BackgroundWhilst there is increasing interest in the efficacy of high-intensity interval training in children and adolescents as a time-effective method of eliciting health benefits, there remains little consensus within the literature regarding the most effective means for delivering a high-intensity interval training intervention. Given the global health issues surrounding childhood obesity and associated health implications, the identification of effective intervention strategies is imperative.ObjectivesThe aim of this review was to examine high-intensity interval training as a means of influencing key health parameters and to elucidate the most effective high-intensity interval training protocol.MethodsStudies were included if they: (1) studied healthy children and/or adolescents (aged 5–18 years); (2) prescribed an intervention that was deemed high intensity; and (3) reported health-related outcome measures.ResultsA total of 2092 studies were initially retrieved from four databases. Studies that were deemed to meet the criteria were downloaded in their entirety and independently assessed for relevance by two authors using the pre-determined criteria. From this, 13 studies were deemed suitable. This review found that high-intensity interval training in children and adolescents is a time-effective method of improving cardiovascular disease biomarkers, but evidence regarding other health-related measures is more equivocal. Running-based sessions, at an intensity of >90% heart rate maximum/100–130% maximal aerobic velocity, two to three times a week and with a minimum intervention duration of 7 weeks, elicit the greatest improvements in participant health.ConclusionWhile high-intensity interval training improves cardiovascular disease biomarkers, and the evidence supports the effectiveness of running-based sessions, as outlined above, further recommendations as to optimal exercise duration and rest intervals remain ambiguous owing to the paucity of literature and the methodological limitations of studies presently available.

PurposeThe purpose of the current study was to investigate the mediatory role between vigorous physical activity, body mass index (BMI), and cardiorespiratory fitness on symptoms of depression and their subsequent direct and indirect effects on quality of life (QoL).MethodsFive hundred and seventy-six adolescents’ (314 boys, 12.5 ± 1.1 years) physical activity levels, cardiorespiratory fitness, BMI, levels of depressive symptoms, and QoL were measured. Structural equation modelling was used to evaluate the difference in linear structural associations between variables.ResultsThe model suggested that cardiorespiratory fitness (β = 0.16, p < 0.001) and symptoms of depression (β = − 0.52, p < 0.001) were both directly associated with physical QoL, with depressive symptoms also directly influencing psychological QoL (β = − 0.79, p < 0.01). Body mass index was indirectly associated with physical QoL, mediated by both symptoms of depression (β = − 0.06, p < 0.001) and cardiorespiratory fitness (β = 0.05, p < 0.001) and psychological QoL mediated by symptoms of depression (β = − 0.09, p < 0.001). Vigorous physical activity was indirectly associated with QoL, mediated by cardiorespiratory fitness (β = − 0.04, p < 0.001).ConclusionsModels suggested that vigorous physical activity, cardiorespiratory fitness and BMI were associated, both directly and indirectly, with mental well-being and QoL. It could, therefore, be postulated that enhancing cardiorespiratory fitness and BMI through increasing vigorous physical activity may be beneficial to both mental well-being and QoL in adolescents.

Whilst exercise is important in the management of asthma, the tendency of those with asthma to withdraw from exercise to avoid adverse events could be addressed through a games-based high-intensity exercise intervention. Furthermore, educating all adolescents on asthma could simultaneously reduce stigmatisation and enhance exercise engagement.

Highlights Adolescents with asthma have similar aerobic fitness to their non-asthma peers. High-intensity interval training may prevent increases in body mass index. High-intensity interval training is equally effective at increasing aerobic fitness, regardless of asthma status.

Little is known regarding the influence of asthma and exercise, and their interaction, on heart rate variability in adolescents. Thirty-one adolescents with asthma (13.7±0.9 years; 21.9±3.9 kg•m-2 ; 19 boys, 12 girls) and thirty-three healthy adolescents (13.8±0.9 years; 20.3±3.2 kg•m-2 ; 16 boys, 17 girls) completed an incremental ramp test and three heavy-intensity constant-work-rate cycle tests. Thirteen adolescents (7 boys, 6 girls; 6 asthma, 7 control) completed six-months high-intensity interval training (HIIT) and were compared to age-and sex-matched controls. Standard time-domain, frequency-domain and non-linear indices of heart rate variability (HRV) were derived at baseline, three-and six-months.

Although an association has been suggested between asthma, obesity, fitness and physical activity, the relationship between these parameters remains to be elucidated in adolescents. Six-hundred and sixteen adolescents were recruited (334 boys; 13.0±1.1years; 1.57±0.10m; 52.6±12.9kg), of which 155 suffered from mild-to-moderate asthma (78 boys). Participants completed a 20-metre shuttle run test, lung function and 7-day objective physical activity measurements and completed asthma control and quality of life questionnaires. Furthermore, 69 adolescents (36 asthma; 21 boys) completed an incremental ramp cycle ergometer test. Although participants with asthma completed significantly fewer shuttle runs than their peers, peak V̇O2 did not differ between the groups. However, adolescents with asthma engaged in less physical activity (53.9±23.5 vs 60.5±23.6minutes) and had higher BMI (22.2±4.8 vs 20.4±3.7kg•m-2), than their peers. Whilst a significant relationship was found between quality of life and cardiorespiratory fitness according to peak V̇O2, only BMI was revealed as a significant predictor of asthma status. The current findings highlight the need to use accurate measures of cardiorespiratory fitness rather than indirect estimates to assess the influence of asthma during adolescence. Furthermore, the present study suggests that BMI and fitness may be key targets for future interventions seeking to improve asthma quality of life.

Purpose: High-intensity interval training (HIIT) represents a potent stimulus to the dynamic oxygen uptake (V̇O2) response in adults but whether the same is evident in youth is unknown.HIIT has also been suggested to place a lower demand on the respiratory system, decreasing the likelihood of exacerbation in those with respiratory conditions, such as asthma.Methods: Sixty-nine adolescents (13.6±0.9 years; 36 asthma) took part, 35 of which ( 17asthma) participated in a 30-minute HIIT intervention three-times/week for six months. Each participant completed an incremental ramp test to volitional exhaustion and three heavyintensity constant work-rate tests to determine the dynamic oxygen uptake (V̇O2), heart rate (HR) and deoxyhaemoglobin ([HHb]) response at baseline, mid-intervention, post-intervention and at a three-month follow-up.Results: There was no influence of asthma at baseline or in response to the intervention. Participants in the intervention group demonstrated a faster V̇O2 time constant (τp) postintervention (intervention: 29.2±5.7 vs. control: 34.2±6.5 s; P=0.003), with these differences maintained at follow-up (intervention: 32.5±5.5 vs. control: 37.3±8.7 s; P=0.008). The intervention was associated with a speeding of the [HHb] τ (Pre: 20.1±4.7 vs. Post: 18.2±4.1 s; P=0.05), compared to a slowing over the same time period in the control participants (Pre: 17.9±4.9 vs. Post: 20.1±4.6 s; P=0.012). HR kinetics were not altered (Pre: 46.5±12.2 vs. Post: 47.7±11.1 s; P=0.98). Conclusion:These findings highlight the potential utility of school-based HIIT as a strategy to enhance the V̇O2 kinetics of youth, regardless of the presence of asthma.

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