High-intensity interval training alleviates liver inflammation by regulating the TLR4/NF-κB signaling pathway and M1/M2 macrophage balance in female rats with cisplatin hepatotoxicity.

Cisplatin (CDDP) is an antineoplastic drug whose adverse effects include hepatotoxicity. The inflammatory process is crucial in the progression of liver injuries. Exercise is known for its anti-inflammatory effects, but the influence of different training modalities on hepatoprotection is still unclear. This study aims to compare the impacts between preconditioning with high-intensity interval training (HIIT) and traditional continuous training of low (LT) and moderate (MT) intensities on inflammatory markers in Wistar female rats with CDDP-induced hepatotoxicity. Thirty-five rats were divided into five groups: control and sedentary (C + Sed), treated with CDDP and sedentary (CDDP + Sed), treated with CDDP and subjected to LT (CDDP + LT), treated with CDDP and subjected to MT (CDDP + MT), and treated with CDDP and subjected to HIIT (CDDP + HIIT). The training protocols consisted of treadmill running for 8 weeks before CDDP treatment. The rats were euthanized 7 days after the treatment. Liver samples were collected to evaluate the expression of various inflammatory markers and types of macrophages. Our results indicated that HIIT was the only protocol to prevent the increase in all analyzed pro-inflammatory cytokines and reduce the number of ED-1-positive cells, attenuating the TLR4/NF-κB signaling pathway in the liver. Additionally, HIIT increased the anti-inflammatory cytokine IL-10 and regulated M1/M2 macrophage polarization. Thus, this study suggests that preconditioning with HIIT is more effective in promoting hepatoprotective effects than LT and MT, regulating inflammatory markers through modulation of the TLR4/NF-κB signaling pathway and M2 macrophage polarization in the hepatic tissue of female rats treated with CDDP.

Endurance Exercise Prevented Diabetic Cardiomyopathy through the Inhibition of Fibrosis and Hypertrophy in Rats.

Background: Exercise training could be essential in preventing pathological cardiac remodeling in diabetes. Therefore, the effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) singly or plus metformin on diabetes-induced cardiomyopathy were investigated in this study. Methods: Forty-nine Wistar rats (male) were recruited. Seven groups of animals were treated for six weeks as control, diabetes, MICT (15 m/min, 40 min/day), HIIT (20 m/min, 40 min/day), metformin (300 mg/kg), HIIT+metformin (Met-HIIT), and MICT+metformin (Met-MICT). The metformin was orally administered with an intragastrical needle, and the exercised rats were trained (5 days/week) with a motorized treadmill. Metabolic parameters, echocardiographic indices, histopathology evaluation, and assessment of gene expression connected with cardiac fibrosis, hypertrophy, mitochondrial performance, and intracellular calcium homeostasis were investigated. Results: Our results demonstrated that all the interventions prevented weight loss and enhanced heart weight/body weight ratio and fasting plasma glucose in diabetic rats. Both types of exercise and their metformin combinations improved diabetic animals' echocardiography indices by enhancing heart rate, fractional shortening (FS), ejection fraction (EF) and reducing end-systolic and end-diastolic diameter of left ventricular (LVESD and LVEDD). Gene expression of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), transforming growth factor (TGF)- ß , and collagen increased in the diabetes group. In contrast, the gene expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 α ), AMP-activated protein kinase (AMPK), ryanodine receptors (RyR), and Ca 2 + ATPase pump of the sarcoplasmic reticulum (SERCA) was reduced in diabetic animals. Exercise training alone or in combination with metformin reversed these changes. Moreover, diabetes-induced cardiac fibrosis was ameliorated in treated groups. All indicators of diabetic cardiomyopathy were improved more in the Met-HIIT group than in other groups. Conclusions: Exercise training, notably with metformin combination, alleviated diabetes-induced cardiac complications. The beneficial effects of exercise could be related to improving pathological cardiac remodeling and enhancing cardiac function.

Effects of Exercise Interventions on Estimated Pulse Wave Velocity and Mean Arterial Pressure in Overweight Adults: The Role of Modality.

Background: Estimated pulse wave velocity (ePWV) is mathematically calculated from age and mean arterial pressure (MAP). We examined the effects of high-intensity interval training (HIIT) vs. moderate-intensity continuous training (MICT) on ePWV and MAP in insufficiently active overweight adults. Methods: Using the randomized controlled trial design, thirteen males (27.46 ± 3.80 years old; body mass index (BMI) = 29.61 ± 5.52) randomly completed either two-week HIIT (n = 7) or MICT (n = 6). HIIT consisted of 8 sessions of cycling, 20 min/session with an exercise-to-rest ratio of 10/50 s at ≥ 90% peak heart rate ( HR peak ). MICT consisted of 8 cycling sessions, 40 min/session at 60-75% HR peak . Oscillometric brachial MAP was measured pre- and post-intervention, and ePWV was calculated. Two-way repeated measure analysis of variance examined the effects of time, intervention, and their interactions on ePWV and MAP. Results: Significant time effects were observed for ePWV and MAP, where both measures comparably decreased over time in HIIT and MICT groups (p < 0.05 for all). However, no significant intervention or interaction effects were detected, indicating no superiority of either exercise modality for ePWV or MAP improvements. Conclusions: This study uniquely revealed that two weeks of HIIT or MICT resulted in significant, comparable, and clinically meaningful decreases in ePWV and MAP among insufficiently active overweight adults. As such, overweight adults who have time as a constraint to engage in traditional exercise (i.e., MICT) can accomplish comparable vascular benefits by performing HIIT.

High-intensity interval training ameliorates postnatal immune activation-induced mood disorders through KDM6B-regulated glial activation.

Postnatal immune activation (PIA) induces persistent glial activation in the brain and causes various neuropathologies in adults. Exercise training improves stress-related mood disorders; however, the role of exercise in psychiatric disorders induced by early-life immune activation and the association between exercise training and glial activation remain unclear. We compared the effects of different exercise intensities on the PIA model, including high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT). Both HIIT and MICT in adolescent mice inhibited neuroinflammation, remodeled synaptic plasticity, and improved PIA-induced mood disorders in adulthood. Importantly, HIIT was superior to MICT in terms of reducing inflammation and increasing body weight. RNA-seq of prefrontal cortex (PFC) tissues revealed a gene expression pattern, confirming that HIIT was more effective than MICT in improving brain glial cell activation through epigenetic modifications of KDM6B. We investigated the role of KDM6B, a specific histone lysine demethylation enzyme - histone 3 lysine 27 demethylase, in inhibiting glial activation against PIA-induced depression and anxiety by regulating the expression of IL-4 and brain-derived neurotrophic factor (BDNF). Overall, our data support the idea that HIIT improves PIA-induced mood disorders by regulating KDM6B-mediated epigenetic mechanisms and indicate that HIIT might be superior to MICT in improving mood disorders with PIA in mice. Our findings provide new insights into the treatment of anxiety and depression disorders.

Exercise-activated hepatic autophagy combined with silymarin is associated with suppression of apoptosis in rats subjected to dexamethasone induced- fatty liver damage.

AIM: There is a need for effective treatments for non-alcoholic fatty liver disease (NAFLD) that are economically inexpensive, and have few side effects. The present study aimed to investigate exercise training and silymarin on hepatocyte death factors in rats with liver damage. METHODS: Forty-nine male Wistar rats were assigned to seven groups: sedentary control, fatty liver control (DEX), fatty liver + high-intensity interval training (HIIT), fatty liver + HIIT + silymarin (HIIT + SILY), fatty liver + continuous training (CT), fatty liver + CT + silymarin (CT + SILY), and fatty liver + silymarin (SILY). A subcutaneous injection of dexamethasone for 7 days was used to induce fatty liver in rats. Masson's trichrome and hematoxylin-eosin staining were done to evaluate hepatic injury. The hepatocyte apoptosis was determined by TUNEL assay. Real-Time PCR was conducted to evaluate the gene expressions of caspase-9, adenosine monophosphate-activated protein kinase (AMPKα1), mitofusin 2 (Mfn2), and damage-regulated autophagy modulator (DRAM). Liver tissue changes and serum levels of liver enzymes were also evaluated. RESULTS: Liver apoptosis was decreased in the CT, HIIT, HIIT + SILY and CT + SILY groups compared to the DEX group. Both continuous and high-intensity training models produced beneficial alterations in liver morphology and hepatic injuries that were significant in exercise training + silymarin group. This impact was accompanied by increased AMPKα1 and DRAM gene expression and decreased caspase-9 and Mfn2 gene expression. Liver enzyme levels were high in the DEX group and treatment with silymarin significantly reduced it. CONCLUSION: Silymarin supplementation combined with interval or continuous training substantially improves DEX-induced hepatic steatosis and hepatocyte injury mostly through suppressing liver apoptosis and upregulating autophagy, which may provide a novel perspective for NAFLD treatment.

Effects of different HIIT protocols on exercise performance, metabolic adaptation, and fat loss in middle-aged and older adults with overweight.

Introduction: There is evidence that aging and obesity are associated with increased oxidative stress and chronic inflammation. High-intensity interval training (HIIT) may be superior to moderate-intensity continuous training (MICT) in anti-inflammatory and anti-obesity benefits. Therefore, the objective of this study is to determine which HIIT prescriptions will be more effective in reducing fat accumulation, inflammation, and improving metabolic adaptation and exercise performance in middle-aged and older overweight adults. Methods: Thirty-six middle-aged with overweight adults were divided into one of three groups: 1. L-HIIT group: the long-interval HIIT group (4 × 4 min Exercise/4 min Rest), 2. M-HIIT group: the medium-interval HIIT group (8 × 2 min Exercise/2 min Rest), 3. Control group: no exercise training intervention. All groups underwent the training stage for eight weeks (three sessions per week), followed by a detraining stage of four weeks in order to investigate the effects induced by different HIIT interventions on inflammation, metabolic adaptation, anti-fatigue and exercise performance, and fat loss Results: There was a significant physiological response in the change rate of heart rate (HR) after an acute L-HIIT session compared with an acute M-HIIT session (ΔHR: ↑49.66±16.09% vs ↑33.22±14.37%, p=0.02); furthermore, systolic blood pressure (SBP) and diastolic blood pressure (DBP) decreased significantly following a single L-HIIT session. After an eight-week training stage, the L-HIIT and M-HIIT groups exhibited a significant increase in aerobic capacity (ΔVO2peak), with values of +27.93±16.79% (p<0.001) and +18.39±8.12% (p<0.001), respectively, in comparison to the control group. Furthermore, in the L-HIIT group, the anaerobic power of relative mean power (RMP) exhibited a significant increase (p=0.019). However, following a four-week detraining stage, the adiponectin concentration remained 1.78 times higher in the L-HIIT group than in the control group (p=0.033). The results of blood sugar, blood lipids, body composition, and inflammatory markers did not indicate any improved it did not indicate any improvements from the two different HIIT protocols. Conclusions: The results indicate that an eight-week L-HIIT or M-HIIT intervention (three sessions per week, 32 minutes per session) may be an effective approach for improving aerobic capacity. It can be posited that L-HIIT may be a more advantageous mode than M-HIIT for enhancing anaerobic power, adipokine levels, and improving blood pressure in an aged and overweight population due to the induced physiological responses.

Effects of Exercise Training Response on Quality of Life and Cardiovascular Risk Factor Profiles in People With Coronary Artery Disease: Insights From the HIIT or MISS UK Trial.

OBJECTIVE: To compare the characteristics of responders and nonresponders to 8 weeks of exercise training to determine differences in key cardiovascular disease outcomes in people with coronary artery disease (CAD). DESIGN: Secondary analysis of data from the HIIT or MISS UK trial. SETTING: Six outpatient National Health Service cardiac rehabilitation (CR) centers in the UK. In people with CAD attending CR, the HIIT or MISS UK trial reported that short-term, low-volume, high-intensity interval training (HIIT) was more effective than moderate-intensity steady state (MISS) exercise training for improving peak oxygen uptake (V̇o2peak). PARTICIPANTS: 382 participants with CAD (N=382) (mean age: 58.8±9.6y; mean body mass index: 29.0±4.3 kg/m2). MAIN OUTCOME MEASURES: We identified responders and nonresponders based on a meaningful change in V̇o2peak, using 2 established methods. Key clinical, quality of life (QoL), and cardiopulmonary exercise test (CPET)-derived outcomes were compared between groups. RESULTS: Responders were more likely to be younger (P<.05), and demonstrate greater improvement in CPET-related outcomes, for example, oxygen uptake efficiency slope, ventilatory efficiency, and peak power output (all comparisons, P<.001). Responders were more likely to observe improvements in QoL (EQ-5D-5L; mean Δ 13.6 vs mean Δ 9.4; P=.045), and high-density lipoprotein cholesterol (HDL-c) (mean Δ 0.09 mmol/L vs mean Δ 0.04 mmol/L; P=.004), compared to nonresponders. CONCLUSIONS: In people with CAD attending CR, responders to exercise training were more likely to be younger and demonstrate greater improvements in health-related QoL and HDL-c.

The effects of high-intensity interval training/moderate-intensity continuous training on the inhibition of fat accumulation in rats fed a high-fat diet during training and detraining.

BACKGROUND: Compared with moderate-intensity continuous training (MICT), high-intensity interval training (HIIT) has at least a comparable effect on inhibiting an increase in fat. However, few studies have been conducted to examine the effects of detraining on body fat in rats fed a high-fat diet. The present study aimed to compare the effects of 10 weeks of HIIT or MICT as well as 6 weeks of detraining on body fat in rats fed a high-fat diet. METHODS: After being fed a high-fat diet for 8 weeks, 54 female rats were randomly assigned to six groups: (1) CON-10, sedentary control for 10 weeks; (2) MICT-10, 10 weeks of MICT; (3) HIIT-10, 10 weeks of HIIT; (4) CON-16, sedentary control for 16 weeks; (5) MICT-16, 10 weeks of MICT followed by 6 weeks of training cessation; and (6) HIIT-16, 10 weeks of HIIT followed by 6 weeks of training cessation. The training was performed 5 days/week. The subcutaneous adipose tissue (inguinal; SCAT), visceral adipose tissue (periuterine; VAT) and serum lipid profile were analysed after 10 or 16 weeks. Adipose tissue triglyceride lipase (ATGL) protein expression in VAT was assessed by western blotting. RESULTS: HIIT-10 and MICT-10 prevented the increase in SCAT, VAT and serum lipid levels seen in the CON group. During the 6-week detraining period, HIIT continued to prevent the increase in adipose tissue mass observed in the CON group, whereas MICT at least maintained this inhibition. The inhibition of fat mass increase was mainly the result of preventing adipocyte hypertrophy. The HIIT-10 and HIIT-16 groups showed the highest ATGL protein expression. CONCLUSIONS: HIIT has a comparable effect to MICT on inhibiting fat accumulation in female rats; however, the inhibition of SCAT and VAT increase by HIIT is superior to MICT after short-term training cessation.

High-intensity interval training and cardiorespiratory fitness in adults: An umbrella review of systematic reviews and meta-analyses.

BACKGROUND: High-intensity interval training (HIIT) is characterized by repeated bouts of relatively intense exercise interspersed with recovery periods. Previous studies have evaluated this exercise strategy with various population subgroups, regimens, and comparator groups, limiting the generalizability of findings. We performed a novel umbrella review to generate an up-to-date synthesis of the available evidence regarding the effect of HIIT on cardiorespiratory fitness (CRF) in adults as compared to non-exercise control and traditional continuous forms of exercise such as moderate-intensity continuous training (MICT). METHODS: An umbrella review was conducted in accordance with the Preferred Reporting Items for Overviews of Reviews guideline. Seven databases (MEDLINE, EMBASE, Cochrane Database, CINAHL, Scopus, SPORTDiscus, and Web of Science) were searched until February 2024. Systematic reviews with meta-analyses comparing HIIT and active/non-active control conditions were included. Literature search, data extraction, and methodological quality assessment (AMSTAR-2) were conducted independently by two reviewers. RESULTS: Twenty-four systematic reviews with meta-analyses, representing 429 primary studies and 12 967 unique participants, met the inclusion criteria. Most of the systematic reviews received moderate-to-critically low AMSTAR-2 scores. The data showed that HIIT, including the particularly intense variant "sprint interval training" (SIT), significantly increases CRF in adults compared to non-exercise control (standardized mean difference [SMD]: 0.28 to 4.31; weighted mean difference [WMD]: 3.25 to 5.5 mL/kg/min) and MICT (SMD: 0.18 to 0.99; WMD: 0.52 to 3.76 mL/kg/min). This effect was consistently observed across specific groups of individuals (e.g., apparently healthy adults, individuals with overweight/obesity, older adults, and high-level athletes) and HIIT modalities (e.g., low-volume HIIT, whole-body HIIT, home-based HIIT, aquatic HIIT, and short SIT). CONCLUSION: Existing evidence from systematic reviews consistently supports the effect of HIIT on enhancing CRF in adults when compared to non-exercise control and MICT. Our findings offer a comprehensive basis that may potentially contribute to informing physical activity guidelines aimed at improving CRF in the general population.

The Effect of Duration on Performance and Perceived Fatigability During Acute High-Intensity Interval Exercise in Young, Healthy Males and Females.

Few studies have explored the kinetics of performance and perceived fatigability during high-intensity interval training, despite its popularity. We aimed to characterize the kinetics of fatigability and recovery during an 8 × 4-min HIIT protocol, hypothesizing that most muscle function impairment would occur during the initial four intervals. Fifteen healthy males and females (mean ± standard deviation; age = 26 ± 5 years, V̇O2max = 46.8 ± 6.1 mL·kg-1·min-1) completed eight, 4-min intervals at 105% of critical power with 3 min of rest. Maximal voluntary knee extension contractions (MVCs) coupled with electrical nerve stimulation were performed at baseline and after the first, fourth, and eighth intervals. MVC, potentiated twitch force (Pt), and Db10:100 ratio all declined throughout HIIT (p < 0.05). MVC sharply declined after interval 1 (-15 ± 9% relative to baseline; p < 0.05) and had only further declined after interval 8 (-26 ± 11%; p < 0.05), but not interval 4 (-19 ± 13%; p > 0.05). Pt and Db10:100 also sharply declined after interval 1 (Pt: -18 ± 13%, Db10:100: -14 ± 20%; p < 0.05) and further declined after interval 4 (Pt: -35 ± 19%, Db10:100: -30 ± 20%; p < 0.05) but not interval 8 (Pt: -41 ± 19%; Db10:100: -32 ± 18%; p > 0.05). Voluntary activation did not significantly change across the HIIT protocol (p > 0.05). Evoked force recovery was significantly blunted as more intervals were completed: after interval 1, Pt recovered by 7 ± 11% compared to -6 ± 7% recovery after interval 8 (p < 0.05). Ratings of perceived effort, fatigue, and leg pain rose throughout the session (p < 0.05 for each) and were greater (effort and fatigue) for females (p < 0.05). Otherwise, males and females exhibited similar performance fatigability kinetics, with contractile function declines blunted in response to additional intervals.

The intensity paradox: A systematic review and meta-analysis of its impact on the cardiorespiratory fitness of older adults.

AIM: The present systematic review and meta-analysis aimed to compare the effect of moderate- versus high-intensity aerobic exercise on cardiorespiratory fitness (CRF) in older adults, taking into account the volume of exercise completed. METHODS: The databases MEDLINE (Ovid), EMBASE (Ovid), and CENTRAL (Cochrane Library) were searched to identify randomized controlled trials (RCTs). Two reviewers extracted data and assessed bias. Comprehensive Meta-Analysis software calculated overall effect size, intensity differences, and performed meta-regression analyses using pre-to-post intervention or change scores of peak oxygen uptake (V̇O2 peak). The review included 23 RCTs with 1332 older adults (intervention group: n = 932; control group: n = 400), divided into moderate-intensity (435 older adults) and high-intensity (476 older adults) groups. RESULTS: Meta-regression analysis showed a moderate, but not significant, relationship between exercise intensity and improvements in V̇O2 peak after accounting for the completed exercise volume (ß = 0.31, 95% CI = [-0.04; 0.67]). Additionally, studies comparing moderate- versus high-intensity revealed a small, but not significant, effect in favor of high-intensity (Hedges' g = 0.20, 95% CI = [-0.02; 0.41]). Finally, no significant differences in V̇O2 peak improvements were found across exercise groups employing various methods, modalities, and intensity monitoring strategies. CONCLUSION: Findings challenge the notion that high-intensity exercise is inherently superior and indicate that regular aerobic exercise, irrespective of the specific approach and intensity, provides the primary benefits to CRF in older adults. Future RCTs should prioritize valid and reliable methodologies for monitoring and reporting exercise volume and adherence among older adults.

Mindfulness induction and executive function after high-intensity interval training with and without mindful recovery intervals.

OBJECTIVES: Determine the effect of incorporating mindfulness-based activities into the recovery intervals of high-intensity interval training (HIIT) on mindfulness induction and subsequent executive function performance. DESIGNS: A within-subject crossover trial. METHODS: Forty adults participated in two experimental conditions, including a 30-min bout of HIIT involving mindfulness recovery intervals (Mindful) and a 30-min bout of HIIT without mindfulness recovery intervals (Non-mindful), on two separate days in counterbalanced order. Before and after each condition, participants completed the flanker task, switch-flanker task, and n-back task to measure inhibitory control, cognitive flexibility, and working memory, respectively. RESULTS: A higher level of mindfulness state was observed following the Mindful condition than the Non-mindful condition. Dispositional mindfulness was positively correlated with the level of the mindful state only during the Mindful condition but not the Non-mindful condition. The switch-flanker response accuracy was improved from the pretest to posttest during the Non-mindful condition but remained unchanged over time during the Mindful condition. Time-related improvements in the flanker and n-back task outcomes were observed for both the Mindful and Non-mindful conditions and did not differ between conditions. CONCLUSION: Although incorporating mindfulness-based activities during the recovery intervals of HIIT successfully led to greater state-related mindfulness, such a heightened mindful state did not correspond with additional modulation in inhibitory control and working memory performance while attenuating HIIT-related positive changes in task performance requiring cognitive flexibility.

Lung molecular and histological changes in type 2 diabetic rats and its improvement by high-intensity interval training.

BACKGROUND: Type 2 diabetes (T2D) leads to serious respiratory problems. This study investigated the effectiveness of high-intensity interval training (HIIT) on T2D-induced lung injuries at histopathological and molecular levels. METHODS: Forty-eight male Wistar rats were randomly allocated into control (CTL), Diabetes (Db), exercise (Ex), and Diabetes + exercise (Db + Ex) groups. T2D was induced by a high-fat diet plus (35 mg/kg) of streptozotocin (STZ) administration. Rats in Ex and Db + Ex performed HIIT for eight weeks. Tumor necrosis factor-alpha (TNFα), Interleukin 10 (IL-10), BAX, Bcl2, Lecithin, Sphingomyelin (SPM) and Surfactant protein D (SPD) levels were measured in the bronchoalveolar lavage fluid (BALF) and malondialdehyde (MDA) and total antioxidant capacity (TAC) levels were measured in lung tissue. Lung histopathological alterations were assessed by using H&E and trichrome mason staining. RESULTS: Diabetes was significantly associated with imbalance in pro/anti-inflammatory, pro/anti-apoptosis and redox systems, and reduced the SPD, lecithin sphingomyelin and alveolar number. Performing HIIT by diabetic animals increased Bcl2 (P < 0.05) and IL10 (P < 0.01) levels as well as surfactants components and TAC (P < 0.05) but decreased fasting blood glucose (P < 0.001), TNFα (P < 0.05), BAX (P < 0.05) and BAX/Bcl2 (P < 0.001) levels as well as MDA (P < 0.01) and MDA/TAC (P < 0.01) compared to the diabetic group. Furthermore, lung injury and fibrosis scores were increased by T2D and recovered in presence of HIIT. CONCLUSION: These findings suggested that the attenuating effect of HIIT on diabetic lung injury mediated by reducing blood sugar, inflammation, oxidative stress, and apoptosis as well as improving pulmonary surfactants components.

Acute Response of Different High-Intensity Interval Training Protocols on Cardiac Auto-Regulation Using Wearable Device.

The purpose of this study was to compare different high-intensity interval training (HIIT) protocols with different lengths of work and rest times for a single session (all three had identical work-to-rest ratios and exercise intensities) for cardiac auto-regulation using a wearable device. With a randomized counter-balanced crossover, 13 physically active young male adults (age: 19.4 years, BMI: 21.9 kg/m2) were included. The HIIT included a warm-up of at least 5 min and three protocols of 10 s/50 s (20 sets), 20 s/100 s (10 sets), and 40 s/200 s (5 sets), with intensities ranging from 115 to 130% Wattmax. Cardiac auto-regulation was measured using a non-invasive method and a wearable device, including HRV and vascular function. Immediately after the HIIT session, the 40 s/200 s protocol produced the most intense stimulation in R-R interval (Δ-33.5%), ln low-frequency domain (Δ-42.6%), ln high-frequency domain (Δ-73.4%), and ln LF/HF ratio (Δ416.7%, all p < 0.05) compared to other protocols of 10 s/50 s and 20 s/100 s. The post-exercise hypotension in the bilateral ankle area was observed in the 40 s/200 s protocol only at 5 min after HIIT (right: Δ-12.2%, left: Δ-12.6%, all p < 0.05). This study confirmed that a longer work time might be more effective in stimulating cardiac auto-regulation using a wearable device, despite identical work-to-rest ratios and exercise intensity. Additional studies with 24 h measurements of cardiac autoregulation using wearable devices in response to various HIIT protocols are warranted.

Effectiveness of a game-based high-intensity interval training on executive function and other health indicators of children with ADHD: A three-arm partially-blinded randomized controlled trial.

Background: Children with ADHD demand for effective intervention with minimum side effect to improve executive function (EF) and health well-being. Method: This study used a three-arm partially-blinded randomized controlled trial to test the effects of two different kinds of 8-week game-based training programs (game-based HIIT program, GameHIIT; and game-based structured aerobic exercise program, GameSAE) on EF and other health indicators of children with ADHD, which was compared with a non-treatment control group. Results: A total of 49 children with ADHD completed the program. Analyses of EF tests and parental survey indicated that (i) there is no significant intragroup difference among all measures between pre-/post-intervention tests for two game-based intervention groups. The only significant intergroup difference was observed in self-monitor score of parent-reported child's EF between GameSAE group and the control (large effect). Similarly, cerebral hemodynamic responses also found no significant group effect for all EF tests. However, the time effects were observed in several channels in the GameHIIT group in two EF tests (Color Words Stroop Test and Tower of London Test). No significant change of participants' overall ADHD symptoms was found in the pre-/post-tests for three groups. Nonetheless, further analyses revealed that both of two game-based training programs exhibited the significant positive effects on child's PA levels and the large effects on levels of physical fitness, when they were compared to the control. Conclusion: By this study, a significant enhancement in physical fitness and PA levels were found in both game-based PA interventions when they were compared with control group. However, the effectiveness of game-based PA interventions on improving EF or reducing ADHD symptoms remains unclear. This implies that a larger intervention dosage or a tailored intervention design may be warranted to improve the EF of children with ADHD.

Effects of volume-matched once-weekly and thrice-weekly high-intensity interval training (HIIT) on body adiposity in adults with central obesity: Study protocol for a randomized controlled trial.

Objective: This study aims to examine the comparative effects of 75 min of volume-matched once-weekly and thrice-weekly high-intensity interval training (HIIT) on body adiposity in adults with central obesity. Methods: This assessor-blinded, three-arm, randomized controlled trial will recruit 315 physically inactive adults with central obesity (aged ≥18 years, body mass index ≥23, waist circumference ≥90 cm for men and ≥80 cm for women). Participants will be randomly allocated to the once-weekly HIIT, thrice-weekly HIIT or usual care control group. Participants in the HIIT groups will receive weekly exercise training sessions for 16 weeks, prescribed either once or three times weekly. Each HIIT session will consist of a supervised program of four 4-min high-intensity intervals at 85%-95% peak heart rate (HRpeak) interspersed with 3-min active recovery intervals at 50%-70% HRpeak. Participants in the once-weekly HIIT group will perform the 25-min HIIT bout three times with a break between each 25-min HIIT bout. The usual care control group will receive bi-weekly health education classes. The outcome assessments will be conducted at baseline, 16 weeks (post-intervention) and 32 weeks (follow-up). The primary outcome will be total body adiposity assessed by dual-energy X-ray absorptiometry (DXA). The secondary outcome measures will include markers of cardiovascular and metabolic health (body composition, cardiorespiratory fitness, blood pressure, and blood lipids), mental health, cognitive performance, health-related quality of life, sleep quality, habitual physical activity, diet, medication, adverse events and adherence to the intervention. Impact of the project: The findings from this study are expected to consolidate the therapeutic efficacy of HIIT for the management of central obesity and inform the comparative compliance, feasibility and suitability of once-weekly and thrice-weekly HIIT as exercise strategies to manage obesity. In particular, the present study is expected to provide a novel perspective on the utility of low-frequency HIIT (i.e., once-weekly) as an effective and sustainable exercise strategy to tackle the obesity pandemic. The anticipated findings will hold substantial translational value by informing public health policies and enhancing exercise compliance in the physically inactive obese population. Trial registration: ClinicalTrials.gov (NCT04887454).

Dynamics of indicators of functional state and physical development of students in the process of high-intensity interval training.

OBJECTIVE: Aim: To investigate the effect of high-intensity interval training (HIIT) based on the CrossFit system on the level of students' functional state and physical development. PATIENTS AND METHODS: Materials and Methods: The research involved 36 male students who were engaged in HIIT during their studies. Indicators of students' functional state and physical development after 1 and 3 years of HIIT were studied. The functional state was assessed by indicators of the cardiovascular and respiratory systems, and physical development - by physical education tests. RESULTS: Results: It has been found that HIIT has a positive effect on the indicators of the functional state of the cardiovascular and respiratory systems of the body and the physical development of students. After three years of HIIT sessions, students significantly improved their heart rate, vital capacity of the lungs, Stange test, Genchi test, duration of recovery heart rate, as well as the level of development of speed qualities, strength qualities, endurance and flexibility. CONCLUSION: Conclusions: It has been established that the sports-oriented form of organization of physical education training sessions with the use of HIIT based on the CrossFit system is quite effective in improving the indicators of the functional state and physical development of students. A high level of these indicators will help to improve students' health, improve their well-being, and increase the effectiveness of their educational and, in the future, professional activities.

Benefits beyond cardiometabolic health: the potential of frequent high intensity 'exercise snacks' to improve outcomes for those living with and beyond cancer.

High intensity interval training (HIIT) has been shown to consistently elicit rapid and significant adaptations in a number of physiological systems, across many different healthy and clinical populations. In addition, there is increasing interest in how some acute, yet transient responses to high intensity exercise potentially reduce the risks of particular diseases. Recent work has shown that discrete, brief bouts of high intensity exercise (termed 'exercise snacks') can improve glucose control and vascular health and thus counter the negative cardiometabolic consequences of prolonged, uninterrupted periods of inactivity. In this brief review, we advance the case, using evidence available from pre-clinical studies in the exercise oncology literature, that brief, frequently completed bouts of high intensity exercise embedded within an individual's overall daily and weekly physical activity schedule, may transiently impact the tumour microenvironment and improve the health outcomes for those who have been diagnosed and treated for cancer.

Resistance training diminishes mitochondrial adaptations to subsequent endurance training in healthy untrained men.

We investigated the effects of performing a period of resistance training (RT) on the performance and molecular adaptations to a subsequent period of endurance training (ET). Twenty-five young adults were divided into an RT+ET group (n = 13), which underwent 7 weeks of RT followed by 7 weeks of ET, and an ET-only group (n = 12), which performed 7 weeks of ET. Body composition, endurance performance and muscle biopsies were collected before RT (T1, baseline for RT+ET), before ET (T2, after RT for RT+ET and baseline for ET) and after ET (T3). Immunohistochemistry was performed to determine fibre cross-sectional area (fCSA), myonuclear content, myonuclear domain size, satellite cell number and mitochondrial content. Western blots were used to quantify markers of mitochondrial remodelling. Citrate synthase activity and markers of ribosome content were also investigated. RT improved body composition and strength, increased vastus lateralis thickness, mixed and type II fCSA, myonuclear number, markers of ribosome content, and satellite cell content (P < 0.050). In response to ET, both groups similarly decreased body fat percentage (P < 0.0001) and improved endurance performance (e.g. V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}\max }}$ , and speed at which the onset of blood lactate accumulation occurred, P < 0.0001). Levels of mitochondrial complexes I-IV in the ET-only group increased 32-66%, while those in the RT+ET group increased 1-11% (time, P < 0.050). Additionally, mixed fibre relative mitochondrial content increased 15% in the ET-only group but decreased 13% in the RT+ET group (interaction, P = 0.043). In conclusion, RT performed prior to ET had no additional benefits to ET adaptations. Moreover, prior RT seemed to impair mitochondrial adaptations to ET. KEY POINTS: Resistance training is largely underappreciated as a method to improve endurance performance, despite reports showing it may improve mitochondrial function. Although several concurrent training studies are available, in this study we investigated the effects of performing a period of resistance training on the performance and molecular adaptations to subsequent endurance training. Prior resistance training did not improve endurance performance and impaired most mitochondrial adaptations to subsequent endurance training, but this effect may have been a result of detraining from resistance training.

Aerobically trained older adults show impaired resting, but preserved exercise-induced circulating progenitor cell count, which was not improved by sprint interval training.

Older adults exhibit a reduced number and function of CD34 + circulating progenitor cells (CPC), a known risk factor for cardiovascular disease. Exercise promotes the mobilisation of CPCs from bone marrow, so whether ageing per se or physical inactivity in older age reduces CPCs is unknown. Thus, this study examined the effect of age on resting and exercise-induced changes in CPCs in aerobically trained adults and the effect of 8 weeks of sprint interval training (SIT) on resting and exercise-induced CPCs in older adults. Twelve young (22-34 years) and nine older (63-70 years) adults participated in the study. Blood was sampled pre and immediately post a graded exercise test to exhaustion in both groups. Older participants repeated the process after 8 weeks of SIT (3 × 20 s 'all-out' sprints, 2 × a week). Total CPCs (CD34+) and endothelial progenitor cells (EPCs: CD34+KDR+) were determined by flow cytometry. Older adults exhibited lower basal total CD34+ CPCs (828 ± 314 vs. 1186 ± 272 cells·mL-1, p = 0.0149) and CD34+KDR+ EPCs (177 ± 128 vs. 335 ± 92 cells·mL-1, p = 0.007) than younger adults. The maximal exercise test increased CPCs in young (CD34+: p = 0.004; CD34+KDR+: p = 0.017) and older adults (CD34+: p < 0.001; CD34+KDR+: p = 0.008), without difference between groups (p = 0.211). SIT did not alter resting or exercise-induced changes in CPCs in the older cohort (p > 0.232). This study suggests age per se does not impair exercise-induced CPC counts, but does lower resting CPC counts.