High-intensity interval training in overweight and obese children and adolescents: systematic review and meta-analysis

Eight weeks of high-intensity interval vs. sprint interval training effects on overweight and obese adolescents carried out during the cool-down period of physical education classes: randomized controlled trial

Objective

The aim of this study was to evaluate the effect of sprint interval training (SIT) and [high intensive interval training (HIIT)] carried out during the cool-down period of the physical education classes on body composition, blood pressure variables (BP) and pulse rate (PR), and cardiorespiratory fitness of adolescents who are overweight and obese, and to compare the differences in enjoyment in response to SIT vs. HIIT.

Methods

For this randomized controlled trial, forty-five adolescents were recruited from a high school and were randomly placed into three groups. SIT and HIIT trained for 8 weeks, twice a week, for 12 min/session. Experimental group (EG) 3 was the control, and they maintained their regular physical education class schedule. The SIT group performed 6 sets of 60 s of work (90-95%HRmax) / 60 s of rest (50-55%HRmax), and the HIIT group performed 3 sets of 2 min of work (80-85%HRmax) / 2 min of rest (50-55%HRmax).

Results

Both experimental groups showed a significant improvement in fat mass (FM) (%) and trunk FM (kg). In addition, EG2 reported a significance improvement in lean mass (kg), blood pressure BP (mmHG), systolic blood pressure (SBP) (mmHg), diastolic blood pressure (DBP) (mmHg), PR (bpm), and VO2max (ml/kg/min).

Conclusion

The present study found that a HIIT protocol performed during the cool-down period of the physical education classes generated adaptations such as improvement in body composition, BP variables and PR, and cardiorespiratory fitness, in overweight and obese adolescents. In contrast, the group of overweight and obese adolescents who performed SIT showed limited benefits, with changes in fat mass only.

A systematic review and cluster analysis approach of 103 studies of high-intensity interval training on cardiorespiratory fitness

AIMS

This study aims to systematically review the systematic reviews and meta-analyses examining the effect of high-intensity interval training (HIIT) protocols on improving cardiorespiratory fitness (CRF) and to characterize the main patterns of HIIT modalities using clustering statistical procedures to examine their potential differences on improving CRF. Finally, we aimed to develop a comprehensive guideline for reporting HIIT protocols.

METHODS AND RESULTS

A systematic review was conducted on PubMed and Web of Science from their inception to 31 October 2022 for systematic reviews and meta-analysis aimed at assessing the effect of HIIT on CRF in the entire study population. The Assessment of Multiple Systematic Reviews 2 tool was used to evaluate the risk of bias of each review. Additionally, a principal component analysis testing the data adequacy for the factor solution through the Kaiser-Meyer-Olkin procedure test was conducted. Once the number of factors was identified, in order to identify data patterns according to the main characteristics of the HIIT protocols, a two-step cluster analysis was conducted. Nineteen systematic reviews and/or meta-analyses comprising 103 studies were included. Clustering of systematic reviews and meta-analyses identified three HIIT modalities ('HIIT-normal mixed', 'HIIT-long running', and 'HIIT-short cycling') underlying the interventions across the included studies. Similar effectiveness in increasing CRF among the three HIIT modalities was observed. Subgroup analyses showed no significant differences in CRF by sex, weight status, study design, and baseline physical activity level (P > 0.05), but differences were observed by age group, and exercise intensity indicator was used in the HIIT programmes (P < 0.05).

CONCLUSION

All three HIIT modalities produced significant improvements of CRF, although some modalities showed greater changes for some specific age groups or intensity indicators.

Effects of short-term supervised exercise training on liver fat in adolescents with obesity: a randomized controlled trial

OBJECTIVE

The objective of this study was to quantify the effects of a 4-week, supervised, high-intensity interval training (HIIT) on intrahepatic triglyceride content (IHTG, percentage), cardiorespiratory fitness (CRF), and cardiometabolic markers in adolescents with obesity.

METHODS

A total of 40 adolescents (age 13-18 y, BMI 36.7 ± 5.8 kg/m2 ) at risk for metabolic dysfunction-associated steatotic liver disease (MASLD) based on obesity and elevated Fibroscan measured controlled attenuation parameter (CAP) scores were randomized to HIIT three times a week for 4 weeks (n = 34) or observation (control; n = 6). Liver magnetic resonance imaging proton-density fat-fraction (MRI-PDFF), CAP, oral glucose tolerance test, serum alanine aminotransferase, dual-energy x-ray absorptiometry, and CRF tests were performed before and after intervention. Within- and between-group differences were compared.

RESULTS

A total of 13 (38%) and 4 (66%) children had MASLD by MRI-PDFF (IHTG ≥ 5%) in the HIIT and control groups, respectively. The implemented HIIT protocol had no impact on CRF or IHTG (baseline 5.26%, Δ = -0.31 percentage points, 95% CI: -0.77 to 0.15; p = 0.179), but it decreased the 2-h glucose concentration (baseline 116 mg/dL, Δ = -11 mg/dL; 95% CI: -17.6 to -5.5; p < 0.001). When limiting the analysis to participants with MASLD (n = 17), HIIT decreased IHTG (baseline 8.81%, Δ = -1.05 percentage points, 95% CI: -2.08 to -0.01; p = 0.048). Between-group comparisons were not different.

CONCLUSIONS

The implemented exercise protocol did not reduce IHTG, but it led to modest improvement in markers of cardiometabolic health.

Effects of combined training or moderate intensity continuous training during a 3-week multidisciplinary body weight reduction program on cardiorespiratory fitness, body composition, and substrate oxidation rate in adolescents with obesity

This study aimed to investigate the effects of combined training (COMB, a combination of moderate-intensity continuous training-MICT and high-intensity interval training-HIIT) vs. continuous MICT administered during a 3-week in-hospital body weight reduction program (BWRP) on body composition, physical capacities, and substrate oxidation in adolescents with obesity. The 3-week in-hospital BWRP entailed moderate energy restriction, nutritional education, psychological counseling, and two different protocols of physical exercise. Twenty-one male adolescents with obesity (mean age: 16.1 ± 1.5 years; mean body mass index [BMI] 37.8 ± 4.5 kg m-2) participated in this randomized control trial study (n:10 for COMB, n:11 MICT), attending ~ 30 training sessions. The COMB group performed 3 repetitions of 2 min at 95% of peak oxygen uptake (V'O2 peak) (e.g., HIIT ≤ 20%), followed by 30 min at 60% of V'O2 peak (e.g., MICT ≥ 80%). Body composition, V'O2 peak, basal metabolic rate (BMR), energy expenditure, and substrate oxidation rate were measured during the first week (W0) and at the end of three weeks of training (W3). The two training programs were equivalent in caloric expenditure. At W3, body mass (BM) and fat mass (FM) decreased significantly in both groups, although the decrease in BM was significantly greater in the MICT group than in the COMB group (BM: - 5.0 ± 1.2 vs. - 8.4 ± 1.5, P < 0.05; FM: - 4.3 ± 3.0 vs. - 4.2 ± 1.9 kg, P < 0.05). V'O2 peak increased only in the COMB by a mean of 0.28 ± 0.22 L min-1 (P < 0.05). The maximal fat oxidation rate (MFO) increased only in the COMB group by 0.04 ± 0.03 g min-1 (P < 0.05). COMB training represents a viable alternative to MICT for improving anthropometric characteristics, physical capacities, and MFO in adolescents with obesity during a 3-week in-hospital BWRP.

Lifestyle interventions to change trajectories of obesity-related cardiovascular risk from childhood onset to manifestation in adulthood: a joint scientific statement of the task force for childhood health of the European Association of Preventive Cardiology and the European Childhood Obesity Group

There is an immediate need to optimize cardiovascular (CV) risk management and primary prevention of childhood obesity to timely and more effectively combat the health hazard and socioeconomic burden of CV disease from childhood development to adulthood manifestation. Optimizing screening programs and risk management strategies for obesity-related CV risk in childhood has high potential to change disease trajectories into adulthood. Building on a holistic view on the aetiology of childhood obesity, this document reviews current concepts in primary prevention and risk management strategies by lifestyle interventions. As an additional objective, this scientific statement addresses the high potential for reversibility of CV risk in childhood and comments on the use of modern surrogate markers beyond monitoring weight and body composition. This scientific statement also highlights the clinical importance of quantifying CV risk trajectories and discusses the remaining research gaps and challenges to better promote childhood health in a population-based approach. Finally, this document provides an overview on the lessons to be learned from the presented evidence and identifies key barriers to be targeted by researchers, clinicians, and policymakers to put into practice more effective primary prevention strategies for childhood obesity early in life to combat the burden of CV disease later in life.

The effects of high-intensity interval training at the anaerobic and psychomotor fatigue thresholds on physiological parameters in young soccer players: a prospective study

This study aimed to investigate the effects of a 4-week specific high-intensity interval training (HIIT) program performed between the anaerobic threshold (ANT) and the psychomotor fatigue threshold (PFT) on physiological parameters in 14 professional soccer players at the under-17 level. The first and second stages of the research protocol included a treadmill running exercise with increasing load and six 3-min four-versus-four games of soccer with a 3-min break between games. Players then participated in a training microcycle involving three specific HIIT exercises twice per week for 4 weeks, after which they repeated stages one and two, followed by an assessment of changes. The measurement of lactate (LA) determined ANT, whereas the choice reaction time (CRT) indicated PFT among other selected physiological parameters. The repeated-measure analysis of variance (ANOVA) compared mean values for the examined variables using Bonferroni post hoc test. It demonstrated significantly increased maximal oxygen consumption (VO2 max) from 45.9 ± 3.0 to 48.7 ± 2.6 at the ANT and from 49.1 ± 3.4 to 52.0 ± 3.6 on the PFT after 4 weeks of training. A significant increase in the running speed (RS) at both thresholds and heart rate (HR) at the ANT (p ≤ 0.05) was also recorded. Moreover, the players exceeded their intensity of effort during ANT while playing four-versus-four soccer matches, but they did not reach intensity during PFT. In conclusion, the findings of the study demonstrated that both thresholds shifted toward higher loads and the proposed specific HIIT effectively increased the exercise capacity of soccer players.

High-intensity interval training in children and adolescents with special educational needs: a systematic review and narrative synthesis

BACKGROUND

High-intensity interval training (HIIT) has been promoted as a time-efficient exercise strategy to improve health and fitness in children and adolescents. However, there remains little consensus in the literature regarding its efficacy in children and adolescents with special educational needs (SEN). This study aimed to examine HIIT as a means of improving key health and fitness parameters in children and adolescents with SEN.

METHODS

A systematic search was conducted on eight databases (MEDLINE, Embase, SPORTDiscus, Web of Science, Scopus, PsycINFO, CINAHL, and Cochrane Library). Studies were eligible if they 1) included an HIIT protocol, 2) examined parameters related to both physical and mental aspects of health and fitness, and 3) examined children and adolescents with SEN aged 5-17 years.

RESULTS

Of the 1727 studies yielded by the database search, 13 (453 participants) were included and reviewed. We found that HIIT generally improved body composition, physical fitness, and cardiometabolic risk biomarkers across a spectrum of SEN (e.g., attention deficit hyperactivity disorder, cerebral palsy, developmental coordination disorder, and mental illness). Improvements in mental health and cognitive performance following HIIT have also been observed.

CONCLUSION

This review provides up-to-date evidence for HIIT as a viable exercise strategy for children and adolescents with SEN. Further research investigating the benefits of HIIT in a wider range of SEN populations is warranted.

TRIAL REGISTRATION

This study was registered in the International Prospective Register of Systematic Review (PROSPERO; registration number CRD42022352696).

Combined high-intensity interval training as an obesity-management strategy for adolescents

Effective and safe exercise protocols for obesity management in adolescents are imperative. This study aimed to analyse compliance, efficacy, and safety of combined high-intensity interval training circuit (HIIT) in the management of obesity (including overweight) in adolescents, compared to traditional training (TT). Data from 55 adolescents (47.3% girls) (TT n = 31; HIIT n = 24), aged 12-18 (mean age of 14.3 ± 1.7), with overweight and obesity (median BMI z-score of 2.95), were assessed at baseline and month 6 (Clinicaltrials.gov/NCT02941770). During the 6-month intervention, participants in both exercise groups attended two exercise sessions/week (60 min/session) along with a set of appointments with a paediatrician, nutritionist, and exercise physiologist. Forty-six participants completed the intervention (TT n = 23; HIIT n = 23). Exercise session attendance (≥80%) was significantly higher among HIIT participants (73.9 vs. 13.0%, p < .001). HIIT, but not TT, showed a significant decrease in BMI z-score (d = 0.40, p < .001), body fat mass (BFM, %) (d = 0.41, p = .001), and trunk fat mass (d = 0.56, p < .001), as well as a significant increase in muscle mass (MM, %) (d = 0.28, p = .001) between baseline and 6 months. According to generalized estimating equations, time-by-attendance interactions (instead of time-by group) were found in BMI z-score (β = 0.25, 95%CI: 0.17, 0.33), BFM (β = 2.29, 95%CI: 1.02, 3.56), trunk fat mass (β = 2.94, 95%CI: 1.70, 4.18), and MM (β = -1.16, 95%CI: -1.87, -0.45). No adverse events were reported during HIIT sessions. Although compliance may mediate the impact of an exercise protocol on health-related outcomes, HIIT showed to be safe, with higher compliance compared to TT, which may result in improved outcomes overtime.

The Relative Importance of Age at Peak Height Velocity and Fat Mass Index in High-Intensity Interval Training Effect on Cardiorespiratory Fitness in Adolescents: A Randomized Controlled Trial

Background: This study aimed to evaluate the role of biological age in the relationship between preintervention fat mass and cardiorespiratory fitness effects (CRF) after High-Intensity Interval Training (HIIT) intervention in adolescents. Methods: A total of 141 boys and girls (16 years) were examined as control (CG) and experimental (EG) groups that conducted a 10-week HIIT implemented in physical education. Measurements: body height, body weight, fat mass index (FMI), CRF (Harvard Step Test). Predicted age at peak height velocity (APHV) was calculated. Pathway analyses were conducted to identify the influences of the measured variables. Results: APHV harmed the level of ΔFI (fitness index) (β = −0.270; p = 0.035), while HIIT had a positive effect on changes in ΔFI (β = 0.246; p = 0.002). Sex affected the changes in CRF (β = 0.344; p = 0.011). Two models were designed respective to sex. The effect of the APHV on ΔFI in girls was close to significant (p = 0.053) but was non-significant in boys (p = 0.311). Changes in CRF in girls were positively and close to significance (p < 0.100) affected by FMIbaseline. Conclusion: HIIT is an effective way of exerting positive changes in CRF in adolescents, which is greater in boys than girls. APHV plays a role only in girls. The HIIT should be tailored to girls depending on their maturity status.

Guidelines for treating child and adolescent obesity: A systematic review

Obesity is a chronic disease that compromises the physical and mental health of an increasing proportion of children globally. In high-income countries, prevalence of paediatric obesity is increasing faster in those from marginalised populations such as low-income households, suggesting the disease as one that is largely systemic. Appropriate treatment should be prioritised in these settings to prevent the development of complications and co-morbidities and manage those that already exist. An array of clinical practice guidelines are available for managing overweight and obesity in children and adolescents, but no systematic review has yet compared their quality or synthesised their recommendations. We aimed to narratively review clinical practice guidelines published in English for treating child and adolescent obesity, to identify the highest quality guidelines, and assess similarities, conflicts, and gaps in recommendations. We systematically searched academic databases and grey literature for guidelines published. We used the AGREE II tool to assess the quality, and identified nine high quality guidelines for inclusion in a narrative review of recommendations. Guidelines predominantly recommended the delivery of multi-component behaviour-change interventions aimed at improving nutrition and physical activity. Treatment outcomes were generally focussed on weight, with less emphasis on managing complications or improving quality-of-life. There was no evidence-based consensus on the best mode of delivery, setting, or treatment format. The guidelines rarely included recommendations for addressing the practical or social barriers to behaviour change, such as cooking skills or supervised physical activity. There is insufficient evidence to evaluate pharmaceutical and surgical interventions in children, and these were generally not recommended. It should be noted that this review addressed documents published in English only, and therefore the included guidelines were applicable predominantly to high-resource settings.

Integrating High-Intensity Interval Training into a School Setting Improve Body Composition, Cardiorespiratory Fitness and Physical Activity in Children with Obesity: A Randomized Controlled Trial

The aim of this study was to examine the effects of school-based high-intensity interval training (HIIT) on cardiorespiratory fitness and visceral adipose tissue (VAT) in children with obesity. A total of 40 students (11.0 ± 0.6 years; 20 boys) were randomized into an intervention group (IG) and control group (CG). The IG group performed a 12-week HIIT intervention with three sessions per week. Each session included 18 min of training (three sets of eight bouts of 15 s run at 100% maximal aerobic speed (MAS) separated by eight bouts of 15 s recovery run at 50% MAS) in PE class; the CG group were instructed to continue their normal behaviors. All subjects had indices of body mass index (BMI), fat mass (FM), body fat percentage (%BF), fat free mass (FFM), VAT, and maximal oxygen uptake (VO2max) measured at baseline and post-intervention. The cooperation of students was high, and all 40 students were included in the final analysis. A significant group−time interaction was determined in body composition (p < 0.05), with a significant decrease in BM (−3.4 ± 1.4 kg, p = 0.001; η2 = 0.63), BMI (−1.7 ± 0.5, p = 0.001; η2 = 0.58), %BF (−3.3 ± 1.4, p = 0.001; η2 = 0.54), and FM (−3.2 ± 1.4 kg, p = 0.001; η2 = 0.69), and VAT (−22.4 ± 9.8 cm2; p = 0.001; η2 = 0.61) in the IG. Furthermore, VO2max exhibited a significant increase in the IG (4.5 ± 1.6 mL/kg/min, p = 0.001; η2 = 0.84) and CG groups (1.7 ± 1.1 mL/kg/min, p = 0.001; η2 = 0.44). Integrating regular school-based HIIT sessions is a suitable method to improve body composition, cardiorespiratory fitness, and physical activity in students with obesity. Trial Registration: ChiCTR2100048737.

Six HIT Sessions Improve Cardiorespiratory Fitness and Metabolic Flexibility in Insulin Resistant and Insulin Sensitive Adolescents with Obesity

To evaluate the effect of high-intensity interval training (HIT) on the cardiorespiratory performance and substrate oxidation pattern in insulin-resistant and insulin-sensitive obese adolescents.

METHODS

We recruited 25 obese adolescents in three schools, and trained them in six HIT sessions, comprising of six series at 100% and recovery at 50% peak velocity (Vpeak). For the evaluation, the participants were divided into two groups: insulin-resistant (IR, n = 12; HOMA index ≥3.16) and insulin-sensitive (IS, n = 13). All participants underwent cardiopulmonary and indirect calorimetry testing. We compared the effects of HIT before and after the intervention among the two groups. The data were analyzed using Student's t and Mann-Whitney (intergroup comparisons) and Student's t and Wilcoxon (pre- and post-training comparisons) tests; and Cohen's d (influence of HIT).

RESULTS

There was a significant post-training increase in Vpeak, oxygen consumption (VO2), velocity (V), and heart rate (HR) at the exertion intensity at the first ventilatory anaerobic threshold (VAT1) in both groups (p < 0.05; d < 0.02). The exercise promoted changes in substrate oxidation rates of the groups, with an increase in carbohydrate oxidation (CHOox) for both IR (p = 0.064) and IS (p = 0.034).

CONCLUSION

Six HIT sessions improved cardiorespiratory performance in both groups and increased CHOox in insulin-sensitive obese adolescents, suggesting its utility for increasing physical fitness and controlling glycemia in these population groups.

Exercise and Cardiovascular Disease Risk Factors in Children and Adolescents With Obesity: A Systematic Review With Meta-Analysis of Randomized Controlled Trials

The purpose of this study was to examine the effects of exercise on cardiovascular disease (CVD) risk factors in children and adolescents with obesity. Randomized controlled trials (RCTs) of exercise ≥4 weeks in children and adolescents with obesity were included if one or more CVD risk factors were included as an outcome. Studies were retrieved by searching 7 electronic databases, cross-referencing, and expert review. Data were pooled using the inverse-variance heterogeneity (IVhet) model and strength of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) instrument. Thirty-nine studies representing 1548 participants (847 exercise, 701 control) met the inclusion criteria. Aerobic exercise improved 10 of 12 (83.3%) outcomes (P < .05 for all) while combined aerobic and strength training improved 5 of 8 (62.5%) outcomes (P < .05 for all). The strength of evidence ranged from "very low" to "moderate." It was concluded that aerobic exercise, as well as combined aerobic and strength training, is associated with improvements in multiple CVD risk factors among children and adolescents with obesity. However, the generally low strength of evidence suggests a need for future well-designed and conducted RCTs on the effects of exercise, especially strength training, in children and adolescents with obesity.

Physical Activity and Exercise Practice to Reduce the Sedentary Behavior in Children and Adolescents Overweight and with Obesity

Childhood obesity remains a serious public health concern all over the world [...]

School-based high-intensity interval training programs in children and adolescents: A systematic review and meta-analysis

PURPOSE

1) To investigate the effectiveness of school-based high-intensity interval training (HIIT) interventions in promoting health outcomes of children and adolescents compared with either a control group or other exercise modality; and 2) to explore the intervention characteristics and process outcomes of published school-based HIIT interventions.

METHODS

We searched Medline, Embase, CINAHL, SPORTDiscus, and Web of Science from inception until 31 March 2021. Studies were eligible if 1) participants aged 5-17 years old; 2) a HIIT intervention within a school setting ≥ 2 weeks duration; 3) a control or comparative exercise group; 4) health-related, cognitive, physical activity, nutrition, or program evaluation outcomes; and 5) original research published in English. We conducted meta-analyses between HIIT and control groups for all outcomes with ≥ 4 studies and meta-regressions for all outcomes with ≥ 10 studies. We narratively synthesised results between HIIT and comparative exercise groups.

RESULTS

Fifty-four papers met eligibility criteria, encompassing 42 unique studies (35 randomised controlled trials; 36 with a high risk of bias). Meta-analyses indicated significant improvements in waist circumference (mean difference (MD) = -2.5cm), body fat percentage (MD = -1.7%), body mass index (standardised mean difference (SMD) = -1.0), cardiorespiratory fitness (SMD = +1.0), resting heart rate (MD = -5bpm), homeostatic model assessment-insulin resistance (MD = -0.7), and low-density lipoprotein cholesterol (SMD = -0.9) for HIIT compared to the control group. Our narrative synthesis indicated mixed findings between HIIT and other comparative exercise groups.

CONCLUSION

School-based HIIT is effective for improving several health outcomes. Future research should address the paucity of information on physical activity and nutrition outcomes and focus on the integration and long-term effectiveness of HIIT interventions within school settings.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42018117567.

Karate Training Improves Metabolic Health in Overweight and Obese Adolescents: A Randomized Clinical Trial

PURPOSE

This study evaluated the effects of 12 weeks of karate training on cardiometabolic parameters, oxidative stress, and inflammation in adolescents with overweight and obesity.

METHOD

Seventy adolescents were randomized into 2 groups: control received nutritional and psychological interventions once a week for 12 weeks, and treatment received nutritional and psychological interventions once a week, plus 3 karate sessions per week, for 12 weeks. The main outcome measure was improvement in cardiometabolic parameters, oxidative stress, and inflammation.

RESULTS

After the intervention period, the treatment group showed a reduction in resting heart rate (77.86 [10.89]), high-density lipoprotein cholesterol (40.86 [8.31]), and triglycerides (75.18 [32.29]) and an increase in low-density lipoprotein cholesterol (95.64 [42.53]) in relation to pretraining. Regarding oxidative stress markers, there was a reduction in protein carbonylation (0.07 [0.06]) and nitric oxide (1.39 [1.11]) and an increase in superoxide dismutase (0.68 [0.31]) and glutathione (0.11 [0.08]) compared with pretraining. With respect to inflammation, adiponectin increased (14.54 [5.36]) after the intervention when compared with preintervention.

CONCLUSION

The study concluded that the intervention may improve cardiometabolic parameters, oxidative stress, and inflammation in adolescents with overweight and obesity. Long-term effects need to be evaluated.

Obesity in children and adolescents: epidemiology, causes, assessment, and management

This Review describes current knowledge on the epidemiology and causes of child and adolescent obesity, considerations for assessment, and current management approaches. Before the COVID-19 pandemic, obesity prevalence in children and adolescents had plateaued in many high-income countries despite levels of severe obesity having increased. However, in low-income and middle-income countries, obesity prevalence had risen. During the pandemic, weight gain among children and adolescents has increased in several jurisdictions. Obesity is associated with cardiometabolic and psychosocial comorbidity as well as premature adult mortality. The development and perpetuation of obesity is largely explained by a bio-socioecological framework, whereby biological predisposition, socioeconomic, and environmental factors interact together to promote deposition and proliferation of adipose tissue. First-line treatment approaches include family-based behavioural obesity interventions addressing diet, physical activity, sedentary behaviours, and sleep quality, underpinned by behaviour change strategies. Evidence for intensive dietary approaches, pharmacotherapy, and metabolic and bariatric surgery as supplemental therapies are emerging; however, access to these therapies is scarce in most jurisdictions. Research is still needed to inform the personalisation of treatment approaches of obesity in children and adolescents and their translation to clinical practice.

Sex Moderated Mediation of the Musculoskeletal Fitness in Relationship between High-Intensive Interval Training Performing during Physical Education Classes and Cardiorespiratory Fitness in Healthy Boys and Girls

High-intensive interval training (HIIT) is indicated as a means of improving cardiorespiratory fitness (CRF) and musculoskeletal fitness (MSF). The relationship between CRF and MSF was examined too. Little is known about gaining CRF from HIIT independence of MSF in adolescents. Therefore, this study is aimed at investigating whether MSF mediated the relationship between HIIT and CRF and whether sex moderate this relation. The study sample included 122 individuals (45 boys, 77 girls) 16.12 ± 0.38 years of secondary school age. Participants were assigned to the HIIT intervention or control groups. The intervention lasted 14 minutes during one physical education lesson per week for ten weeks. Outcome and potential mediator were residual changes calculated from pre- and postintervention results of MSF components: handgrip (HG), sit-ups (ABS), sit-and-reach (FL), vertical jump (VJ), and Harvard step-test representing cardiorespiratory fitness (CRF). MSF index (MSFI) was calculated as a construct, agglomerating all MSF, and tested its usefulness. HIIT significantly impacted CRF in boys and girls (B = 2.32, p = 0.032; B = 2.28, p = 0.005, respectively). The impact of the HIIT program on the ABS and FL was observed only in girls. The moderation effect of sex was confirmed. Significant effect of HIIT on CRF decreased (B_direct < B_total) and was no significant after including FL (B = 1.46, p = 0.62)—complete mediation, but no ABS (B = 2.97, p = 0.001)—partial mediation. CRF was mediated by changes in ABS (B = 2.28, p < 0.001) and FL (4.18, p < 0.001). MSFI was not mediating; its usefulness was limited. HIIT is an effective tool in the development of CRF in both sexes. MSF played a limited role in the relationship between HIIT and CRF. It suggested different mechanisms in both sexes: girls who performed better to the HIIT had better values of FL and ABS, but not boys. HIIT intervention involved modifications in ABS or FL, which also influenced the increase of CRF.

Effects of Exercise in Improving Cardiometabolic Risk Factors in Overweight Children: A Systematic Review and Meta-Analysis

This meta-analysis aims to evaluate the effects of exercise in improving cardiometabolic risk factors in overweight children and adolescents until the adolescent age, which is 18 years. A systemic search was conducted using the electronic databases PubMed/Medline, Cochrane Library, and Google Scholar, from inception to 29 June 2021. All statistical analyses were conducted in Review Manager 5.4.1. All studies meeting the inclusion criteria were selected. A random-effect model was used to pool the studies, and the results are reported in the odds ratio (OR) and corresponding 95% Confidence interval (CI). Twelve randomized control trials were selected for meta-analysis. Significant results were obtained for BMI in children after the interventions (0.38 95% CI 0.14, 0.62; p = 0.002; I² = 65%). LDL level was also found significantly reduced (0.41 95% CI 0.01, 0.82; p = 0.05; I² = 83%). Other factors such as HDL level, blood pressure, blood glucose level, body weight, and waist circumference were also analyzed. We found that exercise interventions significantly improved several cardiometabolic risk factors such as BMI, LDL level, BP, and blood glucose level. However, no significant effect on HDL concentration, waist circumference, and body weight were found. Long-term interventions are needed to attain improvement in all cardiometabolic risk factors.

Bone Response to High-Intensity Interval Training versus Moderate-Intensity Continuous Training in Adolescents with Obesity

INTRODUCTION

Since adolescents with obesity are prone to bone fragility during weight loss, the aim was to compare the impact of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) on bone density, geometry, and strength.

METHODS

Sixty-one adolescents were randomly assigned to 2 cycling trainings (HIIT and MICT) and a control (CTR, without training) group. Anthropometry, dual-energy X-ray absorptiometry with hip structural analysis and the trabecular bone score (TBS) were assessed before and after the 16-week intervention.

RESULTS

Body mass index (BMI) and fat mass (FM) percentage decreased at T1 versus T0 in both training groups (p < 0.001 for HIIT, p = 0.01 for MICT), though to a larger extent in HIIT (p < 0.05). Total body bone mineral density (BMD) and bone mineral content (BMC) increased in both training groups (p < 0.001), but to a greater extent in HIIT for BMC (p < 0.05). Lumbar spine BMD and BMC increased in both training groups (p < 0.001 for HIIT, p < 0.01 for MICT), with a time × group interaction between HIIT and CTR (p < 0.05) only. TBS increased in both training groups (p < 0.01 for HIIT, p < 0.05 for MICT). Hip BMD and BMC increased in both HIIT (p < 0.001 and p < 0.01) and MICT (p < 0.01 and p < 0.05). At the narrow neck (NN), endocortical diameter, width (p < 0.01), cross-sectional moment of inertia, and section modulus (Z) (p < 0.05) increased only in the HIIT group, such as BMD and Z (p < 0.05) at the intertrochanteric region (IT) and average cortical thickness (p < 0.001) and width (p < 0.05) at the femoral shaft. At the NN and IT, the buckling ratio decreased only in the HIIT group (p < 0.05), predicting higher resistance to fracture.

CONCLUSIONS

In addition to inducing greater BMI and FM percentage decreases in comparison to MICT, HIIT improves multisite bone density, geometry, and strength, which heighten the justification for HIIT as part of weight loss interventions in adolescents with obesity.

Process Evaluation of Project FFAB (Fun Fast Activity Blasts): A Multi-Activity School-Based High-Intensity Interval Training Intervention

Introduction: Over the last decade, research into the impact of school-based high-intensity interval training (HIIT) on young people's health has markedly increased. Despite this, most authors have focused on the outcomes of their intervention, rather than the process of how the study was conducted. The aim of our study, therefore, was to conduct a mixed methods process evaluation of Project FFAB (Fun Fast Activity Blasts), a school-based HIIT intervention for adolescents. The objectives were to explore study recruitment, reach, intervention dose, fidelity, participants' experiences, context, and future implementation.

Methods: Recruitment was assessed by comparing the number of students who received study information, to those who provided consent. Reach was described as the number of participants who completed the intervention. Dose was reported via the number of HIIT sessions delivered, total exercise time commitment, HIIT exercise time, and session attendance. Post-intervention focus groups were conducted with intervention participants (n = 33; aged 14.1 ± 0.3 years; mean ± standard deviation). These discussions explored aspects of intervention fidelity (extent that the intervention was delivered as intended); participants' experiences of the HIIT sessions; context (exploration of the nuances of school-based HIIT); and ideas for future implementation.

Results: Recruitment, reach, and dose data indicate that Project FFAB was largely delivered as planned. Focus group data identified a mismatch between perceived vs. prescribed work: rest ratio for the multi-activity HIIT drills. Generally, the HIIT drills were well-received; participants often reported they were fun to complete, and the use of heart rate monitors was helpful for interpreting exercise intensity. Some participants stated that greater variety in the HIIT drills would be preferable. The timing and structure of the HIIT sessions that took place outside of physical education lessons received mixed responses.

Conclusion: Collectively, our study supports the use of school-based HIIT and provides valuable insights into how such interventions can be implemented. Project FFAB could be modified to account for individuals' preferences on when the exercise sessions took place. In addition, a wider range of activities could be included, and the prescribed work: rest ratio of the HIIT drills could be better communicated.

High-Intensity Interval Training and Cardiometabolic Risk Factors in Children: A Meta-analysis

CONTEXT

High-intensity interval training (HIIT) has been widely used to prevent and treat cardiovascular risk factors in adolescents and adults; nevertheless, the available evidence in children is scarce.

OBJECTIVE

To synthesize evidence regarding the effectiveness of HIIT interventions on improving cardiovascular risk factors and cardiorespiratory fitness (CRF) in children from 5 to 12 years old.

DATA SOURCES

We searched 5 databases, Medline, Embase, SPORTDiscus, the Cochrane Library, and Web of Science.

STUDY SELECTION

Randomized controlled trials (RCTs) evaluating the effectiveness of HIIT interventions on cardiometabolic risk factors and CRF in children were included.

DATA EXTRACTION

Meta-analyses were conducted to determine the effect of HIIT on body composition, cardiometabolic and CRF variables in comparison with nontraining control groups.

RESULTS

A total of 11 RCTs and 512 participants were included. The results of the meta-analysis revealed a significant improvement in peak oxygen uptake (standardized mean difference [SMD] = 0.70, 95% confidence interval [CI] = 0.28 to 1.12; P = 0.001], in total cholesterol [SMD = -1.09, 95% CI = -1.88 to -0.30; P = 0.007], in low-density lipoprotein cholesterol [SMD = -1.28, 95% CI = -2.34 to -0.23; P = 0.017] and triglycerides [SMD = -0.71, 95% CI = -1.15 to -0.28; P = 0.001) levels.

LIMITATIONS

Because of the small number of available RCTs, it was not possible to conduct a subgroup analysis or a linear meta-regression analysis.

CONCLUSIONS

HIIT is a feasible and time-efficient approach for improving CRF, total cholesterol, low-density lipoprotein cholesterol, and triglycerides levels in children.

Bibliometric Review to Explore Emerging High-Intensity Interval Training in Health Promotion: A New Century Picture

Background: High-intensity interval training (HIIT) is an emerging exercise strategy and is considered to be a recipe for health promotion. This study aimed to systematically identify collaboration networks, track research trends, highlight current hotspots, and predict future frontiers in HIIT and its applications in health promotion since the start of the new century.

Methods: Relevant original publications were obtained from the Science Citation Index Expanded of the Web of Science Core Collection (WoSCC) database between 2001 and 2020. CiteSpace and VOSviewer software were used to perform bibliometric visualization and comparative analysis of involved indexes that included countries, institutions, journals, authors, references, and keywords.

Results: A total of 572 papers were included, and the trend of annual publications showed a remarkable growth. The United States and the University of Exeter were the most productive country and institutions, respectively, with 107 and 18 publications, respectively. European Journal of Applied Physiology took the lead in the number of published articles, and Medicine and Science in Sports and Exercise ranked first in the cocitation counts. Barker AR and Gibala MJ were considered as the most productive and the most highly-cited authors.

Conclusions: “Health risks,” “adolescent,” and “aging” are the three noteworthy topics during the evolution of HIIT-health promotion (HIIT-HP) research. The current research hotspots of HIIT and its practices in the health promotion domain lies in “metabolic diseases,” “cardiovascular diseases,” “neurological diseases,” and “musculoskeletal diseases.” The authors summarize that “prevention and rehabilitation,” “micro and molecular level,” and “cognition and mental health” are becoming frontiers and focus on the health topics related to HIIT in the upcoming years, which are worthy of further exploration.

Influence of grade of obesity on the achievement of VO2max using an incremental treadmill test in youths

The purpose of this study was to analyze the influence of grade of obesity on the probability of achieving a VO2 plateau and threshold secondary criteria for verifying VO2max during a treadmill walk test in youths with obesity. Therefore, 72 youths with obesity (aged 8-16) performed an incremental treadmill walk test to exhaustion during which oxygen uptake (VO2), minute ventilation (VE), heart rate (HR) and rating of perceived exertion were continuously measured. HR corresponding to a "hard" level of perceived exertion was reported and expressed as a percentage of the predicted HRmax. The rate of achievement of criteria for validation VO2max (VO2 plateau; HR>95% theoretical HRmax; RER>1.0; rating of perceived exertion ≥ "hard") was compared between participants with grade I and grade II obesity. 37% of the participants achieved a VO2 plateau and 23% achieved both an HR>95% and RER >1.0. Youths with grade II obesity had lower minute ventilation (p<0.01) tended to be more likely to reach an HR>95% (OR = 0.33; P=0.06) and a "hard" rating of perceived exertion than grade I (OR = 4.5; P=0.07). However, there was no influence of grade of obesity on the achievement of VO2 plateau, and RER>1.0.

Optimal Values of Body Composition for the Lowest Risk of Failure in Tabata Training's Effects in Adolescents: A Pilot Study

Background

The optimal body mass index (BMI) and fat mass index (FMI) values for a positive change or the lowest risk of no positive change after high-intensity interval training (HIIT) using the Tabata protocol remain unclear. This study is aimed at establishing these optimal BMI and FMI values for the lowest risk of failure of aerobic performance in adolescents.

Methods

A 10-week HIIT programme was introduced into the physical education of 73 students. BMI was calculated using height and weight. Bioelectrical impedance analysis measured body fat, and the InBody apparatus generated the FMI. Based on BMI and FMI, the participants were divided into four groups. Pre- and post-HIIT intervention analyses were carried out using the Harvard step test, which was used to determine the physical efficiency index (PEI).

Results

The Youden index confirmed that the risk of no positive effects in PEI was the lowest for the second BMI interval (19.01-22.00 kg/m²) and FMI Q₂₋₃ (7.96-8.91 kg/m²). The optimal BMI value for the lowest risk of no change in PEI was 20.60 kg/m², and the optimal FMI value was 8.84 kg/m².

Conclusion

A comparison of the two indices shows that FMI had stronger effects on PEI than BMI. In addition, the model obtained for FMI had higher accuracy. Identifying at-risk individuals, those in need of improving health-related fitness (H-RF), and those with a low risk of poor H-RF allows for efficient planning of individual intervention services and training programmes.

Psycho-Physiological Responses to a 4-Month High-Intensity Interval Training-Centered Multidisciplinary Weight-Loss Intervention in Adolescents with Obesity

Background

To evaluate the impact of 4 months of a high-intensity interval training (HIIT)-centered weightmanagement intervention on health-related quality of life (HR-QOL), health perception (HP) and physical selfperception (PSP) in adolescents with obesity.

Methods

Fifty-six adolescents with obesity (28 girls; mean body mass index [BMI], 35±4.89 kg/m²; z-BMI, 2.3±0.3; 11?17 years) followed a multidisciplinary weight-management intervention composed of nutritional counseling, HIIT program, and health-related therapeutic education. Anthropometric parameters, body composition (dual X-ray absorptiometry), and maximal aerobic capacities (maximal oxygen consumption [VO_2peak]) were assessed, and self-reported questionnaires were used to assess HR-QOL (36-item short form survey), HP and PSP at baseline (T0) and post-intervention (T1).

Results

Body weight (92.6±18.9 to 85.9±16.2 kg), BMI (35.0±4.8 to 32.1±4.5 kg/m²), z-BMI (2.3±0.3 to 2.1±0.3) and fat mass percentage (36.0%±9.1% to 30.4%±7.8%) were significantly decreased (P<0.001) between T0 and T1. There was a tendency for VO_2peak to increase from 26.35±5.81 mL/kg/min at T0 to 28.79±6.59 mL/kg/min at T1 (P=0.06). Physical functioning (P=0.002), physical limitation (P=0.048), general health (P<0.001) and bodily pain (P=0.030) were improved at T1. A significant improvement occurred in dimensions of HP such as physical condition (P=0.001), adiposity (P<0.001), alimentation (P<0.001), general health (P=0.038), and perceived general health (P=0.001). In addition, there was an improvement in items of PSP such as self-perceived coordination (P=0.022), endurance (P=0.001) and activity (P=0.001), global self-concept (P=0.015), and appearance (P=0.016). Physical but not mental HR-QOL domains, HP and PSP were associated with weight reduction.

Conclusion

While HIIT favors improved HR-QOL, HP status and PSP in adolescents with obesity, physical but not mental HR-QOL, HP and PSP were associated with weight reduction.

Four Minutes of Sprint Interval Training Had No Acute Effect on Improving Alertness, Mood, and Memory of Female Primary School Children and Secondary School Adolescents: A Randomized Controlled Trial

We investigated whether a 4-min sprint interval training (SIT) protocol had an acute effect (15 min after) on improving alertness, mood, and memory recall in female students. Sixty-three children and 131 adolescents were randomly assigned to either a SIT or control (CON) group by the class Physical Education (PE) teachers. The SIT intervention was delivered twice a week for 3 weeks. SIT participants performed three, 20-s 'all-out' effort sprints interspersed with 60-s intervals of walking while CON group sat down and rested. PE lessons were arranged such that the first two sessions were to familiarise participants with the SIT protocol leading to acute assessments conducted on the third session. On that occasion, both groups rated their alertness and mood on a single-item hedonic scale and underwent an adapted memory recall test. The same assessments were administered to both groups fifteen minutes after delivery of SIT intervention. A 4-min SIT involving three, 20 s 'all-out' effort intensity sprints did not have an acute main effect on improving alertness, mood and, memory recall in female children (η_p² = 0.009) and adolescents (η_p² = 0.012). Students' exercise adherence and feedback from PE teachers are indicatives of the potential scalability of incorporating SIT into PE programmes. Different work-to-rest ratios could be used in future studies.

High-Intensity Interval Training versus Moderate-Intensity Continuous Training on Health Outcomes for Children and Adolescents: A Meta-analysis of Randomized Controlled Trials

Low cardiorespiratory fitness (CRF) is considered as an established risk factor for cardiovascular and metabolic disorders. However, the effectiveness of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) in children and adolescents remained uncertain. Electronic databases of the PubMed, EmBase, and the Cochrane library were searched for randomized controlled trials (RCTs) investigated the role of HIIT versus MICT for children and adolescents throughout December 2019. Sixteen RCTs involving a total of 543 children were selected for final meta-analysis. HIIT versus MICT showed high peak VO2 (weighted mean differences (WMD): 2.68; 95% confidence intervals (CIs): 1.81 to 3.55; $P<0.001$ ), and no evidence of heterogeneity and publication bias was detected. However, there were no significant differences detected between HIIT and MICT on the levels of peak heart rate (HRmax), fat mass, free fat mass, weight, body mass index, waist circumference, systolic blood pressure, diastolic blood pressure, glycemia, insulinemia, total cholesterol, high density lipoprotein, low density lipoprotein, triglycerides, HOMA-IR, HbA1c, and leptinemia. The findings of this study revealed that HIIT versus MICT showed a significant improvement in peak VO2 in children and adolescents. Further large-scale RCTs should be conducted to compare the long-term effects of HIIT versus MICT in children and adolescents.

High intensity training during spaceflight: results from the NASA Sprint Study

Historically, International Space Station (ISS) exercise countermeasures have not fully protected astronauts’ musculoskeletal and cardiorespiratory fitness. Although these losses have been reduced on more recent missions, decreasing the time required to perform in-flight exercise would permit reallocation of that time to other tasks. To evaluate the effectiveness of a new training prescription, ISS crewmembers performed either the high intensity/lower volume integrated Sprint resistance (3 d wk⁻¹) and aerobic (interval and continuous workouts, each 3 d wk⁻¹ in alternating fashion) exercise program (n = 9: 8M/1F, 48 ± 7 y, 178 ± 5 cm, 77.7 ± 12.0 kg) or the standard ISS countermeasure consisting of daily resistance and aerobic exercise (n = 17: 14M/3F, 46 ± 6 y, 176 ± 6 cm, 80.6 ± 10.5 kg) during long-duration spaceflight. Bone mineral density (dual energy X-ray absorptiometry (DXA)), muscle strength (isokinetic dynamometry), muscle function (cone agility test), and cardiorespiratory fitness (VO_2peak) were assessed pre- and postflight. Mixed-effects modeling was used to analyze dependent measures with alpha set at P < 0.05. After spaceflight, femoral neck bone mineral density (−1.7%), knee extensor peak torque (−5.8%), cone agility test time (+7.4%), and VO_2peak (−6.1%) were decreased in both groups (simple main effects of time, all P < 0.05) with a few group × time interaction effects detected for which Sprint experienced either attenuated or no loss compared to control. Although physiologic outcomes were not appreciably different between the two exercise programs, to conserve time and optimally prepare crewmembers for the performance of physically demanding mission tasks, high intensity/lower volume training should be an indispensable component of spaceflight exercise countermeasure prescriptions.

Effects of 2 Methods of Combined Training on Cardiometabolic Risk Factors in Adolescents: A Randomized Controlled Trial

PURPOSE

To analyze the effects of 2 combined training methods on the cardiometabolic risk factors in adolescents.

METHODS

A total of 76 adolescents (16.1 [1.1] y, n = 44 female) were randomized into groups of moderate-intensity continuous training combined with resistance training (MICT + RT), high-intensity interval training combined with resistance training (HIIT + RT), or control. The training sessions were performed twice weekly for 12 weeks. The outcomes evaluated included body fat percentage, waist circumference, fasting blood glucose, fasting insulin, total cholesterol, triglycerides, low-density lipoprotein, high-density lipoprotein, glycated hemoglobin, insulin resistance index, blood pressure, peak oxygen consumption (VO2peak), and cardiometabolic risk Z score.

RESULTS

The intervention groups presented a significant reduction in the cardiometabolic risk Z score after 12 weeks of the combined exercise program. In relation to the cardiometabolic risk Z score between groups, the HIIT + RT group presented a significant intervention effect when compared with the control group (Cohen d = 0.23; P < .05). Significant intervention effects were found when comparing the MICT + RT and control groups for body fat percentage, high-density lipoprotein, and VO2peak. Between the HIIT + RT and control groups, significant intervention effects were found for body fat percentage, blood pressure, and VO2peak. There were not significant differences between the HIIT + RT and MICT + RT groups.

CONCLUSION

Twelve weeks of HIIT + RT and MICT + RT were effective in significantly reducing the cardiometabolic risk in these adolescents.

Respiratory responses and rating of perceived exertion of severely obese adolescents during continuous and intermittent graded walking protocols: Application to cardiorespiratory field tests

During 20 m shuttle tests, obese adolescents may have difficulty achieving maximum cardiorespiratory performance due to the presence of braking-relaunch phases (BRP). Nineteen obese adolescents aged 15.2 ± 1.5 years (body mass index [BMI] = 39.7 ± 5.9 kg.m^-2) performed three graded walking exercises on a 50 m track at speeds between 3 and 6 km/h: a continuous-straight-line protocol (C), a continuous protocol that required turning back every 30 sec (C-BRP) and an intermittent protocol that consisted of successively walking then resting for 15 sec (15-15). Oxygen uptake (VO₂), aerobic cost of walking (Cw), ventilation (VE) and rating of perceived exertion (RPE) were measured at each stage during the protocols. During C-BRP, the responses were not significantly higher compared with C (p > 0.30). During 15-15, the VO₂, Cw and VE were ~ 15 to 25% lower than during C beginning at 4 km/h (p < 0.05). In obese adolescents, the respiratory impact of sudden directional changes during the 20 m shuttle-type test appeared to be minor at walking speeds. During the 15-15 test, the intensity increases more progressively, and this design may encourage obese adolescents to walk further than during a continuous test.

Classroom-Based Micro-Sessions of Functional High-Intensity Circuit Training Enhances Functional Strength but Not Cardiorespiratory Fitness in School Children-A Feasibility Study

The present study assessed the short-term effect of 6 min classroom-based micro-sessions of multi-joint functional high-intensity circuit training (FunctionalHIIT) performed by students during regular classes on parameters related to functional strength and cardiorespiratory fitness. In this randomized controlled 4-week study, 17 students (11 male; 6 female; age: 11.6 ± 0.2 years) performed 6 min of FunctionalHIIT (targeting >17 on the Borg scale) 4 days per week during regular school classes and 18 students (11 male; 7 female; age: 11.7 ± 0.3 years) served as control group (CG) without any additional in-class physical activity. The FunctionalHIIT group completed 86% of all planned sessions (mean duration: 6.0 ± 1.5 min) with a mean RPE of 17.3 ± 2.1. Body height, mass and BMI did not differ between the groups at baseline or between pre- and post-testing (p > 0.05; eta2 ≤ 0.218). The performances in lateral jumping (p < 0.000; part eta2 = 0.382; Δ% 4.6 ± 8.6), sit-ups (p < 0.000; part eta2 = 0.485; Δ% 3.1 ± 8.6) and 20-m sprints (p < 0.000; part eta2 = 0.691; Δ% 15.8 ± 5.4) improved in both groups with greater increase following FunctionalHIIT. No baseline differences and no interaction effects occurred in performance of 6 min run, flexibility, push-ups, balance, and long jump. Classroom-based FunctionalHIIT sessions, performed 4 days per week during 4 weeks did not improve variables related to aerobic endurance performance but enhanced certain parameters of functional strength in schoolchildren. As time is limited in the educational system of schools, FunctionalHIIT during regular school classes could offer a new perspective for increasing functional strength in schoolchildren.

Response of obese schoolchildren to high-intensity interval training applied in the school context

BACKGROUND

High-intensity interval training (HIIT) has been widely used to fight cardiovascular risk factors in adolescents and adults, but no data are available on its applicability in children.

OBJECTIVES

To assess the effects of HIIT on different anthropometric and cardiovascular parameters of overweight and obese children aged 7-9 years.

MATERIAL AND METHODS

Four groups were formed: 1) an overweight control group (OWCG, n=30, BMI=21.60±3.72kg/m²); 2) an obesity control group (OCG, n=34, BMI=23.92±3.11kg/m²); 3) an overweight intervention group (OWIG, n=69, BMI=20.01±1.88kg/m²), and 4) an obesity intervention group (OIG, n=141, BMI=24.12±2.66kg/m²). BMI, body fat (BF), waist circumference, height-waist ratio, systolic and diastolic blood pressure and cardiorespiratory fitness (CRF) were assessed before and after intervention.

RESULTS

There were significant differences in BMI (P<.001), BF (P<.001), and CRF (P<.001) between the groups (control vs. intervention) before and after intervention (OWCG vs. OWIG and OCG vs. OIG). BMI decreased in the OWIG (BMI, 20.01±1.88 at baseline vs. 19.00±2.02 after HIIT, P<.001) and OIG (BMI, 24.12±2.66 at baseline vs. 23.23±3.23 after HIIT, P<.001) groups. Similarly, BF decreased in the OWIG (BF, 21.84±4.97 at baseline vs. 19.55±4.81% after HIIT, P<.001) and OIG (BF, 30.26±11.49 at baseline vs. 26.81±6.80% after HIIT, P<.001) groups. CRF improved in both intervention groups (P<.001). There was a significant decrease in the prevalence rate of schoolchildren with obesity (from 66.4% to 49.6%) (P<.001).

CONCLUSION

The intervention conducted in the school setting improved the anthropometric and cardiovascular parameters of schoolchildren, and also allowed for reducing the proportion of schoolchildren with obesity.

Effects of high-intensity interval training and nutrition advice on cardiometabolic markers and aerobic fitness in adolescent girls with obesity

The aim of the study was to compare the effects of high-intensity interval training (HIIT) and nutrition advice on cardiometabolic biomarkers, hormonal parameters, and cardiorespiratory fitness in adolescent girls with obesity. Adolescent girls with obesity (n = 44, aged 13-19 years) were randomized into a 12-week intervention as follows: (i) dietary advice and HIIT (n = 22), and (ii) dietary advice only (n = 22). The concentration of biomarkers of inflammation, biochemical and hormonal testing, oral glucose tolerance test, cardiorespiratory fitness, physical activity levels, and nutrition were assessed. After a 3-month intervention, the diet+HIIT group significantly increased insulin sensitivity index (-0.34 ± 1.52 vs. 1.05 ± 3.21; p = 0.001) and work load (0.6 ± 11.3 W vs. 14.6 ± 20.2 W; p = 0.024) and decreased glucose area under the curve (-0.29 ± 4.69 vs. -0.98 ± 4.06; p = 0.040), insulin area under the curve (-9.65 ± 117.9 vs. -98.7 ± 201.8; p = 0.003), and high-sensitivity C-reactive protein (hs-CRP) (0.12 ± 1.92 mg/L vs. -1.47 ± 3.67 mg/L; p = 0.039) in comparison with the diet group. Regarding within-group changes, both groups had significant improvements in body mass index (BMI), BMI-standard deviation score, body fat percentage, and systolic blood pressure. Positive impact on waist circumference, waist circumference/height ratio, diastolic blood pressure, hs-CRP, work load, maximal heart rate, and resting heart rate was observed only after the diet+HIIT intervention. No significant change was noted in peak oxygen uptake, lipid profile, and hormonal parameters between groups after intervention. Novelty HIIT and nutrition advice increased insulin sensitivity and decreased BMI, body fat, systolic blood pressure, and diastolic blood pressure. Nutrition advice decreased BMI, body fat, and systolic blood pressure in adolescent girls with obesity.

Perspectives on Interval Exercise Interventions for Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is associated with an increased risk of type 2 diabetes, cardiovascular disease, cirrhosis, and liver cancer. Exercise therapy is the most effective treatment for patients with NAFLD. High-intensity interval training (HIIT) is attracting attention as a time-efficient and an effective exercise modality for treating patients with NAFLD. Previous studies have shown that HIIT can reduce fat mass, visceral adipose tissue, and intrahepatic lipid levels and improve hepatic stiffness. HIIT may be an optimal exercise therapy to improve NAFLD in patients with a lack of time.

Acute Cardiometabolic Responses to Multi-Modal Integrative Neuromuscular Training in Children

Integrative neuromuscular training (INT) has emerged as an effective strategy for improving health- and skill-related components of physical fitness, yet few studies have explored the cardiometabolic demands of this type of training in children. The aim of this study was to examine the acute cardiometabolic responses to a multi-modal INT protocol and to compare these responses to a bout of moderate-intensity treadmill (TM) walking in children. Participants (n = 14, age 10.7 ± 1.1 years) were tested for peak oxygen uptake (VO₂) and peak heart rate (HR) on a maximal TM test and subsequently participated in two experimental conditions on nonconsecutive days: a 12-min INT protocol of six different exercises performed twice for 30 s with a 30 s rest interval between sets and exercises and a 12-min TM protocol of walking at 50% VO₂peak. Throughout the INT protocol mean VO₂ and HR increased significantly from 14.9 ± 3.6 mL∙kg^-1∙min^-1 (28.2% VO₂ peak) to 34.0 ± 6.4 mL∙kg^-1∙min^-1 (64.3% VO₂ peak) and from 121.1 ± 9.0 bpm (61.0% HR peak) to 183.5 ± 7.9 bpm (92.4% HR peak), respectively. While mean VO₂ for the entire protocol did not differ between INT and TM, mean VO₂ and HR during selected INT exercises and mean HR for the entire INT protocol were significantly higher than TM (all Ps ≤ 0.05). These findings suggest that INT can pose a moderate to vigorous cardiometabolic stimulus in children and selected INT exercises can be equal to or more metabolically challenging than TM walking.

Effect of High-Intensity Interval Training versus Moderate-Intensity Continuous Training on Cardiorespiratory Fitness in Children and Adolescents: A Meta-Analysis

Enhancing cardiorespiratory fitness (CRF) can lead to substantial health benefits. Comparisons between high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on CRF for children and adolescents are inconsistent and inconclusive. The objective of this study was to perform a meta-analysis to compare the effects between HIIT and MICT on CRF in children and adolescents. We searched MEDLINE, PubMed, Web of Science, and Google Scholar to identify relevant articles. The standardized mean differences (SMD) and 95% confidence intervals (95% CI) were calculated to determine the pooled effect size of HIIT and MICT on CRF. A total of 563 subjects from 17 studies (18 effects) were identified. The pooled effect size was 0.51 (95% CI = 0.33-0.69) comparing HIIT to MICT. Moreover, intervention duration, exercise modality, work and rest ratio, and total bouts did not significantly modify the effect of HIIT on CRF. It is concluded that compared with endurance training, HIIT has greater improvements on cardiorespiratory fitness among children and adolescents.

Feasibility of incorporating high-intensity interval training into physical education programs to improve body composition and cardiorespiratory capacity of overweight and obese children: A systematic review

BACKGROUND/OBJECTIVE

High-intensity interval training (HIIT) can produce similar or improved results compare with traditional training, but the question as to whether HIIT can be used in the setting of physical education (PE) remains unanswered. The aim of this systematic review was to critically analyze the feasibility of incorporating HIIT programs into PE classes to improve the body compositions and cardiorespiratory fitness of overweight students.

METHODS

We conducted database searches for literature dating between January 2012 and January 2017. Of the final six studies selected, three were conducted in children under 12 years old and three involved adolescents between 12 and 18 years old.

RESULTS

The HIIT protocols consisted of 2-3 sessions per week, with intervals of 15 s and passive or active rests of 15 s, totaling up to 6 min of work with 4 min of rest. The duration of HIIT programs was 6-24 weeks. Significant changes were reported in body composition, body mass index, body fat (%), waist circumference, and sum of skinfolds; and increases in muscle mass were observed. The inclusion of HIIT programmes improved maximal oxygen uptake (VO2max), performance in the intermittent Yo-Yo test and maximal aerobic speed.

CONCLUSIONS

The HIIT programmes showed improvements in the variables studied, with interventions two or three times weekly. Therefore, they can be used in schools, as a strategy to combat the childhood obesity pandemic and HIIT can be use alongside with existing PE activities within the same lesson or in specific periods during day school.

High-Intensity Interval Training Performed by Young Athletes: A Systematic Review and Meta-Analysis

Background: High-intensity interval training (HIIT) is as a time-efficient alternative to moderate- or low-intensity continuous exercise for improving variables related to endurance and anaerobic performance in young and adolescent athletes.

Objectives: To assess original research about enhancement of endurance and anaerobic exercise performance in young and adolescent athletes performing HIIT.

Method: Relevant articles published in peer-reviewed journals were retrieved from the electronic databases PubMed and SPORTDiscus in December 2017. Inclusion criteria were: (i) controlled trials (HIIT vs. alternative training protocol) with pre-post design; (ii) healthy young athletes (≤18 years); (iii) assessing variables related to endurance and exercise performance. Hedges' g effect size (ES), and associated 95% confidence intervals were calculated for comparison of any outcome between experimental (HIIT) and alternative training protocol.

Results: Twenty four studies, involving 577 athletes (mean age: 15.5 ± 2.2 years), were included in this review. HIIT exerted no or small positive mean ES on peak oxygen uptake (VO_2peak), running performance, repeated sprint ability, jumping performance and submaximal heart rate. Although the mean ES for changes in VO_2peak with HIIT is small (mean g = 0.10±0.28), the average increase in VO_2peak from pre to post HIIT-interventions were 7.2 ± 6.9% vs. 4.3 ± 6.9% with any other alternative intervention. HIIT largely and positively affected running speed and oxygen consumption at various lactate- or ventilatory-based thresholds, as well as for sprint running performance. Calculations showed negative mean ES for change-of-direction ability (large), and peak blood lactate concentrations (small). Mean duration per training session for HIIT was shorter than for control interventions (28 ± 15 min vs. 38 ± 24 min).

Conclusion: The present findings suggest that young athletes performing HIIT may improve certain important variables related to aerobic, as well as anaerobic, performance. With HIIT, most variables related to endurance improved to a higher extent, compared to alternative training protocols. However, based on ES, HIIT did not show clear superiority to the alternative training protocols. Nevertheless, young athletes may benefit from HIIT as it requires less time per training session leaving more time for training sport specific skills.

Effects of Aerobic Exercise on Metabolic Syndrome, Cardiorespiratory Fitness, and Symptoms in Schizophrenia Include Decreased Mortality

Schizophrenia is a severe psychiatric disorder with a lifetime prevalence of about 1%. People with schizophrenia have a 4-fold higher prevalence of metabolic syndrome than the general population, mainly because of antipsychotic treatment but perhaps also because of decreased physical activity. Metabolic syndrome is a risk factor for cardiovascular diseases, and the risk of these diseases is 2- to 3-fold higher in schizophrenia patients than in the general population. The suicide risk is also higher in schizophrenia, partly as a result of depression, positive, and cognitive symptoms of the disease. The higher suicide rate and higher rate of cardiac mortality, a consequence of the increased prevalance of cardiovascular diseases, contribute to the reduced life expectancy, which is up to 20 years lower than in the general population. Regular physical activity, especially in combination with psychosocial and dietary interventions, can improve parameters of the metabolic syndrome and cardiorespiratory fitness. Furthermore, aerobic exercise has been shown to improve cognitive deficits; total symptom severity, including positive and negative symptoms; depression; quality of life; and global functioning. High-intensity interval endurance training is a feasible and effective way to improve cardiorespiratory fitness and metabolic parameters and has been established as such in somatic disorders. It may have more beneficial effects on the metabolic state than more moderate and continuous endurance training methods, but to date it has not been investigated in schizophrenia patients in controlled, randomized trials. This review discusses physical training methods to improve cardiorespiratory fitness and reduce metabolic syndrome risk factors and symptoms in schizophrenia patients. The results of studies and future high-quality clinical trials are expected to lead to the development of an evidence-based physical training program for patients that includes practical recommendations, such as the optimal length and type of aerobic exercise programs and the ideal combination of exercise, psychoeducation, and individual weight management sessions.