When Studying Affective Responses to Exercise, the Definition of "Intensity" Must Reference Homeostatic Perturbations: A Retort to Vollaard et al

In articles on the methodology of studies investigating affective and enjoyment responses to high-intensity interval training, we noted that, occasionally, exercise conditions described as involving "high" intensity exhibited heart rates that were only as high as, or even lower than, heart rates recorded during comparator conditions described as being of "moderate" intensity. Drs. Vollaard, Metcalfe, Kinghorn, Jung, and Little suggest instead that exercise intensity in high-intensity interval-training studies can be defined in terms of percentages of peak workload. Although we maintain that defining exercise intensity in terms of percentages of maximal heart rate is a suboptimal way to quantify the degree of homeostatic perturbations in response to exercise, we are unconvinced that definitions of intensity relying solely on workload are appropriate for studies investigating affective and enjoyment responses to exercise. The reason is that affect is theorized to have evolved to relay information about homeostatic perturbations to consciousness.

Physiological and psychological outcomes of high intensity interval training in patients with heart failure compared to moderate continuous training and usual care: A systematic review with meta analysis

BACKGROUND

An important component of secondary prevention of CVD (including HF) is comprehensive cardiac rehab, including exercise. Novel, individualised approaches are needed to increase uptake and adherence to exercise programmes, one area offering potential is HIIT. HIIT has been shown to be both safe and effective for improving cardiovascular fitness in both coronary artery disease and HF patients.

OBJECTIVES

To provide a current and up to date evaluation of the physiological and psychological outcomes of HIIT in patients with HF compared to MCT and UC. Secondly to perform sub-group analyses comparing short and long HIIT protocols.

METHODS

A systematic review and meta-analysis of randomised controlled trials was undertaken. Medline, Embase, Scopus, CINAHL and SportDISCUS were searched up to July 2022. Trials were included if they carried out a HIIT intervention (defined at intensity ≥ 80% peak HR or ≥ 80% VO2peak) in HF patients (HFpEF or HFrEF) for at least 6 weeks. Comparator group was UC or MCT.

RESULTS

HIIT was shown to be superior to MCT and UC for improving VO2peak (HIIT mean improvement 3.1 mL.kg-1min-1). HITT was superior to MCT and UC for improving LVEF (HIIT mean improvement 5.7%). HIIT was superior to MCT and UC for improving HRQoL, using the MLHFQ (HIIT mean point change of -12.8). Subgroup analysis showed no difference between long and short HIIT.

CONCLUSION

HIIT improves VO2peak, LVEF and HRQoL in patients with HF, the improvements seen in VO2peak and LVEF are superior in HIIT compared to MCT and UC.

Exercise in the workplace: examining the receptivity of practical and time-efficient stair-climbing "exercise snacks"

In the workplace, people are often sedentary for prolonged time and do not regularly engage in physical activity-two factors independently linked to premature morbidity and mortality. This study aimed to determine the receptivity of incorporating practical stair-climbing "exercise snacks" (Snacks; three isolated bouts of ascending 53-60 stairs performed sporadically throughout the day) into workplace settings compared to more traditional high-intensity interval training (HIIT; performed as three bouts of 53-60 stairs within a structured HIIT workout) and to explore if these exercise strategies could influence sedentary and physical activity behaviour. Fourteen participants (12 women; Mage = 38.9 ± 10.2 years) completed two supervised exercise trials (Snacks and HIIT) followed by 1 week participating in either form of exercise in their workplace. Ratings of perceived exertion (RPE), affective valence, enjoyment, and self-efficacy were measured at the supervised exercise sessions. During the follow-up period, sedentary behaviour and physical activity were measured with an accelerometer. Affective valence was more positive (p = 0.03; η2 p = 0.21) and there was a lower rise in RPE (p = 0.01; η2 p = 0.29) during Snacks than HIIT. Post-exercise enjoyment of, and self-efficacy towards, Snacks and HIIT were high and similar (ps > 0.05). After the supervised trials, 10/14 of the participants preferred Snacks and 4/14 preferred HIIT (p = 0.18). On days when participants chose to perform either exercise modality, the average number of sit-to-stands in a 24 h period was increased (48.3 ± 8.7 to 52.8 ± 7.8; p = 0.03; Hedge's g = 0.73) and moderate-to-vigorous physical activity tended to increase (21.9 ± 18.2 to 38.1 ± 22.1 min; p = 0.06; Hedge's g = 0.60) compared to days when they chose not to exercise. Stair-climbing exercise snacks may be an attractive approach to implement in the workplace setting and has potential to positively impact sedentary behaviour and physical activity metrics.

A Methodological Checklist for Studies of Pleasure and Enjoyment Responses to High-Intensity Interval Training: Part I. Participants and Measures

For decades, the exercise psychology research literature echoed the conclusion that exercise makes most people feel better, with no clear evidence that this "feel-better effect" is moderated by intensity. An overhaul of the methodological approach subsequently showed that high-intensity exercise is experienced as unpleasant, and the "feel-better effect," although possible, is conditional and therefore not as robust or prevalent as initially thought. Recently, several studies investigating high-intensity interval training (HIIT) have concluded that HIIT is pleasant and enjoyable, despite the high intensity. Considering that HIIT is emerging as an option in physical activity recommendations and exercise prescription guidelines, in part due to these claims, a methodological checklist is presented to aid researchers, peer reviewers, editors, and other readers in critically appraising studies examining the effects of HIIT on affect and enjoyment. This first part addresses the characteristics and number of participants, as well as the selection of measures of affect and enjoyment.

A Methodological Checklist for Studies of Pleasure and Enjoyment Responses to High-Intensity Interval Training: Part II. Intensity, Timing of Assessments, Data Modeling, and Interpretation

Recent studies have concluded that high-intensity interval training should be seen as a "viable alternative" to, and may be more enjoyable than, moderate-intensity continuous exercise. If true, these claims have the potential to revolutionize the science and practice of exercise, establishing high-intensity interval training as not only a physiologically effective exercise modality but also a potentially sustainable one. However, these claims stand in contrast to voluminous evidence according to which high levels of exercise intensity are typically experienced as less pleasant than moderate levels. To help researchers, peer reviewers, editors, and critical readers appreciate possible reasons for the apparently conflicting results, we present a checklist that identifies crucial methodological elements in studies investigating the effects of high-intensity interval training on affect and enjoyment. This second installment covers how "high-intensity" and "moderate-intensity" experimental conditions are defined, the timing of assessments of affect, the modeling of affective responses, and data interpretation.

Effects of High-Intensity Interval Training and Continuous Aerobic Training on Health-Fitness, Health Related Quality of Life, and Psychological Measures in College-Aged Smokers

The study examined the effects of exercise on health-fitness, health related quality of life (HRQOL), and psychological measures in college-aged smokers. Outcomes included HRQOL, hemodynamic, anthropometric, lung function, and cardiorespiratory endurance. Sixty physically inactive college-aged male smokers (18-30 years) were randomly assigned into three groups: high-intensity interval training (HIIT), continuous aerobic training (CAT), and a control (CON). Both HIIT and CAT groups completed 8 weeks of non-consecutive cycling sessions thrice weekly. The CON group were not subjected to the exercise intervention. Sixty participants met the inclusion criteria. Of these, 48 (HIIT: n = 18, CAT: n = 16, CON: n = 14) participants completed the study and were included in the final analysis. Compared to CON, HIIT significantly (p = 0.01) improved forced expiratory flow (FEF_75%) more than the CAT group (p = 0.29). HIIT provided a significant (p = 0.04) improvement in FEF_75% compared to CAT. Recovery heart rate (RHR) was significantly improved in participants assigned to HIIT (p = 0.00) and CAT (p = 0.002) groups compared with the CON. A significant difference in RHR was found in HIIT compared to CAT. The study findings indicate that both HIIT and CAT exercise interventions significantly improve markers of lung function and cardiorespiratory endurance, respectively. However, findings suggested that HIIT should be the preferred form of exercise regime among college-aged smokers for more significant, healthier benefits.

Effects of music on psychophysiological responses during high intensity interval training using body weight exercises

The use of music in exercise sessions is considered an interesting strategy as it facilitates, through motivation, an improvement in physical performance, as well as a reduction in the subjective perception of effort and an improvement in mood. Such factors are important for the maintenance of physical exercise programs, however, considering high intensity interval training, the effects of music remain inconclusive. Thus, the objective of this study was to evaluate the influence of music during high intensity interval training sessions using body weight (HIIT-B) on the physiological parameters and mood state of adults.

METHODS

11 CrossFit male practitioners were randomly submitted to three sessions of HIIT-C under the following experimental conditions: preference music (PM), non-preference music (nPM) and without music (WM). The HIIT-B protocol consisted of 20 sets of 30 seconds of stimulus using maximal intensities followed by 30 seconds of passive recovery. The following exercises were used: jumping jacks, burpee, mountain climbing and squat jumping. The following parameters were analyzed: heart rate (HR), lactate (La), total amount of movements (TAM), affective response (AR), rating of perceived exertion (RPE) and recovery (RPR) and mood states.

RESULTS

although an increase (p< 0.05) of HR, RPE and La reduction of RPR was found after performing the HIIT session, no differences were found between the three conditions to these parameters. The nPM condition promoted lower (p< 0.001) TAM compared to the WM and PM conditions, which also differed from each other. However, for AR, a music effect was found among the protocols (p< 0.0001), indicating that the PM session promoted an increase in pleasure, unlike WM and nPM session which provided pleasure reduction and displeasure respectively. The WM session did not promote any changes. There were no main effects on time for depression and anger, which were different for vigor, fatigue, mental confusion, tension and mood disturbance. Additionally, differences were found after session to tension (p= 0.0229), vigor (p= 0.0424) and fatigue (p= 0.0400) for PM condition, vigor (p= 0.0424), fatigue (p= 0.0400) mental confusion (p= 0.0302) and mood disturbance (p= 0.0129) and vigor (p= 0.0363) and fatigue (p= 0.0468) to WM conditions.

CONCLUSION

Listening to preferred music during an 'all out' HIIT-B session increases exercise performance and elicits more positive affective responses in recreationally active adult males, despite similar HR, blood lactate, RPE and fatigue compared to nonpreferred music or no-music.

Probiotic Supplementation and High-Intensity Interval Training Modify Anxiety-Like Behaviors and Corticosterone in High-Fat Diet-Induced Obesity Mice

Evidence supports the role of exercise training and probiotics on reducing obesity. Considering the relationship between obesity and high-fat diet with anxiety indices, the aim of this study was to assess the effect of probiotic supplementation and high-intensity interval training (HIIT) on anxiety-like behaviors, corticosterone and obesity indices in high-fat diet (HFD)-induced obesity mice. Thirty male adult C57BL/6 mice were randomly divided into five groups: (1) Control with normal diet (CON), (2) High-fat diet (HFD), (3) HFD + exercise training (HT), (4) HFD + probiotics supplement (HP) and (5) HFD + exercise training +probiotics (HTP). Exercise training consisted of 8 weeks of high-intensity interval training (HIIT) programs. Probiotics supplement included 0.2 mL Lactobacillus rhamnosus GG. Anxiety-like behaviors were measured by open field (OF) and Elevated plus maze (EPM). OF and EPM tests, visceral fat mass (VFM) measurement, and blood sampling for corticosterone were performed after the intervention. Bodyweight was measured at different stages during the intervention. HFD regime in C57BL/6 mice increased bodyweight, VFM, and serum corticosterone levels and anxiety-like behaviors (p < 0.05). HIIT, probiotic and their combination, decreased bodyweight, VFM, and serum corticosterone levels and improved anxiety-like behavior in the HFD mice (p < 0.05). The effect of a combination of HIIT and probiotic on most of the anxiety indices was more than each one separately (p < 0.5). HIIT and probiotic supplements separately or above all in combination, may have beneficial effects in reducing obesity and anxiety indices.

Exercise Time and Intensity: How Much Is Too Much?

The growing prevalence and popularity of interval training necessitate additional guidelines in regard to maximal levels of time and intensity.

PURPOSE

To correlate salivary hormones and time in varying heart-rate (HR) zones. The hypothesis was that chronic exercise durations >9% of total exercise time in the >90% maximum HR zone would lead to decreased variation in salivary cortisol concentration after exercise in a 2-bout high-intensity protocol compared with less or more time in this zone.

METHODS

A total of 35 healthy adults who regularly exercised for an average of 8 hours per week recorded their HR during every training session for 3 weeks. Later, they completed an experimental day composed of two 30-minute high-intensity interval sessions separated by 4 hours of nonactive recovery. The authors collected saliva samples before, immediately following, and 30 minutes after each exercise session to assess changes in cortisol concentrations.

RESULTS

There was a correlation between weekly time training at an intensity >90% maximum HR and the variables associated with overtraining. Salivary cortisol concentration fluctuated less in the participants who exercised in this extreme zone for >40 minutes per week (P < .001).

CONCLUSION

Based on the current study data, for individuals who regularly exercise, 4% to 9% total training time above 90% maximum HR is the ideal duration to maximize fitness and minimize symptoms related to overreaching.

Identifying facilitators and barriers for adolescents participating in a school-based HIIT intervention: the eXercise for asthma with commando Joe's® (X4ACJ) programme

BACKGROUND

High-intensity interval training (HIIT) elicits numerous health benefits, but little evidence is available regarding the feasibility of delivering school-based HIIT interventions. The aim of this study was to explore adolescents' perceptions of a 6-month, 3 × 30-min sessions per week, HIIT intervention delivered either before or after school.

METHOD

Eighty adolescents allocated to the intervention group (13.3 ± 1.0 years; 45 boys) were invited to take part in semi-structured focus groups post-intervention. Participants were categorised as attendees (≥40% attendance) or non-attendees (< 5% attendance). Data were transcribed verbatim and thematically analysed deductively, with key emergent themes represented using pen profiles.

RESULTS

Results showed that a school-based HIIT intervention can be an enjoyable form of exercise. Irrespective of attendance, similar facilitators and barriers to participating were highlighted, including benefits of participation, content of the exercise session and the intervention instructor.

CONCLUSION

This study provides support for the delivery of a HIIT intervention in a school setting but highlights the importance of a flexible design and delivery to accommodate competing interests. There is a need to educate adolescents on the possible benefits of participation and to make the sessions enjoyable in order to increase their extrinsic and intrinsic motivation to sustain participation.

Can high-intensity interval training improve physical and mental health outcomes? A meta-review of 33 systematic reviews across the lifespan

High-intensity-interval-training (HIIT) has been suggested to have beneficial effects in multiple populations across individual systematic reviews, although there is a lack of clarity in the totality of the evidence whether HIIT is effective and safe across different populations and outcomes. The aim of this meta-review was to establish the benefits, safety and adherence of HIIT interventions across all populations from systematic reviews and meta-analyses. Major databases were searched for systematic reviews (with/without meta-analyses) of randomised & non-randomised trials that compared HIIT to a control. Thirty-three systematic reviews (including 25 meta-analyses) were retrieved encompassing healthy subjects and people with physical health complications. Evidence suggested HIIT improved cardiorespiratory fitness, anthropometric measures, blood glucose and glycaemic control, arterial compliance and vascular function, cardiac function, heart rate, some inflammatory markers, exercise capacity and muscle mass, versus non-active controls. Compared to active controls, HIIT improved cardiorespiratory fitness, some inflammatory markers and muscle structure. Improvements in anxiety and depression were seen compared to pre-training. Additionally, no acute injuries were reported, and mean adherence rates surpassed 80% in most systematic reviews. Thus, HIIT is associated with multiple benefits. Further large-scale high-quality studies are needed to reaffirm and expand these findings.Abbreviations: ACSM: American College of Sports Medicine; BMI: Body Mass Index; BNP: Brain Natriuretic Peptide; BP: Blood Pressure; CAD: Coronary Artery Disease; CHD: Coronary Heart Disease; COPD: Chronic Obstructive Pulmonary Disease; CRP: c- reactive Protein; CVD: Cardiovascular Disease; DBP: Diastolic Blood Pressure; ES: Effect Size; FAS: Reduced Fatty Acid Synthase; FATP-1: Reduced Fatty Acid Transport Protein 1; FMD: Flow Mediated Dilation; Hs-CRP: High-sensitivity c- reactive Protein; HDL: High Density Lipoprotein; HIIT: High-Intensity Interval Training; HOMA: Homoeostatic Model Assessment; HR: Heart Rate; HTx: Heart Transplant Recipients; IL-6: Interleukin-6; LDL: Low Density Lipoprotein; LV: Left Ventricular; LVEF: Left Ventricular Ejection Fraction; MD: Mean Difference; MetS: Metabolic Syndrome; MPO: Myeloperoxidase; MICT: Moderate-Intensity Continuous Training; NO: Nitric Oxide; NRCT: Non-Randomised Controlled Trial; PA: Physical Activity; PAI-1: Plasminogen-activator-inhibitor-1; QoL: Quality of Life; RCT: Randomised Controlled Trial; RoB: Risk of Bias; RPP: Rate Pressure Product; RT: Resistance Training; SBP: Systolic Blood Pressure; SD: Standardised Difference; SMD: Standardised Mean Difference; TAU: Treatment-As-Usual; T2DM: Type 2 Diabetes Mellitus; TC: Total Cholesterol; TG: Triglycerides; TNF-alfa: Tumour Necrosis Factor alpha; UMD: Unstandardised Mean Difference; WC: Waist Circumference; WHR: Waist-to-Hip Ratio; WMD: Weighted Mean DifferenceKey points: HIIT may improve cardiorespiratory fitness, cardiovascular function, anthropometric variables, exercise capacity, muscular structure and function, and anxiety and depression severity in healthy individuals and those with physical health disorders.Additionally, HIIT appears to be safe and does not seem to be associated with acute injuries or serious cardiovascular events.

High Intensity Interval training (HIIT) for people with severe mental illness: A systematic review & meta-analysis of intervention studies- considering diverse approaches for mental and physical recovery

There is a mortality gap of 15 to 20 years for people with severe mental illness (SMI - psychotic spectrum, bipolar, major depressive disorders). Modifiable risk factors include inactivity and low cardiorespiratory fitness (CRF). Exercise can improve mental and physical outcomes; optimal type and intensity of exercise for people with SMI has yet to be determined. High Intensity Interval training (HIIT) is an exercise with distinct cardio-metabolic advantages in other disease populations compared to traditional moderate intensity continuous training (MCT). We investigated the feasibility and efficacy of HIIT for people with SMI. Major electronic databases were searched, identifying HIIT studies for adults experiencing SMI.Data on feasibility, safety, study design, sample characteristics, and physical and psychological outcomes were extracted and systematically reviewed. Meta-analyses were conducted within group, pre and post HIIT interventions, and between group, to compare HIIT with control conditions. Nine articles were identified including three pre/post studies, one non randomised and five randomised trials, (366 participants, 45.1% female). HIIT appears as feasible as MCT, with few safety concerns. Following HIIT, there was a moderate improvement in CRF and depression. There was no difference between HIIT and MCT for adherence or CRF.HIIT improved depression more than MCT.

Psychophysiological Intervention to Improve Preparedness in Military Special Operations Forces

BACKGROUND: Actual studies in military training support the use of new methodological approaches such as high intensity interval training and inverse periodization training rather than conventional approaches. However, the application and analysis of success of these new methodologies are as yet unknown.METHODS: The military adapted the civil reverse periodization training system, composed of 6 wk and five sessions per week. For the first 3 wk soldiers performed two sessions with the objective of increasing the maximal strength of the upper and lower body muscles, and three sessions of short high-intensity interval training (HIIT). In the following 3 wk they combined two endurance HIIT and two resistance HIIT sessions with military equipment while conducting a military task.RESULTS: After the training a significant body mass index decrease was found, along with an increase in lower limb muscular strength, aerobic and anaerobic performance, resilience, stress tolerance, and psychological flexibility. Regarding the ratio of acceptance there was an increased ratio compared to previous years of 7%. In addition, married soldiers with children presented greater resilience, stress tolerance, psychological flexibility, and a higher ratio of success.DISCUSSION: Accepted soldiers presented greater psychological status and stress tolerance, highlighting the importance of the work of the unit psychologists to reinforce and monitor the psychometric profile of the soldiers as well as their intrinsic characteristics of personality and emotionality. The greater baseline physical condition and higher performance in all physical tests proves how reverse periodization training models are a great stimuli and training approach in soldiers.Tornero-Aguilera JF, Gregório Pelarigo J, Clemente-Suarez VJ. Psychophysiological intervention to improve preparedness in military Special Operations forces. Aerosp Med Hum Perform. 2019; 90(11):953-958.

Affective and enjoyment responses to 12 weeks of high intensity interval training and moderate continuous training in adults with Crohn's disease

The aim was to undertake secondary data analysis from a three-arm randomised feasibility trial of high intensity interval training (HIIT), moderate intensity continuous training (MICT), and usual care control in adults with Crohn’s disease (CD; n = 36), with a primary focus on exploring affective and enjoyment responses. Twenty-five participants with quiescent or mildly-active CD were randomised to one of the two exercise groups: HIIT (n = 13) and MICT (n = 12). Both groups were offered thrice weekly sessions for 12 weeks. MICT consisted of cycling for 30 minutes at 35% peak power (Wpeak), whereas HIIT involved ten 1-minute bouts at 90% Wpeak, interspersed with 1-minute bouts at 15% Wpeak. Heart rate (HR), differentiated ratings of perceived exertion for legs (RPE-L) and central (RPE-C), along with feeling state (Feeling Scale; FS) were measured at 92.5% of each session. Enjoyment was measured at the end of training using the Physical Activity Enjoyment Scale (PACES). Post-hoc exploratory analysis involved a mixed-model two-way ANOVA to compare HR, RPE-L, RPE-C and FS for the exercise sessions in weeks 1, 6 and 12 between groups. Overall, HR was greater (p < 0.01) during HIIT (173 ± 8 bpm) compared with MICT (128 ± 6 bpm). Similarly, RPE-L and RPE-C responses were greater overall (p = 0.03 and p = 0.03, respectively) during HIIT (5.5 ± 1.6 and 5.1 ± 1.7, respectively) compared to MICT (3.3 ± 1.5 and 2.9 ± 1.5, respectively). Overall, FS was 2.2 ± 1.9 for HIIT and 2.1 ± 1.4 for MICT with no effect of treatment group (p = 0.25) or time (p = 0.94). There was also no significant difference in PACES scores between HIIT (99.4 ± 12.9) and MICT (101.3 ± 17.4; p = 0.78). The findings suggest HIIT and MICT protocols elicited similar enjoyment and affect in adults with quiescent or mildly-active CD.

Psycho-physiological responses to perceptually-regulated interval runs in hypoxia and normoxia

We investigated whether perceptually-regulated high-intensity intervals in hypoxia are associated with slower running velocities versus normoxia, when physiological responses and exercise-related sensations remain the same. Nineteen trained runners (33.4 ± 9.1 years) completed a high-intensity interval running protocol (4 × 4-min intervals at a clamped perceived rating exertion of 16 on the 6-20 Borg scale, 3-min passive recoveries) in either hypoxic (HYP; FiO₂ 15.0%) or normoxic (NOR; FiO₂ 20.9%) conditions. Participants adjusted to a progressively slower running velocity from interval 1-4 (-7.0%), and more so in HYP vs. NOR for intervals 2, 3 and 4 (-4.6%, -6.4% and - 7.9%, respectively; p < .01). Heart rate increased from interval 1-4 (+4.8%; p < .01), independent of condition. Arterial oxygen saturation was lower in HYP vs. NOR (86.0% vs. 94.8%; p < .01). Oxyhemoglobin (-23.7%) and total hemoglobin (-77.0%) decreased, whilst deoxyhemoglobin increased (+44.9%) from interval 1-4 (p < .01), independent of condition. Perceived recovery (-41.6%) and motivation (-21.8%) were progressively lower from interval 1-4, and more so in HYP vs. NOR for intervals 2, 3 and 4 (recovery: -8.8%, -24.2% and - 29.3%; motivation: -5.3%, -20.3% and - 22.4%, respectively; p < .01). Perceived breathlessness (+18.6%), limb discomfort (+44.0%) and pleasure (-32.2%) changed from interval 1-4, with significant differences (+21.8%, +11.3% and - 31.3%, respectively) between HYP and NOR (p < .01). Slower interval running velocities in hypoxia achieve similar heart rate and muscle oxygenation responses to those observed in normoxia when perceptually-regulated, yet at the expense of less favourable exercise-related sensations.

School-based physical activity intervention for older adolescents: rationale and study protocol for the Burn 2 Learn cluster randomised controlled trial

INTRODUCTION

This trial aims to investigate the impact of a school-based physical activity programme, involving high-intensity interval training (HIIT), on the physical, mental and cognitive health of senior school students.

METHODS AND ANALYSIS

The Burn 2 Learn (B2L) intervention will be evaluated using a two-arm parallel group cluster randomised controlled trial with allocation occurring at the school level (to treatment or wait-list control). Schools will be recruited in two cohorts from New South Wales, Australia. The trial will aim to recruit ~720 senior school students (aged 16-18 years) from 20 secondary schools (ie, 10 schools per cohort). A range of implementation strategies will be provided to teachers (eg, training, equipment and support) to facilitate the delivery of HIIT sessions during scheduled classes. In phase I and II (3 months each), teachers will facilitate the delivery of at least two HIIT sessions/week during lesson-time. In phase III (6 months), students will be encouraged to complete sessions outside of lesson-time (teachers may continue to facilitate the delivery of B2L sessions during lesson-time). Study outcomes will be assessed at baseline, 6 months (primary end point) and 12 months. Cardiorespiratory fitness (shuttle run test) is the primary outcome. Secondary outcomes include: vigorous physical activity, muscular fitness, cognition and mental health. A subsample of students will (i) provide hair samples to determine their accumulated exposure to stressful events and (ii) undergo multimodal MRI to examine brain structure and function. A process evaluation will be conducted (ie, recruitment, retention, attendance and programme satisfaction).

ETHICS AND DISSEMINATION

This study has received approval from the University of Newcastle (H-2016-0424) and the NSW Department of Education (SERAP: 2017116) human research ethics committees.

TRIAL REGISTRATION NUMBER

ACTRN12618000293268; Pre-results.

Perceptual and Cardiorespiratory Responses to High-Intensity Interval Exercise in Adolescents: Does Work Intensity Matter?

High-intensity interval exercise (HIIE) may not elicit prominent unpleasant feelings even with elevated perceived exertion and physiological stress in adolescents. However, the influence of different HIIE work intensities on the affective experience and cardiorespiratory responses is unknown. This study examined the acute affective, enjoyment, perceived exertion and cardiorespiratory responses to HIIE with different work intensities in adolescents. Participants (n = 16; 8 boys; age 12.0 ± 0.3 years) performed, on separate days, HIIE conditions consisting of 8 x 1-minute work-intervals at 70%, 85%, or 100% peak power separated by 75 seconds recovery at 20 W. Affect, enjoyment and rating of perceived exertion (RPE) were recorded before, during, and after HIIE. Heart rate (HR) and oxygen uptake were collected during HIIE. Affect declined in all conditions (p < 0.01) but 100%HIIE elicited significantly lower affect than 70%HIIE and 85%HIIE at work-interval 8 (all p < 0.02, ES > 1.74; 70%HIIE = 2.5 ± 0.8; 85%HIIE = 1.1 ± 1.5; 100%HIIE = -1.5 ± 1.4 on feeling scale). Similar enjoyment was evident during and after all conditions (all p > 0.44). RPE was significantly higher during 100%HIIE than 70%HIIE and 85%HIIE across all work-intervals (all p < 0.01, ES > 1.56). The majority of the participants attained ≥90%HR_max during 85%HIIE (87%) and 100%HIIE (100%), but not during 70%HIIE (6%). Affect responses during HIIE are dependent on the intensity of the work-interval and are not entirely negative (unpleasant feelings). Despite similar enjoyment, positive affect experienced during 70%HIIE and 85%HIIE could serve as a strategy to encourage exercise adoption and adherence in adolescents, but only 85%HIIE elicits sufficient HR stimulus to facilitate potential health benefits.

Physiological and Psychological Responses during Low-Volume High-Intensity Interval Training Sessions with Different Work-Recovery Durations

We compared physiological and psychological responses between low-volume high-intensity interval training (LV-HIIT) sessions with different work-recovery durations. Ten adult males performed two LV-HIIT sessions in a randomized, counter-balanced order. Specifically, 60/60 s LV-HIIT and 30/30 s LV-HIIT. Oxygen uptake (VO₂), carbon dioxide output (VCO₂), ventilation (VE), respiratory exchange ratio (RER), perceived exertion (RPE), and affect were assessed. During intervals, the VO₂ (3.25 ± 0.57 vs. 2.83 ± 0.50 L/min), VCO₂ (3.15 ± 0.61 vs. 2.93 ± 0.58 L/min), VE (108.59 ± 27.39 vs. 94.28 ± 24.98 L/min), and RPE (15.9 ± 1.5 vs. 13.9 ± 1.5) were higher (ps ≤ 0.01), while RER (0.98 ± 0.05 vs. 1.03 ± 0.03) and affect (-0.8 ± 1.4 vs. 1.1 ± 2.0) were lower (ps ≤ 0.007) in the 60/60 s LV-HIIT. During recovery periods, VO₂ (1.85 ± 0.27 vs. 2.38 ± 0.46 L/min), VCO₂ (2.15 ± 0.35 vs. 2.44 ± 0.45 L/min), and affect (0.6 ± 1.7 vs. 1.7 ± 1.8) were lower (ps ≤ 0.02), while RER (1.20 ± 0.05 vs. 1.03 ± 0.05; p < 0.001) was higher in the 60/60 s LV-HIIT. Shorter LV-HIIT (30 s) elicits lower physiological response and attenuated negative affect than longer LV-HIIT (60 s).

Predictors of change in affect in response to high intensity interval exercise (HIIE) and sprint interval exercise (SIE)

Affect is typically positive at intensities below the lactate or ventilatory threshold, yet more aversive responses occur at supra-threshold intensities which may reduce positive perceptions of exercise. Completion of high intensity interval exercise (HIIE) typically elicits a reduction in affect, yet greater post-exercise enjoyment has been reported in response to HIIE versus moderate intensity continuous exercise (MICE). This study examined affectual responses to HIIE and sprint interval exercise (SIE) in 71 active men and women (age = 24.0 ± 4.8 year). Participants performed various HIIE and SIE regimes on the cycle ergometer during which affect (+5 - -5 scale), rating of perceived exertion (RPE, Borg 1-10 scale), and blood lactate concentration (BLa) were determined. Enjoyment was measured post-exercise using the PACES scale. Predictors of change in these variables in response to exercise were identified using multiple regression. Results showed a significant reduction in affect (p = .001) which was greater (p = .03) with SIE (-5.7 ± 2.7) compared to HIIE (-4.3 ± 2.4). Nevertheless, there was marked variability in the affect response across participants, as its change ranged from -1 to -7 units from pre- to post-exercise in 85% of all sessions. Sixty two percent of the change in affect seen across regimes was explained by baseline affect, BLa, and enjoyment. Significant associations were shown between the change in affect and baseline affect (r = -0.46, p < .001) and change in RPE (r = -0.59, p < .001). In addition, RPE significantly increased in response to HIIE (6.1 ± 1.7) and SIE (6.9 ± 2.0) but was not different (p = .050) between regimes. Our findings document an intensity-dependent relationship between affect and intensity during interval training, as supramaximal intensities elicit a larger decline in affect compared to submaximal intensities. In addition, pre-exercise affect is associated with the magnitude of change in affect reported in response to interval exercise.

Interval training elicits higher enjoyment versus moderate exercise in persons with spinal cord injury

BACKGROUND

High intensity interval training (HIIT) is a robust and time-efficient approach to improve multiple health indices including maximal oxygen uptake (VO2max). Despite the intense nature of HIIT, data in untrained adults report greater enjoyment of HIIT versus continuous exercise (CEX). However, this has yet to be investigated in persons with spinal cord injury (SCI).

OBJECTIVE

To examine differences in enjoyment in response to CEX and HIIT in persons with SCI.

DESIGN

Repeated measures, within-subjects design.

SETTING

University laboratory in San Diego, CA.

PARTICIPANTS

Nine habitually active men and women (age = 33.3 ± 10.5 years) with chronic SCI.

INTERVENTION

Participants performed progressive arm ergometry to volitional exhaustion to determine VO2peak. During subsequent sessions, they completed CEX, sprint interval training (SIT), or HIIT in randomized order.

OUTCOME MEASURES

Physical activity enjoyment (PACES), affect, rating of perceived exertion (RPE), VO2, and blood lactate concentration (BLa) were measured.

RESULTS

Despite a higher VO2, RPE, and BLa consequent with HIIT and SIT (P < 0.05), PACES was significantly higher (P = 0.03) in response to HIIT (107.4 ± 13.4) and SIT (103.7 ± 12.5) compared to CEX (81.6 ± 25.4). Fifty-five percent of participants preferred HIIT and 45% preferred SIT, with none identifying CEX as their preferred exercise mode.

CONCLUSION

Compared to CEX, brief sessions of submaximal or supramaximal interval training elicit higher enjoyment despite higher metabolic strain. The long-term efficacy and feasibility of HIIT in this population should be explored considering that it is not viewed as more aversive than CEX.

High-Intensity Interval Training for Overweight Adolescents: Program Acceptance of a Media Supported Intervention and Changes in Body Composition

High-intensity interval training (HIIT) consists of short intervals of exercise at high intensity intermitted by intervals of lower intensity and is associated with improvement of body composition and metabolic health in adults. Studies in overweight adolescents are scarce. We conducted a randomized controlled trial in overweight adolescents to compare acceptance and attendance of HIIT with or without weekly motivational encouragement through text messages and access to a study website. HIIT was offered for six months (including summer vacation) twice a week (60 min/session). Participation rates were continuously assessed and acceptance was measured. Clinical parameters were assessed at baseline and after six months. Twenty-eight adolescents participated in this study (age 15.5 ± 1.4; 54% female). The standard deviation score for body mass index over all participants was 2.33 at baseline and decreased by 0.026 (95% CI -0.048 to 0.10) units, p = 0.49. Waist to height ratio was 0.596 at baseline and decreased by 0.013 (95% CI 0.0025 to 0.024), p = 0.023. Participation within the first two months ranged from 65% to 75%, but fell to 15% within the last three months. Attendance in the intervention group was 14% (95% CI -8 to 37), p = 0.18, higher than the control group. Overall program content was rated as "good" by participants, although high drop-out rates were observed. Summer months constitute a serious problem regarding attendance. The use of media support has to be assessed further in appropriately powered trials.

Comparison of High-Intensity Interval Training and Moderate-to-Vigorous Continuous Training for Cardiometabolic Health and Exercise Enjoyment in Obese Young Women: A Randomized Controlled Trial

Objective

The aim of this study was to compare the effects of 5-week high-intensity interval training (HIIT) and moderate-to-vigorous intensity continuous training (MVCT) on cardiometabolic health outcomes and enjoyment of exercise in obese young women.

Methods

A randomized controlled experiment was conducted that involved thirty-one obese females (age range of 18–30) randomly assigned to either HIIT or MVCT five-week training programs. Participants in HIIT condition performed 20 min of repeated 8 s cycling interspersed with 12 s rest intervals, and those in MVCT condition cycled continuously for 40 min at 60–80% of peak oxygen consumption (V˙O_2peak), both for four days in a week. Outcomes such as V˙O_2peak, body composition estimated by bioimpedance analysis, blood lipids, and serum sexual hormones were measured at pre-and post-training. The scores of Physical Activity Enjoyment Scale (PAES) were collected during the intervention.

Results

After training, V˙O_2peak increased significantly for both training programs (9.1% in HIIT and 10.3% in MVCT) (p = 0.010, η² = 0.41). Although MVCT group had a significant reduction in total body weight (TBW, −1.8%, p = 0.034), fat mass (FM, - 4.7%, p = 0.002) and percentage body fat (PBF, −2.9%, p = 0.016), there were no significant between-group differences in the change of the pre- and post-measures of these variables. The HIIT group had a higher score on PAES than the MVCT group during the intervention. For both conditions, exercise training led to a decline in resting testosterone and estradiol levels, but had no significant effect on blood lipids.

Conclusion

Both HIIT and MVCT are effective in improving cardiorespiratory fitness and in reducing sexual hormones in obese young women; however, HIIT is a more enjoyable and time-efficient strategy. The mild-HIIT protocol seems to be useful for at least maintaining the body weight among sedentary individuals.