Effect of HIIT with Tabata Protocol on Serum Irisin, Physical Performance, and Body Composition in Men

Exploring the Effect of Acute and Regular Physical Exercise on Circulating Brain-Derived Neurotrophic Factor Levels in Individuals with Obesity: A Comprehensive Systematic Review and Meta-Analysis

Obesity is a major global health concern linked to cognitive impairment and neurological disorders. Circulating brain-derived neurotrophic factor (BDNF), a protein crucial for neuronal growth and survival, plays a vital role in brain function and plasticity. Notably, obese individuals tend to exhibit lower BDNF levels, potentially contributing to cognitive decline. Physical exercise offers health benefits, including improved circulating BDNF levels and cognitive function, but the specific impacts of acute versus regular exercise on circulating BDNF levels in obesity are unclear. Understanding this can guide interventions to enhance brain health and counter potential cognitive decline in obese individuals. Therefore, this study aimed to explore the impact of acute and regular physical exercise on circulating BDNF in individuals with obesity. The target population comprised individuals classified as overweight or obese, encompassing both acute and chronic protocols involving all training methods. A comprehensive search was conducted across computerized databases, including PubMed, Academic Search Complete, and Web of Science, in August 2022, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Initially, 98 studies were identified, from which 16 studies, comprising 23 trials, met the selection criteria. Substantial heterogeneity was observed for both acute (I2 = 80.4%) and long-term effects (I2 = 88.7%), but low risk of bias for the included studies. A single session of exercise increased circulating BDNF levels among obese patients compared to the control group (ES = 1.25, 95% CI = 0.19 to 2.30, p = 0.021). However, with extended periods of physical exercise, there was no significant increase in circulating BDNF levels when compared to the control group (ES = 0.49, 95% CI = -0.08 to 1.06, p = 0.089). These findings highlight the need to consider exercise duration and type when studying neurobiological responses in obesity and exercise research. The study's results have implications for exercise prescription in obesity management and highlight the need for tailored interventions to optimize neurotrophic responses. Future research should focus on elucidating the adaptive mechanisms and exploring novel strategies to enhance BDNF modulation through exercise in this population. However, further research is needed considering limitations such as the potential age-related confounding effects due to diverse participant ages, lack of sex-specific analyses, and insufficient exploration of how specific exercise parameters (e.g., duration, intensity, type) impact circulating BDNF.

Enhancing cardiometabolic health: unveiling the synergistic effects of high-intensity interval training with spirulina supplementation on selected adipokines, insulin resistance, and anthropometric indices in obese males

This study investigated the combined effects of 12 weeks of high-intensity interval training (HIIT) and spirulina supplementation on adipokine levels, insulin resistance, anthropometric indices, and cardiorespiratory fitness in 44 obese males (aged 25-40 years). The participants were randomly assigned to one of four groups: control (CG), supplement (SG), training (TG), or training plus supplement (TSG). The intervention involved daily administration of either spirulina or a placebo and HIIT three times a week for the training groups. Anthropometric indices, HOMA-IR, VO2peak, and circulating adipokines (asprosin and lipocalin2, omentin-1, irisin, and spexin) were measured before and after the 12-week intervention. Post-intervention analysis indicated differences between the CG and the three interventional groups for body weight, fat-free mass (FFM), percent body fat (%BF), HOMA-IR, and adipokine levels (p < 0.05). TG and SG participants had increased VO2peak (p < 0.05). Spirulina supplementation with HIIT increased VO2peak, omentin-1, irisin, and spexin, while causing decreases in lipocalin-2 and asprosin levels and improvements in body composition (weight, %fat), BMI, and HOMA-IR. Notably, the combination of spirulina and HIIT produced more significant changes in circulating adipokines and cardiometabolic health in obese males compared to either supplementation or HIIT alone (p < 0.05). These findings highlight the synergistic benefits of combining spirulina supplementation with HIIT, showcasing their potential in improving various health parameters and addressing obesity-related concerns in a comprehensive manner.

HIIT serves as an efficient training strategy for basketball players by improving blood fluidity and decreasing oxidative stress

BACKGROUND

A challenge for coaches and athletes is to find the best combination of exercises during training. Considering its favorable effects, HIIT has been very popular recently.

OBJECTIVE

The goal of this study was to investigate anthropometric features, performance, erythrocyte deformability, plasma viscosity (PV) and oxidative stress in response to acute and long-term (6 weeks) HIIT in adolescent basketball players.

METHODS

22 sportsmen between the ages of 14-16 were included. Tabata protocol was applied to the HIIT group in addition to their routine training program 3 days/week, for 6 weeks. Erythrocyte deformability was determined using an ectacytometer (LORCA), PV with a rotational viscometer. Total oxidant status (TOS), total antioxidant status (TAS) were measured by kits.

RESULTS

HIIT for 6 weeks induced an improvement in performance tests and waist circumference. 6 weeks of HIIT resulted in a decrement, while the last exercise session yielded an increment in RBC deformability. PV and TOS of HIIT groups were decreased on the 6th week.

CONCLUSIONS

Our results demonstrate that, HIIT in addition to the routine exercise program is beneficial for improving performance and blood fluidity as well as decreasing oxidative stress in basketball players. Therefore, HIIT seems as an efficient training strategy for highly-trained individuals.

Effects of high-intensity interval training (HIIT) on skeletal muscle atrophy, function, and myokine profile in diabetic myopathy

PURPOSE

Diabetes is a metabolic disorder characterized by chronic hyperglycemia due to insulin deficiency and/or loss of its action. Diabetic myopathy causes functional limitations in diabetic patients. The beneficial effects of high-intensity interval training (HIIT) are widely reported. We have hypothesized that HIIT application would prevent the development of diabetic myopathy.

METHODS

Male, Wistar albino rats (10 W) were randomly divided into four groups (1)Control(C), (2)Diabetes(DM), (3)Training(HIIT), and (4)Diabetes + Training(DM + HIIT). Streptozotocin(60 mg/kg) was injected for the induction of diabetes. The maximum exercise capacity(MEC) of animals was determined by an incremental load test. HIIT protocol (4 min 85-95 % MEC, 2 min 40-50 % MEC, 6 cycles, 5 days/week) was applied for 8 weeks. In the end, functional parameters, atrophy, and resistance to fatigue in soleus and EDL muscles were evaluated. IL-6, FNDC5, and myonectin levels were measured in EDL, soleus, and serum.

RESULTS

We observed atrophy, fatigue sensitivity, and proinflammatory alterations (IL-6 increase) in the EDL samples due to diabetic myopathy which were not observed in the soleus samples. HIIT application prevented the aforementioned detrimental alterations. Both force-frequency response and parallelly the twitch amplitude increased significantly in the DM + HIIT group. Half relaxation time (DT50) increased in both exercising and sedentary diabetics. FNDC5 was significantly higher in the exercising animals in soleus samples. Myonectin was significantly higher in the soleus muscle only in the DM + HIIT group.

CONCLUSION

Current findings show that diabetic myopathy develops earlier in glycolytic-fast-twitch fibers(EDL) than in oxidative-slow-twitch fibers(soleus). Furthermore, HIIT application prevents atrophy in skeletal muscle, increases resistance to fatigue, and has an anti-inflammatory effect.

NEW FINDINGS

The current study analyzes the myokine profile and skeletal muscle function under the effect of diabetes HIIT-type exercise. We also measured maximal exercise capacity and tailored the exercise program individually according to the result. Diabetic myopathy is an important complication of diabetes yet still, it is not understood completely. Our results show that HIIT-type training would be beneficial in diabetic myopathy but further investigation is needed to understand the whole molecular mechanism.

High-Intensity Interval Training and Cardiometabolic Health in the General Population: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

BACKGROUND

High-intensity interval training (HIIT) remains a promising exercise mode in managing cardiometabolic health. Large-scale analyses are necessary to understand its magnitude of effect on important cardiometabolic risk factors and inform guideline recommendations.

OBJECTIVE

We aimed to perform a novel large-scale meta-analysis on the effects of HIIT on cardiometabolic health in the general population.

METHODS

PubMed (MEDLINE), the Cochrane library and Web of Science were systematically searched. Randomised controlled trials (RCTs) published between 1990 and March 2023 were eligible. Research trials reporting the effects of a HIIT intervention on at least one cardiometabolic health parameter with a non-intervention control group were considered.

RESULTS

This meta-analysis included 97 RCTs with a pooled sample size of 3399 participants. HIIT produced significant improvements in 14 clinically relevant cardiometabolic health parameters, including peak aerobic capacity (VO2) [weighted mean difference (WMD): 3.895 ml min-1 kg-1, P < 0.001), left ventricular ejection fraction (WMD: 3.505%, P < 0.001), systolic (WMD: - 3.203 mmHg, P < 0.001) and diastolic (WMD: - 2.409 mmHg, P < 0.001) blood pressure, resting heart rate (WMD: - 3.902 bpm, P < 0.001) and stroke volume (WMD: 9.516 mL, P < 0.001). Body composition also significantly improved through reductions in body mass index (WMD: - 0.565 kg m-2, P < 0.001), waist circumference (WMD: - 2.843 cm, P < 0.001) and percentage body fat (WMD: - 0.972%, P < 0.001). Furthermore, there were significant reductions in fasting insulin (WMD: - 13.684 pmol L-1, P = 0.004), high-sensitivity C-reactive protein (WMD: - 0.445 mg dL-1, P = 0.043), triglycerides (WMD: - 0.090 mmol L-1, P = 0.011) and low-density lipoprotein (WMD: - 0.063 mmol L-1, P = 0.050), concurrent to a significant increase in high-density lipoprotein (WMD: 0.036 mmol L-1, P = 0.046).

CONCLUSION

These results provide further support for HIIT in the clinical management of important cardiometabolic health risk factors, which may have implications for physical activity guideline recommendations.

Body composition, cardiorespiratory fitness, and neuromuscular adaptations induced by a home-based whole-body high intensity interval training

Background/objective

Bodyweight exercises performed at home could be a complementary approach to improve health-related fitness in people having little spare time and during stay-at-home periods. This study then investigated body composition, cardiorespiratory fitness, and neuromuscular adaptations to a home-based, video-directed, whole-body high-intensity interval training (WB-HIIT).

Methods

Fourteen subjects participated to an 8-week WB-HIIT (6 females, 23 ± 1 years) and fourteen were included in a non-exercise control group (CTL; 6 females, 24 ± 4 years). All took part to pre- and post-intervention assessments of body composition, peak oxygen uptake (VO₂peak) and first ventilatory threshold (VT1; index of aerobic capacity), dynamic (leg press 3-repetition maximum) and isometric strength (knee extensors maximal isometric contractions with assessment of voluntary activation), and muscle endurance during an isometric submaximal contraction maintained till exhaustion. WB-HIIT consisted in 30-s all-out whole-body exercises interspaced with 30 s of active recovery. Training sessions were performed at home by means of videos with demonstration of exercises. Heart rate was monitored during sessions.

Results

WB-HIIT increased VO₂peak (5%), VT1 (20%), leg lean mass (3%), dynamic (13%) and isometric strength (6%), and muscle endurance (28%; p < 0.05), while they did not improve in CTL. VO₂peak increase was correlated (r = 0.56; p < 0.05) with the time spent above 80% of maximal heart rate during training sessions. Isometric strength increase was correlated with change in voluntary activation (r = 0.74; p < 0.01).

Conclusion

The home-based WB-HIIT induced concomitant cardiorespiratory fitness and neuromuscular improvements. The predominant effect was observed for aerobic capacity and muscle endurance which could improve exercise tolerance and reduce fatigability.

The effect of Tabata-style functional high-intensity interval training on cardiometabolic health and physical activity in female university students

Introduction: The increasing prevalence of metabolic syndrome and physical inactivity enhances exposure to cardiometabolic risk factors in university students. High-intensity interval training (HIIT) improved cardiometabolic health in clinical adults but the evidence in the university setting is limited. Furthermore, few studies examined the effect of low-volume HIIT on habitual physical activity (PA). Therefore, the primary aim of this study was to evaluate the efficacy of 12-week Tabata-style functional HIIT for improving multiple cardiometabolic health outcomes and habitual PA. We also investigated whether changes in habitual PA over the intervention period had an impact on exercise-induced health outcomes. Methods: 122 female freshmen were randomized into the Tabata group (n = 60) and the control (n = 62). The Tabata training protocol involved 8 × 20 s maximal repeated functional exercises followed by 10 s rest with a frequency of 3 times per week for 12 weeks. Body composition, maximal oxygen uptake (VO_2max), blood pressure (BP), blood lipids, fasting glucose and insulin, C-reactive protein and PA were objectively measured using standardized methods. Dietary intake was measured using a valid food frequency questionnaire. All variables were measured pre- and post-intervention. Results: Mixed linear modelling results showed that there were large intervention effects on VO_2max (p < 0.001, d = 2.53, 95% CI: 2.03 to 3.00 for relative VO_2max; p < 0.001, d = 2.24, 95% CI: 1.76 to 2.68 for absolute VO_2max), resting heart rate (p < 0.001, d = -1.82, 95% CI: -2.23 to -1.37), systolic BP (p < 0.001, d = -1.24, 95% CI: -1.63 to -0.84), moderate-to-vigorous intensity physical activity (MVPA) (p < 0.001, d = 2.31, 95% CI: 1.83 to 2.77), total PA (p < 0.001, d = 1.98, 95% CI: 1.53 to 2.41); moderate effects on %BF (p < 0.001, d = -1.15, 95% CI: -1.53 to -0.75), FM (p < 0.001, d = -1.08, 95% CI: -1.46 to -0.69), high-density lipoprotein (HDL) (p < 0.001, d = 1.04, 95% CI: 0.65 to 1.42), total cholesterol (p = 0.001, d = -0.64, 95% CI: -1.00 to -0.26); small effects on BMI (p = 0.011, d = -0.48, 95% CI: -0.84 to 0.11), WC (p = 0.043, d = -0.37, 95% CI: -0.74 to -0.01), low-density lipoprotein (p = 0.003, d = -0.57, 95% CI: -0.93 to -0.19), HOMA-IR (p = 0.026, d = -0.42, 95% CI: -0.78 to -0.05) and fasting insulin (p = 0.035, d = -0.40, 95% CI: -0.76 to -0.03). Regression analysis showed that only the percentage change of HDL was associated with the change of MVPA (b = 0.326, p = 0.015) and TPA (b = 0.480, p = 0.001). Conclusion: From the findings of the study we can conclude that 12-week low-volume Tabata-style functional HIIT was highly effective for university female students to improve cardiorespiratory fitness, body fat, some cardiometabolic health outcomes and habitual PA.

Profiling the Typical Training Load of a Law Enforcement Recruit Class

Law enforcement academies, designed to prepare recruits for their prospective career, represent periods of high physical and mental stress, potentially contributing to recruits' injuries. Managing stress via monitoring training loads may mitigate injuries while ensuring adequate preparation. However, it is vital to first understand an academy's typical training load. The aim of this study was to profile the typical training load of law enforcement recruits over the course of 22 weeks. Data were prospectively collected using global positioning system (GPS) units placed on recruits during a portion of the academy training, while a desktop analysis was retrospectively applied to six other classes. A Bland-Altman plot was conducted to assess the agreement between the two methods. A linear mixed model was conducted to analyse the difference in distances covered per week, while other variables were presented graphically. Adequate agreement between the desktop analysis and GPS units was observed. Significant differences (p-value < 0.01) in distance covered (9.64 to 11.65 km) exist between weeks during early academy stages, which coincide with increases (~6 h) in physical training. Significant decreases in distances were experienced during the last five weeks of academy training. Most acute:chronic workload ratios stayed between the proposed 0.8 to 1.3 optimal range. Results from this study indicate that large increases in training occur early in the academy, potentially influencing injuries. Utilizing a desktop analysis is a pragmatic and reliable approach for instructors to measure load.

The Relative Importance of Age at Peak Height Velocity and Fat Mass Index in High-Intensity Interval Training Effect on Cardiorespiratory Fitness in Adolescents: A Randomized Controlled Trial

Background: This study aimed to evaluate the role of biological age in the relationship between preintervention fat mass and cardiorespiratory fitness effects (CRF) after High-Intensity Interval Training (HIIT) intervention in adolescents. Methods: A total of 141 boys and girls (16 years) were examined as control (CG) and experimental (EG) groups that conducted a 10-week HIIT implemented in physical education. Measurements: body height, body weight, fat mass index (FMI), CRF (Harvard Step Test). Predicted age at peak height velocity (APHV) was calculated. Pathway analyses were conducted to identify the influences of the measured variables. Results: APHV harmed the level of ΔFI (fitness index) (β = −0.270; p = 0.035), while HIIT had a positive effect on changes in ΔFI (β = 0.246; p = 0.002). Sex affected the changes in CRF (β = 0.344; p = 0.011). Two models were designed respective to sex. The effect of the APHV on ΔFI in girls was close to significant (p = 0.053) but was non-significant in boys (p = 0.311). Changes in CRF in girls were positively and close to significance (p < 0.100) affected by FMIbaseline. Conclusion: HIIT is an effective way of exerting positive changes in CRF in adolescents, which is greater in boys than girls. APHV plays a role only in girls. The HIIT should be tailored to girls depending on their maturity status.

Influence of Training and Single Exercise on Leptin Level and Metabolism in Obese Overweight and Normal-Weight Women of Different Age

Leptin is one of the important hormones secreted by adipose tissue. It participates in the regulation of energy processes in the body through central and peripheral mechanisms. The aim of this study was to analyse the anthropological and physical performance changes during 9 month training in women of different age and body mass. The additional aim was the analysis of leptin levels in the fasting stage and after a control exercise. Obese (O), overweight (OW), and normal-weight (N) women participated in the study. Additional subgroups of premenopausal (PRE) (<50 years) and postmenopausal (POST) (50+) women were created for leptin level analysis. The main criterion of the division into subgroups was the age of menopause in the population. The control submaximal test and maximal oxygen uptake (VO_2max) according to Astrand-Rhyming procedures was performed at baseline and after 3, 6, and 9 months. Before each control test, body weight (BM), body mass index (BMI), percentage of adipose tissue (% FAT), and mass (FAT (kg)) were measured. Moreover, before and after each test, leptin level was measured. After 9 months, there was a significant decrease in BM in the O (p < 0.05) and OW (p < 0.05) groups with no significant changes in the N group. There was a decrease in BMI in both the O (p < 0.05) and the OW (p < 0.05) groups, with no changes in the N group. The % FAT reduction was noted only in the O group (p < 0.05). VO_2max increased in each of the measured groups (p < 0.05). The fasting leptin level at 0, 3, 6, and 9 months were the highest in the O group. The fasting leptin level before training was highest in the O group compared to the OW group (p < 0.01) and the N group (p < 0.01). It was also higher in the OW group compared to the N group at baseline (0) (p < 0.01) and after 3 and 6 months (p < 0.01). After 9 months, the leptin concentration decreased by 20.2% in the O group, 40.7% in the OW group, and 33% in the N group. Moreover, the fasting leptin level was higher in the POST subgroup compared to the PRE group in the whole group of women (p < 0.05). After a single exercise, the level of leptin in the whole study group decreased (p < 0.05). This was clearly seen, especially in the POST group. The 9 month training had a reducing effect on the blood leptin concentration in groups O, OW, and N. This may have been a result of weight loss and the percentage of fat in the body, as well as systematically disturbed energy homeostasis.

The effects of different types of exercise on circulating irisin levels in healthy individuals and in people with overweight, metabolic syndrome and type 2 diabetes

Irisin is a myokine secreted during exercise. It has drawn the attention of researchers as it regulates several effects of exercise that are considered beneficial. It has also been proposed as a therapeutic tool to treat metabolic disorders. In recent years, the effect of different types of training on circulating irisin has been studied in large populations. An overall beneficial result has been shown, however, the outcome of the investigations has raised some controversy. Herein we evaluated the existing literature on the effects of different types of training on the circulating irisin levels in healthy subjects and in those displaying different metabolic condition. We conducted queries in the PubMed and Web of Science databases for literature published between January 2010 and January 2021. Thirty-seven original articles were retrieved and they were included in this review. Any letter to the editor, meta-analyses, reviews, and systematic review articles were excluded. From these 37 articles, 19 of them reported increased levels of circulating irisin. The interventions encompassed aerobic, resistance, combined, circuit, and interval training types. Such increase of circulating irisin was reported for healthy subjects and for those displaying different metabolic condition. A training that is steadily kept with a moderate to high intensity, including that characterized by brief highly intense intervals, were distinguishable from the rest. Nevertheless, the training effectiveness as evaluated by the increased circulating irisin levels depends on the subject’s metabolic condition and age.

Effectiveness of Whole-Body High-Intensity Interval Training on Health-Related Fitness: A Systematic Review and Meta-Analysis

Due to its versatility, whole-body high-intensity interval training (WB-HIIT) can be proposed to the general population and patients to improve health-related fitness. However, its effectiveness compared to traditional aerobic continuous or interval trainings has yet to be determined. A search of four electronic databases was conducted. Studies reporting the effects of WB-HIIT on cardiorespiratory fitness (CRF), fat mass, fat-free mass, musculoskeletal fitness and metabolic risk factors were included. Standardized mean differences (SMD) between WB-HIIT and no exercise or traditional aerobic trainings were calculated. A meta-regression assessed the effect of total training time on the different outcomes. Twenty-two studies were included in the systematic review and nineteen in the meta-analysis. Compared to no exercise, WB-HIIT improves CRF (SMD: 0.75; 95%CI: 0.28, 1.23; p < 0.001), fat-free mass (SMD: 0.38; 95%CI: 0.11, 0.65; p < 0.001), fat mass (SMD: 0.40; 95%CI: 0.09, 0.72; p < 0.001) and musculoskeletal fitness (SMD: 0.84; 95%CI: 0.61, 1.08; p < 0.001). Compared to other aerobic trainings, WB-HIIT has a lower effect on CRF (SMD: −0.40; 95%CI: −0.70, −0.11; p = 0.007), a similar effect on fat-free mass (SMD: −0.04; 95%CI: −0.44, 0.35; p = 0.8) and fat mass (SMD: −0.07; 95%CI: −0.39, 0.25; p = 0.7), and a larger effect on musculoskeletal fitness (SMD: 0.42; 95%CI: 0.14, 0.71; p = 0.003). WB-HIIT overall effect and specific effect on CRF and fat mass were associated with total training time. The systematic review did not provide evidence of metabolic risk improvement. Despite a slightly lower effect on CRF, WB-HIIT is equally effective as traditional aerobic trainings to improve body composition and more effective to enhance musculoskeletal fitness, which is essential for execution of daily tasks.

Comparative Impact of Various Exercises on Circulating Irisin in Healthy Subjects: A Systematic Review and Network Meta-Analysis

Irisin is a myokine that is secreted from skeletal muscle during exercise and increases lipid metabolism, converting white adipose tissue to brown adipose tissue. Recent studies have shown conflicting results in relation to chronic and acute exercise and irisin. The aim of this study was to evaluate the effects of chronic and acute exercise training on circulating (plasma/serum) irisin level in healthy subjects. We conducted a search of Cochrane Library, PubMed, ISI, Scopus, Embase, and Pedro up to September 2021. A random effects network meta-analysis was performed to calculate the pooled estimate of standardized mean difference (SMD) for acute and chronic exercise effects on irisin level, using Hedge's g statistic. Of the 16 studies included, six were acute exercise studies (175 participants). The aerobic (Hedge's g = 0.23; 95% CI: -0.58, 1.03) and the anaerobic exercises (Hedge's g = 0.12; 95% CI: -0.45, 0.70) were associated with the increased level of irisin, compared to the control. In the ten chronic exercise studies (433 participants), the resistance training was superior to anaerobic and aerobic training (P score = 0.632). However, comparing acute and chronic exercise studies, acute training showed the most excellent potential as the best treatment to improve the irisin level (P score = 0.721). This network meta-analysis showed that acute aerobic exercise has a more effect on irisin levels than acute anaerobic exercise. Also, chronic resistance training has the greatest additive effect on irisin levels compared to chronic aerobic and anaerobic training.

A Bibliometric Analysis of the Literature on Irisin from 2012-2021

Irisin is a hormone-like molecule mainly released by skeletal muscles in response to exercise, which is proposed to induce the ‘browning’ of white adipose tissue. Since its identification, irisin was reported to be closely associated with many metabolic diseases, including type 2 diabetes mellitus (T2DM), obesity, cardiovascular disease (CVD), and metabolic bone diseases. In recent years, irisin has attracted increasing research interest, and numerous studies have been published in this field. Thus, it is essential to identify the current research status of irisin and measure research hotspots and possible future trends. In this study, by utilizing two visualization software named CiteSpace and VOSviewer, we analyzed 1510 Web of Science publications on irisin published from 2012 to 2021. Our results show that the number of irisin-related articles published annually has increased significantly. China participates in the most studies, followed by the United States and Turkey. Firat University, Harvard University, and Shandong University are three major institutions with larger numbers of publications. The analysis of keywords co-occurrence indicates that insulin resistance, inflammation, and circulating irisin levels in serum are the research hotspots. Apoptosis, BDNF, and osteoporosis will likely become the focus of future research related to irisin. Overall, this study may provide helpful insights for researchers to understand the current research situation and identify the potential frontiers of irisin.

Effects of Small-Sided Games Training versus High-Intensity Interval Training Approaches in Young Basketball Players

This study aimed to investigate the effects of the 6-week small-sided games training (SSGs) vs. high-intensity interval training (HIIT) on the psychophysiological and performance responses, and technical skills of young basketball players. Thirty-two male players (age: 14.5 ± 0.5 years of age) were randomly divided into SSGs group (n = 16) and HIIT group (n = 16) training methods thrice per week for 6 weeks. The players in the SSGs group performed two 5-8 min of 2 vs. 2 with 2 min rest periods, while the players in HIIT performed 12-18 min of runs at intensities (90 to 95%) related to the velocity obtained in the 30-15 intermittent fitness test (IFT). Pre-testing and post-testing sessions involved assessments of Yo-Yo Intermittent Recovery Test level 1, 30-15 intermittent fitness test, 5 and 30 m sprint times, vertical jump height, repeated sprint ability, defensive and offensive agility, and technical skills. The SSGs group demonstrated significantly higher agility-based technical responses in terms of the control dribbling and shooting skills (d = 1.71 vs. 0.20, d = 1.41 vs. 0.35, respectively) compared with the HIIT group. Conversely, the HIIT induced greater improvements in 30 m sprint times (d = 3.15 vs. 0.68). These findings provided that SSGs in youth basketball players may allow similar positive physical adaptations to HIIT, with an extra advantage of improving technical skills while improving enjoyability.

Irisin response to acute moderate intensity exercise and high intensity interval training in youth of different obesity statuses: A randomized crossover trial

Limited data exist regarding the impact of an acute bout of exercise with varying intensities on irisin levels in the youth of different obesity statuses. The objectives were to (1) compare an acute bout of moderate continuous intensity (MCI) exercise and an acute bout of high‐intensity interval training (HIIT) on irisin response in youth with different obesity statuses and, (2) investigate whether changes in irisin levels are correlated with exploratory outcomes. A randomized crossover design study was conducted on 25 youth aged 12–18 years old. Participants were classified as either healthy weight (BMI percentile <85; n = 14) or overweight/obese (BMI percentile ≥85; n = 11). Participants performed an MCI exercise session at 50% of heart rate reserve for 35 min and a HIIT exercise session for 35 min, with intervals every 5 min increasing from 50% heart rate reserve to 85–90% for 2 min. Irisin was measured using an enzyme‐linked immunoabsorbent assay from plasma sampling obtained throughout the exercise (at times 0, 7, 14, 21, 28, and 35 min). A time effect was observed throughout the HIIT session [F(1,5) = 6.478, p < 0.001]. Bonferonni post‐hoc analysis revealed significant differences in irisin levels post‐exercise (35 min) compared to times 7, 14, 21, and 28 min. Irisin increased during HIIT (81.0% ± 71.3; p = 0.012) in youth with a healthy weight. No differences were observed for youth living as overweight or with obesity. Overall, HIIT elicits a higher peak irisin response compared to MCI exercise training in youth.

The effect of exercise interventions on Irisin level: a systematic review and meta-analysis of randomized controlled trials

Irisin is a hormone that is offered to be a hopeful remedial target in obesity and type 2 diabetes. It has received striking attention recently, whereas, the interactions between exercise training and irisin are still unclear. Therefore, this systematic review and meta-analysis investigated the impacts of exercise interventions on circulating irisin in adults. A systematic search was conducted in PubMed, CINAHL, MEDLINE, Cochrane, Google Scholar, and Scopus up to July 15, 2021. Twenty-four studies, which assessed a total of 921 participants were included and analyzed using a random-effects model to estimate weighted mean differences (MD) with 95 % confidence intervals (CI). Overall, data revealed that exercise training significantly increased circulating irisin (MD: 0.01, 95 % CI: 0.00, 0.01, p = 0.005), and declined insulin (MD: -2.09, 95 % CI: -2.81, -1.37, p < 0.00001), glucose (MD: -12.89, 95 % CI: -16.52, -9.26, p < 0.00001), and insulin resistance (MD: -0.89, 95 % CI: -1.15, -0.62, p < 0.00001). Subgroup analysis revealed that irisin raised significantly when resistance training (p = 0.04) and combined training (p = 0.002) were applied, and for the type 2 diabetes and prediabetes (p = 0.002 for both) groups. Moreover, subgroup analysis by the type of intervention demonstrated that insulin reduced when aerobic training (p < 0.00001) and combined training (p = 0.0003) were employed, but glucose and HOMA-IR reduced after all three types of exercise training. These findings demonstrate that exercise interventions may produce ameliorations in circulating irisin. Further long-term studies are required to confirm these findings.

Effects of low and high intensity interval training exercises on VO2max and components of neuromuscular and vascular system in male volunteers

OBJECTIVES

To evaluate the effects of different intensity exercises on maximal oxygen consumption (VO_2max and levels of components, namely brain-derived neurotrophic factor (BDNF), tyrosine kinase receptor B (TrKB), vascular endothelial growth factor (VEGF), peroxisome proliferator activated receptor-gamma coactivator (PGC-1α), and irisin.

METHODS

Thirty-six male participants were divided into control (CNT), low-intensity (LIIT), and high-intensity interval training (HIIT) groups. LIIT and HIIT groups consisted of 8 exercises (20 s work and rest in each repetition, respectively) conducted for 4 weeks. VO_2max and protein component levels were determined pre- and post-training. VO_2max capacity was also determined using the Yo Yo Intermittent Recovery Test-1 (Yo Yo IR-1). Statistical analysis was conducted to determine significance of the differences observed.

RESULTS

According to the YoYo IR-1, VO_2max, serum BDNF, VEGF, PGC1α, irisin, and TrkB data obtained in the study, a statistically significant difference between the groups was observed (p<0.05). While the interaction effect was found to be statistically significant in the study using PGC1α, VEGF, and TrkB data (p<0.05), it was not found to be statistically significant using YoYo IR-1, VO_2max, serum BDNF, or irisin data (p>0.05).

CONCLUSION

HIIT and LIIT improved all study parameters, while HIIT showed a greater effect than LIIT.

Long-Term Effect of Exercise on Irisin Blood Levels-Systematic Review and Meta-Analysis

Physical exercise may activate a number of important biochemical processes in the human body. The aim of this systematic review and meta-analysis was to identify the long-term effect of physical activity on irisin blood levels. We searched PubMed, Scopus, and Web of Science for articles addressing the long-term effect of physical exercise on irisin blood levels. Fifty-nine articles were included in the final qualitative and quantitative syntheses. A statistically significant within-group effect of exercise on irisin blood levels was in 33 studies; out of them, the irisin level increased 23× and decreased 10×. The significant positive between-groups effect was found 11×. Furthermore, the meta-analysis indicated that physical exercise had a significant positive effect on irisin blood levels (SMD = 0.39 (95% CI 0.27–0.52)). Nevertheless, considerably high heterogeneity was found in all the analyses. This systematic review and meta-analysis indicate that physical exercise might increase irisin blood levels; however, the results of individual studies were considerably inconsistent, which questions the methodological detection of irisin by ELISA kits.

From Exercise to Cognitive Performance: Role of Irisin

The beneficial effects of exercise on the brain are well known. In general, exercise offers an effective way to improve cognitive function in all ages, particularly in the elderly, who are considered the most vulnerable to neurodegenerative disorders. In this regard, myokines, hormones secreted by muscle in response to exercise, have recently gained attention as beneficial mediators. Irisin is a novel exercise-induced myokine, that modulates several bodily processes, such as glucose homeostasis, and reduces systemic inflammation. Irisin is cleaved from fibronectin type III domain containing 5 (FNDC5), a transmembrane precursor protein expressed in muscle under the control of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). The FNDC5/irisin system is also expressed in the hippocampus, where it stimulates the expression of the neurotrophin brain-derived neurotrophic factor in this area that is associated with learning and memory. In this review, we aimed to discuss the role of irisin as a key mediator of the beneficial effects of exercise on synaptic plasticity and memory in the elderly, suggesting its roles within the main promoters of the beneficial effects of exercise on the brain.

Effect of four different forms of high intensity training on BDNF response to Wingate and Graded Exercise Test

This study examined the effects of a nine-week intervention of four different high-intensity training modalities [high-intensity functional training (HIFT), high-intensity interval training (HIIT), high-intensity power training (HIPT), and high-intensity endurance training (HIET)] on the resting concentration of brain-derived neurotropic factor (BDNF). In addition, we evaluated the BDNF responses to Graded Exercise Test (GXT) and Wingate Anaerobic Test (WAnT) in men. Thirty-five healthy individuals with body mass index 25.55 ± 2.35 kg/m2 voluntarily participated in this study and were randomly assigned into four training groups. During nine-weeks they completed three exercise sessions per week for one-hour. BDNF was analyzed before and after a GXT and WAnT in two stages: (stage 0-before training and stage 9-after nine weeks of training). At stage 0, an increase in BDNF concentration was observed in HIFT (33%; p < 0.05), HIPT (36%; p < 0.05) and HIIT (38%; p < 0.05) after GXT. Even though HIET showed an increase in BDNF (10%) this was not statistically significant (p > 0.05). At stage 9, higher BDNF levels after GXT were seen only for the HIFT (30%; p < 0.05) and HIIT (18%; p < 0.05) groups. Reduction in BDNF levels were noted after the WAnT in stage 0 for HIFT (- 47%; p < 0.01), HIPT (- 49%; p < 0.001), HIET (- 18%; p < 0.05)], with no changes in the HIIT group (- 2%). At stage 9, BDNF was also reduced after WAnT, although these changes were lower compared to stage 0. The reduced level of BDNF was noted in the HIFT (- 28%; p < 0.05), and HIPT (- 19%;p < 0.05) groups. Additionally, all groups saw an improvement in VO2max (8%; p < 0.001), while BDNF was also correlated with lactate and minute ventilation and selected WAnT parameters. Our research has shown that resting values of BDNF after nine weeks of different forms of high-intensity training (HIT) have not changed or were reduced. Resting BDNF measured at 3th (before GXT at stage 9) and 6th day after long lasting HITs (before WAnT at stage 9) did not differed (before GXT), but in comparison to the resting value before WAnT at the baseline state, was lower in three groups. It appears that BDNF levels after one bout of exercise is depended on duration time, intensity and type of test/exercise.

The production, detection, and origin of irisin and its effect on bone cells

Irisin is a muscle factor discovered in 2012 that plays an important role in many tissues, including bone. Eight years since its discovery, there are still many controversies regarding its molecular biology, detection, and effects on bone. This article summarizes the points raised to date, and discusses the mechanisms by which irisin regulates bone cells. The information reviewed here provides a useful foundation for future research.

Irisin and Autophagy: First Update

Aging and sedentary life style are considered independent risk factors for many disorders. Under these conditions, accumulation of dysfunctional and damaged cellular proteins and organelles occurs, resulting in a cellular degeneration and cell death. Autophagy is a conserved recycling pathway responsible for the degradation, then turnover of cellular proteins and organelles. This process is a part of the molecular underpinnings by which exercise promotes healthy aging and mitigate age-related pathologies. Irisin is a myokine released during physical activity and acts as a link between muscles and other tissues and organs. Its main beneficial function is the change of subcutaneous and visceral adipose tissue into brown adipose tissue, with a consequential increase in thermogenesis. Irisin modulates metabolic processes, acting on glucose homeostasis, reduces systemic inflammation, maintains the balance between resorption and bone formation, and regulates the functioning of the nervous system. Recently, some of its pleiotropic and favorable properties have been attributed to autophagy induction, posing irisin as an important regulator of autophagy by exercise. This review article proposes to bring together for the first time the "state of the art" knowledge regarding the effects of irisin and autophagy. Furthermore, treatments on relation between exercise/myokines and autophagy have been also achieved.