Interval Training for Cardiometabolic Health: Why Such A HIIT?

Characteristics of physical activity during beginner-level group tennis lessons and the effect daily activity

Tennis is a popular leisure sport, and studies have indicated that playing tennis regularly provides many health benefits. We aimed to clarify the characteristics of physical activity during beginner-level group tennis lessons and daily physical activity of the participants. Physical activity was measured using an accelerometer sensor device for four weeks, including the 80-min duration tennis lessons held twice a week. Valid data were categorized for tennis and non-tennis days. The mean physical activity intensity during the tennis lesson was 3.37 METs. The mean ratio of short-bout rest periods to the tennis lesson time in 90 and 120 s was 7% and 4%, respectively. The mean physical activity intensity was significantly higher (p < 0.0001) and the duration of vigorous-intensity physical activity (VPA) was increased in 76% of participants on days with tennis lessons compared to without tennis lessons. Beginner-level tennis lesson has characteristics of less short-bout rest physical activity than previously reported competitive tennis match and increased the duration of VPA in daily activity compared to without tennis lessons, suggesting that beginner-level tennis lessons contribute physical activity of health benefits.

Both moderate- and high-intensity exercise training increase intramyocellular lipid droplet abundance and modify myocellular distribution in adults with obesity

Exercise training modifies lipid metabolism in skeletal muscle, but the effect of exercise training on intramyocellular lipid droplet (LD) abundance, size, and intracellular distribution in adults with obesity remains elusive. This study compared high-intensity interval training (HIIT) with more conventional moderate-intensity continuous training (MICT) on intramyocellular lipid content, as well as LD characteristics (size and number) and abundance within the intramyofibrillar (IMF) and subsarcolemmal (SS) regions of type I and type II skeletal muscle fibers in adults with obesity. Thirty-six adults with obesity [body mass index (BMI) = 33 ± 3 kg/m2] completed 12 wk (4 days/wk) of either HIIT (10 × 1 min, 90% HRmax + 1-min active recovery; n = 19) or MICT (45-min steady-state exercise, 70% HRmax; n = 17), while on a weight-maintaining diet throughout training. Skeletal muscle biopsies were collected from the vastus lateralis before and after training, and intramyocellular lipid content and intracellular LD distribution were measured by immunofluorescence microscopy. Both MICT and HIIT increased total intramyocellular lipid content by more than 50% (P < 0.01), which was attributed to a greater LD number per µm2 in the IMF region of both type I and type II muscle fibers (P < 0.01). Our findings also suggest that LD lipophagy (autophagy-mediated LD degradation) may be transiently upregulated the day after the last exercise training session (P < 0.02 for both MICT and HIIT). In summary, exercise programs for adults with obesity involving either MICT or HIIT increased skeletal muscle LD abundance via a greater number of LDs in the IMF region of the myocyte, thereby providing more lipid in close proximity to the site of energy production during exercise.NEW & NOTEWORTHY In this study, 12 wk of either moderate-intensity continuous training (MICT) or high-intensity interval training (HIIT) enhanced skeletal muscle lipid abundance by increasing lipid droplet number within the intramyofibrillar (IMF) region of muscle. Because the IMF associates with high energy production during muscle contraction, this adaptation may enhance lipid oxidation during exercise. Despite differences in training intensity and energy expenditure between MICT and HIIT, their effects on muscle lipid abundance and metabolism were remarkably similar.

Exercise-induced skeletal muscle angiogenesis: impact of age, sex, angiocrines and cellular mediators

Exercise-induced skeletal muscle angiogenesis is a well-known physiological adaptation that occurs in humans in response to exercise training and can lead to endurance performance benefits, as well as improvements in cardiovascular and skeletal tissue health. An increase in capillary density in skeletal muscle improves diffusive oxygen exchange and waste extraction, and thus greater fatigue resistance, which has application to athletes but also to the general population. Exercise-induced angiogenesis can significantly contribute to improvements in cardiovascular and metabolic health, such as the increase in muscle glucose uptake, important for the prevention of diabetes. Recently, our understanding of the mechanisms by which angiogenesis occurs with exercise has grown substantially. This review will detail the biochemical, cellular and biomechanical signals for exercise-induced skeletal muscle angiogenesis, including recent work on extracellular vesicles and circulating angiogenic cells. In addition, the influence of age, sex, exercise intensity/duration, as well as recent observations with the use of blood flow restricted exercise, will also be discussed in detail. This review will provide academics and practitioners with mechanistic and applied evidence for optimising training interventions to promote physical performance through manipulating capillarisation in skeletal muscle.

Effect of supervised sprint interval training on cardiorespiratory fitness and body composition in adolescent boys with obesity

This study examined the effect of a supervised 12-week sprint interval training (SIT) on cardiorespiratory fitness (CRF) and body composition in adolescent boys with obesity. Twenty-eight adolescents with obesity were allocated to either an intervention group (SIT) (13.1 ± 0.3 yrs; body mass index [BMI]: 30.3 ± 0.9 kg.m^-2) or a control group (CONT) (13.7 ± 0.4 yrs; BMI: 32.6 ± 1.6 kg.m^-2). The SIT group performed 4-6 × 30s "all-out" cycling bouts, interspersed with 4 min of recovery 3 days a week for 12 weeks. CRF was measured by direct peak oxygen consumption (VO₂peak) defined as VO₂peak per kg of body mass (mL.min^-1kg^-1) or by VO₂peak per kg of lean body mass (mL.min^-1LBM^-1) and body composition was assessed by dual-energy X-ray absorptiometry. SIT intervention led to a significant and large between-group difference in VO₂peak (p = 0.004; η² = 0.29). Although SIT group had a significant reduction in body fat percentage (BF%) (from 41.1 ± 1.3% to 39.2 ± 1.5%; p = 0.006), there were no between-group differences in the change of the pre- and post-measures in BF% (p = 0.067). In conclusion, 12-week SIT is effective in increasing CRF and decreasing BF% in adolescent boys with obesity.

Effect of a Low-Carbohydrate Diet With or Without Exercise on Anxiety and Eating Behavior and Associated Changes in Cardiometabolic Health in Overweight Young Women

Background

The effectiveness of low-carbohydrate diets (LCDs) on weight loss and exercise for improving cardiometabolic fitness have been well documented in the literature, but the effects of LCDs and whether adding exercise to a LCD regime could additionally benefit mental health (e. g., by lowering the level of anxiety) and associated changes in eating behavior are less clear in overweight and obese populations. Therefore, this study aimed to investigate the effects of a 4-week LCD with or without exercise on anxiety and eating behavior, and to explore the associations between changes in the psychological state and physiological parameters (i.e., body composition, aerobic fitness, blood pressure, lipid profile, and metabolic hormones).

Methods

Seventy-four overweight Chinese women [age: 20.8 ± 3.0 years, body mass index (BMI): 25.3 ± 3.3 kg·m-2] completed the 4-week randomized controlled trial, which included a LCD group (i.e., ~50 g daily carbohydrate intake) with exercise training 5 days/week (LC-EXE, n = 26), a LCD group without exercise training (LC-CON, n = 25) and a control group that did not modify their habitual diets and physical activity (CON, n = 23). Levels of anxiety, eating behavior scores and physiological parameters (i.e., body weight, V̇O2peak, blood pressure, fasting glucose, blood lipids, and serum metabolic hormones including insulin, C-peptide, leptin, and ghrelin) were measured before and after the intervention.

Results

There were significant reductions in anxiety levels in the LC-EXE compared with the LC-CON group, while no statistical changes were found in eating behaviors in any conditions after the 4-week intervention. Significant reduction in weight (~3.0 kg or 4%, p < 0.01) and decreases in insulin (~30% p < 0.01), C-peptide (~20% p < 0.01), and leptin (~40%, p < 0.01) were found in both LC-CON and LC-EXE groups, but adding exercise to a LCD regime generated no additional effects. There were significant improvements in V̇O2peak (~15% p < 0.01) and anxiety (~25% p < 0.01) in the LC-EXE compared with the LC-CON group, while no statistical differences were found between CON and LC-CON treatments. Further analysis revealed a negative association (r = -0.32, p < 0.01) between changes in levels of anxiety and changes in V̇O2peak in all participates, no other correlations were found between changes in psychological and physiological parameters.

Conclusion

Although the combination of a LCD and exercise may not induce additional reductions in body weight in overweight young females, exercise could be a useful add-on treatment along with a LCD to improve cardiometabolic health and lower anxiety levels.

Physiological, perceptual and affective responses to high-intensity interval training using two work-matched programs with different bout duration in obese males

Objectives

This study compared physiological, perceptual, and affective responses to high-intensity interval training (HIIT) between two work-matched programs with different bout durations in obese males.

Methods

Sixteen low-to-moderately active obese men completed an eight-week cycling program of supervised HIIT (3 days/week) using either short bouts [48 × 10 s at 100% of peak power output (PPO) with 15 s of recovery (HIIT10)] or long bouts [8 × 60 s at 100% PPO with 90 s of recovery (HIIT60)]. Workload was progressively adjusted, to maintain high intensity (100% PPO), throughout training. Blood lactate (BLa), heart rate (HR), ratings of perceived exertion (RPE), and feeling scale ratings (pleasure/displeasure) were measured in each HIIT session.

Results

Average HR decreased in the last 2 weeks of training in both groups by 2.2 ± 1.8% of peak HR (p < 0.001). Training resulted in a reduction in BLa during exercise by 28 ± 19% (p < 0.001) from the 10th min onward only in HIIT10. Similarly, during the last weeks of training, RPE decreased (by 1.0 ± 1.1 units, p < 0.05) and feeling scale ratings were improved only in HIIT10, while RPE remained unchanged and feeling scale ratings deteriorated in HIIT60 (from 3.0 ± 1.1 to 2.1 ± 0.9 units, p < 0.001). No differences in post-exercise enjoyment were found.

Conclusion

Both HIIT formats induced similar HR adaptations, but improvement of BLa, perceptual and affective responses occurred only when bout duration was shorter. Our findings suggest that, in low-to-moderately active obese men, HIIT may be more effective in improving metabolic, perceptual, and affective responses when shorter, rather than longer, bouts of exercise are used.

High Intensity Interval Training reduces hypoglycemic events compared with continuous aerobic training in individuals with type 1 diabetes: HIIT and hypoglycemia in type 1 diabetes

AIMS

to investigate if a High Intensity Interval Training (HIIT) protocol improves glycemic control and fitness capacity, compared to traditional moderate Intensity Continuous Training (MICT) exercise.

METHODS

30 sedentary individuals with type 1 diabetes (T1D) and 26 healthy controls were assigned to a 3-week HIIT or MICT protocol. Blood glucose levels by continuous glucose monitoring system and fitness status were compared before and after the study period.

RESULTS

During workouts, blood glucose levels remained stable in HIIT exercise (+3.2 ± 16.2 mg/dl (p = 0.43)), while decreased in MICT (-27.1 ± 17.5 mg/dl (p < 0.0001)) exercise. In addition, out of the 9 training sessions, HIIT volunteers needed to take carbohydrate supplements to avoid hypoglycemia in 0.56 ± 0.9 sessions, compared to 1.83 ± 0.5 sessions (p < 0.04) in MICT individuals. In the analysis of blood glucose levels between rest and training days (24h-period), training significantly reduced mean glycemic levels in both groups, but the MICT exercise results in an increase in the frequency of hypoglycemic episodes. The response to exercise seems to be attenuated in individuals with T1D, especially in HIIT group.

CONCLUSION

HIIT training results in a greater glycemic stability, with reduction of hypoglycemic episodes.

Effects of Low-Volume High-Intensity Interval Exercise on 24 h Movement Behaviors in Inactive Female University Students

The purpose of this study was to examine if low-volume, high-intensity interval exercise (HIIE) was associated with changes in 24-h movement behaviors. A quasi-experimental study design was used. We collected accelerometry data from 21 eligible participants who consistently wore an ActiGraph for a period of two-weeks. Differences in behaviors were analyzed using a paired t-test and repeated measures analysis of variance. Regression analysis was used to explore relationships with factors that impacted changes. The results indicated a compensatory increase in sedentary time (ST) (4.4 ± 6.0%, p < 0.01) and a decrease in light-intensity physical activity (LPA) (−7.3 ± 16.7%, p < 0.05). Meanwhile, moderate-intensity physical activity (MPA), vigorous-intensity physical activity (VPA), and total physical activity (TPA) increased following exercise (p < 0.001). Sleep duration and prolonged sedentary time were reduced (p < 0.05). Exercise intensity and aerobic capacity were associated with changes in ST. The results from the study indicate that participating in a low-volume HIIE encouraged participants who were previously inactive to become more active. The observations of increases in ST may have displaced a prolonged sitting time. The decrease in sleeping time observed may be reflecting an increased sleep quality in connection with increased higher-intensity PA.

Increased Lean Body Mass After Bodyweight-Based High Intensity Interval Training in Overweight and Obese Men

Purpose: The effects of 8 weeks of bodyweight exercise-based, high-intensity interval training (BWHIIT) on body composition and blood-based markers of metabolic health were investigated in overweight and obese, sedentary young men. Methods: In a parallel group, PRE-POST design, n = 30 men (age, 25.7 ± 4.3 y; body mass index, 27.7 ± 2.1 kg m^-2; 26.1 ± 5.2% body fat) were randomized to BWHIIT (n = 20) or a control group (CON; n = 10). BWHIIT consisted of supervised, group-based training sessions (~30 minutes) performed 3 times weekly. Each session consisted of 6 high-intensity bodyweight-based exercises, with each exercise being performed for 4 minutes in the manner of 8 sets of 20 seconds of exercise, 10 seconds of rest. Prior to commencing training (PRE), and 36 h after the final training session (POST), an overnight fasted blood sample was drawn, and body composition was assessed by dual-energy X-ray absorptiometry. Eighteen participants completed the intervention (CON, n = 9; BWHIIT, n = 9). Results: Lean body mass (LBM) was increased at POST in BWHIIT compared to CON (P = .011, η²_p = .359), with the mean (95% confidence limits) increase in LBM from PRE to POST within BWHIIT being 1.23 (0.55, 1.92) kg. Body mass and fat mass were unchanged in both groups from PRE to POST. BWHIIT had no effect on serum concentrations of total cholesterol, HDL-C, LDL-C, triglycerides, NEFA, hsCRP, or glucose. Conclusion: Eight weeks of bodyweight exercise-based high intensity interval training by overweight and obese sedentary young men increased LBM by ~2%, but fat mass and blood-based markers of metabolic health were unchanged.

Post-Exercise Serum from Humans Influences the Biological Tug of War of APP Processing in Human Neuronal Cells

Neurodegenerative diseases such as Alzheimer's disease (AD) are becoming more prevalent in our aging society. One specific neuropathological hallmark of this disease is the accumulation of amyloid-β (Aβ) peptides, which aggregate to form extra-neuronal plaques. Increased Aβ peptides are often observed well before symptoms of AD develop, highlighting the importance of targeting Aβ producing pathways early on in disease progression. Evidence indicates that exercise has the capacity to reduce Aβ peptide production in the brain however the mechanisms remain unknown. Exercise-induced signaling mediators could be the driving force behind some of the beneficial effects observed in the brain with exercise. The purpose of this study was to examine if post-exercise serum and the factors it contains can alter neuronal APP processing. Human SH-SY5Y neuronal cells were differentiated with retinoic acid for 5 days and treated with 10% pre- or post-exercise serum from humans for 30 minutes. Cells were collected for analysis of acute (30 minutes; n=6) or adaptive (24 hours post-treatment; n=6) responses. There were no statistical differences in ADAM10 and BACE1 mRNA or protein expression with post-exercise serum treatment at either time point. However, there was an increase in the ratio of sAPPa to sAPPβ protein content (p=0.05) after 30 minutes of post-exercise serum treatment. Additionally, 30 minutes of post-exercise serum treatment increased ADAM10 (p=0.01) and BACE1 (p=0.02) activity. These findings suggest that post-exercise serum modulates important enzymes involved in APP processing, pushing the cascade towards the non-amyloidogenic arm.

Type and Intensity as Key Variable of Exercise in Metainflammation diseases: A Review

Monocyte and lymphocyte subpopulations exhibit functions that vary between the anti- and pro-inflammatory spectrum, such as classic CD16- and non-classical CD16+ monocytes, as well as T helper 2 lymphocytes (Th2), the Th1/Th17 lymphocytes ratio, and T regulatory lymphocytes (Treg). Metabolic disease-associated inflammation is accompanied by an imbalance in monocyte and lymphocyte phenotypes and functionality, as well as a stronger proportion of inflammatory subpopulations. These changes appear to be important for the development and progression of diseases like diabetes and cardiovascular disease. On the other hand, the regular practice of physical exercise is an important tool to restore the functionality of monocytes and lymphocytes, and to balance the subtypes ratio. However, key variables regarding exercise prescription, such as the type of exercise, intensity, and volume differentially impact on the acute and chronic immune response in individuals diagnosed with meta inflammation diseases. Here, we discuss the impact of different physical exercise protocols, acutely and chronically, on monocytes and lymphocytes of individuals with metabolic disease-associated inflammation. In this review, we focus on the best effects of different exercise protocols to dose the "exercise pill" in different inflammatory status.

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

CONTEXT

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

OBJECTIVE

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

DATA SOURCES

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

STUDY SELECTION

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

DATA EXTRACTION

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

RESULTS

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

LIMITATIONS

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

CONCLUSIONS

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

Exercise, Nutrition, and Supplements in the Muscle Carnitine Palmitoyl-Transferase II Deficiency: New Theoretical Bases for Potential Applications

Carnitine palmitoyltransferase II (CPTII) deficiency is the most frequent inherited disorder regarding muscle fatty acid metabolism, resulting in a reduced mitochondrial long-chain fatty acid oxidation during endurance exercise. This condition leads to a clinical syndrome characterized by muscle fatigue and/or muscle pain with a variable annual frequency of severe rhabdomyolytic episodes. While since the CPTII deficiency discovery remarkable scientific advancements have been reached in genetic analysis, pathophysiology and diagnoses, the same cannot be said for the methods of treatments. The current recommendations remain those of following a carbohydrates-rich diet with a limited fats intake and reducing, even excluding, physical activity, without, however, taking into account the long-term consequences of this approach. Suggestions to use carnitine and medium chain triglycerides remain controversial; conversely, other potential dietary supplements able to sustain muscle metabolism and recovery from exercise have never been taken into consideration. The aim of this review is to clarify biochemical mechanisms related to nutrition and physiological aspects of muscle metabolism related to exercise in order to propose new theoretical bases of treatment which, if properly tested and validated by future trials, could be applied to improve the quality of life of these patients.

Using Focus Groups and Interviews to Inform the Design of a Workplace Exercise Programme: An Example From a High-Intensity Interval Training Intervention

OBJECTIVE

Using a formative evaluation of a high-intensity interval training (HIIT) intervention, we illustrate how qualitative data can inform the development of workplace exercise interventions.

METHOD

Eight focus groups and four interviews were conducted with employees (n = 38) and management (n = 4) from six office-based organisations before intervention implementation.

RESULTS

Some participants thought workplace-based HIIT would be practical, given the limited time required. Others perceived it may not be acceptable for all individuals, given the exercise intensity. With consideration of identified barriers (workload/family commitments effecting time availability) and facilitators (flexible working conditions) participants' perspectives were incorporated into the intervention protocol. A short-term group-based intervention was preferred, with a choice of exercise modes (based on stair climbing, stepping or boxing).

CONCLUSION

This study provides a framework to incorporate stakeholders' perspectives into the development of workplace exercise interventions.

Indoor Cycling Energy Expenditure: Does Sequence Matter?

Although cycling class intensity can be modified by changing interval intensity sequencing, it has not been established whether the intensity order can alter physiological and perceptual responses. Therefore, this study aimed to determine the effects of interval intensity sequencing on energy expenditure (EE), physiological markers, and perceptual responses during indoor cycling. Healthy volunteers (10 males = 20.0 ± 0.8years; 8 females = 21.3 ± 2.7years) completed three randomly ordered interval bouts (mixed pyramid—MP, ascending intervals—AI, descending intervals—DI) including three 3-min work bouts at 50%, 75%, and 100% of peak power output (PPO) and three 3-min recovery periods at 25% PPO. Heart rate (HR) and oxygen consumption (VO₂) were expressed as percentages of maximal HR (%HR_max) and VO₂ (%VO_2max). EE was computed for both the work bout and for the 5-min recovery period. Session Rating of Perceived Exertion (sRPE) and Exercise Enjoyment Scale (EES) were recorded. No differences emerged for % HR_max (MP = 73.3 ± 6.1%; AI = 72.1 ± 4.9%; DI = 71.8 ± 4.5%), % VO_2max (MP = 51.8 ± 4.6%; AI = 51.4 ± 3.9%; DI = 51.3 ± 4.5%), EE (MP = 277.5 ± 39.9 kcal; AI = 275.8 ± 39.4 kcal; DI = 274.9 ± 42.1 kcal), EES (MP = 4.9 ± 1.0; AI = 5.3 ± 1.1; DI = 4.9 ± 0.9), and sRPE (MP = 4.9 ± 1.0; AI = 5.3 ± 1.1; DI = 4.9 ± 0.9). EE during recovery was significantly (p < 0.005) lower after DI (11.9 ± 3.2 kcal) with respect to MP (13.2 ± 2.5 kcal) and AI (13.3 ± 2.5 kcal). Although lower EE was observed during recovery in DI, interval intensity sequencing does not affect overall EE, physiological markers, and perceptual responses.

Does sedentary time increase in older adults in the days following participation in intense exercise?

BACKGROUND

Older adults have the highest sedentary time across all age groups, and only a small portion is meeting the minimum recommendations for weekly physical activity. Little research to date has looked at how changes in one of these behaviours influences the other.

AIM

To assess changes in 24-h movement behaviours (sedentary time, light intensity physical activity (LPA), moderate-vigorous PA (MVPA) and sleep) over three consecutive days, following acute bouts of exercise of varying intensity in older adults.

METHODS

Participants (n = 28, 69.7 ± 6.5 years) completed a maximal exercise test and the following exercise protocols in random order: moderate continuous exercise (MOD), high-intensity interval exercise (HI) and sprint interval exercise (SPRT). A thigh-worn device (ActivPAL™) was used to measure movement behaviours at baseline and the 3 days following each exercise session.

RESULTS

Repeated measures analysis of variance indicated that compared to baseline, participants decreased MVPA in the 3 days following all exercise sessions and decreased LPA following HI and SPRT (p < 0.05). Over half of the sample had clinically meaningful increases in sedentary time (30 min/day) in the days following exercise participation.

DISCUSSION

Older adults who compensate for exercise participation by reducing physical activity and increasing sedentary time in subsequent days may require behavioural counseling to ensure that incidental and recreational physical activities are not reduced.

CONCLUSION

It appears that older adults compensate for acute exercise by decreasing MVPA and LPA, and increasing sedentary time in the days following exercise. Future research is needed to determine whether compensation persists with regular engagement.

Do vigorous-intensity and moderate-intensity physical activities reduce mortality to the same extent? A systematic review and meta-analysis

Objective

To examine whether vigorous-intensity physical activity confers additional reductions on all-cause and cause-specific mortality compared with moderate-intensity physical activity.

Design

A systematic review (registered in PROSPERO CRD42019138995) and meta-analysis.

Data sources

Three electronic databases up to April 14 2020.

Eligibility criteria

Inclusion criteria were prospective studies that contained information about (1) moderate-intensity (3–5.9 metabolic equivalent tasks (METs)) and vigorous-intensity (≥6 METs) physical activities and (2) all-cause and/or cause-specific mortality. Exclusion criteria were prospective studies that (1) exclusively recruited diseased patients (eg, hypertensive patients and diabetics) or (2) did not account for total physical activity in their multivariable models (3) or did not adjust or exclude individuals with comorbidities at baseline or (4) used physically inactive participants as reference group.

Results

Five studies (seven cohorts using sex-specific results) were pooled into a meta-analysis. For all-cause mortality and controlling by total physical activity, vigorous-intensity physical activity (vs moderate) was not associated with a larger reduction in mortality (HR 0.95, 95% CI 0.83 to 1.09). After the exclusion of one study judged with critical risk of bias (Risk Of Bias in Non randomized Studies, ROBINS tool) from meta-analysis, results remained similar (HR 0.98, 95% CI 0.85 to 1.12). Due to the limited number of studies, meta-analyses for cancer and cardiovascular mortality were not performed.

Conclusions

Prospective studies suggest that, for the same total physical activity, both vigorous-intensity and moderate-intensity physical activities reduce all-cause mortality to the same extent. However, absence of evidence must not be interpreted as evidence of absence due to the existing methodological flaws in the literature.

Moderate-Intensity Exercise and High-Intensity Interval Training Affect Insulin Sensitivity Similarly in Obese Adults

OBJECTIVE

We compared the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on insulin sensitivity and other important metabolic adaptations in adults with obesity.

METHODS

Thirty-one inactive adults with obesity (age: 31 ± 6 years; body mass index: 33 ± 3 kg/m2) completed 12 weeks (4 sessions/week) of either HIIT (10 × 1-minute at 90%HRmax, 1-minute active recovery; n = 16) or MICT (45 minutes at 70%HRmax; n = 15). To assess the direct effects of exercise independent of weight/fat loss, participants were required to maintain body mass.

RESULTS

Training increased peak oxygen uptake by ~10% in both HIIT and MICT (P < 0.0001), and body weight/fat mass were unchanged. Peripheral insulin sensitivity (hyperinsulinemic-euglycemic clamp) was ~20% greater the day after the final exercise session compared to pretraining (P < 0.01), with no difference between HIIT and MICT. When trained participants abstained from exercise for 4 days, insulin sensitivity returned to pretraining levels in both groups. HIIT and MICT also induced similar increases in abundance of many skeletal muscle proteins involved in mitochondrial respiration and lipid and carbohydrate metabolism. Training-induced alterations in muscle lipid profile were also similar between groups.

CONCLUSION

Despite large differences in training intensity and exercise time, 12 weeks of HIIT and MICT induce similar acute improvements in peripheral insulin sensitivity the day after exercise, and similar longer term metabolic adaptations in skeletal muscle in adults with obesity. These findings support the notion that the insulin-sensitizing effects of both HIIT and MICT are mediated by factors stemming from the most recent exercise session(s) rather than adaptations that accrue with training.

Evidence-Based, High-Intensity Exercise and Physical Activity for Compressing Morbidity in Older Adults: A Narrative Review

Recent research in exercise science has important applications for middle-aged and older adults and points to how the programming of individual and multicomponent interventions including theory-based health behavior change strategies may be improved to compress morbidity by delaying or reducing the disabling process. High-intensity interval training and sprint interval training until recently were seen as only applicable to athletes. But recent lab-based research has adapted these interventions for even older adults and demonstrated their safety with beneficial outcomes on cardiometabolic risk factors comparable to or surpassing the usual lower- to moderate-intensity endurance training, and their potential translatability by showing the efficacy of much lower duration and frequency of training, even by systematic stair climbing. Moreover, people report positive affect while engaged in such training. For a century, resistance training was conceived as weightlifting with heavy weights required. Recent research has shown that using a higher degree of effort with lighter to moderate resistance in simple, time efficient protocols result in gains in strength and muscle mass similar to heavy resistance, as well as improvement of cardiometabolic risk factors, strength, body composition, and cognitive, affective, and functional abilities. More effort-based resistance training with moderate resistance may make resistance training more appealing and accessible to older adults. A key potential translational finding is that with correct technique and a high degree of effort, training with inexpensive, portable elastic bands, useable virtually anywhere, can provide appreciable benefits. More emphasis should be placed on long-term, translational interventions, resources, and programs that integrate interval and resistance trainings. This work may improve public health programs for middle-aged and older adults and reflects an emerging evidence base.

High-intensity interval training followed by postexercise cold-water immersion does not alter angiogenic circulating cells, but increases circulating endothelial cells

High-intensity interval training (HIIT) induces vascular adaptations that might be attenuated by postexercise cold-water immersion (CWI). Circulating angiogenic cells (CAC) participate in the vascular adaptations and circulating endothelial cells (CEC) indicate endothelial damage. CAC and CEC are involved in vascular adaptation. Therefore, the aim of the study was to investigate postexercise CWI during HIIT on CAC and CEC and on muscle angiogenesis-related molecules. Seventeen male subjects performed 13 HIIT sessions followed by 15 min of passive recovery (n = 9) or CWI at 10 °C (n = 8). HIIT comprised cycling (8-12 bouts, 90%-110% peak power). The first and the thirteenth sessions were similar (8 bouts at 90% of peak power). Venous blood was drawn before exercise (baseline) and after the recovery strategy (postrecovery) in the first (pretraining) and in the thirteenth (post-training) sessions. For CAC and CEC identification lymphocyte surface markers (CD133, CD34, and VEGFR2) were used. Vastus lateralis muscle biopsies were performed pre- and post-training for protein (p-eNOS^ser1177) and gene (VEGF and HIF-1) expression analysis related to angiogenesis. CAC was not affected by HIIT or postexercise CWI. Postexercise CWI increased acute and baseline CEC number. Angiogenic protein and genes were not differently modulated by post-CWI. HIIT followed by either recovery strategy did not alter CAC number. Postexercise CWI increased a marker of endothelial damage both acutely and chronically, suggesting that this postexercise recovery strategy might cause endothelial damage. Novelty HIIT followed by CWI did not alter CAC. HIIT followed by CWI increased CEC. Postexercise CWI might cause endothelial damage.

Reproducibility in the cardiometabolic responses to high-intensity interval exercise in adults with type 1 diabetes

AIMS

Patients with type 1 diabetes (T1D) often report a rise in their blood glucose level following brief intense exercise. We sought to determine the reproducibility of the cardiometabolic responses to high-intensity interval training (HIIT).

METHODS

Sixteen adults with T1D, using an optimized multiple daily injection with basal insulin glargine 300 U/mL (Gla-300), performed four fasted HIIT sessions over a 4-6-week period. Exercise consisted of high-intensity interval cycling and multimodal training over 25 min.

RESULTS

Heart rate and rating of perceived exertion rose similarly in all sessions, as did lactate, catecholamine and growth hormone levels. Plasma glucose increased in response to HIIT in 62 of 64 visits (97%), with an overall increase of 3.7 ± 1.6 mmol/L (Mean ± SD) (P < 0.001). In within-patient comparisons, the change in plasma glucose among the four HIIT sessions was significantly correlated with a composite correlation of 0.58 ([r² = 0.34]; 95% CI 0.35-0.80; P < 0.01).

CONCLUSIONS

Intersession observations of four separate HIIT sessions showed high intrasubject reproducibility in the cardiometabolic responses to exercise, including the rise in plasma glucose, when adults with T1D perform the activity in a fasted state.

High-Intensity Interval Training Improves Markers of Oxidative Metabolism in Skeletal Muscle of Individuals With Obesity and Insulin Resistance

Background: The excess body fat characteristic of obesity is related to various metabolic alterations, which includes insulin resistance (IR). Among the non-pharmacological measures used to improve insulin sensitivity are aerobic physical training, such as high-intensity interval training (HIIT). This study investigated the effects of 8 weeks of HIIT on blood and skeletal muscle markers related to IR and oxidative metabolism in physically inactive individuals with obesity and compared the changes between insulin resistant and non-insulin resistant phenotypes.

Methods: Initially to investigate the effect of obesity and IR in the analyzed parameters, insulin-sensitive eutrophic volunteers (CON; n = 9) and obese non-insulin (OB; n = 9) and insulin-resistant (OBR; n = 8) were enrolled. Volunteers with obesity completed 8 weeks of HIIT in a cycle ergometer. Venous blood and vastus lateralis muscle samples were obtained before and after the HIIT. Body composition and peak oxygen consumption (VO₂peak) were estimated before and after HIIT.

Results: HIIT reduced IR assessed by the homeostatic model assessment of insulin resistance (HOMA-IR) in OBR (4.4 ± 1.4 versus 4.1 ± 2.2 μU L⁻²), but not in OB (HOMA-IR 1.8 ± 0.5 versus 2.3 ± 1.0 μU L⁻²) volunteers. HIIT increased VO₂peak with no change in body fat in both groups. In skeletal muscle, HIIT increased the phosphorylation of IRS (Tyr612), Akt (Ser473), and increased protein content of β-HAD and COX-IV in both groups. There was a reduction in ERK1/2 phosphorylation in OBR after HIIT.

Conclusion: Eight weeks of HIIT increased the content of proteins related to oxidative metabolism in skeletal muscle of individuals with obesity, independent of changes total body fat.