High-volume High-intensity Interval Training Research Articles

Effects of low-versus high-volume high-intensity interval training on glycemic control and quality of life in obese women with type 2 diabetes: A randomized controlled trial

Background/objectiveComparison between different training volumes of high-intensity interval training (HIIT) is understudied in type 2 diabetes. This study aimed to compare the effects of low- and high-volume HIIT on glycemic control, blood lipids, blood pressure, anthropometric adiposity measures, cardiorespiratory fitness, and health-related quality of life (HRQoL) in women with type 2 diabetes. MethodsSeventy-two obese women with type 2 diabetes aged 36–55 were randomly assigned to a low-volume HIIT group (i.e., 2 × 4-min high-intensity treadmill exercise at 85%–90% of peak heart rate, with a 3-min active recovery interval in between), a high-volume HIIT group (i.e., 4 × 4-min high-intensity treadmill exercise at 85%–90% of peak heart rate, with three 3-min active recovery intervals in between), and a non-exercising control group. Patients in HIIT groups exercised three days a week for 12 weeks. All patients received oral hypoglycemic medications with no calorie restrictions. The outcome measures were glycosylated hemoglobin (HbA1c), fasting blood glucose (FBG), 2-hour postprandial blood glucose (2-hr PPBG), total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), waist circumference (WC), waist-to-hip ratio, time to maximal exhaustion determined from a maximal treadmill exercise test (i.e., a measure of cardiorespiratory fitness), and HRQoL assessed by the 12-item Short Form (SF-12) Health Survey. ResultsThe low- and high-volume HIIT groups showed significant improvements in all outcome measures compared to the baseline and the non-exercising group (P < 0.05), except for DBP in the low-volume HIIT group (p > 0.05). Also, both low- and high-volume HIIT groups showed similar improvements in TC, HDL, SBP, DBP, BMI, WC, waist-to-hip ratio, and the SF-12 scores, with no significant between-groups difference (p > 0.05). The high-volume HIIT group, however, showed more significant improvements in HbA1c, FBG, 2-hr PPBG, TG, LDL, and treadmill time to maximal exhaustion than the low-volume HIIT group (p < 0.05). The non-exercising group showed non-significant changes in all outcome measures (p > 0.05). ConclusionLow-volume HIIT could be equally effective as high-volume HIIT for improving TC, HDL, blood pressure, anthropometric adiposity measures, and HRQoL in obese women with type 2 diabetes. Nevertheless, high-volume HIIT could have a greater impact on glycemic control, TG, LDL, and cardiorespiratory fitness in these patients. Trial registrationClinicalTrials.gov, NCT05110404.

The effects of high-intensity interval training and moderate-to-vigorous intensity on cardiorespiratory fitness in patients with permanent or persistent atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): the Innovations Fund of the Alternate Funding Plan for the Academic Health Sciences Centre of the Ministry of Ontario. Background Lower cardiorespiratory fitness (CRF) in atrial fibrillation (AF) is associated with higher risk of mortality. Moderate-to-vigorous intensity continuous training (MICT) increases CRF; however, growing evidence indicates that high-intensity interval training (HIIT) elicits similar or greater improvements in CRF in people with cardiovascular disease. Purposes The purposes of this study were to: (1) compare the effects of HIIT and MICT on CRF in patients with persistent and permanent AF; and, (2) assess the proportion of participants who achieved a clinically meaningful increase in CRF (i.e., 3.5 mL/kg/min, associated with significant reduction in mortality in AF). Methods This was a subanalysis of an RCT to examine the effects of HIIT and MICT on functional capacity. Participants completed cardiopulmonary exercise test (CPET) and were randomly assigned to 12-week, twice weekly supervised HIIT or MICT. Each HIIT session was 23 min in duration, completed on a stationary bike, and consisted of: (1) a 2-min warm up; (2) two blocks of 8 x 30-sec high-intensity work periods at 80-100% peak power output interspersed with 30-sec active recovery periods, with 4 min active recovery between the blocks; and, a 1-min cooldown. Each MICT session consisted of (1) a 15-min warm up; (2) 30-min of continuous aerobic exercise; and, (3) a 15-min cooldown. A subset of willing participants completed follow-up CPET. Repeated measures ANOVA was used to compare the changes in CRF between HIIT and MICT. Descriptive statistics was used to assess the proportion of patients meeting the clinically meaningful increase in CRF. Results Of 94 patients consented, 13 in HIIT (67±4 years old, 26% females) and 10 in MICT (71±9 years old, 40% females) completed pre and post CPET. Exercise adherence (i.e., % of sessions attended) was 91% for HIIT and 85% for MICT, respectively, and did not differ between the groups. At week 12, 76% of participants in HIIT and 80% in MICT achieved the prescribed exercise intensity targets. Our per-protocol analysis showed no overall change in CRF (pre: 19.0±5.1 vs. post: 19.4±4.6 mL/kg/min, p=0.461). No significant differences in changes in CRF were observed between HIIT (pre: 20.1±5.3 vs. post: 20.3±4.5 mL/kg/min) and MICT (pre: 17.6±4.8 vs. post: 18.4±4.7 mL/kg/min, interaction effect p=0.681). Two participants in HIIT (15.4%) and two in MICT (20.0%) achieved clinically meaningful increases. Conclusions Twice weekly HIIT or MICT for 12 weeks did not improve CRF in patients with persistent and permanent AF who completed CPET. Further, a small proportion of these patients (≤ 20%) achieved clinically meaningful increase in CRF. Considering a greater increase in CRF (3.2±2.5 mL/kg/min) in patients with non-permanent AF following high-volume HIIT (a total of 16 min at high intensity per session, three times per week) in a previous RCT, a larger exercise volume may be required to improve the CRF of patients with persistent and permanent AF.

Low-Volume and High-Intensity Aerobic Interval Training May Attenuate Dysfunctional Ventricular Remodeling after Myocardial Infarction: Data from the INTERFARCT Study

Background: Aerobic high-intensity interval training (HIIT) has demonstrated benefits for ventricular remodeling after myocardial infarction (MI) through various mechanisms. Despite this, the optimal training volume is not well known. The present study aimed to assess the effects of different (low vs. high volume) aerobic HIIT compared to an attentional control (AC) group on echocardiographic and biochemical indicators of left ventricular (LV) remodeling in adults after MI. Methods: Randomized clinical trial conducted on post-MI patients with preserved ventricular function. Participants were assigned to three study groups. Two groups performed HIIT 2 d/week, one group with low-volume HIIT (20 min, n = 28) and another with high-volume HIIT (40 min, n = 28). A third group was assigned to AC (n = 24) with recommendations for unsupervised aerobic training. Left ventricular echocardiographic parameters and cardiac biomarker levels (N-terminal pro-b-type natriuretic peptide, NT-proBNP; soluble growth stimulation expressed gene 2, ST2; troponin T; and creatine kinase) were assessed at baseline and after the intervention (16 weeks). Results: Eighty participants (58.4 ± 8.3 yrs, 82.5% male) were included. Both low- and high-volume HIIT showed increases (p &lt; 0.05) in left ventricular end-diastolic diameter (1.2%, 2.6%), and volume (1.1%, 1.3%), respectively. Interventricular septal and posterior walls maintained their thickness (p = 0.36) concerning the AC. Significant (p &lt; 0.05) gain in diastolic function was shown with the improvements in E (–2.1%, –3.3%), e’ waves (2.2%, 5.5%), and the deceleration time (2.1%, 2.9%), and in systolic function with a reduction in global longitudinal strain (–3.2%, –4.7%), respectively. Significant (p &lt; 0.05) reductions of N-terminal pro-B-type natriuretic peptide (NT-proBNP) (–4.8%, –11.1%) and of ST2 (–21.7%, –16.7%)were found in both HIIT groups respectively compared to the AC group. Creatine kinase elevation was shown only in high-volume HIIT (19.3%, p &lt; 0.01). Conclusions: Low-volume HIIT is proposed as a clinically time-efficient and safer strategy to attenuate dysfunctional remodeling by preventing wall thinning and improving LV function in post-MI patients.

A Mixed Comparisons of Aerobic Training With Different Volumes and Intensities of Physical Exercise in Patients With Hypertension: A Systematic Review and Network Meta-Analysis.

It is essential for patients with hypertension to effectively reduce and maintain appropriate blood pressure levels. As one of the non-pharmacological and invasive methods, physical exercise seems to improve blood pressure of the patients with hypertension. However, different volumes and intensities of physical exercise on the improvement of hypertension are different. To understand the effects of the type of exercise training on blood pressure and the other health status of patients with hypertension, a network meta-analysis was used to compare the mixed effects of different types of exercise training. This systematic review includes all eligible randomized controlled trials of PubMed, Medline, Cochrane Library, and CINAHL. Twelve studies met the inclusion criteria (n = 846 participants at the end of the study). The results show that a medium-intensity training (MIT) is best in improving the blood pressure of patients with hypertension, while a high-volume high-intensity interval training (HVHIIT) is better in reducing body mass and resting heart rate. In addition, the analysis of the exercise capacity shows that HVHIIT has a better effect on the improvement of patients with hypertension. Noticeably, long-term high-volume and appropriate intensity exercise can effectively improve the health status of patients with hypertension. In short, for patients with high blood pressure, MIT seems to be better at lowering blood pressure, while HVHIIT can better improve exercise ability and physical fitness. However, larger randomized controlled trials with a longer duration than those included in this meta-analysis are needed to confirm these results.

High-Intensity Interval Training in Polycystic Ovary Syndrome: A Two-Center, Three-Armed Randomized Controlled Trial.

Exercise training is recommended to improve cardiometabolic health and fertility in women with polycystic ovary syndrome (PCOS), yet there are few randomized controlled trials on the effects of different exercise protocols on clinical reproductive outcomes. Our aim was to determine the effect of high-intensity interval training (HIT) on menstrual frequency, as a proxy of reproductive function, in women with PCOS. The IMPROV-IT study was a two-center randomized controlled trial undertaken in Norway and Australia. Women with PCOS were eligible for inclusion. After stratification for body mass index <27 or ≥27 kg·m-2 and study center, participants were randomly allocated (1:1:1) to high-volume HIT (HV-HIT), low-volume HIT (LV-HIT), or a control group. Measurements were assessed at baseline, after the 16-wk exercise intervention, and at 12-month follow-up. The primary outcome was menstrual frequency after 12 months. Secondary outcomes included markers of cardiometabolic and reproductive health, quality of life, and adherence to and enjoyment of HIT. We randomly allocated 64 participants to the HV-HIT (n = 20), LV-HIT (n = 21), or control group (n = 23). There were no differences in menstrual frequency at 12 months between the LV-HIT and control groups (frequency ratio, 1.02; 95% confidence interval [CI], 0.73-1.42), the HV-HIT and control groups (frequency ratio, 0.93; 95% CI, 0.67-1.29), or the LV-HIT and HV-HIT groups (frequency ratio, 1.09; 95% CI, 0.77-1.56). Menstrual frequency increased in all groups from baseline to 12 months. More participants became pregnant in the LV-HIT group (n = 5) than in the control group (n = 0, P = 0.02). A semisupervised HIT intervention did not increase menstrual frequency in women with PCOS.Clinical Trial Registration Number:ClinicalTrials.gov (NCT02419482).

Chronotropic Responses to Exercise and Recovery in Myocardial Infarction Patients Taking β-Blockers Following Aerobic High-Intensity Interval Training: AN INTERFARCT STUDY.

The objectives of this study were to compare the effects of two different high-intensity interval training (HIIT) programs (low-volume vs high-volume) on chronotropic responses during exercise and recovery, and to contrast the results of the HIIT groups together to only physical activity recommendations in post-myocardial infarction (MI) patients taking β-blockers. Resting heart rate (HRrest), peak HR (HRpeak), HR reserve (HRreserve = HRpeak-HRrest), HR recovery (HRR) as the difference between HRpeak and post-exercise HR, and chronotropic incompetence were assessed in 70 patients (58 ± 8 yr) following MI with a cardiopulmonary exercise test to peak exertion before and after a 16-wk exercise intervention period. All participants were randomized to either attention control (AC) (physical activity recommendations) or one of the two supervised HIIT groups (2 d/wk). After the intervention, no significant between-HIIT group differences were observed. The HRpeak increased (P < .05) in low- (Δ= 8 ± 18%) and high-volume HIIT (Δ= 6 ± 9%), with a small decrease in AC (Δ=- 2 ± 12%, P > .05) resulting in large differences (P < .05) between HIIT and AC. The HRreserve increased (P < .05) in high-volume HIIT. The HRR slightly increased (P < .05) in low-volume (5th min, Δ= 19 ± 31%) and high-volume HIIT (2nd min, Δ= 15 ± 29%, and 5th min, Δ= 19 ± 28%). These findings suggest that both low- and high-volume HIIT elicit similar improvements in chronotropic responses after MI, independent of β-blocker treatment. Supervised HIIT was more effective than giving physical activity recommendations alone. Low-volume HIIT is presented as a potent and time-efficient exercise strategy that could enhance the sympathovagal balance in this population.

Low-volume high-intensity interval training for cardiometabolic health.

High-intensity interval training (HIIT) is characterised by short bouts of high-intensity submaximal exercise interspersed with rest periods. Low-volume HIIT, typically involving less than 15min of high-intensity exercise per session, is being increasingly investigated in healthy and clinical populations due to its time-efficient nature and purported health benefits. The findings from recent trials suggest that low-volume HIIT can induce similar, and at times greater, improvements in cardiorespiratory fitness, glucose control, blood pressure, and cardiac function when compared to more traditional forms of aerobic exercise training including high-volume HIIT and moderate intensity continuous training, despite requiring less time commitment and lower energy expenditure. Although further studies are required to elucidate the precise mechanisms of action, metabolic improvements appear to be driven, in part, by enhanced mitochondrial function and insulin sensitivity, whereas certain cardiovascular improvements are linked to increased left ventricular function as well as greater central and peripheral arterial compliance. Beyond the purported health benefits, low-volume HIIT appears to be safe and well-tolerated in adults, with high rates of reported exercise adherence and low adverse effects.

Improving Reproductive Function in Women With Polycystic Ovary Syndrome With High-Intensity Interval Training (IMPROV-IT): A Two-Centre, Three-Armed Randomized Controlled Trial

Background: A physically active lifestyle is recommended to improve cardiometabolic health and fertility in women with polycystic ovary syndrome (PCOS), yet there are few randomized controlled trials investigating the effects of different exercise protocols on clinical reproductive outcomes. Our aim was to determine the effect of high-intensity interval training (HIT) on menstrual frequency, as a proxy of reproductive function, in women with PCOS. Methods: The IMPROV-IT study was a two-centre randomized controlled trial undertaken in Norway and Australia. Women with PCOS (Rotterdam criteria) were eligible for inclusion. After stratification for body mass index < or ≥27 kg/m2 and study centre, participants were randomly allocated by computer-generated random numbers (1:1:1) to high-volume HIT (HV-HIT), low-volume HIT (LV-HIT), or a control group. Measurements were assessed at baseline, after the 16-week exercise intervention and at 12-months follow-up. The primary outcome was menstrual frequency after 12 months. Secondary outcomes included markers of cardiometabolic and reproductive health, quality of life, and adherence to and enjoyment of HIT. Analysis was by intention-to-treat. Findings: The study took place between June 2015 and February 2020. We randomly allocated 64 participants to HV-HIT (n=20), LV-HIT (n=21), or the control group (n=23). There were no difference in menstrual frequency at 12 months between LV-HIT and control (frequency-ratio 0·09, 95%CI 0·06-0·12), HV-HIT and control (frequency-ratio 0·07, 95%CI 0·05-0·10) or LV-HIT and HV-HIT (frequency-ratio 0·09, 95%CI 0·07-0·13). More participants became pregnant in the LV-HIT group (n=5, 33·3%) than in the control group (n=0, p=0·02). Interpretation: HIT did not improve menstrual frequency in women with PCOS, but significantly increased pregnancy rate. Trial Registration: The study was registered in ClinicalTrials.gov (NCT02419482). Funding Statement: The Liaison Committee for Education, Research and Innovation in Central Norway, Norwegian University of Science and Technology, Australian Catholic University. Declaration of Interests: All authors declare no competing interests. Ethics Approval Statement: Ethics approval was obtained from the Regional Committee for Medical and Health Research Ethics in Central Norway (REK-midt 2015/468) and the ACU Human Research Ethics Committee (2017-260H). The procedures for data entry, coding, and storage have been approved by the Regional Committee Medical Research Ethics in Central Norway. All participants were informed about the experimental protocol and potential risks verbally and in writing before providing their written informed consent.

Impact on Health-Related Quality of Life after Different Aerobic Exercise Programs in Physically Inactive Adults with Overweight/Obesity and Primary Hypertension: Data from the EXERDIET-HTA Study.

Primary hypertension (HTN) and obesity are associated with a worse health-related quality of life (QoL). This research was carried out to analyze the health-related QoL measurements in a physically inactive and obese population with HTN (n = 253) in comparison to a HEALTHY sample (n = 30), to determine the HTN sample changes in QoL following different (high-volume moderate-intensity continuous training, high-volume high-intensity interval training (HIIT), low-volume HIIT) 16-week supervised aerobic exercise training (ExT) programs compared to attention control, and to assess the differences in QoL variables between the different ExT programs. The SF-36 questionnaire was used to assess health-related QoL. At baseline, HTN showed lower scores (p < 0.05) in physical function (88.6 vs. 99.2), general health (63.3 vs. 82.4), vitality (58.2 vs. 68.7), social functioning (88.5 vs. 95.2), and mental health (76.1 vs. 81.8) compared to HEALTHY. Following intervention, all HTN subgroups showed higher (p < 0.05) vitality, but physical functioning and general health significantly improved only in the ExT groups, with even better values in general health for both HIIT subgroups. Only the low-volume HIIT showed positive changes (p < 0.05) in social functioning (∆ = 6.9%) and mental health (∆ = 6.4%) domains after the intervention. These results highlight the important role of supervised exercise in improving physical and psychological health.

The Effect of Exercise Intensity and Volume on Metabolic Phenotype in Patients with Metabolic Syndrome: A Randomized Controlled Trial.

Background: Moderate intensity continuous training (MICT) ameliorates dysmetabolism in patients with metabolic syndrome (MetS). The impact of low- (1HIIT) versus high-volume high-intensity interval training (4HIIT) versus MICT on central adiposity, insulin resistance, and atherogenic dyslipidemia in patients with MetS has not yet been reported. Methods: Twenty-nine patients with MetS according to International Diabetes Federation criteria (nine females, age 61 ± 5 years, body mass index 31.1 ± 3.7 kg/m2, waist circumference (WC) ♀ 102.2 ± 10.6 cm, ♂ 108.5 ± 8.6 cm) were randomized (1:1:1) to 16 weeks of (1) MICT (5 × 30 min/week, 35%-50% heart rate reserve (HRR), (2) 1HIIT (3 × 17 min/week incl. 4 min @80%-90% HRR), and (3) 4HIIT (3 × 38 min/week incl. 4 × 4 min @80%-90% HRR). Peak oxygen uptake (O2peak), WC and anthropometric/metabolic indices indicative of MetS, fasting glucose/insulin, Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), dyslipidemia, and respiratory exchange ratio (RER) at warm-up were quantified at baseline and study completion. Analysis of variance and paired t tests were used for statistical analysis. Analyses were performed after checking for parametric distribution. Results: There were no significant differences between groups in waist-to-height ratio (♀: Δ -0.10 ± -0.05, ♂: Δ -0.08 ± -0.06, P = 0.916), WC (♀: Δ -1.4 ± -0.1 cm, ♂: Δ 0.1 ± 0.9 cm, P = 0.590), fasting glucose (Δ -1.18 ± 16.7 μU/mL, P = 0.773), fasting insulin (Δ 0.76 ± 13.4 μU/mL, P = 0.509), HOMA-IR (Δ 0.55 ± 4.1, P = 0.158), atherogenic dyslipidemia [triglycerides (TAG) Δ -10.1 ± 46.9 mg/dL, P = 0.468, high-density lipoprotein cholesterol (HDL-C) Δ 1.5 ± 5.4, P = 0.665, TAG/HDL-C -0.19 ± 1.3, P = 0.502], O2peak (P = 0.999), or RER (P = 0.842). In the entire group, waist-to-height-ratio and O2peak significantly improved by a clinically meaningful amount (Δ 2.7 ± 0.9 mL/min/kg; P < 0.001) and RER at warm-up significantly decreased (Δ -0.03 ± 0.06, P = 0.039). Conclusion: In patients with MetS, there was no significant difference between HIIT, irrespective of volume, to MICT for improving exercise capacity or metabolic health.

Circulating and Adipose Tissue miRNAs in Women With Polycystic Ovary Syndrome and Responses to High-Intensity Interval Training.

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression post-transcriptionally. In women with polycystic ovary syndrome (PCOS), several miRNAs are differentially expressed compared to women without PCOS, suggesting a role for miRNAs in PCOS pathophysiology. Exercise training modulates miRNA abundance and is primary lifestyle intervention for women with PCOS. Accordingly, we measured the expression of eight circulating miRNAs selected a priori along with miRNA expression from gluteal and abdominal adipose tissue (AT) in 12 women with PCOS and 12 women matched for age and body mass index without PCOS. We also determined the miRNA expression “signatures” before and after high-intensity interval training (HIT) in 42 women with PCOS randomized to either: (1) low-volume HIT (LV-HIT, 10 × 1 min work bouts at maximal, sustainable intensity, n = 13); (2) high-volume HIT (HV-HIT, 4 × 4 min work bouts reaching 90–95% of maximal heart rate, n = 14); or (3) non-exercise control (Non-Ex, n = 15). Both HIT groups trained three times/week for 16 weeks. miRNAs were extracted from plasma, gluteal and abdominal AT, and quantified via a customized plate array containing eight miRNAs associated with PCOS and/or exercise training responses. Basal expression of circulating miRNA-27b (c-miR-27b), implicated in fatty acid metabolism, adipocyte differentiation and inflammation, was 1.8-fold higher in women with compared to without PCOS (P = 0.006) despite no difference in gluteal or abdominal AT miR-27b expression. Only the HV-HIT protocol increased peak oxygen uptake (VO2peak L/min; 9%, P = 0.008). There were no changes in body composition. In LV-HIT, but not HV-HIT, the expression of c-miR-27b decreased (0.5-fold, P = 0.007). None of the remaining seven circulating miRNAs changed in LV-HIT, nor was the expression of gluteal or abdominal AT miRNAs altered. Despite increased cardiorespiratory fitness, HV-HIT did not alter the expression of any circulating, gluteal or abdominal AT miRNAs. We conclude that women with PCOS have a higher basal expression of c-miR-27b compared to women without PCOS and that 16 weeks of LV-HIT reduces the expression of this miRNA in women with PCOS. Intense exercise training had little effect on the abundance of the selected miRNAs within subcutaneous AT depots in women with PCOS.

Optimizing the Interaction of Exercise Volume and Metformin to Induce a Clinically Significant Reduction in Metabolic Syndrome Severity: A Randomised Trial.

Insulin resistance is a central mediating factor of the metabolic syndrome (MetS), with exercise training and metformin proven antidotes to insulin resistance. However, when the two therapies are combined there is conflicting data regarding whether metformin blunts or improves exercise training-induced adaptations. The volume of exercise (duration, intensity, and frequency) on the interaction of exercise training and metformin has yet to be investigated. The aim of this study is therefore to explore the impact of a combination of different exercise volumes and metformin on MetS severity. This is a secondary analysis of data from one of the sites of the ‘Exercise in Prevention of Metabolic Syndrome’ (EX-MET) study. Ninety-nine adults with MetS were randomized into a 16-week exercise program completing either: (i) moderate-intensity continuous training (MICT) at 60–70% of peak heart rate (HRpeak) for 30 min/session (n = 34, 150 min/week); (ii) high-volume high-intensity interval training (HIIT) consisting of 4 × 4 min bouts at 85–95% HRpeak, interspersed with 3 min of active recovery at 50–70% HRpeak (n = 34, 38 min/session, 114 min/week); or (iii) low volume HIIT, 1 × 4 min bout of HIIT at 85–95% HRpeak (n = 31, 17 min/session, 51 min/week). Metformin intake was monitored and recorded throughout the trial. MetS severity was calculated as z-scores derived from MetS risk factors assessed at pre- and post-intervention. Sixty-five participants had complete pre- and post-intervention data for MetS z-score, of which 18 participants (28%) were taking metformin. Over the 16-week intervention, a similar proportion of participants clinically improved MetS severity (Δ ≥ −0.87) with metformin (8/18, 44%) or without metformin (23/47, 49%) (p = 0.75). While there were no between-group differences (p = 0.24), in those who did not take metformin low-volume HIIT had more likely responders (10/15, 67%) compared to MICT (6/16, 38%) and high-volume HIIT (7/16, 44%). In those taking metformin, there was a lower proportion of participants who clinically improved MetS severity following high-volume HIIT (1/6, 17%) compared to MICT (2/4, 50%) and low-volume HIIT (5/8, 63%), but with no between-group difference (p = 0.23). Moreover, in those who performed high-volume HIIT, there was a statistically significantly higher proportion (p = 0.03) of likely non-responders with improved MetS severity in participants taking metformin (4/6, 67%) compared to those not taking metformin (3/16, 19%). In individuals with MetS, the effect of high volume HIIT on MetS severity may be blunted in those taking metformin. These findings need to be confirmed in a larger study.

Effect of Different HIIT Protocols on the Glycemic Control and Lipids Profile in Men with type 2 diabetes: A Randomize Control Trial

Objective: : High intensity interval training (HIITs) can induce weight control, lowering blood pressure and beneficial effects on cardiovascular health in type 2 diabetic patients. The effect of different volumes of these exercises is unclear in type 2 diabetic patients. The aim of this study was to compare the effect of low volume and high volume of short-term intensive training on glycemic indexes of men with type 2 diabetes. Materials and Methods: Thirty type 2 diabetes male patients who were referred to Yazd diabetes research center (30 - 46 years old) were selected and randomly divided into 3 groups of low and high volume HIITs groups and control group. The intensity of the exercises in low volume was up to 110% and in high volume up to 80% of the maximum heart rate. The two training groups performed exercises 3 days of week for 8 weeks. Glycemic factors and lipids profile were measured before and after the last training session. Data were analyzed by covariance and paired T-test. Results: Low volume HIIT exercises significantly decreased the glucose ( P -value: 0.01), HbA1c ( P -value: 0.01), insulin ( P -value: 0.005), insulin resistance ( P -value: 0.001), and triglyceride ( P -value: 0.04). Low volume HIIT in the insulin resistance had a significant difference with the control group ( P -value: 0.04). High density lipoprotein in high volume group had a significant difference with the control group ( P -value: 0.021). Conclusion: Low-volume HIIT exercises can be a nonpharmacological approach to improving glycemic factors in type 2 diabetic patients.

High Intensity Interval Training (HIIT) Improves Cardiorespiratory Fitness (CRF) in Healthy, Overweight and Obese Adolescents: A Systematic Review and Meta-Analysis of Controlled Studies.

Background: High Intensity Interval Training (HIIT) is a sustainable and effective method for improving Cardiorespiratory Fitness (CRF) in adolescents. HIIT is proven to produce equal or greater improvements in CRF when compared to moderate intensity continuous exercise (MICE) in adolescents. Methods: The studies included were considered eligible if: (1) Participants were adolescents (11–18 years old); (2) Examined changes in CRF measured either directly or indirectly; (3) Included a non-exercising control group or MICE comparison group; (4) Participants were matched at enrolment; (5) Reported HIIT protocol information; (6) Provided HIIT intensity. A meta-analysis was conducted to determine the effect of HIIT on CRF. Meta-regression and moderator analyses were performed out to quantitatively examine moderators of protocol design on CRF improvements. Results: HIIT displays a moderate effect to improve CRF (g = 0.86, 95% CI 0.518–1.106, p < 0.001). Neither study duration (weeks), nor total or weekly accumulated HIIT volume (min) displayed any significant moderation effect on pooled improvement on CRF (p > 0.05). Conclusions: HIIT is an effective method to improve CRF in adolescents, irrespective of body composition. Notably, meta regression analysis identified that prolonged high volume HIIT programs are similarly effective to short term low volume HIIT programs. This becomes of particular interest for those involved in school curricula, where short HIIT exercise may provide a pragmatic adjunct to the health benefits of Physical Education (PE) lessons.

Effect of the Low or High Volume of High-Intensity Interval Training Protocols on the Leptin and Lipid Profile in Men with Type 2 Diabetes

Introduction: Sport activity leads to metabolic and physiological adaptations, which may have a beneficial role for diabetic patients. The purpose of this study was to compare the effects of low volume and high volume high-intensity interval training (HIIT) on serum leptin and some of the lipid profiles of type 2 diabetic men.&#x0D; Materials and Method: In this randomized clinical trial, 30 males with type 2 diabetes mellitus were divided into three groups of 10, including low volume and high volume HIIT and control groups. The low volume groups underwent intensive training for up to two minutes and a high volume group up to six minutes for 8 weeks. Blood lipid profile indicators were measured before and 48 hours after the last exercise session. The paired t-test, ANCOVA and LSD as a post hoc test were used to analyze the data.&#x0D; Results: There was a significant difference before and after 8 weeks of low-volume HIIT training at triglyceride (p = 0.049). However, there was no significant difference in serum leptin, cholesterol, LDL-C, and HDL-C in men with type 2 diabetes (p &gt; 0.05). ANCOVA only found a differences between groups on BMI (F2, 26 = 3.61, p = 0.041). Also, the post hoc in two by two comparisons of HDL showed that there was a significant difference between high volume HIIT and control groups (p = 0.021) and low volume and control group (p = 0.011). The HDL-C levels in HIIT training groups increased significantly compared to controls.&#x0D; Discussion: Considering other proven adaptations of HIIT training on triglyceride, HDL and improving glycemic indexes is a useful and safe training for type 2 diabetic patients. Therefore, needing a very short time for this training, metabolic, functional and physiological adaptations of HIIT training, along with other exercises are recommended to improve the condition and reduce the risk of cardiovascular disease and complications of type 2 diabetes&#x0D; &#x0D;

A Multi-Center Comparison of O2peak Trainability Between Interval Training and Moderate Intensity Continuous Training.

There is heterogeneity in the observed O2peak response to similar exercise training, and different exercise approaches produce variable degrees of exercise response (trainability). The aim of this study was to combine data from different laboratories to compare O2peak trainability between various volumes of interval training and Moderate Intensity Continuous Training (MICT). For interval training, volumes were classified by the duration of total interval time. High-volume High Intensity Interval Training (HIIT) included studies that had participants complete more than 15 min of high intensity efforts per session. Low-volume HIIT/Sprint Interval Training (SIT) included studies using less than 15 min of high intensity efforts per session. In total, 677 participants across 18 aerobic exercise training interventions from eight different universities in five countries were included in the analysis. Participants had completed 3 weeks or more of either high-volume HIIT (n = 299), low-volume HIIT/SIT (n = 116), or MICT (n = 262) and were predominately men (n = 495) with a mix of healthy, elderly and clinical populations. Each training intervention improved mean O2peak at the group level (P < 0.001). After adjusting for covariates, high-volume HIIT had a significantly greater (P < 0.05) absolute O2peak increase (0.29 L/min) compared to MICT (0.20 L/min) and low-volume HIIT/SIT (0.18 L/min). Adjusted relative O2peak increase was also significantly greater (P < 0.01) in high-volume HIIT (3.3 ml/kg/min) than MICT (2.4 ml/kg/min) and insignificantly greater (P = 0.09) than low-volume HIIT/SIT (2.5 mL/kg/min). Based on a high threshold for a likely response (technical error of measurement plus the minimal clinically important difference), high-volume HIIT had significantly more (P < 0.01) likely responders (31%) compared to low-volume HIIT/SIT (16%) and MICT (21%). Covariates such as age, sex, the individual study, population group, sessions per week, study duration and the average between pre and post O2peak explained only 17.3% of the variance in O2peak trainability. In conclusion, high-volume HIIT had more likely responders to improvements in O2peak compared to low-volume HIIT/SIT and MICT.

Effects of Different Dosages of Interval Training on Glycemic Control in People With Prediabetes: A Randomized Controlled Trial

High-intensity interval training (HIIT) has been used as an alternative to moderate-intensity exercise training. Research has shown that HIIT produces better effects on glycemic control and hence the cardiometabolic risk in prediabetes. This randomized controlled trial was conducted to compare the effect of low-volume HIIT (LV-HIIT) with high-volume HIIT (HV-HIIT) on A1C and fasting blood glucose (FBG) in overweight adults with prediabetes. The trial included 60 young adults with prediabetes (32 male, 28 female). Subjects were randomly assigned to one of three equal-sized groups (n = 20): an LV-HIIT group (10 × 1-minute intervals at an interval intensity of ∼90% HRmax on a treadmill separated by 1 minute of easy recovery, with total exercise of 25 minutes/session), an HV-HIIT group (4 × 4-minute intervals at 90% of HRmax with 3 minutes of active recovery at 70% of HRmax between intervals, with total exercise of 40 minutes/session), and a control group (no exercise intervention). Exercise programs consisted of 3 sessions/week for 12 successive weeks. All participants followed a low-calorie diet for the 12-week intervention period. A1C and FBG were measured before and at the end of the 12-week trial. There were statistically significant effects on A1C and FBG from both exercise interventions (P <0.05). LV-HIIT and HV-HIIT significantly reduced A1C and FBG; however, HV-HIIT yielded a greater reduction in A1C than LV-HIIT (26.07 vs. 14.50%) and in FBG (17.80 vs. 13.22%) after exercise training, respectively. HIIT was found to be effective for glycemic control in prediabetes, with HV-HIIT being more effective than LV-HIIT in reducing A1C, FBG, and progression to type 2 diabetes in young adults with prediabetes.

Comparison of Acute Physiological and Psychological Responses Between Moderate-Intensity Continuous Exercise and Three Regimes of High-Intensity Interval Training.

Olney, N, Wertz, T, LaPorta, Z, Mora, A, Serbas, J, and Astorino, TA. Comparison of acute physiological and psychological responses between moderate-intensity continuous exercise and three regimes of high intensity interval training. J Strength Cond Res 32(8): 2130-2138, 2018-High-intensity interval training (HIIT) elicits similar physiological adaptations as moderate-intensity continuous training (MICT) despite less time commitment. However, there is debate whether HIIT is more aversive than MICT. This study compared physiological and perceptual responses between MICT and 3 regimes of HIIT. Nineteen active adults (age = 24.0 ± 3.3 years) unfamiliar with HIIT initially performed ramp exercise to exhaustion to measure maximal oxygen uptake (V[Combining Dot Above]O2max) and determine workload for subsequent sessions, whose order was randomized. Sprint interval training (SIT) consisted of six 20-second bouts of "all-out" cycling at 140% of maximum watts (Wmax). Low-volume HIIT (HIITLV) and high-volume HIIT (HIITHV) consisted of eight 60-second bouts at 85% Wmax and six 2-minute bouts at 70% Wmax, respectively. Moderate-intensity continuous training consisted of 25 minutes at 40% Wmax. Across regimes, work was not matched. Heart rate (HR), V[Combining Dot Above]O2, blood lactate concentration (BLa), affect, and rating of perceived exertion (RPE) were assessed during exercise. Ten minutes postexercise, Physical Activity Enjoyment (PACES) was measured via a survey. Results revealed significantly higher (p ≤ 0.05) V[Combining Dot Above]O2, HR, BLa, and RPE in SIT, HIITLV, and HIITHV vs. MICT. Despite a decline in affect during exercise (p < 0.01) and significantly lower affect (p ≤ 0.05) during all HIIT regimes vs. MICT at 50, 75, and 100% of session duration, PACES was similar across regimes (p = 0.65), although it was higher in women (p = 0.03). Findings from healthy adults unaccustomed to interval training demonstrate that HIIT and SIT are perceived as enjoyable as MICT despite being more aversive.

Effects of different aerobic exercise programmes with nutritional intervention in sedentary adults with overweight/obesity and hypertension: EXERDIET-HTA study.

Background Both exercise training and diet are recommended to prevent and control hypertension and overweight/obesity. Purpose The purpose of this study was to determine the effectiveness of different 16-week aerobic exercise programmes with hypocaloric diet on blood pressure, body composition, cardiorespiratory fitness and pharmacological treatment. Methods Overweight/obese, sedentary participants ( n = 175, aged 54.0 ± 8.2 years) with hypertension were randomly assigned into an attention control group (physical activity recommendations) or one of three supervised exercise groups (2 days/week: high-volume with 45 minutes of moderate-intensity continuous training (MICT), high-volume and high-intensity interval training (HIIT), alternating high and moderate intensities, and low-volume HIIT (20 minutes)). All variables were assessed pre- and post-intervention. All participants received the same hypocaloric diet. Results Following the intervention, there was a significant reduction in blood pressure and body mass in all groups with no between-group differences for blood pressure. However, body mass was significantly less reduced in the attention control group compared with all exercise groups (attention control -6.6%, high-volume MICT -8.3%, high-volume HIIT -9.7%, low-volume HIIT -6.9%). HIIT groups had significantly higher cardiorespiratory fitness than high-volume MICT, but there were no significant between-HIIT differences (attention control 16.4%, high-volume MICT 23.6%, high-volume HIIT 36.7%, low-volume HIIT 30.5%). Medication was removed in 7.6% and reduced in 37.7% of the participants. Conclusions The combination of hypocaloric diet with supervised aerobic exercise 2 days/week offers an optimal non-pharmacological tool in the management of blood pressure, cardiorespiratory fitness and body composition in overweight/obese and sedentary individuals with hypertension. High-volume HIIT seems to be better for reducing body mass compared with low-volume HIIT. The exercise-induced improvement in cardiorespiratory fitness is intensity dependent with low-volume HIIT as a time-efficient method in this population. ClinicalTrials.gov Registration: NCT02283047.

High-intensity interval training and cardiac autonomic control in individuals with metabolic syndrome: A randomised trial

BackgroundInsulin resistance has been postulated to play a central role in the co-appearance of various cardiovascular disease risk factors constituting the metabolic syndrome (MetS). There is evidence that altered cardiac autonomic function (CAF) may precede the onset of insulin resistance. Exercise training has been shown to improve CAF in different populations, yet little is known regarding the exercise dose response for CAF. The aim of this study was to investigate the impact of different volumes of high-intensity interval training (HIIT) and traditional moderate-intensity continuous training (MICT) on CAF in participants with MetS. MethodsIndividuals with MetS (n=56) were randomised into the following 16-week training interventions: i) MICT (n=16, 30min at 60–70%HRpeak, 5×/week); ii) 4HIIT (n=19, 4×4min bouts at 85–95%HRpeak, interspersed with 3min of active recovery at 50–70%HRpeak, 3×/week); or iii) 1HIIT (n=21, 1×4min bout at 85–95%HRpeak, 3×/week). R-R interval recorded for 5min in a supine position at pre- and post-intervention was used to derive linear (SDNN, RMSSD, pNN50, LF, HF, LF/HF) and non-linear (SD1, SD2, Alpha1, Alpha2, SampEn) heart rate variability (HRV) indices as measures of CAF. Group×time interaction effects were examined (ANCOVA) and Eta squared (η2) interaction effect sizes calculated. ResultsWhile there were no significant between-group differences in CAF indices, there were small-to-medium group×time interaction effects on SDNN [F(2,52)=0.70, p=0.50, η2=0.02], RMSSD [F(2,52)=1.35, p=0.27, η2=0.03], HF power [F(2,52)=1.27, p=0.29, η2=0.03], SD1 [F(2,52)=0.47, p=0.63, η2=0.01], and SD2 [F(2,52)=0.41, p=0.67, η2=0.01]. The following represent the relative percentage increases across these variables for 4HIIT, MICT, and 1HIIT respectively (SDNN, +30%, +17%, 9%; RMSSD, +30%, +22%, −2%; HF power, +69%, +18%, +7%; SD1, +30%, +22%,-2%; SD2, +22%, +14%, 4%). ConclusionsThere were no significant between-group differences for the effects of exercise dose on CAF indices, however; high-volume HIIT demonstrated the greatest magnitude of effect for improving CAF in individuals with MetS.