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

Influence of Educational Level and Healthy Habits on the Prevalence of Diabesity in a Spanish Working Population

Background: Diabesity is a growing problem internationally. Taking into account the importance of physical activity and diet in its prevention and treatment, the objective of this study was to delve into the impact of healthy habits on diabesity. Methods: A descriptive, cross-sectional study was carried out in 386,924 Spanish adult workers. Obesity was determined according to eleven different formulas. Life habits were also valued; sociodemographic variables; and educational level; as well as analytical and clinical variables such as blood pressure and blood glucose levels. The association between the different variables was performed using the chi-square and the Student’s t-tests when the samples were independent. A multivariate analysis was performed using the multinomial logistic regression test by calculating the odds ratio and a 95% confidence interval. The Hosmer–Lemeshow goodness-of-fit test was also performed. Results: The overall prevalence of diabesity ranged between 0.3% (95% CI 0.3–0.4) when obesity was assessed according to the abdominal volume index and 8.3% (95% CI 8.2–8.4) when evaluated according to the CUN-BAE (Clínica Universitaria de Navarra Body Adiposity Estimator) formula. The prevalence of diabesity was also higher in workers with a non-heart-healthy diet and in those who did not exercise regularly. Conclusions: The most disadvantaged socioeconomic classes are those with the highest prevalence of diabesity. It is important to prioritise prevention in populations and communities with the most unfavourable social and environmental conditions to reduce the burden of diabesity.

Comparison of the acute physiological and perceptual responses between resistance-type and cycling high-intensity interval training

Purpose: The purpose of the present study was to compare the acute physiological and perceptual responses between resistance-type high-intensity interval training (R-HIIT)and cycling high-intensity interval training (C-HIIT).

Methods: Twelve healthy and active men randomly performed C-HIIT and R-HIIT. The C-HIIT protocol was performed on a cycle ergometer and consisted of ten 60 s working intervals at 90% PPO separated by a 60 s active recovery at 25% PPO. The R-HIIT protocol consisted of ten 60 s working intervals (barbell back squat with a load of 20% bodyweight, maximum 30 reps) separated by 60 s passive recovery period in an unloaded standing position. Oxygen consumption (V˙O₂), heart rate (HR), energy expenditure (EE) and rating of perceived exertion (RPE) were measured during exercise. Blood lactate concentration (Blac), serum testosterone and cortisol, and heart rate variability (HRV) were measured before and after exercise.

Results: Peak (p < 0.05) and average V˙O₂ (p < 0.001), aerobic (p < 0.001) and total EE (p < 0.05) were higher during C-HIIT compared to R-HIIT. Blac after exercise (p < 0.05) and anaerobic glycolytic EE (p < 0.05) during exercise were higher in R-HIIT compared to C-HIIT. No differences (p > 0.05) in peak and average HR, serum testosterone and cortisol, HRV, and RPE responses were observed between C-HIIT and R-HIIT.

Conclusion: The R-HIIT protocol can elicit similar cardiovascular, hormones, and perceptual responses as C-HIIT but with a higher contribution to the anaerobic glycolysis energy system. In contrast, C-HIIT is superior to R-HIIT for increasing oxygen consumption during exercise. Therefore, the two types of HIIT may lead to different metabolic and neuromuscular adaptations.

Effects of exercise training in hypoxia versus normoxia on fat-reducing in overweight and/or obese adults: A systematic review and meta-analysis of randomized clinical trials

Objective: Fat loss theory under various oxygen conditions has been disputed, and relevant systematic review studies are limited. This study is a systematic review and meta-analysis to assess whether hypoxic exercise training (HET) leads to superior fat-reducing compared with normoxic exercise training (NET).

Methods: We searched PubMed, Web of Science, CNKI, ProQuest, Google Scholar, Cochrane Library, and EBSCOhost from inception to June 2022 for articles comparing the effects of hypoxic and normoxic exercise on body composition indicators, glycometabolism, and lipometabolism indicators in obese and overweight adults. Only randomized controlled trials (RCTs) were included. The effect sizes were expressed as standardized mean difference (SMD) and 95% confidence intervals (CI). Between-study heterogeneity was examined using the I² test and evaluated publication bias via Egger’s regression test. The risk of bias assessment was performed for each included trial using Cochrane Evaluation Tool second generation. The meta-analysis was performed by using R 4.1.3 and RevMan 5.3 analytic tools.

Results: A total of 19 RCTs with 444 subjects were analyzed according to the inclusion and exclusion criteria. Among them, there were 14 English literature and five Chinese literature. No significant difference in body composition (SMD -0.10, 95% CI -0.20 to -0.01), glycometabolism and lipid metabolism (SMD -0.01, 95% CI -0.13 to -0.10) has been observed when comparing the HET and NET groups. We only found low heterogeneity among trials assessing glycometabolism and lipometabolism (I² = 20%, p = 0.09), and no publication bias was detected.

Conclusion: The effects of HET and NET on fat loss in overweight or obese people are the same. The application and promotion of HET for fat reduction need further exploration.

Dose-response association of aerobic and muscle-strengthening physical activity with mortality: a national cohort study of 416 420 US adults

OBJECTIVES

To investigate the dose-response association of aerobic physical activity (PA) and muscle-strengthening exercise (MSE) with all-cause mortality.

METHODS

National Health Interview Survey data (1997-2014) were linked to the National Death Index through 2015, which produced a cohort of 416 420 US adults. Cox proportional-hazard models were used to estimate HRs and 95% CIs for the associations of moderate aerobic PA (MPA), vigorous aerobic PA (VPA) and MSE with mortality risk. Models controlled for age, sex, race-ethnicity, income, education, marital status, survey year, smoking status, body mass index and chronic conditions.

RESULTS

Relative to those who engaged in no aerobic PA, substantial mortality risk reduction was associated with 1 hour/week of aerobic PA (HR: 0.85, 95% CI: 0.83 to 0.86) and levelled off at 3 hours/week of aerobic PA (0.73, 0.71 to 0.75). Similar results were observed for men and women and for individuals younger and older than 60 years. MSE conferred additional mortality risk reduction at 1 time/week (0.89, 0.81 to 0.97) and appeared no longer beneficial at 7 times/week (0.99, 0.94 to 1.04).

CONCLUSION

The minimum effective dose of aerobic PA for significant mortality risk reduction was 1 hour/week of MPA or VPA, with additional mortality risk reduction observed up to 3 hours/week. For older adults, only small decreases in mortality risk were observed beyond this duration. Completing MSE in combination with aerobic PA conferred additional mortality risk reduction, with a minimum effective dose of 1-2 times/week.

Clinical and Biological Adaptations in Obese Older Adults Following 12-Weeks of High-Intensity Interval Training or Moderate-Intensity Continuous Training

Sarcopenia and obesity are considered a double health burden. Therefore, the implementation of effective strategies is needed to improve the quality of life of older obese individuals. The aim of this study was to compare the impact of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on functional capacities, muscle function, body composition and blood biomarkers in obese older adults. Adipose tissue gene expression and markers of muscle mitochondrial content and quality control involved in exercise adaptations were also investigated. Sixty-eight participants performed either HIIT (n = 34) on an elliptical trainer or MICT (n = 34) on a treadmill, three times per week for 12 weeks. HIIT produced significantly higher benefits on some physical parameters (six-minute walking test (HIIT: +12.4% vs. MICT: +5.2%); step test (HIIT: +17.02% vs. MICT: +5.9%); ten-repetition chair test (HIIT: −17.04% vs. MICT: −4.7%)). Although both HIIT and MICT led to an improvement in lower limb power (HIIT: +25.2% vs. MICT: +20.4%), only MICT led to higher improvement in lower limb muscle strength (HIIT: +4.3% vs. MICT: +23.2%). HIIT was more beneficial for increasing total lean body mass (HIIT: +1.58% vs. MICT: −0.81%), while MICT was more effective for decreasing relative gynoid fat mass (HIIT: −1.09% vs. MICT: −4.20%). Regarding adipose tissue gene expression, a significant change was observed for cell death-inducing DFFA (DNA fragmentation factor-alpha)-like effector A (CIDEA) in the HIIT group (A.U; HIIT at T0: 32.10 ± 39.37 vs. HIIT at T12: 48.2 ± 59.2). Mitochondrial transcription factor A (TFAM) content, a marker of mitochondrial biogenesis, increased significantly following HIIT (+36.2%) and MICT (+57.2%). A significant increase was observed in the HIIT group for Translocase of Outer Membrane 20 (TOM20; +54.1%; marker of mitochondrial content), Mitofusin-2 (MFN2; +71.6%; marker of mitochondrial fusion) and Parkin RBR E3 Ubiquitin Protein Ligase (PARKIN; +42.3%; marker of mitophagy). Overall, our results indicate that even though MICT (walking on treadmill) and HIIT (on an elliptical) are effective intervention strategies in obese older adults, HIIT appears to have slightly more beneficial effects. More specifically, HIIT led to higher improvements than MICT on functional capacities, lean mass and skeletal muscle markers of mitochondrial content, fusion, and mitophagy. Thus, MICT but also HIIT (time-efficient training) could be recommended as exercise modalities for obese older adults to maintain or improve mobility, health and quality of life.

Replacing Sedentary Time with Physically Active Behaviour Predicts Improved Body Composition and Metabolic Health Outcomes

Background: Discretionary leisure time for health-promoting physical activity (PA) is limited. This study aimed to predict body composition and metabolic health marker changes from PA reallocation using isotemporal substitution analysis. Methods: Healthy New Zealand women (n = 175; 16–45 y) with high BMI (≥25 kg/m2) and high body fat percentage (≥30%) were divided into three groups by ethnicity (Māori n = 37, Pacific n = 54, and New Zealand European n = 84). PA, fat mass, lean mass, and metabolic health were assessed. Isotemporal substitution paradigms reallocated 30 min/day of sedentary behaviour to varying PA intensities. Results: Reallocating sedentary behaviour with moderate intensity, PA predicted Māori women would have improved body fat% (14.83%), android fat% (10.74%), and insulin levels (55.27%) while the model predicted Pacific women would have improved waist-to-hip (6.40%) and android-to-gynoid (19.48%) ratios. Replacing sedentary time with moderate-vigorous PA predicted Māori women to have improved BMI (15.33%), waist circumference (9.98%), body fat% (16.16%), android fat% (12.54%), gynoid fat% (10.04%), insulin (55.58%), and leptin (43.86%) levels; for Pacific women, improvement of waist-to-hip-ratio (5.30%) was predicted. Conclusions: Sedentary behaviour must be substituted with PA of at least moderate intensity to reap benefits. Māori women received the greatest benefits when reallocating PA. PA recommendations to improve health should reflect the needs and current activity levels of specific populations.

The effect of exercise training on adipose tissue insulin sensitivity: A systematic review and meta-analysis

This systematic review and meta-analysis determined the impact of exercise training on adipose tissue insulin sensitivity in adults. Its scope extended to studies measuring whole-body and localized subcutaneous adipose tissue insulin sensitivity using validated techniques. Consensus from four studies demonstrates that exercise training improved whole-body adipose tissue insulin sensitivity when measured via stable-isotope lipid tracers (rate of appearance suppression in response to hyperinsulinemia). Meta-analysis of 20 studies (26 intervention arms) employing the adipose tissue insulin resistance index (ADIPO-IR) supported these findings (-10.63 [-14.12 to -7.15] pmol·L^-1  × mmol·L^-1 ). With ADIPO-IR, this response was greater in studies documenting weight loss and shorter sampling time (≤48 h) post-training. Overall, exercise training did not affect whole-body adipose tissue insulin sensitivity in seven studies (11 intervention arms) measuring the suppression of circulating non-esterified fatty acids in response to insulin infusion (1.51 [-0.12 to 3.14]%); however, subgroup analysis identified an enhanced suppression post-training in trials reporting weight loss. From four microdialysis studies, consensus indicates no effect of exercise training on localized (abdominal/femoral) adipose tissue insulin sensitivity, potentially suggesting that enhanced whole-body responses are related to improvements in central adipose depots. However, heterogeneity within microdialysis protocols dictates that findings must be viewed with caution.

Very Low-Carbohydrate High-Fat Diet Improves Risk Markers for Cardiometabolic Health More Than Exercise in Men and Women With Overfat Constitution: Secondary Analysis of a Randomized Controlled Clinical Trial

Purpose

This randomized controlled parallel-group study examined the effects of a very low-carbohydrate high-fat (VLCHF) diet and high-intensity interval training (HIIT) program over 12-weeks on cardiometabolic risk factors in individuals with overfat constitution.

Methods

Ninety-one participants out of 109 completed the study. The participants were randomly allocated to the HIIT (N = 22), VLCHF (N = 25), VLCHF+HIIT (N = 25), or control (N = 19) groups for 12 weeks. Fasting plasma samples were collected before the intervention and after 4 and 12 weeks. The analyzed outcomes included complete blood count, glucose, insulin, glycated hemoglobin, triglycerides (TG), cholesterol, high- and low-density lipoprotein (HDL-C and LDL-C), lipoprotein(a), adiponectin (Adpn), leptin (Lep), tumor necrosis factor α (TNF-α), other interleukins (hs-IL-6, IL-1β, and IL-10), and IL-1RA. The homeostasis model assessment of insulin resistance (HOMA-IR), Adpn/Lep ratio, TG/HDL-C ratio, and TyG index were calculated and analyzed. Blood pressure was measured before the intervention, after 4, 8, and 12 weeks (ClinicalTrials.gov: NCT03934476).

Results

Absolute changes in HOMA-IR, Adpn/Lep ratio, LDL-C, and diastolic blood pressure after 12 weeks differed by study groups (p < 0.05). The most pronounced changes were revealed in the VLCHF (ΔM [95% CI]; HOMA-IR: -0.75 [-1.13; -0.55]; Adpn/Lep: 9.34 [6.33; 37.39]; LDL-C: 0.06 [-0.12; 0.50] mmol/l) and VLCHF+HIIT (HOMA-IR: -0.44 [-1.14; 0.12]; Adpn/Lep: 4.26 [2.24; 13.16]; LDL-C: 0.25 [-0.04; 0.50] mmol/l) groups.

Conclusions

A 12-week VLCHF diet intervention in individuals with overfat constitution is effective for favorable changes in HOMA-IR (compared to HIIT), Adpn/Lep ratio, and diastolic blood pressure. HIIT, or HIIT combined with the VLCHF diet, had no additional benefits for the analyzed variables. No adverse side effects were observed.

Metabolic health status and fecundability in a Singapore preconception cohort study

BACKGROUND

Obesity compromises metabolic health and female fertility, yet not all obese women are similar in metabolic status. The extent to which fecundability is influenced by the metabolic health status of women who are overweight or obese before conception is unknown.

OBJECTIVE

This study aimed to: (1) determine the metabolic health status, and (2) examine the association between metabolic health status and fecundability of overweight and obese women trying to conceive in the Singapore PREconception Study of long-Term maternal and child Outcomes cohort study.

STUDY DESIGN

We conducted a prospective preconception cohort study of Asian women (Chinese, Malay, and Indian) aged 18 to 45 years trying to conceive who were treated from 2015 to 2017 in KK Women's and Children's Hospital in Singapore (n=834). We defined women to have metabolically unhealthy status if they: (1) met 3 or more modified Joint Interim Statement metabolic syndrome criteria; or (2) had homeostasis model assessment-insulin resistance index ≥2.5. Body mass index was categorized as normal (18.5-22.9 kg/m2), overweight (23-27.4 kg/m2), or obese (≥27.5 kg/m2) on the basis of cutoff points for Asian populations. Fecundability was measured by time to pregnancy in menstrual cycles within a year of enrolment. Discrete-time proportional hazards models were used to estimate fecundability odds ratios, with adjustment for confounders and accounting for left truncation and right censoring.

RESULTS

Of 232 overweight women, 28 (12.1%) and 25 (10.8%) were metabolically unhealthy by metabolic syndrome ≥3 criteria and homeostasis model assessment-insulin resistance ≥2.5, respectively. Of 175 obese women, 54 (30.9%) and 93 (53.1%) were metabolically unhealthy by metabolic syndrome ≥3 criteria and homeostasis model assessment-insulin resistance ≥2.5, respectively. Compared with metabolically healthy normal-weight women, lower fecundability was observed in metabolically unhealthy overweight women on the basis of metabolic syndrome criteria (fecundability odds ratios, 0.38 [95% confidence interval, 0.15-0.92]) and homeostasis model assessment-insulin resistance (fecundability odds ratios, 0.68 [95% confidence interval, 0.33-1.39]), with metabolic syndrome criteria showing a stronger association. Metabolically unhealthy obese women showed lower fecundability than the healthy normal-weight reference group by both metabolic syndrome (fecundability odds ratios, 0.35; 95% confidence interval, 0.17-0.72) and homeostasis model assessment-insulin resistance criteria (fecundability odds ratios, 0.43; 95% confidence interval, 0.26-0.71). Reduced fecundability was not observed in overweight or obese women who showed healthy metabolic profiles by either definition.

CONCLUSION

Overweight or obesity was not synonymous with having metabolic syndrome or insulin resistance. In our preconception cohort, metabolically unhealthy overweight and obese women showed reduced fecundability, unlike their counterparts who were metabolically healthy. These findings suggest that metabolic health status, rather than simply being overweight and obese per se, plays an important role in fecundability.

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

PURPOSE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

A semisupervised HIT intervention did not increase menstrual frequency in women with PCOS.Clinical Trial Registration Number:ClinicalTrials.gov (NCT02419482).

High Intensity Interval Training: A Potential Method for Treating Sarcopenia

Sarcopenia, an age-related disease characterized by loss of muscle strength and muscle mass, has attracted the attention of medical experts due to its severe morbidity, low living quality, high expenditure of health care, and mortality. Traditionally, persistent aerobic exercise (PAE) is considered as a valid way to attenuate muscular atrophy. However, nowadays, high intensity interval training (HIIT) has emerged as a more effective and time-efficient method to replace traditional exercise modes. HIIT displays comprehensive effects on exercise capacity and skeletal muscle metabolism, and it provides a time-out for the recovery of cardiopulmonary and muscular functions without causing severe adverse effects. Studies demonstrated that compared with PAE, HIIT showed similar or even higher effects in improving muscle strength, enhancing physical performances and increasing muscle mass of elder people. Therefore, HIIT might become a promising way to cope with the age-related loss of muscle mass and muscle function. However, it is worth mentioning that no study of HIIT was conducted directly on sarcopenia patients, which is attributed to the suspicious of safety and validity. In this review, we will assess the effects of different training parameters on muscle and sarcopenia, summarize previous papers which compared the effects of HIIT and PAE in improving muscle quality and function, and evaluate the potential of HIIT to replace the status of PAE in treating old people with muscle atrophy and low modality; and point out drawbacks of temporary experiments. Our aim is to discuss the feasibility of HIIT to treat sarcopenia and provide a reference for clinical scientists who want to utilize HIIT as a new way to cope with sarcopenia.

Effect of High-Intensity Interval Training Combined with Fasting in the Treatment of Overweight and Obese Adults: A Systematic Review and Meta-Analysis

OBJECTIVES

A systematic review and meta-analysis is conducted to compare the effects of high-intensity interval training (HIIT) combined with fasting (HIIT + fasting) and other interventions (HIIT alone, fasting alone, or normal intervention) in adults with overweight and obesity on body composition (body mass, body mass index (BMI), waist circumference (WC), percent fat mass (PFM), fat mass (FM), fat-free mass (FFM)), maximal oxygen uptake (VO2peak), and glucose metabolism (fasting plasma glucose (FPG)), fasting plasma insulin (FPI)).

METHODS

The databases of PubMed, the Cochrane Library, Embace, Web of Science, CNKI, Wangfang Data, and CBM were searched from their inception to February 2022. Randomized controlled trials comparing the effects of HIIT + fasting and other interventions on adults with overweight and obesity were included in this meta-analysis. The risk of bias was assessed by the Cochrane risk of bias tool. The effect size was completed by using mean difference (MD) and standard deviation. If there were varying units or large differences among the included studies, the standardized mean difference (SMD) would be used. The certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE).

RESULTS

Nine randomized controlled trials with 230 overweight and obese adults were conducted in accordance with our inclusion criteria. The results of the meta-analysis revealed that compared to the control group HIIT + fasting had better effects on the body mass, WC, FM, and VO2peak, while there were no significant differences in PFM, FFM, FPG, and FPI.

CONCLUSIONS

Despite the number of included trials being small and the GRADE of all outcomes being very low, HIIT + fasting has a positive effect on the body composition of overweight and obese adults, and significantly improves VO2peak. For adults with overweight and obesity who have long-term comorbidity, HIIT + fasting was a better way to improve FPG than HIIT alone or fasting alone. More studies are required to investigate different combinations of HIIT + fasting; and the safety of HIIT + fasting intervention on overweight and obese adults.

High intramuscular triglyceride turnover rates and the link to insulin sensitivity: influence of obesity, type 2 diabetes and physical activity

Large intramuscular triglyceride (IMTG) stores in sedentary, obese individuals have been linked to insulin resistance, yet well-trained athletes exhibit high IMTG levels whilst maintaining insulin sensitivity. Contrary to previous assumptions, it is now known that IMTG content per se does not result in insulin resistance. Rather, insulin resistance is caused, at least in part, by the presence of high concentrations of harmful lipid metabolites, such as diacylglycerols and ceramides in muscle. Several mechanistic differences between obese sedentary individuals and their highly trained counterparts have been identified, which determine the differential capacity for IMTG synthesis and breakdown in these populations. In this review, we first describe the most up-to-date mechanisms by which a low IMTG turnover rate (both breakdown and synthesis) leads to the accumulation of lipid metabolites and results in skeletal muscle insulin resistance. We then explore current and potential exercise and nutritional strategies that target IMTG turnover in sedentary obese individuals, to improve insulin sensitivity. Overall, improving IMTG turnover should be an important component of successful interventions that aim to prevent the development of insulin resistance in the ever-expanding sedentary, overweight and obese populations. Novelty: A description of the most up-to-date mechanisms regulating turnover of the IMTG pool. An exploration of current and potential exercise/nutritional strategies to target and enhance IMTG turnover in obese individuals. Overall, highlights the importance of improving IMTG turnover to prevent the development of insulin resistance.

Carbohydrate-Energy Replacement Following High-Intensity Interval Exercise Blunts Next-Day Glycemic Control in Untrained Women

Background

Improved glycemic control has been reported for ∼24 h following low-volume high-intensity interval exercise (HIIE), but it is unclear if this is a direct effect of exercise or an indirect effect of the exercise-induced energy deficit. The purpose of this study was to investigate the effect of carbohydrate-energy replacement after low-volume HIIE on 24 h glycemic control in women.

Methods

Seven untrained women (age: 22 ± 2 yr; BMI: 22 ± 3 kg/m2; VO2peak: 33 ± 7 ml/kg/min) completed three 2-day trials in the mid-follicular phase of the menstrual cycle. Continuous glucose monitoring was used to measure blood glucose concentrations during, and for 24 h following three conditions: (1) HIIE followed by a high-carbohydrate energy replacement drink (EX-HC); (2) HIIE followed by a non-caloric taste-matched placebo drink (EX-NC); and (3) seated control with no drink (CTL). HIIE involved an evening session (1,700 h) of 10 × 1-min cycling efforts at ∼90% maximal heart rate with 1 min recovery. Diet was standardized and identical across all three 2-day trials, apart from the post-exercise carbohydrate drink in EX-HC, which was designed to replenish the exercise-induced energy expenditure. Postprandial glycemic responses to the following days breakfast, snack, lunch, and dinner, as well as 24 h indices of glycemic control, were analyzed.

Results

The day after HIIE, postprandial glycemia following breakfast and snack were reduced in EX-NC compared to EX-HC, as reflected by lower 3 h glucose mean (breakfast: 5.5 ± 0.5 vs. 6.7 ± 1, p = 0.01, Cohen’s d = 1.4; snack: 4.9 ± 0.3 vs. 5.7 ± 0.8 mmol/L, p = 0.02, d = 1.4) and/or area under the curve (AUC) (breakfast: 994 ± 86 vs. 1,208 ± 190 mmol/L x 3 h, p = 0.01, d = 1.5). Postprandial glycemic responses following lunch and dinner were not different across conditions (p &gt; 0.05). The 24 h glucose mean (EX-NC: 5.2 ± 0.3 vs. EX-HC: 5.7 ± 0.7 mmol/L; p = 0.02, d = 1.1) and AUC (EX-NC: 7,448 ± 425 vs. EX-HC: 8,246 ± 957 mmol/L × 24 h; p = 0.02, d = 1.1) were reduced in EX-NC compared to EX-HC.

Conclusion

Post-exercise carbohydrate-energy replacement attenuates glycemic control the day following a single session of low-volume HIIE in women.

Prior arm crank exercise has no effect on postprandial lipaemia in non-disabled adults

A single bout of cycling or running performed in the evening can reduce postprandial lipaemia (PPL) the following morning, although this is currently unknown for upper-body exercise. The aim of this study was to determine if a bout of arm crank exercise (high-intensity interval [HIIE] or moderate-intensity continuous [MICE]), can attenuate PPL in non-injured individuals. Eleven healthy and recreationally active participants (eight males, three females; age: 27 ± 7 yr; body mass index: 23.5 ± 2.5 kg · m-2) volunteered to participate in three trials: HIIE (10 x 60 s at 80% peak power output), MICE (50% peak power output of isocaloric duration), and a no-exercise control condition. Each exercise bout was performed at 18:00, and participants consumed a standardized evening meal at 20:00. Following an overnight fast, a 5-h mixed-macronutrient tolerance test was performed at 08:00. There were no significant differences in triglyceride incremental area under the curve between HIIE (192 ± 94 mmol. L-1 per 300 min), MICE (184 ± 111 mmol. L-1 per 300 min), and the no-exercise condition (175 ± 90 mmol. L-1 per 300 min) (P=0.46). There were no significant differences in incremental area under the curve for glucose (P=0.91) or insulin (P=0.59) between conditions. Upper-body MICE and HIIE performed in the evening do not influence PPL the following morning, in normotriglyceridemic individuals. Clinical Trials Registration: NCT04277091 Novelty: • Arm crank exercise has no effect on PPL when performed the evening prior to a mixed-macronutrient meal test • Upper-body sprint interval exercise should be investigated as a potential solution to reduce PPL.

The Acute Physiological and Perceptual Responses Between Bodyweight and Treadmill Running High-Intensity Interval Exercises

Objective

The purpose of this study was to compare the acute physiological, perceptual, and enjoyment responses between bodyweight high-intensity interval exercise (BW-HIIE) and treadmill running high-intensity interval exercise HIIE (RUN-HIIE).

Methods

Twelve adults [age: 29.5 ± 5.3 years; weight: 70.9 ± 15.0 kg; height: 167.9 ± 8.9 cm; peak oxygen consumption (VO2 peak): 48.7 ± 6.5 ml min-1·kg-1] performed both RUN-HIIE and BW-HIIE. RUN-HIIE consisted of two sets of 5, 60-s (s) run intervals at 100% of the speed achieved during VO2 peak testing followed by 60s of walking at 4.02 km/h. BW-HIIE consisted of two sets of 5, 60s 'all-out' effort calisthenic exercises followed by 60s of marching in place at 100 steps per minute. Oxygen consumption (VO2), blood lactate (Blac), heart rate (HR), and rating of perceived exertion (RPE) were measured during exercise. Physical activity enjoyment (PACES) was assessed post-exercise. Creatine Kinase (CK) was measured before exercise and 48-h post-exercise. Muscle soreness was assessed before exercise, post-exercise, and 48-h post-exercise.

Results

Oxygen consumption relative to VO2 peak was higher (p < 0.001) during RUN-HIIE (88 ± 3%) compared to BW-HIIE (77 ± 4%). HR relative to HRpeak was higher (p = 0.002) for RUN-HIIE (93 ± 1%) compared to BW-HIIE (88 ± 2%). Blac was higher (p < 0.001) after BW-HIIE (11.2 ± 3.2 mmol/l) compared to RUN-HIIE (6.9 ± 2.0 mmol/l). Average RPE achieved was higher (p = 0.003) during BW-HIIE (16 ± 2) than RUN-HIIE (14 ± 2). PACES was similar for RUN-HIIE and BW-HIIE (p > 0.05). No differences (p > 0.05) in CK were observed between RUN-HIIE and BW-HIIE.

Conclusion

Our results indicate 'all-out' calisthenic exercise can elicit vigorous cardiorespiratory, Blac, and RPE responses. Implementing this style of exercise into training requires minimal space, no equipment, and may elicit cardiometabolic adaptations seen with traditional forms of high-intensity exercise.

Exercise training remodels subcutaneous adipose tissue in adults with obesity even without weight loss

Excessive adipose tissue mass underlies much of the metabolic health complications in obesity. Although exercise training is known to improve metabolic health in individuals with obesity, the effects of exercise training without weight loss on adipose tissue structure and metabolic function remain unclear. Thirty-six adults with obesity (body mass index = 33 ± 3 kg · m^-2 ) were assigned to 12 weeks (4 days week^-1 ) of either moderate-intensity continuous training (MICT; 70% maximal heart rate, 45 min; n = 17) or high-intensity interval training (HIIT; 90% maximal heart rate, 10 × 1 min; n = 19), maintaining their body weight throughout. Abdominal subcutaneous adipose tissue (aSAT) biopsy samples were collected once before and twice after training (1 day after last exercise and again 4 days later). Exercise training modified aSAT morphology (i.e. reduced fat cell size, increased collagen type 5a3, both P ≤ 0.05, increased capillary density, P = 0.05) and altered protein abundance of factors that regulate aSAT remodelling (i.e. reduced matrix metallopeptidase 9; P = 0.02; increased angiopoietin-2; P < 0.01). Exercise training also increased protein abundance of factors that regulate lipid metabolism (e.g. hormone sensitive lipase and fatty acid translocase; P ≤ 0.03) and key proteins involved in the mitogen-activated protein kinase pathway when measured the day after the last exercise session. However, most of these exercise-mediated changes were no longer significant 4 days after exercise. Importantly, MICT and HIIT induced remarkably similar adaptations in aSAT. Collectively, even in the absence of weight loss, 12 weeks of exercise training induced changes in aSAT structure, as well as factors that regulate metabolism and the inflammatory signal pathway in adults with obesity. KEY POINTS: Exercise training is well-known to improve metabolic health in obesity, although how exercise modifies the structure and metabolic function of adipose tissue, in the absence of weight loss, remains unclear. We report that both 12 weeks of moderate-intensity continuous training (MICT) and 12 weeks of high-intensity interval training (HIIT) induced modifications in adipose tissue structure and factors that regulate adipose tissue remodelling, metabolism and the inflammatory signal pathway in adults with obesity, even without weight loss (with no meaningful differences between MICT and HIIT). The modest modifications in adipose tissue structure in response to 12 weeks of MICT or HIIT did not lead to changes in the rate of fatty acid release from adipose tissue. These results expand our understanding about the effects of two commonly used exercise training prescriptions (MICT and HIIT) on adipose tissue remodelling that may lead to advanced strategies for improving metabolic health outcomes in adults with obesity.

Molecular Mechanisms of Exercise and Healthspan

Healthspan is the period of our life without major debilitating diseases. In the modern world where unhealthy lifestyle choices and chronic diseases taper the healthspan, which lead to an enormous economic burden, finding ways to promote healthspan becomes a pressing goal of the scientific community. Exercise, one of humanity's most ancient and effective lifestyle interventions, appears to be at the center of the solution since it can both treat and prevent the occurrence of many chronic diseases. Here, we will review the current evidence and opinions about regular exercise promoting healthspan through enhancing the functionality of our organ systems and preventing diseases.

Trimetazidine and exercise offer analogous improvements to the skeletal muscle insulin resistance of mice through Nrf2 signaling

INTRODUCTION

Insulin resistance (IR) plays a key role in the pathogenesis and clinical course of patients with multiple metabolic diseases and diabetes. This study aimed to explore the effect of trimetazidine (TMZ) on skeletal muscle IR in mice fed a high-fat diet (HFD) and explore the possible underlying mechanism.

RESEARCH DESIGN AND METHODS

In vivo, a HFD mouse IR model was adopted and TMZ and exercise were used to intervene. Postintervention the following were determined: blood levels of glucose and insulin, homeostasis model assessment of IR index, expression of skeletal muscle insulin signaling-related proteins phosphorylated insulin receptor substrate 1 (p-IRS1/IRS1) and phosphorylated protein kinase B (p-AKT/AKT), nuclear factor erythroid 2 related factor 2 (Nrf2) signaling pathway, and oxidative stress. In vitro, a palmitate-treated C2C12 myotube IR model was constructed. Cellular glucose uptake, p-IRS1/IRS1, and p-AKT/AKT were determined, and reactive oxygen species (ROS) production was analyzed based on treatments with specific small interfering RNA of Nrf2 with or without TMZ. Western blot was used to obtain the protein expression level and ROS production by functional analysis kits.

RESULTS

In vivo, TMZ and exercise decreased the blood glucose and insulin levels and homeostasis model assessment of IR index, increased skeletal muscle insulin signaling-related protein ratios of p-IRS1/IRS1 and p-AKT/AKT, and both interventions activated Nrf2 signaling and reduced oxidative stress production in HFD mice. In vitro, TMZ reduced the oxidative stress reaction, increased the ratios of p-AKT/AKT and p-IRS1/IRS1, and attenuated the insulin stimulation of PA-induced glucose uptake. However, in the absence of Nrf2, TMZ failed to resist the effects of IR.

CONCLUSIONS

This study showed that TMZ, like exercise, brought about marked improvements to HFD-induced skeletal muscle IR through TMZ, a common pathway with exercise in the form of Nrf2, regulating oxidative stress. We provide new evidence to support the use of TMZ for diabetes treatment.

The Effect of High-intensity Interval Training vs Moderate-intensity Continuous Training on Liver Fat: A Systematic Review and Meta-Analysis

CONTEXT

Non-alcoholic fatty liver disease, characterized by excess fat accumulation in the liver, is considered the hepatic manifestation of metabolic syndrome. Recent findings have shown that high-intensity interval training (HIIT) can reduce liver fat but it is unclear whether this form of exercise is superior to traditional moderate-intensity continuous training (MICT).

OBJECTIVE

The aim of this systematic review was to determine the effect of HIIT vs MICT on liver fat in adults. A secondary aim was to investigate the interaction between total weekly exercise volume and exercise-related energy expenditure and change in liver fat.

METHODS

Relevant databases were searched up to December 2020 for randomized trials, comparing HIIT to control, MICT to control, or HIIT to MICT. Studies were excluded if they did not implement 2 or more weeks' intervention or assess liver fat using magnetic resonance-based techniques. Weighted mean differences and 95% CIs were calculated. Regression analyses were undertaken to determine the interaction between weekly exercise volume in minutes and kilocalories (kcal) with change in liver fat content.

RESULTS

Of the 28 268 studies screened, 19 were included involving 745 participants. HIIT and MICT both elicited moderate reductions in liver fat content when compared to control (HIIT: -2.85%, 95% CI, -4.86 to -0.84, P = .005, I2 = 0%, n = 114, low-certainty evidence; MICT: -3.14%, 95% CI, -4.45 to -1.82, P < .001, I2 = 5.2%, n = 533, moderate-certainty evidence). There was no difference between HIIT and MICT (-0.34%, 95% CI, -2.20 to 1.52, P = .721, I2 = 0%, n = 177, moderate-certainty evidence). Neither total exercise volume in minutes (β = .0002, SE = 0.0017, Z = 0.13, P = .89) nor exercise-related energy expenditure in kcal (β = .0003, SE = 0.0002, Z = 1.21, P = .23) were related to changes in liver fat content.

CONCLUSION

HIIT elicits comparable improvements in liver fat to MICT despite often requiring less energy and time commitment. Further studies should be undertaken to assess the relative importance of aerobic exercise prescription variables, such as intensity, on liver fat.

Effects of high-intensity interval training on improving arterial stiffness in Chinese female university students with normal weight obese: a pilot randomized controlled trial

Background

High intensity interval training (HIIT) has been reported to exert better effects on cardiovascular fitness in obesity, but little known about the arterial stiffness (AS) in female university students with normal weight obesity (NWO). Thus, this study aimed to investigate the effects of HIIT on the body composition, heart rate (HR), blood pressure (BP), blood lipids metabolism as well as the novel parameters of propensity for AS (arterial velocity pulse index [AVI], arterial pressure volume index [API]) for female university students with NWO.

Methods

Forty female university students with NWO were randomly assigned to control group (n = 20) and HIIT group (3 bouts of 9‑min intervals at 90% of the maximal heart rate [HR_max], interspersed by 1 min rest, 5 days a week, n = 20). Tests were performed before and after 4 weeks of training. Repeated measures ANOVA and simple effect test analysis were used to analyze dependent variable changes.

Results

After 4 weeks HIIT statistically significantly improved the body composition by decreasing the body mass index, body fat percent, total body fat mass (BFM), BFM of left arm, measured circumference of left arm, and obesity degree, and increasing the total body skeletal muscle mass, protein content, total body water, fat free mass, body cell mas, and InBody score. HIIT also statistically significantly decreased the HR and BP. As for the lipid profile, HIIT obviously ameliorated the blood lipids metabolism by decreasing the levels of total cholesterol (TC), triglyceride, low-density lipoprotein, and TC/HDL, and increasing the levels of high-density lipoprotein (HDL). In addition, the AVI and API were markedly decreased via HIIT intervention.

Conclusions

HIIT produced significant and meaningful benefits for body composition, HR, BP, and blood lipids metabolism, and could decrease AS in female university students with NWO. This suggests that HIIT may effectively reduce the risk of arteriosclerosis and protect the cardiovascular function for female university students with NWO.

Trial registration ChiCTR2100050711. Registered 3 September 2021. Retrospectively registered.

Exercise/Physical Activity in Individuals with Type 2 Diabetes: A Consensus Statement from the American College of Sports Medicine

ABSTRACT

This consensus statement is an update of the 2010 American College of Sports Medicine position stand on exercise and type 2 diabetes. Since then, a substantial amount of research on select topics in exercise in individuals of various ages with type 2 diabetes has been published while diabetes prevalence has continued to expand worldwide. This consensus statement provides a brief summary of the current evidence and extends and updates the prior recommendations. The document has been expanded to include physical activity, a broader, more comprehensive definition of human movement than planned exercise, and reducing sedentary time. Various types of physical activity enhance health and glycemic management in people with type 2 diabetes, including flexibility and balance exercise, and the importance of each recommended type or mode are discussed. In general, the 2018 Physical Activity Guidelines for Americans apply to all individuals with type 2 diabetes, with a few exceptions and modifications. People with type 2 diabetes should engage in physical activity regularly and be encouraged to reduce sedentary time and break up sitting time with frequent activity breaks. Any activities undertaken with acute and chronic health complications related to diabetes may require accommodations to ensure safe and effective participation. Other topics addressed are exercise timing to maximize its glucose-lowering effects and barriers to and inequities in physical activity adoption and maintenance.

Alternating high-intensity interval training and continuous training is efficacious in improving cardiometabolic health in obese middle-aged men

Background

High-intensity interval training (HIIT) or moderate-intensity continuous training (MICT) alone has been shown to improve metabolic health, but the effects of alternating the two training approaches as often practiced in real life remained unclear.

Purpose

To examine the effects of HIIT or MICT alone or alternating HIIT-MICT on cardiometabolic responses in inactive obese middle-aged men.

Methods

Forty-two participants (age: 42 ± 5 y; BMI: 26.3 ± 2.1 kg m⁻²) were randomly assigned to four groups: HIIT (12 x 1-min running bouts at 80–90% HR_max interspersed with 1-min active recovery at 50% HR_max), MICT (40-min brisk walk at 65–70% HR_max), alternating HIIT-MICT or a non-exercise control group (CON). Exercise sessions were conducted three times per week for 16 weeks. Maximal oxygen uptake (VO_2max), body composition (by bioelectrical impedance analysis), blood pressure, fasting blood glucose, insulin resistance (HOMA-IR) and lipid profile were assessed at baseline and after the 16-week intervention. Enjoyment and self-efficacy were also assessed at the end of intervention.

Results

All exercise groups showed a similar VO_2max increase of ∼15% (HIIT: 34.3 ± 4.4 vs 39.1 ± 5.4; MICT: 34.9 ± 5.0 vs 39.4 ± 7.2; and alternating HIIT-MICT: 34.4 ± 5.0 vs 40.3 ± 4.6 mL kg⁻¹min⁻¹) compared to baseline and CON (all p < 0.05). Weight, BMI, % fat and waist circumference also showed similar reductions in all exercise groups compared to baseline and CON (all p < 0.05). No significant group difference was observed for all blood markers. Compared to baseline, total cholesterol decreased after HIIT-MICT, while HIIT significantly decreased fasting insulin level and improved insulin resistance (p < 0.05). Enjoyment, self-efficacy and adherence were similar among all exercise groups.

Conclusion

HIIT or MICT alone or alternating HIIT-MICT similarly improve cardiovascular fitness and body composition in obese middle-aged men despite differences in total training volume and time commitment.

High-intensity interval training combining rowing and cycling efficiently improves insulin sensitivity, body composition and VO2max in men with obesity and type 2 diabetes

AIMS

Non-weight-bearing high-intensity interval training (HIIT) involving several muscle groups may efficiently improve metabolic health without compromising adherence in obesity and type 2 diabetes. In a non-randomized intervention study, we examined the effect of a novel HIIT-protocol, recruiting both lower and upper body muscles, on insulin sensitivity, measures of metabolic health and adherence in obesity and type 2 diabetes.

METHODS

In 15 obese men with type 2 diabetes and age-matched obese (n=15) and lean (n=18) glucose-tolerant men, the effects of 8-weeks supervised HIIT combining rowing and cycling on ergometers (3 sessions/week) were examined by DXA-scan, incremental exercise test and hyperinsulinemic-euglycemic clamp combined with indirect calorimetry.

RESULTS

At baseline, insulin-stimulated glucose disposal rate (GDR) was ~40% reduced in the diabetic vs the non-diabetic groups (all p<0.01). In response to HIIT, insulin-stimulated GDR increased ~30-40% in all groups (all p<0.01) entirely explained by increased glucose storage. These changes were accompanied by ~8-15% increases in VO₂max, (all p<0.01), decreased total fat mass and increased lean body mass in all groups (all p<0.05). There were no correlations between these training adaptations and no group-differences in these responses. HbA1c showed a clinically relevant decrease in men with type 2 diabetes (4±2 mmol/mol; p<0.05). Importantly, adherence was high (>95%) in all groups and no injuries were reported.

CONCLUSIONS

A novel HIIT-protocol recruiting lower and upper body muscles efficiently improves insulin sensitivity, VO₂max and body composition with intact responses in obesity and type 2 diabetes. The high adherence and lack of injuries show that non-weight-bearing HIIT involving several muscle groups is a promising mode of exercise training in obesity and type 2 diabetes.

Cerebrovascular response to an acute bout of low-volume high-intensity interval exercise and recovery in young healthy adults

High-intensity interval exercise (HIIT) is performed widely. However, there is a gap in knowledge regarding the acute cerebrovascular response to low-volume HIIT. Our objective was to characterize the middle cerebral artery blood velocity (MCAv) response during an acute bout of low-volume HIIT in young healthy adults. We hypothesized that MCAv would decrease below the baseline (BL), 1) during HIIT, 2) immediately following HIIT, and 3) 30 min after HIIT. As a secondary objective, we investigated sex differences in the MCAv response during HIIT. Twenty-four young healthy adults completed HIIT [12 males, age = 25 (SD = 2)]. HIIT included 10 min of 1-min high intensity (∼70% estimated maximal Watts) and active recovery (10% estimated maximal Watts) intervals on a recumbent stepper. MCAv, mean arterial pressure (MAP), heart rate (HR), and end-tidal carbon dioxide ([Formula: see text]) were recorded at BL, during HIIT, immediately following HIIT, and 30 min after HIIT. Contrary to our hypothesis, MCAv remained above BL during HIIT. MCAv peaked at minute 3 then decreased concomitantly with [Formula: see text]. MCAv was lower than BL immediately following HIIT (P < 0.001). Thirty minutes after HIIT, MCAv returned to BL (P = 0.47). Compared with men, women had a higher MCAv at BL (P = 0.001), during HIIT (P = 0.009), immediately following HIIT (P = 0.004), and 30 min after HIIT (P = 0.001). MCAv did not decrease below BL during low-volume HIIT. However, MCAv decreased below BL immediately following HIIT and returned to resting values 30 min after HIIT. MCAv also differed between sexes.NEW & NOTEWORTHY We are the first, to our knowledge, to characterize the cerebrovascular and hemodynamic response to low-volume high-intensity interval exercise (HIIT, 1-min intervals) in young healthy adults. Middle cerebral artery blood velocity (MCAv) decreased during the HIIT bout and rebounded during active recovery. Women demonstrated a significantly higher resting MCAv than men and the difference remained during HIIT. Here, we report a novel protocol and characterized the MCAv response during an acute bout of low-volume HIIT.

The Effect of Traditional Aerobic Exercise and Sprint Interval Training on Insulin Resistance in Men With Prediabetes: A Randomised Controlled Trial

Introduction

Prediabetes is an intermediate stage with hyperglycaemia below the threshold of diabetes mellitus. Insulin resistance is a significant factor in its pathogenesis. Lifestyle modifications are suggested and found to be more beneficial in this stage. Moderate-intensity exercise for 30 to 45 minutes a day is routinely recommended but has low compliance, and lack of time is a significant deterrent. Sprint interval training (SIT) is an alternate exercise regimen with higher intensity and less time requirement. The present study compares the effect of a three-month intervention of traditional aerobic exercise and sprint interval training on insulin resistance in prediabetic men.

Methods

The study subjects were males aged 25 to 40 years with prediabetes as per the American Diabetes Association criteria of fasting and two-hour plasma glucose levels. The study is a parallel-group randomised trial with one arm (AE group) involved in the traditional aerobic exercise (brisk walking) for 30 minutes, five days a week. The other arm was the sprint interval training (SIT) group performing an ‘all-out’ run effort for one minute followed by a recovery rest period of one and a half minutes, completing one cycle of two and half minutes. Four such cycles were completed in each session. Thus, the exercise sessions were just 10 minutes daily, three days a week. The duration of the intervention was three months. One hundred and sixty participants were recruited after screening and randomly assigned in a 1:1 ratio to the two groups. The primary outcome measure was insulin resistance estimated by homeostasis model assessment -estimated insulin resistance (HOMA-IR). The secondary outcome measures were fasting plasma glucose and serum insulin, glycated haemoglobin, body mass index and waist-hip ratio.

Results

The mean age of the AE group was 30.7 ± 3.3 years, and the SIT group was 31 ± 3.4 years. Seventy-two men from the AE group and 74 from the SIT group completed the study. After the three-month AE and SIT exercise, the per-protocol analysis reflected a significant reduction in insulin resistance, i.e., HOMA-IR (3.6 ± 1.1 to 3 ± 1.2, p<0.0001) after traditional aerobic exercise. Similarly, the HOMA-IR was significantly reduced after sprint interval training (3.3 ± 1.2 to 2.5 ± 1, p<0.0001). The intention-to-treat analysis also found that the reductions in HOMA-IR after both exercise protocols were statistically significant. The change in insulin resistance compared for the SIT vs AE group was not statistically significant. Secondary outcome measures HbA1c, fasting glucose, fasting insulin, BMI, and waist-hip ratio showed significant improvement with AE and SIT. 

Conclusions

The sprint interval training similarly improved insulin resistance and other parameters compared to the traditional exercise group. SIT can be a time-efficient exercise protocol suggested as a part of lifestyle modification for men with prediabetes.

Effects of Different Intensity Exercise on Glucose Metabolism and Hepatic IRS/PI3K/AKT Pathway in SD Rats Exposed with TCDD

The objective of the study was to investigate the effects of different intensity exercise and 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exposure on glucose metabolism in Sprague Dawley (SD) rats, as well as the action of insulin receptor substrate (IRS)/phosphatidylinositol-3-kinases (PI3K)/protein kinase (AKT) signaling pathway in it. Besides that, we explored whether exercise can alleviate the toxicity induced by TCDD. Sixty male SD rats (8 weeks old) were randomly divided into non-exercise group, none-exercise toxic group, moderate-intensity exercise group, moderate-intensity exercise toxic group, high-intensity exercise group, high-intensity exercise toxic group. The toxic groups were intraperitoneally injected with TCDD, which the dose was 6.4 µg/kg· BW for the first week, then 21% of the above week dose for continuous 8 weeks. The 8-week treadmill running of moderate intensity (15 m/min, 60 min/day) and high intensity (26 m/min, 35 min/day) were implemented separately in exercise groups five times a week. After detecting the concentration of fasting serum glucose, insulin and C-peptide, the index of the homeostasis model assessment of insulin resistance (HOMA-IR) and islet β-cell secretion (HOMA-β) were calculated. We measured the hepatic mRNA expression levels of IRS2, phosphatidylinositol-3-kinases catalytic subunit alpha (PIK3CA), AKT by real-time PCR. The protein expression of total IRS2 (tIRS2), phosphorylated IRS2 at Ser731 (pSer731), total PIK3CA (tPIK3CA), total Akt (tAkt), phosphorylated Akt at Thr308 (pThr308) in liver were analyzed by western blot. We observed that compared to the non-exercise group, insulin and HOMA-IR index were significantly higher in the none-exercise toxic group (p < 0.05), while glucose, insulin, C-peptide and HOMA-IR index were significantly lower in the moderate-intensity exercise group (p < 0.05). In the high-intensity exercise group, the HOMA-IR index was significantly lower and the gene expression of IRS2 was significantly higher than in the non-exercise group (p < 0.05). Besides that, the HOMA-β index in the moderate-intensity exercise toxic group was significantly higher compared to the none-exercise toxic group and moderate-intensity exercise group (p < 0.05). The level of IRS2mRNA was significantly lower in the high-intensity exercise toxic group than in the high-intensity exercise group (p < 0.05). Our results demonstrated that 8-week TCDD exposure could induce insulin resistance in rats, while exercise could improve insulin sensitivity in which moderate intensity was more obvious than high intensity exercise. Meanwhile, both intensity exercise could not effectively alleviate the insulin resistance induced by TCDD, but high intensity exercise could promote compensatory insulin secretion to maintain glucose homeostasis. Although the gene expression of IRS2 was changed in high-intensity exercise groups, the mediation role of the hepatic IRS2/PI3K/AKT pathway in the effects of exercise and TCDD exposure on glucose metabolism remains very limited.

Physiological Responses to Low-Volume Interval Training in Women

Interval training is a form of exercise that involves intermittent bouts of relatively intense effort interspersed with periods of rest or lower-intensity exercise for recovery. Low-volume high-intensity interval training (HIIT) and sprint interval training (SIT) induce physiological and health-related adaptations comparable to traditional moderate-intensity continuous training (MICT) in healthy adults and those with chronic disease despite a lower time commitment. However, most studies within the field have been conducted in men, with a relatively limited number of studies conducted in women cohorts across the lifespan. This review summarizes our understanding of physiological responses to low-volume interval training in women, including those with overweight/obesity or type 2 diabetes, with a focus on cardiorespiratory fitness, glycemic control, and skeletal muscle mitochondrial content. We also describe emerging evidence demonstrating similarities and differences in the adaptive response between women and men. Collectively, HIIT and SIT have consistently been demonstrated to improve cardiorespiratory fitness in women, and most sex-based comparisons demonstrate similar improvements in men and women. However, research examining insulin sensitivity and skeletal muscle mitochondrial responses to HIIT and SIT in women is limited and conflicting, with some evidence of blunted improvements in women relative to men. There is a need for additional research that examines physiological adaptations to low-volume interval training in women across the lifespan, including studies that directly compare responses to MICT, evaluate potential mechanisms, and/or assess the influence of sex on the adaptive response. Future work in this area will strengthen the evidence-base for physical activity recommendations in women.

Effects of indulgent food snacking, with and without exercise training, on body weight, fat mass, and cardiometabolic risk markers in overweight and obese men

We hypothesized that exercise training would prevent gains in body weight and body fat, and worsening of cardiometabolic risk markers, during a 4-week period of indulgent food snacking in overweight/obese men. Twenty-eight physically inactive men (ages 19-47 yr) with body mass index (BMI) ≥25 kg/m2 consumed 48 donuts (2/day, 6 days/week; ~14,500 kcal total) for 4 weeks while maintaining habitual diet. Men were randomly assigned to control (n = 9), moderate-intensity continuous training (MICT; n = 9), or high-intensity interval training (HIIT; n = 10). Exercise training occurred 4 days/week, ~250 kcal/session. Controls did not increase body weight, body fat, or visceral abdominal fat. This was partially explained by a decrease in self-reported habitual energy (-239 kcal/day, p = 0.05) and carbohydrate (-47 g/day; p = 0.02) intake. Large inter-individual variability in changes in body weight, fat, and fat-free mass was evident in all groups. Fasting blood pressure, and blood concentrations of glucose, insulin, and lipids were unchanged in all groups. Glucose incremental area under the curve during an oral glucose tolerance test was reduced by 25.6% in control (p = 0.001) and 32.8% in MICT (p = 0.01) groups. Flow-mediated dilation (FMD) was not changed in any group. VO2max increased (p ≤ 0.001) in MICT (9.2%) and HIIT (12.1%) groups. We conclude that in physically inactive men with BMI ≥25 kg/m2 , consuming ~14,500 kcal as donuts over 4 weeks did not adversely affect body weight and body fat, or several markers of cardiometabolic risk. Consumption of the donuts may have prevented the expected improvement in FMD with HIIT.

HIIT'ing or MISS'ing the Optimal Management of Polycystic Ovary Syndrome: A Systematic Review and Meta-Analysis of High- Versus Moderate-Intensity Exercise Prescription

Introduction: Polycystic Ovary syndrome (PCOS) is a metabolic disorder associated with increased cardiovascular disease risk. Exercise is an effective treatment strategy to manage symptoms and reduce long-term health risk. High-intensity interval training (HIIT) has been suggested as a more efficient exercise mode in PCOS; however, it is not clear whether HIIT is superior to moderate intensity steady state exercise (MISS).

Methods: We synthesized available data through a systematic review and meta-analysis to compare the effectiveness of isolated HIIT and MISS exercise interventions. Our primary outcome measures were cardiorespiratory fitness and insulin resistance, measured using V˙O_2max and HOMA-IR respectively.

Results: A total of 16 studies were included. Moderate-quality evidence from 16 studies identified significant improvements in V˙O_2max following MISS (Δ = 1.081 ml/kg/min, p < 0.001, n = 194), but not HIIT (Δ = 0.641 ml/kg/min, p = 0.128, n = 28). Neither HIIT nor MISS improved HOMA-IR [(Δ = −0.257, p = 0.374, n = 60) and (Δ = −0.341, p = 0.078, n = 159), respectively].

Discussion: A significant improvement in V˙O_2max was evident following MISS, but not HIIT exercise in women with PCOS. This contrasts with previous literature in healthy and clinical cohorts that report superior benefits of HIIT. Therefore, based on available moderate-quality evidence, HIIT exercise does not provide superior outcomes in V˙O_2max compared with MISS, although larger high-quality interventions are needed to fully address this. Additional dietary/pharmacological interventions may be required in conjunction with exercise to improve insulin sensitivity.

Physical Activity, Dietary Patterns, and Glycemic Management in Active Individuals with Type 1 Diabetes: An Online Survey

Individuals with type 1 diabetes (T1D) are able to balance their blood glucose levels while engaging in a wide variety of physical activities and sports. However, insulin use forces them to contend with many daily training and performance challenges involved with fine-tuning medication dosing, physical activity levels, and dietary patterns to optimize their participation and performance. The aim of this study was to ascertain which variables related to the diabetes management of physically active individuals with T1D have the greatest impact on overall blood glucose levels (reported as A1C) in a real-world setting. A total of 220 individuals with T1D completed an online survey to self-report information about their glycemic management, physical activity patterns, carbohydrate and dietary intake, use of diabetes technologies, and other variables that impact diabetes management and health. In analyzing many variables affecting glycemic management, the primary significant finding was that A1C values in lower, recommended ranges (<7%) were significantly predicted by a very-low carbohydrate intake dietary pattern, whereas the use of continuous glucose monitoring (CGM) devices had the greatest predictive ability when A1C was above recommended (≥7%). Various aspects of physical activity participation (including type, weekly time, frequency, and intensity) were not significantly associated with A1C for participants in this survey. In conclusion, when individuals with T1D are already physically active, dietary changes and more frequent monitoring of glucose may be most capable of further enhancing glycemic management.

Metabolic effects of high-intensity interval training and essential amino acids

High-intensity interval training (HIIT) promotes positive cardiometabolic and body composition changes. Essential amino acids (EAA) may support changes associated with HIIT, but evaluation of potential synergistic effects is lacking. The purpose of this study was to compare independent and combined effects of HIIT and EAA on total body composition and metabolism in men and women considered overweight/obese; an exploratory aim was to evaluate the modulatory effects of sex. Sixty-six healthy adults (50% female; Age: 36.7 ± 6.0 years; BMI: 32.0 ± 4.2 kg/m²) completed 8 weeks of: (1) HIIT, 2 days/weeks; (2) EAA supplementation, 3.6 g twice daily; (3) HIIT + EAA; or (4) control. Body composition, resting metabolic rate (RMR), substrate metabolism (respiratory exchange ratio; RER), and cardiorespiratory fitness were measured at baseline, 4 weeks, and 8 weeks; cardiometabolic blood markers were measured at baseline and 8 weeks. Differences between groups were assessed by linear mixed models covaried for baseline values, followed by 95% confidence intervals (CI) on adjusted mean change scores. There were no significant changes in body composition (p > 0.05) for any group. Changes in RER, but not RMR, occurred with HIIT (mean change; [95% CI]: - 0.04; [- 0.07, - 0.02]) and EAA (- 0.03; [- 0.06, - 0.01]) after 8 weeks. Cardiorespiratory fitness increased following 8 weeks of HIIT (+ 5.1 ml/kg/min [3.3,6.8]) and HIIT + EAA (+ 4.1 ml/kg/min [1.0,6.4]). Changes with HIIT + EAA were not significantly different from HIIT. There were no changes in cardiometabolic markers (p > 0.05) and no sex interaction (p > 0.05). HIIT is efficacious for promoting positive changes in cardiorespiratory fitness and resting substrate metabolism in adults considered overweight/obese. Addition of EAA did not significantly enhance HIIT-induced adaptations. ClinicalTrials.gov ID#NCT04080102.

Exercise-nutrient interactions for improved postprandial glycemic control and insulin sensitivity

Type 2 diabetes (T2D) is a rapidly growing yet largely preventable chronic disease. Exaggerated increases in blood glucose concentration following meals is a primary contributor to many long-term complications of the disease that decrease quality of life and reduce lifespan. Adverse health consequences also manifest years prior to the development of T2D due to underlying insulin resistance and exaggerated postprandial concentrations of the glucose-lowering hormone insulin. Postprandial hyperglycemic and hyperinsulinemic excursions can be improved by exercise, which contributes to the well-established benefits of physical activity for the prevention and treatment of T2D. The aim of this review is to describe the postprandial dysmetabolism that occurs in individuals at risk for and with T2D, and highlight how acute and chronic exercise can lower postprandial glucose and insulin excursions. In addition to describing the effects of traditional moderate-intensity continuous exercise on glycemic control, we highlight other forms of activity including low-intensity walking, high-intensity interval exercise, and resistance training. In an effort to improve knowledge translation and implementation of exercise for maximal glycemic benefits, we also describe how timing of exercise around meals and post-exercise nutrition can modify acute and chronic effects of exercise on glycemic control and insulin sensitivity. Novelty: Exaggerated postprandial blood glucose and insulin excursions are associated with disease risk. Both a single session and repeated sessions of exercise improve postprandial glycemic control in individuals with and without T2D. The glycemic benefits of exercise can be enhanced by considering the timing and macronutrient composition of meals around exercise.

Considerations for Maximizing the Exercise "Drug" to Combat Insulin Resistance: Role of Nutrition, Sleep, and Alcohol

Insulin resistance is a key etiological factor in promoting not only type 2 diabetes mellitus but also cardiovascular disease (CVD). Exercise is a first-line therapy for combating chronic disease by improving insulin action through, in part, reducing hepatic glucose production and lipolysis as well as increasing skeletal muscle glucose uptake and vasodilation. Just like a pharmaceutical agent, exercise can be viewed as a "drug" such that identifying an optimal prescription requires a determination of mode, intensity, and timing as well as consideration of how much exercise is done relative to sitting for prolonged periods (e.g., desk job at work). Furthermore, proximal nutrition (nutrient timing, carbohydrate intake, etc.), sleep (or lack thereof), as well as alcohol consumption are likely important considerations for enhancing adaptations to exercise. Thus, identifying the maximal exercise "drug" for reducing insulin resistance will require a multi-health behavior approach to optimize type 2 diabetes and CVD care.

The impact of high intensity interval training on liver fat content in overweight or obese adults: A meta-analysis

Liver fat is a marker of the metabolic derangements associated with obesity for which exercise training is a potential therapy. We therefore performed a systematic meta-analysis to investigate the effect of high intensity interval training (HIIT) on liver fat content in overweight or obese adults with metabolic disorders. PubMed, Scopus, Web of Science and the Cochrane were searched up to October 2020 for HIIT vs. Control (CON) or HIIT vs. moderate intensity interval training (MICT) studies on liver fat content in overweight and obese individuals with metabolic disorders. Standardized mean differences (SMD) and 95% confidence intervals (95% CIs) were calculated. Ten studies involving 333 participants were included in the meta-analysis. Based on studies that directly compared HIIT and CON (6 studies), HIIT was beneficial for promoting a reduction in liver fat [-0.51 (95% CI: -0.85 to -0.17), p = 0.003]. However, there were no significant evidence for an effect of HIIT on liver fat [-0.07 (95% CI: -0.33 to 0.19), p = 0.59], when compared with MICT (7 studies). These results suggest that a HIIT could induce improvements in liver fat of overweight and obese adults with metabolic disorders despite no weight loss.

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 15 min 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.

Exercise training decreases whole-body and tissue iron storage in adults with obesity

NEW FINDINGS

What is the central question of this study? Does exercise training modify tissue iron storage in adults with obesity? What is the main finding and its importance? Twelve weeks of moderate-intensity exercise or high-intensity interval training lowered whole-body iron stores, decreased the abundance of the key iron storage protein in skeletal muscle (ferritin) and tended to lower hepatic iron content. These findings show that exercise training can reduce tissue iron storage in adults with obesity and might have important implications for obese individuals with dysregulated iron homeostasis.

ABSTRACT

The regulation of iron storage is crucial to human health, because both excess and deficient iron storage have adverse consequences. Recent studies suggest altered iron storage in adults with obesity, with increased iron accumulation in their liver and skeletal muscle. Exercise training increases iron use for processes such as red blood cell production and can lower whole-body iron stores in humans. However, the effects of exercise training on liver and muscle iron stores in adults with obesity have not been assessed. The aim of this study was to determine the effects of 12 weeks of exercise training on whole-body iron stores, liver iron content and the abundance of ferritin (the key iron storage protein) in skeletal muscle in adults with obesity. Twenty-two inactive adults (11 women and 11 men; age, 31 ± 6 years; body mass index, 33 ± 3 kg/m² ) completed 12 weeks (four sessions/week) of either moderate-intensity continuous training (MICT; 45 min at 70% of maximal heart rate; n = 11) or high-intensity interval training (HIIT; 10 × 1 min at 90% of maximal heart rate, interspersed with 1 min active recovery; n = 11). Whole-body iron stores were lower after training, as indicated by decreased plasma concentrations of ferritin (P = 3 × 10^-5 ) and hepcidin (P = 0.02), without any change in C-reactive protein. Hepatic R2*, an index of liver iron content, was 6% lower after training (P = 0.06). Training reduced the skeletal muscle abundance of ferritin by 10% (P = 0.03), suggesting lower muscle iron storage. Interestingly, these adaptations were similar in MICT and HIIT groups. Our findings indicate that exercise training decreased iron storage in adults with obesity, which might have important implications for obese individuals with dysregulated iron homeostasis.

Combination of Metformin and Exercise in Management of Metabolic Abnormalities Observed in Type 2 Diabetes Mellitus

Excess nutrient intake and lack of exercise characterize the problem of obesity and are common factors in insulin resistance (IR). With an increasing number of prediabetic, and type 2 diabetic populations, metformin is still the most prescribed glucose-lowering drug and is often accompanied by recommendations for regular physical exercise. Metformin, by the inhibition of complex 1 of the electron transport chain, and exercise, by increasing energy expenditure, both elicit a low cellular energy state that leads to improvements in glucose control via activation of adenosine 5' monophosphate-activated protein kinase (AMPK). An augmented stimulation of the energy-sensing enzyme AMPK by either of the two modalities leads to an increase in glycogenolysis, glucose uptake, fat oxidation, a decrease in glycogen and protein synthesis, and gluconeogenesis in muscle and the liver, which are remarked as having positive effects on metabolic pathophysiology observed in IR and type 2 diabetes mellitus (T2DM). While both modalities exploit the energy-sensing enzyme AMPK to attain glucose homeostasis, the synergistic effect of these two treatments is not distinctly supported by the literature. Further, an antagonistic dynamic has been observed in cases where metformin and exercise were combined. Reduction of insulin-sensitizing effects of exercise and an overall hindrance of exercise performance and adaptations have been reported and could suggest the possible incongruity of these two modalities. The aim of this review is to elucidate the effect that metformin and exercise have on the management of the metabolic abnormalities observed in T2DM and to provide an insight into the interaction of these two modalities.

Mechanisms underlying the metabolic actions of testosterone in humans: A narrative review

The role of testosterone in improving sexual symptoms in men with hypogonadism is well known. However, recent studies indicate that testosterone plays an important role in several metabolic functions in males. Multiple PubMed searches were conducted with the use of the terms testosterone, insulin sensitivity, obesity, type 2 diabetes, anaemia, bone density, osteoporosis, fat mass, lean mass and body composition. This narrative review is focused on detailing the mechanisms that underlie the metabolic aspects of testosterone therapy in humans. Testosterone enhances insulin sensitivity in obese men with hypogonadism by decreasing fat mass, increasing lean mass, decreasing free fatty acids and suppressing inflammation. At a cellular level, testosterone increases the expression of insulin receptor β subunit, insulin receptor substrate-1, protein kinase B and glucose transporter type 4 in adipose tissue and adenosine 5'-monophosphate-activated protein kinase expression and activity in skeletal muscle. Observational studies show that long-term therapy with testosterone prevents progression from prediabetes to diabetes and improves HbA1c. Testosterone increases skeletal muscle satellite cell activator, fibroblast growth factor-2 and decreases expression of the muscle growth suppressors, myostatin and myogenic regulatory factor 4. Testosterone increases haematocrit by suppressing hepcidin and increasing expression of ferroportin along with that of transferrin receptor and plasma transferrin concentrations. Testosterone also increases serum osteocalcin concentrations, which may account for its anabolic actions on bone. In conclusion, testosterone exerts a series of potent metabolic effects, which include insulin sensitization, maintenance and growth of the skeletal muscle, suppression of adipose tissue growth and maintenance of erythropoiesis and haematocrit.

Are Alterations in Skeletal Muscle Mitochondria a Cause or Consequence of Insulin Resistance?

As a major site of glucose uptake following a meal, skeletal muscle has an important role in whole-body glucose metabolism. Evidence in humans and animal models of insulin resistance and type 2 diabetes suggests that alterations in mitochondrial characteristics accompany the development of skeletal muscle insulin resistance. However, it is unclear whether changes in mitochondrial content, respiratory function, or substrate oxidation are central to the development of insulin resistance or occur in response to insulin resistance. Thus, this review will aim to evaluate the apparent conflicting information placing mitochondria as a key organelle in the development of insulin resistance in skeletal muscle.

Skeletal muscle ferritin abundance is tightly related to plasma ferritin concentration in adults with obesity

NEW FINDINGS

What is the central question of this study? Obesity is associated with complex perturbations to iron homeostasis: is plasma ferritin concentration (a biomarker of whole-body iron stores) related to the abundance of ferritin (the key tissue iron storage protein) in skeletal muscle in adults with obesity? What is the main finding and its importance? Plasma ferritin concentration was tightly correlated with the abundance of ferritin in skeletal muscle, and this relationship persisted when accounting for sex, age, body mass index and plasma C-reactive protein concentration. Our findings suggest that skeletal muscle may be an important iron store.

ABSTRACT

Obesity is associated with complex perturbations to whole-body and tissue iron homeostasis. Recent evidence suggests a potentially important influence of iron storage in skeletal muscle on whole-body iron homeostasis, but this association is not clearly resolved. The primary aim of this study was to assess the relationship between whole-body and skeletal muscle iron stores by measuring the abundance of the key iron storage (ferritin) and import (transferrin receptor) proteins in skeletal muscle, as well as markers of whole-body iron homeostasis in men (n = 19) and women (n = 43) with obesity. Plasma ferritin concentration (a marker of whole-body iron stores) was highly correlated with muscle ferritin abundance (r = 0.77, P = 2 × 10^-13 ) and negatively associated with muscle transferrin receptor abundance (r = -0.76, P = 1 × 10^-12 ). These relationships persisted when accounting for sex, age, BMI and plasma C-reactive protein concentration. In parallel with higher whole-body iron stores in our male versus female participants, men had 2.2-fold higher muscle ferritin abundance (P = 1 × 10^-4 ) compared with women. In accordance with lower muscle iron storage, women had 2.7-fold higher transferrin receptor abundance (P = 7 × 10^-10 ) compared with men. We conclude that muscle iron storage and import proteins are tightly and independently related to plasma ferritin concentration in adults with obesity, suggesting that skeletal muscle may be an underappreciated iron store.

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.