis of the Standardized mean difference (SMD) in CVD risk factors.

Results

HIIT and MICT resulted in statistically significant reductions in Weight, BMI, fat%, total cholesterol(TC), and improvement in VO_2max. Compared with MICT, subgroup of durations of HIIT training interval ≥2 min can significantly increase VO_2max (SMD = 0.444, 95% CI:0.037~0.851,P = 0.032), subgroup of energy expenditure of HIIT equal to MICT can significantly increase VO_2max (SMD = 0.399, 95% CI:0.106~0.692,P = 0.008).

Conclusions

HIIT appears to provide similar benefits to MICT for improving body composition, VO_2maxand TC, but HIIT spent less time than MICT by 9.7 min on one session. HIIT is superior to MICT in improving cardiopulmonary fitness when durations of HIIT training interval ≥2 min or energy expenditure of HIIT same as MICT. PROSPERO ID: CRD42016045835.

Resistance Training Effects on Metabolic Function Among Youth: A Systematic Review

PURPOSE

This systematic review evaluates the relationship between resistance training and metabolic function in youth.

METHODS

PubMed, Embase, Cochrane Library, Web of Science, CINAHL, and ClinicalTrials. gov were searched for articles that (1): studied children (2); included resistance training (3); were randomized interventions; and (4) reported markers of metabolic function. The selected studies were analyzed using the Cochrane Risk-of-Bias Tool.

RESULTS

Thirteen articles met inclusion criteria. Mean age ranged from 12.2 to 16.9 years, but most were limited to high school (n = 11) and overweight/obese (n = 12). Sample sizes (n = 22-304), session duration (40-60min), and intervention length (8-52 wks) varied. Exercise frequency was typically 2-3 d/wk. Resistance training was metabolically beneficial compared with control or resistance plus aerobic training in 5 studies overall and 3 out of the 4 studies with the fewest threats to bias (p ≤ .05); each was accompanied by beneficial changes in body composition, but only one study adjusted for change in body composition.

CONCLUSIONS

Limited evidence suggests that resistance training may positively affect metabolic parameters in youth. Well-controlled resistance training interventions of varying doses are needed to definitively determine whether resistance training can mitigate metabolic dysfunction in youth and whether training benefits on metabolic parameters are independent of body composition changes.

Epidemiology of Childhood Obesity in Korea

Over the past several decades, the prevalence of obesity has increased dramatically worldwide and is increasing not only in developed countries, but also in developing countries. This increase may lead to an increase in the incidence of chronic diseases throughout the lifespan. In Korean children and adolescents, the prevalence of obesity increased from 6.8% in 1998 to 10.0% in 2013. Obesity is a state that more commonly influences children and adolescents of lower socioeconomic status (SES) than those with a higher SES. However, the prevalence of metabolic syndrome in a nationally representative sample of Korean adolescents decreased from 1998 to 2012. According to the Diabetes Fact Sheet of the Korean Diabetes Association, the prevalence of type 2 diabetes among children aged 18 years or younger was 153.5 per 100,000 in 2006 and 205.0 per 100,000 in 2013. Obesity is a complex disease influenced by many interacting factors, such as adipocytokines, lipopolysaccharide-binding protein, adenovirus 36 infection, birth weight, lifestyle, and endocrine-disrupting chemicals. Obesity in youth can adversely impact practically every organ system and lead to serious consequences, such as metabolic, gastrointestinal, pulmonary, cardiovascular, and psychosocial complications. Therefore, coordinated efforts by governments, organizations, communities, and individuals are needed to prevent and treat childhood obesity. In particular, a long-term policy to improve the social environment will also be necessary.

The response of circulating omentin-1 concentration to 16-week exercise training in male children with obesity

OBJECTIVES

The purpose of the present study was to investigate the effects of the 16-week exercise training program on serum omentin-1 in relation to change in insulin resistance in obese male children.

METHODS

Thirty-two obese male children, aged 9-12 years, were randomly assigned into Exercise Group (ExG; n = 16) and Control Group (CG; n = 16). ExG participated in a 16-week exercise training program which combined various forms of aerobic activities and resistance training. Body composition, body mass index (BMI), waist circumference (WC), fasting glucose and insulin, homeostasis model assessment estimate of insulin resistance (HOMA2-IR), blood lipids and serum omentin-1 were assessed before and after 16 weeks of training.

RESULTS

Exercise training significantly decreased body mass (7.5%), BMI (7.6%), WC (4.3%), body fat % (15%), fasting insulin (18.5%), total cholesterol (TC) (5.4%), low-density lipoprotein cholesterol (LDL-C) (17%) and triglyceride (TG) (7.4%) compared to CG. Between-groups comparison showed a considerable exercise-induced upregulation in omentin-1 (ES = 89; P < 0.05) levels. Furthermore, in ExG serum omentin-1 levels were significantly increased from 24.5 ± 8.4 to 35.9 ± 9.3 ng/ml (45%; P < 0.001) after the training program, which was accompanied with significantly decreased fasting insulin (P < 0.001). The changes in omentin-1 concentrations correlated with the changes in BMI (r = -0.67, P < 0.001), WC (r = -0.62, P = 0.002), body fat % (r = -0.50, P = 0.004), insulin (r = -0.65, P = 0.001), HOMA2-IR (r = -0.60, P = 0.004), TC (r = -0.53, P = 0.004) and LDL-C (r = -0.51, P = 0.004) in ExG. BMI (β = -0.50, P = 0.009) and fasting insulin (β = -0.54, P = 0.006) changes were found to be independent predictors of omentin-1 increment in multiple regression analysis.

CONCLUSION

Exercise training resulted in a significant increase in serum omentin-1 concentrations in children with obesity. The findings suggest that exercise-induced changes in omentin-1 may be associated with the beneficial effects of exercise on reduced insulin and weight lost.

Does exercise training affect resting metabolic rate in adolescents with obesity?

We evaluated the hypothesis that resistance exercise training performed alone or in combination with aerobic exercise training would increase resting metabolic rate (RMR) relative to aerobic-only and nonexercising control groups. Postpubertal adolescents (N = 304) aged 14-18 years with obesity (body mass index (BMI) ≥ 95th percentile) or overweight (BMI ≥ 85th percentile + additional diabetes risk factor(s)) were randomized to 4 groups for 22 weeks: Aerobic exercise training, Resistance exercise training, Combined aerobic and resistance exercise training, or Control. All participants received dietary counselling targeting a daily energy deficit of 250 kcal. RMR was measured by indirect calorimetry and body composition by magnetic resonance imaging. There was no significant change in RMR in any group, in spite of significant within-group increases in fat-free mass in the Aerobic, Resistance, and Combined exercise training groups. RMR at baseline and 6 months were Aerobic: 1972 ± 38 and 1990 ± 41; Resistance: 2024 ± 37 and 1992 ± 41; Combined: 2023 ± 38 and 1995 ± 38; Control: 2075 ± 38 and 2073 ± 39 kcal/day (p > 0.05). There were no between-group differences in RMR after adjustment for total body weight or fat-free mass between groups over time. Per-protocol analyses including only participants with ≥70% adherence, and analyses stratified by sex, also showed no within- or between-group differences in RMR. In conclusion, despite an increase in fat-free mass in all exercise groups, 6 months of aerobic, resistance, or combined training with modest dietary restriction did not increase RMR compared with diet only in adolescents with obesity.

Effects of aerobic training, resistance training, or both on cardiorespiratory and musculoskeletal fitness in adolescents with obesity: the HEARTY trial

The purpose of this study was to examine the effects of aerobic, resistance, and combined exercise training on cardiorespiratory and musculoskeletal fitness in postpubertal adolescents with obesity. After a 4-week supervised moderate-intensity exercise run-in, 304 adolescents aged 14-18 years with body mass index ≥85th percentile were randomized to 4 groups for 22 weeks of aerobic training, resistance training, combined training, or a nonexercising control. All participants received dietary counselling with a maximum daily energy deficit of 250 kcal. Cardiorespiratory fitness (peak oxygen consumption) was measured by indirect calorimetry using a graded treadmill exercise test. Musculoskeletal fitness was measured using the 2003 Canadian Physical Activity Fitness and Lifestyle Appraisal tests (hand grip, push-ups, partial curl-ups, sit and reach, and vertical jump). Muscular strength was assessed using an 8-repetition maximum test on the bench press, seated row, and leg press machines. A greater increase in peak oxygen consumption in the aerobic exercise group (30.6 ± 0.6 to 33.4 ± 0.7 mLO2/kg/min) was measured relative to the control group (30.6 ± 0.5 to 30.9 ± 0.7 mLO2/kg/min) (p = 0.002). Similarly, the number of partial curl-ups increased in the aerobic group (19 ± 1 to 23 ± 1) while no differences were measured in the control group (19 ± 1 to 20 ± 1) (p = 0.015). Increases in muscular strength and number of push-ups were greatest in the resistance group versus the control and combined groups versus the aerobic group (p < 0.05). In conclusion, aerobic training had the strongest effect on cardiorespiratory fitness, while resistance and combined training improved both muscular strength and endurance more than control and aerobic training alone, respectively, in adolescents with obesity.

Abdominal obesity and low physical activity are associated with insulin resistance in overweight adolescents: a cross-sectional study

BACKGROUND

Previous studies have assessed the metabolic changes and lifestyles associated with overweight adolescents. However, these associations are unclear amongst overweight adolescents who have already developed insulin resistance. This study assessed the associations between insulin resistance and anthropometric, metabolic, inflammatory, food consumption, and physical activity variables amongst overweight adolescents.

METHODS

This cross-sectional study divided adolescents (n = 120) between 10 and 18 years old into 3 groups: an overweight group with insulin resistance (O + IR), an overweight group without insulin resistance (O-IR), and a normal-weight control group (NW). Adolescents were matched across groups based on age, sex, pubertal maturation, and socioeconomic strata. Anthropometric, biochemical, physical activity, and food consumption variables were assessed. Insulin resistance was assessed using homeostatic model assessment (HOMA Calculator Version 2.2.2 from ©Diabetes Trials Unit, University of Oxford), and overweight status was assessed using body mass index according to World Health Organization (2007) references. A chi-square test was used to compare categorical variables. ANOVAs or Kruskal-Wallis tests were used for continuous variables. Multiple linear regression models were used to calculate the probability of the occurrence of insulin resistance based on the independent variables.

RESULTS

The risk of insulin resistance amongst overweight adolescents increases significantly when they reach a waist circumference > p95 (OR = 1.9, CIs = 1.3-2.7, p = 0.013) and watch 3 or more hours/day of television (OR = 1.7, CIs = 0.98-2.8, p = 0.033). Overweight status and insulin resistance were associated with higher levels of inflammation (hsCRP ≥1 mg/L) and cardiovascular risk according to arterial indices. With each cm increase in waist circumference, the HOMA index increased by 0.082; with each metabolic equivalent (MET) unit increase in physical activity, the HOMA index decreased by 0.026.

CONCLUSIONS

Sedentary behaviour and a waist circumference > p90 amongst overweight adolescents were associated with insulin resistance, lipid profile alterations, and higher inflammatory states. A screening that includes body mass index, in waist circumference, and physical activity evaluations of adolescents might enable the early detection of these alterations.

What is the effect of resistance training on the strength, body composition and psychosocial status of overweight and obese children and adolescents? A Systematic review and meta-analysis

BACKGROUND

Overweight and obese children and adolescents face many physical and psychosocial hardships. Resistance training is a modality of exercise which allows this at-risk group to excel and therefore has the potential to positively affect not only their physical but also psychosocial health.

OBJECTIVE

To systematically review and meta-analyse the peer-reviewed literature to determine the effect of resistance training on the strength, body composition and psychosocial status of overweight and/or obese children and/or adolescents.

DATA SOURCES

Relevant databases (MEDLINE, Embase, Scopus, Web of Science, SPORTDiscus, CINAHL, PsycINFO, Cochrane library, ProQuest) were searched up to and including 30 January 2013.

STUDY SELECTION

Included studies (n = 40, from the 2,247 identified) were randomised controlled trials (RCTs), non-randomised controlled trials (NRCTs) and uncontrolled trials (UCTs) which had run an exercise intervention, with a resistance training component, for overweight and/or obese children and/or adolescents, and which had examined the effect of resistance training on either strength, body composition or psychosocial outcomes.

STUDY APPRAISAL AND SYNTHESIS METHODS

Studies were initially critically appraised for risk of bias by the lead author, following which both co-authors critically appraised five randomly selected studies to assess reliability.

RESULTS

Randomised controlled trials and NRCTs were analysed separately from UCTs. To determine the overall intervention effect for each outcome variable for each study design group, standardised mean differences were calculated with each individual study/data set weighted by the inverse of the pooled variance. The overall intervention effect reported for RCTs and NRCTs was relative to the control group whereas the effect reported for UCTs shows an overall post-intervention effect. Subgroup analyses, which determined whether the overall intervention effect was influenced by intervention type, training volume, age, sex, risk of bias or study design (for RCT/NRCT group only), were run using the same summary measure. Typically, resistance training had very small to small effects on body composition and moderate to large effects on strength in favour of the intervention. However, the magnitude and direction of the effect of resistance training on psychological outcomes are still unclear given the limited number of studies which looked at psychosocial outcomes and the inconclusive results shown by this review. Uncontrolled trials typically showed larger intervention effects than RCTs and NRCTs; however, these results may be greatly influenced by maturational changes rather than the intervention itself.

LIMITATIONS

The included studies employed a number of different exercise intervention types (e.g. resistance training, resistance plus aerobic training etc.) that ranged from 6 to 52 weeks in duration. Studies also employed a number of different methodologies to assess similar outcome measures (e.g. dual energy X-ray absorptiometry versus skinfolds to assess body composition; one-repetition maximum testing versus hand grip strength to assess strength). However, by completing subgroup analyses and using a standardised summary measure these limitations have been accounted for.

CONCLUSION

While the effect of resistance training on the body composition and strength of overweight and obese children and adolescents is clear, given the paucity of conclusive data more studies are needed to fully understand the effect of resistance training on the psychosocial status of this population.

Exercise and insulin resistance in youth: a meta-analysis

BACKGROUND AND OBJECTIVES

The prevalence of obesity and diabetes is increasing among children, adolescents, and adults. Although estimates of the efficacy of exercise training on fasting insulin and insulin resistance have been provided, for adults similar estimates have not been provided for youth. This systematic review and meta-analysis provides a quantitative estimate of the effectiveness of exercise training on fasting insulin and insulin resistance in children and adolescents.

METHODS

Potential sources were limited to peer-reviewed articles published before June 25, 2013, and gathered from the PubMed, SPORTDiscus, Physical Education Index, and Web of Science online databases. Analysis was limited to randomized controlled trials by using combinations of the terms adolescent, child, pediatric, youth, exercise training, physical activity, diabetes, insulin, randomized trial, and randomized controlled trial. The authors assessed 546 sources, of which 4.4% (24 studies) were eligible for inclusion. Thirty-two effects were used to estimate the effect of exercise training on fasting insulin, with 15 effects measuring the effect on insulin resistance. Estimated effects were independently calculated by multiple authors, and conflicts were resolved before calculating the overall effect.

RESULTS

Based on the cumulative results from these studies, a small to moderate effect was found for exercise training on fasting insulin and improving insulin resistance in youth (Hedges' d effect size = 0.48 [95% confidence interval: 0.22-0.74], P < .001 and 0.31 [95% confidence interval: 0.06-0.56], P < .05, respectively).

CONCLUSIONS

These results support the use of exercise training in the prevention and treatment of type 2 diabetes.

A review of randomized controlled trials of aerobic exercise training on fitness and cardiometabolic risk factors in obese adolescents

Aerobic training is the most prescribed exercise modality for the management of pediatric obesity. There is strong evidence that it decreases waist circumference, percent body fat and visceral fat, increases cardiorespiratory fitness, and decreases blood pressure in obese adolescents. However, the independent effects of aerobic exercise training on other cardiometabolic risk factors (ie, insulin resistance markers, plasma lipid levels, and inflammatory markers) are limited and yield inconsistent findings. Our article reviews randomized controlled trials evaluating the effects of aerobic exercise training on body composition, fitness, lipid levels, and insulin resistance in obese adolescents (aged 13-18 years) and outlines future research directions for this population.

Muscle strength in youth and cardiovascular risk in young adulthood (the European Youth Heart Study)

BACKGROUND

Whether muscle strength in youth is related to cardiovascular risk later in life independent of cardiorespiratory fitness is unclear.

METHODS

We examined the independent association of isometric muscle strength in youth with cardiovascular risk factors in young adulthood using data from the Danish European Youth Heart Study; a population-based prospective cohort study among boys and girls (n=332) followed for up to 12 years. In youth maximal voluntary contractions during isometric back extension and abdominal flexion were determined using a strain-gauge dynamometer and cardiorespiratory fitness was obtained from a maximal cycle ergometer test. Cardiovascular risk factors were obtained in youth and in young adulthood. Associations were examined using multivariable-adjusted regression models including major confounding factors.

RESULTS

Each 1 SD difference in isometric muscle strength in youth (0.17 N/kg) was inversely associated with body mass index (BMI; -0.60 kg/m(2), 95% CI -0.97 to -0.22), triglyceride (-0.09 mmol/l, 95% CI -0.16 to -0.02), diastolic blood pressure (BP) (-1.22 mm Hg, 95% CI -2.15 to -0.29) and a composite cardiovascular risk factor score (-0.61 SD, 95% CI -1.03 to -0.20) in young adulthood in multivariable-adjusted analyses including fitness. Associations to triglyceride, diastolic BP and the cardiovascular risk factor score remained with additional adjustment for waist circumference or BMI. Each 1 SD difference in isometric muscle strength in youth was significantly associated with 0.59 (95% CI 0.40 to 0.87) lower odds of general overweight/obesity in young adulthood (p=0.007) and was marginally associated with incident raised BP, raised triglyceride and low high-density lipoprotein cholesterol.

CONCLUSIONS

This study suggests that greater isometric muscle strength in youth is associated with lower levels of cardiovascular risk factors in young adulthood independent of fitness, adiposity and other confounding factors.

Effects of aerobic versus resistance exercise without caloric restriction on abdominal fat, intrahepatic lipid, and insulin sensitivity in obese adolescent boys: a randomized, controlled trial

The optimal exercise modality for reductions of abdominal obesity and risk factors for type 2 diabetes in youth is unknown. We examined the effects of aerobic exercise (AE) versus resistance exercise (RE) without caloric restriction on abdominal adiposity, ectopic fat, and insulin sensitivity and secretion in youth. Forty-five obese adolescent boys were randomly assigned to one of three 3-month interventions: AE, RE, or a nonexercising control. Abdominal fat was assessed by magnetic resonance imaging, and intrahepatic lipid and intramyocellular lipid were assessed by proton magnetic resonance spectroscopy. Insulin sensitivity and secretion were evaluated by a 3-h hyperinsulinemic-euglycemic clamp and a 2-h hyperglycemic clamp. Both AE and RE prevented the significant weight gain that was observed in controls. Compared with controls, significant reductions in total and visceral fat and intrahepatic lipid were observed in both exercise groups. Compared with controls, a significant improvement in insulin sensitivity (27%) was observed in the RE group. Collapsed across groups, changes in visceral fat were associated with changes in intrahepatic lipid (r = 0.72) and insulin sensitivity (r = -0.47). Both AE and RE alone are effective for reducing abdominal fat and intrahepatic lipid in obese adolescent boys. RE but not AE is also associated with significant improvements in insulin sensitivity.