Is interval training the magic bullet for fat loss? A systematic review and meta-analysis comparing moderate-intensity continuous training with high-intensity interval training (HIIT)

Influence of Acute and Chronic Exercise on Abdominal Fat Lipolysis: An Update

Exercise is a powerful and effective preventive measure against chronic diseases by increasing energy expenditure and substrate mobilization. Long-duration acute exercise favors lipid mobilization from adipose tissue, i.e., lipolysis, as well as lipid oxidation by skeletal muscles, while chronic endurance exercise improves body composition, facilitates diet-induced weight loss and long-term weight maintenance. Several hormones and factors have been shown to stimulate lipolysis in vitro in isolated adipocytes. Our current knowledge supports the view that catecholamines, atrial natriuretic peptide and insulin are the main physiological stimuli of exercise-induced lipolysis in humans. Emerging evidences indicate that contracting skeletal muscle can release substances capable of remote signaling to organs during exercise. This fascinating crosstalk between skeletal muscle and adipose tissue during exercise is currently challenging our classical view of the physiological control of lipolysis, and provides a conceptual framework to better understand the pleotropic benefits of exercise at the whole-body level.

Low-volume high-intensity interval training improves cardiometabolic health, work ability and well-being in severely obese individuals: a randomized-controlled trial sub-study

BACKGROUND

Obesity is associated with impaired health and lower work ability. Increased physical activity is a cornerstone in the treatment of obesity and related risk factors. Recently, high-intensity interval training (HIIT) has emerged as a popular exercise option. However, data regarding the effects on cardiometabolic health, perceived work ability and well-being in severely obese individuals are lacking.

METHODS

Sixty-five obese individuals with sedentary occupation (48.7 ± 9.9 years, BMI: 39.6 ± 7.1 kg/m2) were randomly allocated to an extremely time-efficient HIIT (5 × 1 min at 80-95% maximal heart rate on cycle ergometers, 2×/week for 12 weeks) or an inactive control group (CON). Both groups received nutritional counseling to support weight loss. Primary outcome was maximal oxygen uptake (VO2max), secondary outcomes were cardiometabolic risk indices, body composition, work ability index (WAI), quality of life (QoL, EQ-5D-5L-questionnaire) and perceived stress (PSQ-questionnaire).

RESULTS

Mean body weight reduction was 5.3 kg [95% confidence interval (95% CI) - 7.3 to - 3.3 kg] in the HIIT group (P < 0.001) and 3.7 kg (95% CI - 5.3 to - 2.1 kg) in CON (P < 0.001), respectively. Only the HIIT group showed significant (P < 0.001) changes in VO2max [+ 3.5 mL/kg/min (95% CI 2.5 to 4.6 mL/kg/min)], waist circumference [-7.5 cm (95% CI - 9.8 to - 5.1 kg)], mean arterial blood pressure [- 11 mmHg (95% CI - 14 to - 8 mmHg)], WAI [+ 3.0 points (95% CI 1.7 to 4.3 points)] and QoL [+ 10% (95% CI 5 to 16%)]. In CON, none of these parameters improved significantly.

CONCLUSIONS

Low-volume HIIT may induce significant improvements in cardiometabolic health, especially VO2max, WAI and well-being in obese individuals after only 12 weeks. Our results underpin the wide range of benefits on health and subjective measures through exercise that go well beyond simple weight loss through dietary restriction alone.

TRIAL REGISTRATION

ClinicalTrials.gov Id: NCT03306069. Registered 10 October 2017, https://clinicaltrials.gov/ct2/show/NCT03306069 .

High-Intensity Interval Training: Methodological Considerations for Interpreting Results and Conducting Research

In recent years, high-intensity interval training (HIIT) has gained prominence in the health and fitness area, becoming a worldwide trend. Given the positive results of HIIT, researchers have compared it with moderate-intensity continuous training (MICT). However, much of that research has presented methodological challenges. Therefore, the aim of this opinion article is to address an important risk of bias common in research comparing HIIT and MICT: the lack of equalisation among protocols. This limitation can be considered a risk of bias that limits the conclusions of many studies. Thus, it is necessary to achieve the equalisation of sessions in some way such as using equalisation by energy expenditure, by workload performed in the session, or by duration of the session.

Profile of blood pressure and glycemic responses after interval exercise in older women attending (in) a public health physical activity program

BACKGROUND

and purpose: Interval exercise causes a positive impact on health status. Our aim was to evaluate the effects of a feasible and low-cost interval exercise on blood pressure and glycemic responses in people with controlled systemic arterial hypertension.

METHODS

Thirteen women with hypertension (HG; age: 60.2 ± 2.8 years) and 11 without hypertension (CG; age: 54.4 ± 3.8 years) were recruited. Groups performed one session of interval exercise with elastic resistance (10 series of 1:1 min/effort:rest).

RESULTS

There were slight reductions of absolute systolic blood pressure values for HG at 10, 30, and 60 min (4, 9, and 8 mmHg, respectively) at post-compared to pre-exercise. Glycemia was reduced (respectively, 17.6%, 17.6%, 19.4%, and 23.1%; p < 0.05) at pre-exercise vs. 0 min and 10, 30, and 60 min post-exercise for the HG.

CONCLUSION

A single session of a feasible and low-cost interval exercise modifies and promotes significant clinical effects in blood pressure and glycemic levels in female older adults with and without hypertension.

Short-term interval exercise suppresses acylated ghrelin and hunger during caloric restriction in women with obesity

Caloric restriction is suggested to increase hunger, in part, through complex interactions of hormones and behavior that contribute to challenges in long-term weight loss. Although intense exercise may attenuate appetite, no data exist testing the effects of interval exercise (INT) during a low-calorie diet (LCD) on appetite regulation. We hypothesized that LCD+INT would favorably influence satiety when compared with an energy-deficit matched LCD in women with obesity. Twenty-six women with obesity (47.3±2.4 yrs; 37.3 ± 1.2 kg/m2) were randomized to either LCD (n = 13; mixed meals of ~1200 kcal/d) or LCD+INT (n = 13; 60 min/d of supervised interval exercise at 90% HRpeak for 3 min and 50% HRpeak for 3 min) for 2 weeks. An additional 350kcal (shake) was provided to LCD+INT individuals post-exercise to equate energy availability between groups. Total PYY, acylated ghrelin and des-ghrelin were measured at 0, 30 and 60 min of a 75g OGTT before and after the intervention. Visual analog scales were also administered at 0 and 120 min of the OGTT to assess appetite perception. Food logs were recorded prior to and during the intervention to ensure caloric intake compliance. Compared with pre-intervention conditions, both interventions decreased food intake (P = 0.001) and body fat (P < 0.01). There was no effect on fasting PYY, but both LCD and LCD+INT increased post-prandial PYY iAUC (P < 0.001) relative to pre-intervention. LCD+INT maintained fasting acylated ghrelin (P = 0.06) and suppressed post-prandial acylated ghrelin iAUC (P = 0.04) compared to LCD. Neither intervention impacted circulating des- ghrelin before or following the OGTT. Interestingly, LCD+INT attenuated fasting hunger and maintained fullness compared with LCD (P = 0.05 and P = 0.06, respectively). Taken together, interval exercise favors acylated ghrelin suppression and perception of hunger during a LCD in women with obesity.

H″IT″ting the Barriers for Exercising during Social Isolation

Aerobic exercise is traditionally recommended to improve general health and prevent many non-communicable diseases. However, the measures adopted to control the novel Coronavirus (COVID-19) outbreak culminated with closing of exercise facilities and fitness centers and, as a primary consequence, impaired aerobic exercise practice. This contributed to an increase in risk factors associated with physical inactivity such as insulin resistance, high blood pressure, low-grade inflammation, weight gain, and mental health problems. The scenario is worrisome, and it is important to propose alternatives for exercise practice during the COVID-19 pandemic. Interval training (IT) emerges as an exercise mode that might be feasible, low-cost, and potentially safe to be performed in many different places. IT consists of interspersing relative brief bouts of high-intensity exercise with recovery periods and promotes similar or greater health benefits when compared to moderate-intensity continuous exercise. Among the different types of IT, sprint interval training and "Tabata protocols" might be particularly useful during social isolation. These protocols can be controlled and performed without the need of complex equipment and can be adapted to different places, including domestic environments. In this article, we present variations of IT as possible alternatives to cope physical inactivity during COVID-19 pandemics with a focus on its practical applications. The protocols suggested can be performed without the need of specialized equipment or facilities, in a time-efficient manner, and aiming to prevent detraining or even improve physical fitness and general health.

Continuous walking and time- and intensity-matched interval walking: Cardiometabolic demand and post-exercise enjoyment in insufficiently active, healthy adults

We compared cardiometabolic demand and post-exercise enjoyment between continuous walking (CW) and time- and intensity-matched interval walking (IW) in insufficiently active adults. Sixteen individuals (13 females and three males, age 25.3 ± 11.1 years) completed one CW and one IW session lasting 30 min in a randomised-counterbalanced design. For CW, participants walked at a mean intensity of 65-70% predicted maximum heart rate (HR_max). For IW, participants alternated between 3 min at 80% HR_max and 2 min at 50% HR_max. Expired gas was measured throughout each protocol. Participants rated post-exercise enjoyment following each protocol. Mean HR and V˙O₂ showed small positive differences in IW vs. CW (2, 95%CL 0, 4 beat.min^-1; d = 0.23, 95%CL 0.06, 0.41 and 1.4, 95%CL 1.2 ml.kg^-1.min^-1, d = 0.36, 95%CL 0.05, 0.65, respectively). There was a medium positive difference in overall kcal expenditure in IW vs. CW (25, 95%CL 7 kcal, d = 0.58, 95%CL 0.33, 0.82). Post-exercise enjoyment was moderately greater following IW vs. CW (9.1, 95%CL 1.4, 16.8 AU, d = 0.62, 95%CL 0.06, 0.90), with 75% of participants reporting IW as more enjoyable. Interval walking elicits meaningfully greater energy expenditure and is more enjoyable than CW in insufficiently active, healthy adults.

Effects of exercise cessation on adipose tissue physiological markers related to fat regain: A systematic review

Tissues usually super compensate during the period that follow physical exercise. Although this is widely accepted for muscle and glycogen, the compensatory effect is not usually applied to fat tissues. Notwithstanding, evidence for this has been present since the 1970s when it was first suggested that the increased lipogenic activity in response to training might be an adaptation that enables to restore an energy reserve that can be used in times of need. In this context, the present review aimed to summarize information about the effect of detraining on fat metabolism and the physiological responses associated with fat regain. A systematic search on PubMed and Scielo was performed using "training cessation," "detraining," "exercise detraining," and "exercise cessation" combined with "fat tissue," "adipose tissue," "adipose metabolism," and "fat metabolism," as descriptors. From 377 results, 25 were included in this review, 12 humans and 13 rodents, resulting in a sample of 6772 humans and 613 animals. The analysis provided evidence for fat super compensation, as well as differences in humans and rodents, among different protocols and possible mechanisms for fat gain after exercise cessation. In summary, exercise cessation appears to increase the ability of the adipose tissue to store energy. However, caution should be taken, especially regarding conclusions based on investigations on humans, considering the multiple factors that could affect fat metabolism.

Increasing Exercise Intensity: Teaching High-Intensity Interval Training to Individuals with Developmental Disabilities Using a Lottery Reinforcement System

Rates of overweight and obesity are above 70% in typically developing adults in the United States, with higher rates observed in individuals diagnosed with developmental disability (DD). Lottery reinforcement systems have been validated as effective exercise interventions for individuals with DD. Although high-intensity interval training (HIIT) has demonstrated health benefits, it has not been studied using individuals within this population. The purpose of this study was to implement a lottery reinforcement system to systematically increase heart rate (HR) during 30-min HIIT sessions with 3 adults with DD. Results demonstrated increases in HR from below to within the prescribed range in all 3 participants. For 1 participant, weight decreased by 10.8 pounds during the 9-week program. Implications include that lottery systems increase exercise intensity with adults with DD, that HR during exercise can be reliably controlled using a lottery system, and that similar programs may result in health benefits.

Effects of short-term high-intensity interval and continuous exercise training on body composition and cardiac function in obese sarcopenic rats

AIM

We investigated the effects of high-intensity interval and continuous short-term exercise on body composition and cardiac function after myocardial ischemia-reperfusion injury (IRI) in obese rats.

METHODS

Rats fed with a standard chow diet (SC) or high-fat diet (HFD) for 20 weeks underwent systolic blood pressure (SBP), glycemia and dual-energy X-ray absorptiometry analyses. Then, animals fed with HFD were subdivided into three groups: sedentary (HFD-SED); moderate-intensity continuous training (HFD-MICT); and high-intensity interval training (HFD-HIIT). Exercised groups underwent four isocaloric aerobic exercise sessions, in which HFD-MICT maintained the intensity continuously and HFD-HIIT alternated it. After exercise sessions, all groups underwent global IRI and myocardial infarct size (IS) was determined histologically. Fat and muscle mass were weighted, and protein levels involved in muscle metabolism were assessed in skeletal muscle.

RESULTS

HFD-fed versus SC-fed rats reduced lean body mass by 31% (P < 0.001), while SBP, glycemia and body fat percentage were increased by 10% (P = 0.04), 30% (P = 0.006) and 54% (P < 0.001); respectively. HFD-induced muscle atrophy was restored in exercised groups, as only HFD-SED presented lower gastrocnemius (32%; P = 0.001) and quadriceps mass (62%; P < 0.001) than SC. PGC1-α expression was 2.7-fold higher in HFD-HIIT versus HFD-SED (P = 0.04), whereas HFD-HIIT and HFD-MICT exhibited 1.7-fold increase in p-mTOR^Ser2481 levels compared to HFD-SED (P = 0.04). Although no difference was detected among groups for IS (P = 0.30), only HFD-HIIT preserved left-ventricle developed pressure after IRI (+0.7 mmHg; P = 0.9).

SIGNIFICANCE

Short-term exercise, continuous or HIIT, restored HFD-induced muscle atrophy and increased mTOR expression, but only HIIT maintained myocardial contractility following IRI in obese animals.

Is It Time to Rethink Our Weight Loss Paradigms?

Strategies aiming to promote weight loss usually include anything that results in an increase in energy expenditure (exercise) or a decrease in energy intake (diet). However, the probability of losing weight is low and the probability of sustained weight loss is even lower. Herein, we bring some questions and suggestions about the topic, with a focus on exercise interventions. Based on the current evidence, we should look at how metabolism changes in response to interventions instead of counting calories, so we can choose more efficient models that can account for the complexity of human organisms. In this regard, high-intensity training might be particularly interesting as a strategy to promote fat loss since it seems to promote many physiological changes that might favor long-term weight loss. However, it is important to recognize the controversy of the results regarding interval training (IT), which might be explained by the large variations in its application. For this reason, we have to be more judicious about how exercise is planned and performed and some factors, like supervision, might be important for the results. The intensity of exercise seems to modulate not only how many calories are expended after exercise, but also where they came from. Instead of only estimating the number of calories ingested and expended, it seems that we have to act positively in order to create an adequate environment for promoting healthy and sustainable weight loss.

Cardiovascular Remodeling Experienced by Real-World, Unsupervised, Young Novice Marathon Runners

Aims

Marathon running is a popular ambition in modern societies inclusive of non-athletes. Previous studies have highlighted concerning transient myocardial dysfunction and biomarker release immediately after the race. Whether this method of increasing physical activity is beneficial or harmful remains a matter of debate. We examine in detail the real-world cardiovascular remodeling response following competition in a first marathon.

Methods

Sixty-eight novice marathon runners (36 men and 32 women) aged 30 ± 3 years were investigated 6 months before and 2 weeks after the 2016 London Marathon race in a prospective observational study. Evaluation included electrocardiography, cardiopulmonary exercise testing, echocardiography, and cardiovascular magnetic resonance imaging.

Results

After 17 weeks unsupervised marathon training, runners revealed a symmetrical, eccentric remodeling response with 3-5% increases in left and right ventricular cavity sizes, respectively. Blood pressure (BP) fell by 4/2 mmHg (P < 0.01) with reduction in arterial stiffness, despite only 11% demonstrating a clinically meaningful improvement in peak oxygen consumption with an overall non-significant 0.4 ml/min/kg increase in peak oxygen consumption (P = 0.14).

Conclusion

In the absence of supervised training, exercise-induced cardiovascular remodeling in real-world novice marathon runners is more modest than previously described and occurs even without improvement in cardiorespiratory fitness. The responses are similar in men and women, who experience a beneficial BP reduction and no evidence of myocardial fibrosis or persistent edema, when achieving average finishing times.

Cardiorespiratory fitness and accelerometer-determined physical activity following one year of free-living high-intensity interval training and moderate-intensity continuous training: a randomized trial

Background

Free-living adherence to high-intensity interval training (HIIT) has not been adequately tested. This randomized trial examined changes in cardiorespiratory fitness (CRF) and accelerometer-measured purposeful physical activity over 12 months of free-living HIIT versus moderate-intensity continuous training (MICT).

Methods

Ninety-nine previously low-active participants with overweight/obesity were randomly assigned to HIIT (n = 47) or MICT (n = 52). Both interventions were combined with evidence-based behaviour change counselling consisting of 7 sessions over 2 weeks. Individuals in HIIT were prescribed 10 X 1-min interval-based exercise 3 times per week (totalling 75 min) whereas individuals in MICT were prescribed 150 min of steady-state exercise per week (50 mins 3 times per week). Using a maximal cycling test to exhaustion with expired gas analyses, CRF was assessed at baseline and after 6 and 12 months of free-living exercise. Moderate-to-vigorous physical activity of 10+ minutes (MVPA10+) was assessed by 7-day accelerometry at baseline, 3, 6, 9, and 12 months. Intention to treat analyses were conducted using linear mixed models.

Results

CRF was improved over the 12 months relative to baseline in both HIIT (+ 0.15 l/min, 95% CI 0.08 to 0.23) and MICT (+ 0.11 l/min, 95% CI 0.05 to 0.18). Both groups improved 12-month MVPA10+ above baseline (HIIT: + 36 min/week, 95% CI 17 to 54; MICT: + 69 min/week, 95% CI 49 to 89) with the increase being greater (by 33 min, 95% CI 6 to 60) in MICT (between group difference, P = 0.018).

Conclusion

Despite being prescribed twice as many minutes of exercise and accumulating significantly more purposeful exercise, CRF improvements were similar across 12 months of free-living HIIT and MICT in previously low-active individuals with overweight/obesity.

A systematic review and meta-analysis of affective responses to acute high intensity interval exercise compared with continuous moderate- and high-Intensity exercise

There is evidence for the physical health benefits of high intensity interval exercise (HIIE), but its public health potential has been challenged. It is purported that compared with moderate-intensity continuous exercise (MICE) the high intensity nature of HIIE may lead to negative affective responses. This systematic review (PROSPERO CRD42017058203) addressed this proposition and synthesised research that compares affective responses to HIIE with MICE and vigorous intensity continuous exercise (VICE), during-, end-, and post-exercise. Searches were conducted on five databases, and findings from 33 studies were meta-analysed using random effects models or narratively synthesised. A meta-analysis of affect showed a significant effect in favour of MICE vs HIIE at the lowest point, during and post-exercise, but not at end, and the narrative synthesis supported this for other affective outcomes. Differences on affect between VICE vs HIIE were limited. Pooled data showed arousal levels were consistently higher during HIIE. For enjoyment there was a significant effect in favour of HIIE vs MICE, no difference for HIIE vs VICE at post-exercise, and mixed findings for during-exercise. Although the findings are clouded by methodological issues they indicate that compared to MICE, HIIE is experienced less positively but post-exercise is reported to be more enjoyable.

Effects of high vs moderate-intensity intermittent training on functionality, resting heart rate and blood pressure of elderly women

BACKGROUND

The present study compared the effects of training and detraining periods of high-intensity interval training (HIIT), moderate-intensity interval training (MIIT) and moderate-intensity continuous training (MICT) on functional performance, body composition, resting blood pressure and heart rate in elderly women nursing home residents.

METHODS

Forty-six volunteers (age, 80.8 ± 5.2 y; body mass, 69.8 ± 5.2 kg, height, 164.2 ± 4.12 cm) were divided into groups that performed treadmill exercise twice-weekly HIIT (4 bouts of 4-min intervals at 85-95% of the maximal heart rate [HRmax], interspersed by 4 min at 65% HRmax), MIIT (4 bouts of 4 min intervals at 55-75% HRmax, interspersed by 4 min at 45-50% HRmax) and MICT (30-min at 55-75% HRmax). Tests were performed before and after 8 weeks of training and 2 and 4 weeks of detraining. ANCOVA was used to analyze dependent variable changes.

RESULTS

After 8 weeks HIIT promoted greater reductions in body mass (HIIT = - 1.6 ± 0.1 kg; MICT = - 0.9 ± 0.1 kg; MIIT = - 0.9 ± 0.1 kg; p = 0.001), fat mass (HIIT = - 2.2 ± 0.1%; MICT = - 0.7 ± 0.1%; MIIT = - 1.2 ± 0.1%; p < 0.001) and resting heart rate (HIIT = - 7.3 ± 0.3%; MICT = - 3.6 ± 0.3%; MIIT = - 5.1 ± 0.3%; p < 0.001) and greater improvement in the chair stand test (HIIT = 3.4 ± 0.1 reps; MICT = 2.5 ± 0.1 reps; MIIT = 3.1 ± 0.1 reps; p < 0.001) when compared to MIIT and MICT. These improvements were sustained after 2 and 4 weeks of detraining only in the HIIT group.

CONCLUSION

HIIT promoted greater benefits for body composition and functional performance than MICT and MIIT and also showed less pronounced effects of detraining. This suggests that the intensity of physical exercise is an important factor to consider when prescribing exercise to the elderly.

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.

Psychological Responses to High-Intensity Interval Training: A Comparison of Graded Walking and Ungraded Running at Equivalent Metabolic Loads

High-intensity interval training (HIIT) is highly beneficial for health and fitness and is well tolerated. Treadmill-based HIIT normally includes running interspersed with walking. The purpose of this study was to compare ungraded running and graded walking HIIT on perceived exertion, affective valence, and enjoyment. Thirty-four active, healthy adults completed maximal testing and two 20-min HIIT trials alternating between 85% of VO2peak and a comfortable walking speed. Affective valence, enjoyment, and perceived exertion, both overall (ratings of perceived exertion [RPE]-O) and legs only (RPE-L), were measured. RPE-O and affective valence were similar between HIIT trials (p > .05), RPE-L was higher for walk HIIT (p < .05), and enjoyment was higher for run HIIT (p < .05). Findings indicate that both walk and run HIIT produce exertion, affective, and enjoyment responses that are positive and possibly supportive of exercise behavior. Walk HIIT may be desirable for individuals who are unable or do not want to run.

Mechanistic and methodological perspectives on the impact of intense interval training on post-exercise metabolism

The post-exercise recovery period is associated with an elevated metabolism known as excess post-exercise oxygen consumption (EPOC). The relationship between exercise duration and EPOC magnitude is thought to be linear whereas the relationship between EPOC magnitude and exercise intensity is thought to be exponential. Accordingly, near-maximal and supramaximal protocols such as high-intensity interval training (HIIT) and sprint interval training (SIT) protocols have been hypothesized to produce greater EPOC magnitudes than submaximal moderate-intensity continuous training (MICT). This review updates previous reviews by focusing on the impact of HIIT and SIT on EPOC. Research to date suggests small differences in EPOC post-HIIT compared to MICT in the immediate (<1 hour) recovery period, but greater EPOC values post-HIIT when examined over 24 hours. Conversely, differences in EPOC post-SIT are more pronounced, as SIT tends to produce a larger EPOC vs MICT at all time points. We discuss potential mechanisms that may drive the EPOC response to interval training (eg, glycogen resynthesis, mitochondrial uncoupling, and protein turnover among others) and also consider the role of EPOC as one of the potential contributors to fat loss following HIIT/SIT interventions. Lastly, we highlight a number of methodological shortcomings related to the measurement of EPOC following HIIT and SIT.

A Qualitative Analysis of an Aerobic Interval Training Programme for Obese Outpatients Carried Out in a Hospital Context

Purpose: To describe the experience of obese adults following participation in an indoor aerobic interval training (AIT) intervention. Methodology: Qualitative, in-depth semi-structured individual interviews, using phenomenology, with 24 obese adults (body mass index (BMI) ≥30 kg/m²) from the Endocrinology Department, at the Severo Ochoa Hospital in Leganés (Madrid). Questions were related to: (a) The physical activity (PA) programme, (b) their perspectives of the activity and exercise environment and (c) the perceived benefits from participation. Data were analysed with a constant comparison approach. Results: The main patients' reasons for beginning the programme were motivations to take part including weight loss, health improvement and doctors' recommendation. Also, patients showed doubts and feelings of apprehension at the beginning of the intervention. Patients highlighted the role of the instructor, feelings of exercising in a safe environment, a good intervention and accessibility of the facility. They reported an improvement in their quality of life and recommended continuing the program. Conclusions: (1) Common themes in the qualitative analysis included enjoyment of the activity and a desire to maintain physical fitness, (2) AIT was perceived as a suitable exercise programme for this population and (3) recommendations for further investigation to understand the role of PA programmes for people with obesity.

Exercise-Induced Adaptations to Adipose Tissue Thermogenesis

Exercise training results in beneficial adaptations to numerous tissues and offers protection against metabolic disorders including obesity and type 2 diabetes. Multiple studies have indicated that both white (WAT) and brown (BAT) adipose tissue may play an important role to mediate the beneficial effects of exercise. Studies from both rodents and humans have identified exercise-induced changes in WAT including increased mitochondrial activity and glucose uptake, an altered endocrine profile, and in rodents, a beiging of the WAT. Studies investigating the effects of exercise on BAT have resulted in conflicting data in terms of mitochondrial activity, glucose uptake, and thermogenic activity in rodents and humans, and remain an important area of investigation. This review discusses the exercise-induced adaptations to white and brown adipose tissue, distinguishing important differences between rodents and humans and highlighting the latest studies in the field and their implications.

Cardiorespiratory fitness and muscular endurance responses immediately and 2 months after a whole-body Tabata or vigorous-intensity continuous training intervention

Young adults (52 females, 16 males; age = 21 ± 3 years; V̇O_2peak: 41 ± 6 mL/(kg·min)) were randomized into 3 groups: (i) no-exercise control (CTL; n = 15), (ii) Tabata (n = 27), or (iii) vigorous-intensity continuous training (VICT; n = 26) groups for a 4-week supervised training period (4 sessions/week). V̇O_2peak, time-to-fatigue (TTF), 5 km time-trial performance (TT), and muscular endurance were assessed at baseline, post-training (POST), and 2-month follow-up (FU). Response confidence intervals (CI) were used to classify individuals as likely responders (R; CI > 0). Both exercise interventions increased TTF and TT at POST (both p < 0.01), but these benefits were maintained at FU after VICT only (p < 0.01). Push-up performance was increased at POST and FU (both p < 0.01) after Tabata. VICT resulted in a greater proportion of TTF R versus both groups at POST (CTL: 1/15; VICT: 19/26; Tabata: 9/27) and versus Tabata at FU (3/15; 13/26; 4/27). VICT also had a greater proportion of TT R versus CTL at POST (2/15; 17/26; 10/27). Tabata had a greater proportion of R for maximum push-up repetitions versus both groups at POST (3/15; 6/26; 18/27) and versus CTL at FU (2/15; 10/26; 18/27). Collectively, VICT appears to be more effective for improving cardiorespiratory fitness, whereas whole-body Tabata confers larger improvements in push-up performance following short-term training. Novelty: Vigorous-intensity continuous training elicits larger improvements in cardiorespiratory fitness versus whole-body Tabata. Individual response profiles parallel group-level changes in cardiorespiratory fitness and muscular endurance.

Acute p-synephrine ingestion increases whole-body fat oxidation during 1-h of cycling at Fatmax

PURPOSE

p-Synephrine, the principal alkaloid of bitter orange (Citrus aurantium), is widely used in dietary supplements for weight loss due to its purported effect of increasing fat oxidation. However, there is a paucity of scientific information about its effectiveness in enhancing fat oxidation during exercise. The aim of this investigation was to determine the effect of an acute dose of p-synephrine on substrate oxidation during prolonged and constant intensity exercise.

METHODS

In a double-blind and randomized experiment, 14 healthy subjects performed two acute experimental trials after ingesting either p-synephrine (3 mg kg^-1) or a placebo (cellulose). Energy expenditure and fat oxidation rates were continuously measured by indirect calorimetry during 1 h of continuous cycling at Fatmax, the intensity that induces maximal fat oxidation rate.

RESULTS

In comparison to the placebo, energy expenditure during 1 h of cycling remained unchanged with p-synephrine (698 ± 129 vs. 686 ± 123 kcal, P = 0.08). However, p-synephrine increased whole-body fat oxidation (33.6 ± 10.4 vs. 37.3 ± 9.8 g, P < 0.01) while also reducing carbohydrate oxidation (99.5 ± 30.4 vs. 85.0 ± 28.4 g, P < 0.01). However, the magnitude of the shift on substrate oxidation induced by p-synephrine was small.

CONCLUSION

Acute ingestion of p-synephrine augments fat oxidation during prolonged and constant-intensity exercise.

Beer or Ethanol Effects on the Body Composition Response to High-Intensity Interval Training. The BEER-HIIT Study

High-intensity interval training (HIIT) is promoted as a time-efficient strategy to improve body composition but concomitant beer intake, which is common among physically active individuals, may interfere with these effects. The primary aim of this study is to determine the effects of a 10-week (2 days/week) HIIT program on anthropometric and body composition measurements, and to assess whether those effects are influenced by the moderate consumption of beer (at least 5 days/week), or its alcohol equivalent. Young (24 ± 6 years old) healthy adults (n = 72, 35 females) volunteered for a non-training group (Non-Training group) or for HIIT training. Those going for training choose whether they preferred to receive alcohol or not. Those choosing alcohol were randomly allocated for receiving beer (5.4%; T-Beer group) or the equivalent amount of alcohol (vodka; T-Ethanol group) in sparkling water. Those choosing no-alcohol were randomly allocated for receiving alcohol-free beer (0.0%; T-0.0Beer group) or sparkling water (T-Water group). From Monday through Friday, men ingested 330 mL of the beverage with lunch and 330 mL with dinner; women ingested 330 mL with dinner. Before and after the intervention, anthropometry and body composition, through dual-emission X-ray absorptiometry, were measured. No changes in body mass, waist circumference, waist/hip ratio, visceral adipose tissue or bone mineral density occurred in any of the groups. By contrast, in all the training groups, significant decreases in fat mass together with increases in lean mass (all p < 0.05) occurred. These positive effects were not influenced by the regular intake of beer or alcohol. In conclusion, a moderate beer intake does not blunt the positive effect of 10-week HIIT on body composition in young healthy adults.

Long-term effects of high-intensity resistance and endurance exercise on plasma leptin and ghrelin in overweight individuals: the RESOLVE Study

The objective of this study was to evaluate the effects of high-intensity resistance and endurance exercise on body composition and plasma leptin and ghrelin concentrations in overweight individuals. One hundred participants were randomly assigned to 3 exercise interventions: high-resistance-low-aerobic exercise (Re), low-resistance-high-aerobic exercise (rE), low-resistance-low-aerobic exercise (re). Interventions began with 3 weeks of residential supervision (phase 1) after which participants had to manage the physical activity programs individually (phase 2). Body composition and plasma variables were measured at baseline and after phase 1 as well as after 3, 6, and 12 months. Significant decreases in body weight and fat were observed after phase 1 (p < 0.001) and continued at a lower rate for up to 3 months and then remained stable for the rest of the protocol. Once a body weight plateau was reached, body fat loss after the Re and rE conditions exceeded the fat loss observed in the re condition by 1.5-2 kg (p < 0.05). Leptin was significantly decreased after day 21 and month 3 (p < 0.001) and remained stable for the rest of the study. Ghrelin was significantly increased after day 21 and month 3 (p < 0.001) and returned to a level comparable to baseline between month 6 and 12 when body weight and fat had reached a plateau. In conclusion, this study reinforces the idea that an increase in exercise intensity may accentuate body fat loss before the occurrence of a body weight plateau. Resistance to further fat loss was accompanied by a decrease in plasma leptin and an increase in plasma ghrelin.

Interval Training Improves Depressive Symptoms But Not Anxious Symptoms in Healthy Women

Background: Despite important advances in the relationship between exercise and mood disorders, especially regarding moderate-intensity continuous training, there is a lack of information about the chronic effects of interval training protocols. We compared the effects of two different interval training protocols [sprint interval training (SIT) and high-intensity interval training (HIIT)] on depressive and anxious symptoms in healthy women. Methods: Thirty-six women were randomly allocated to HIIT (n = 18) or SIT (n = 18) groups and performed 24 training sessions over 8 weeks (thrice a week). Levels of state-trait anxiety and depressive symptoms were evaluated using State-Trait Anxiety Inventory and Beck Depression Inventory, respectively, before and after training intervention. Results: Two-way analysis of variance (ANOVA) did not reveal a significant effect of time (p > 0.05), group intervention (p > 0.05), or time × group interaction (p > 0.05) on state-trait anxiety; however, two-way ANOVA showed a significant effect of time on depressive symptoms (p = 0.025) but not group effect (p = 0.548) or time × group interaction (p = 0.373). Depressive symptoms of the participants in both HIIT and SIT groups were reduced from baseline, (Δ_HIIT) -17.5 ± 27.9% and (Δ_SIT) -28.6 ± 47.5%, respectively. Conclusion: HIIT and SIT groups similarly improved depressive symptoms but not anxiety levels in healthy and physically active young adult women.