Moderate-intensity Continuous Training Protocols Research Articles

Comparison of moderate-intensity continuous training and high-intensity interval training effects on the Ido1-KYN-Ahr axis in the heart tissue of rats with occlusion of the left anterior descending artery

Myocardial infarction (MI) affects many molecular pathways in heart cells, including the Ido1-KYN-Ahr axis. This pathway has recently been introduced as a valuable therapeutic target in infarction. We examined the effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) on the axis in the heart tissue of male Wistar rats with occluded left anterior descending (OLAD). Thirty rats (age 10–12 weeks, mean weight 275 ± 25 g) were divided into five groups with 6 animals: Control (Ct) group, MICT group, rats with OLAD as MI group, rats with OLAD treated with MICT (MIMCT group) and rats with OLAD treated with HIIT (MIHIIT group). Rats performed the training protocols for 8 weeks, 5 days a week. HIIT included 7 sets of 4 min running with an intensity of 85–90% VO2max and 3 min of recovery activation between sets. MICT included continuous running at the same distance as HIIT with an intensity of 50–60% VO2max for 50 min. The expressions of Ahr, Cyp1a1, and Ido1 were assayed by real-time PCR. Malondialdehyde (MDA) and Kynurenine levels, and AHR, CYP1A1, and IDO1 proteins were detected using ELISA. Data were analyzed using the ANOVA and MANOVA tests. Compared to the CT group, MI caused an increase in all studied factors, but only statistically significant (P < 0.05) for MDA and IDO1. With a greater effect of HIIT, both protocols significantly lowered the proteins expressions in the MIHIIT and MIMCT groups, compared with the MI group (P < 0.001). In healthy rats, only AHR protein significantly decreased in the MICT group compared to the Ct group (P < 0.05). HIIT and MICT protocols significantly reduced the gene and protein expression of Cyp1a1 (P < 0.05) and Ido1 (P < 0.01), and HIIT had a greater effect. In conclusion, both protocols were effective at reducing the levels of Ido1-Kyn-Ahr axis components and oxidative stress in the infarcted heart tissue and HIIT had a higher significant effect.

Protective Effect of High-Intensity Interval Training (HIIT) and Moderate-Intensity Continuous Training (MICT) against Vascular Dysfunction in Hyperglycemic Rats.

Hyperglycemia is a major risk factor for endothelial dysfunction. Endothelial dysfunction is associated with the inability of endothelial cells to maintain homeostasis of the cardiovascular system. Regular exercise may be considered as an effective and low-cost nonpharmacological tool for improving vascular function, though there is no agreement on the best type of exercise. To determine how high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) may prevent endothelial dysfunction under hyperglycemic conditions, and to compare these two interventions. Twenty-four eight-week-old male Wistar rats were randomly assigned into four groups: healthy nonexercising control (C), hyperglycemic control (HG-C), hyperglycemic + HIIT (HG-IT), and hyperglycemic + MICT (HG-CT). Hyperglycemia was induced by a single injection of streptozotocin. Hyperglycemic animals were subjected to HIIT or MICT protocols six days a week for six weeks. Decapitation was performed the day after the exercise protocols were completed. The ascending aorta (until the abdominal artery) was examined. An enzyme-linked immunosorbent assay (ELISA) was used to measure the glucagon-likepeptide-1 (GLP-1), endothelial nitric oxide synthase (eNOS), and tumor necrosis factor-alpha (TNFα) levels. A colorimetric assay was used to measure superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels. Quantitative real-time polymerase chain reaction (PCR) was used to measure the expression of the receptor for advanced glycation end-products (RAGE) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Hematoxylin and eosin (H&E) staining was used to histologically analyze the aortas. There was a significantly higher level of GLP-1 and lower expression of RAGE, NF-κB, and TNFα in the HG-IT and HG-CT group compared to the HG-C group. Microscopic examination of aortic tissue showed a better tissue arrangement in both treatment groups than in the HG-C group. Except for the MDA level, there were no significant differences in any of the measured parameters between the HG-IT and HG-CT groups. Under hyperglycemic conditions, both HIIT and MICT have a protective role against endothelial dysfunction.

Comparison of the effects of high-intensity interval training and moderate-intensity continuous training on indices of liver and muscle tissue in high-fat diet-induced male rats with non-alcoholic fatty liver disease

BackgroundNon-alcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases. It is shown that moderate to high physical activities can play a crucial role in improving this disease.AimThe purpose of this study was to explore the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on the levels of the myonectin in serum and tissue levels and fatty acid transport protein 4 (FATP4) in male rats with NAFLD.Materials and methodsThirty-three male rats were randomly divided into five groups: high-fat diet to confirm NAFLD induction (n = 5), normal diet sedentary (n = 7), high-fat diet sedentary (n = 7), high-fat diet with HIIT (n = 7), and high-fat diet with MCIT (n = 7). Induction of NAFLD was performed by feeding rats for 12 weeks with a high-fat diet containing 60% fat. The training protocols were performed in five sessions per week for 8 weeks. The HIIT group has performed 4 × 4 min interval running on a treadmill up to 80–95% maximal oxygen uptake (VO2max) and then recovered at 50–60% VO2max. The MICT protocol has performed up to 50–60% VO2max for 50 min. myonectin and FATP4 were also measured by the animal Elisa kit (Zellbio, Germany) with a sensitivity of 0.02 ng/L. Insulin resistance was evaluated by the insulin resistance homeostasis assessment index using the following formula (HOMA-IR): “fasting glucose (mg/dl) × fasting in insulin (mg/L) ÷ 405”. One-way ANOVA analysis of variance was utilized for statistical analyses and Tukey’s post hoc test at a significant level of p < 0.05.ResultsThe 8-week intervention showed that both HIIT and MICT positively influenced the serum myonectin and FATP4 levels (p < 0.05). Moreover, there was a significant difference between the trained groups in tissue levels of the myonectin and serum levels of FATP4 (p < 0.05).ConclusionsAltogether, both HIIT and MICT can lead to valuable adaptations and recovery of NAFLD in male rats.

Cardioprotective Effects of Physical Activity: Focus on Ischemia and Reperfusion

Abstract This review aimed to revisit the old and introduce some of the new various cardioprotective effects of physical exercise, focusing on ischemia-reperfusion injury. A wealth of data shows that regular physical exercise is necessary to prevent cardiovascular diseases. In the last few years, a number of new training regimes, usually modified variations of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) protocols, have been rising in popularity among people of all ages. Since exercising is not limited to only healthy people, our study emphasized the benefits of HIIT and MICT in preventing or mitigating cardiac ischemia-reperfusion injury. Different kinds of research are being performed, studying the various positive and side effects of these training regimes, all in hopes of finding the most optimal ones. So far, all of them have shown that exercising to any extent, even for a short period of time, is beneficial in one way or another, and outweighs the possible risks it might have. We also revisited some of the known molecular mechanisms responsible for many of the effects of physical exercise and introduced some new findings related to them. Lastly, we summarized and compared the benefits of different HIIT and MICT protocols to narrow down the search for the most efficient training method.

Does Intensity Really Matter to Improve Cardiorespiratory Fitness in Patients With Heart Failure With Preserved Ejection Fraction?

Does Intensity Really Matter to Improve Cardiorespiratory Fitness in Patients With Heart Failure With Preserved Ejection Fraction?

High-Intensity Interval Training Improves Cardiac Function by miR-206 Dependent HSP60 Induction in Diabetic Rats.

ObjectiveA role for microRNAs is implicated in several biological and pathological processes. We investigated the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on molecular markers of diabetic cardiomyopathy in rats.MethodsEighteen male Wistar rats (260 ± 10 g; aged 8 weeks) with streptozotocin (STZ)-induced type 1 diabetes mellitus (55 mg/kg, IP) were randomly allocated to three groups: control, MICT, and HIIT. The two different training protocols were performed 5 days each week for 5 weeks. Cardiac performance (end-systolic and end-diastolic dimensions, ejection fraction), the expression of miR-206, HSP60, and markers of apoptosis (cleaved PARP and cytochrome C) were determined at the end of the exercise interventions.ResultsBoth exercise interventions (HIIT and MICT) decreased blood glucose levels and improved cardiac performance, with greater changes in the HIIT group (p < 0.001, η2: 0.909). While the expressions of miR-206 and apoptotic markers decreased in both training protocols (p < 0.001, η2: 0.967), HIIT caused greater reductions in apoptotic markers and produced a 20% greater reduction in miR-206 compared with the MICT protocol (p < 0.001). Furthermore, both training protocols enhanced the expression of HSP60 (p < 0.001, η2: 0.976), with a nearly 50% greater increase in the HIIT group compared with MICT.ConclusionsOur results indicate that both exercise protocols, HIIT and MICT, have the potential to reduce diabetic cardiomyopathy by modifying the expression of miR-206 and its downstream targets of apoptosis. It seems however that HIIT is even more effective than MICT to modulate these molecular markers.

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

Aimsto investigate if a High Intensity Interval Training (HIIT) protocol improves glycemic control and fitness capacity, compared to traditional moderate Intensity Continuous Training (MICT) exercise. Methods30 sedentary individuals with type 1 diabetes (T1D) and 26 healthy controls were assigned to a 3-week HIIT or MICT protocol. Blood glucose levels by continuous glucose monitoring system and fitness status were compared before and after the study period. ResultsDuring workouts, blood glucose levels remained stable in HIIT exercise (+3.2 ± 16.2 mg/dl (p = 0.43)), while decreased in MICT (-27.1 ± 17.5 mg/dl (p < 0.0001)) exercise. In addition, out of the 9 training sessions, HIIT volunteers needed to take carbohydrate supplements to avoid hypoglycemia in 0.56 ± 0.9 sessions, compared to 1.83 ± 0.5 sessions (p < 0.04) in MICT individuals. In the analysis of blood glucose levels between rest and training days (24h-period), training significantly reduced mean glycemic levels in both groups, but the MICT exercise results in an increase in the frequency of hypoglycemic episodes. The response to exercise seems to be attenuated in individuals with T1D, especially in HIIT group. ConclusionHIIT training results in a greater glycemic stability, with reduction of hypoglycemic episodes.

Differential Effects of Exercise Programs on Neuregulin 4, Body Composition and Cardiometabolic Risk Factors in Men With Obesity.

BackgroundNeuregulin 4 (Nrg4) is an adipokine that is sensitive to energy expenditure and with a potential role in metabolic homeostasis and obesity. This study examined the effects of 12 weeks of three different exercise training protocols on Nrg4 levels, cardiometabolic risk factors, and body composition parameters in men with obesity.MethodsSixty adult men with obesity (Mean ± SD; age: 27.60 ± 8.4 yrs.; height: 168.4 ± 2.6 cm; weight: 96.7 ± 7.2 kg) were randomly allocated into four equal (n = 15) groups: High- Intensity Interval Training (HIIT), Circuit Resistance Training (CRT), Moderate Intensity Continuous Training (MICT) or a control group. The HIIT protocol involved six bouts of 3-min high-intensity exercise (90% VO2peak) followed by 3-min low-intensity exercise (50% VO2peak). The CRT group performed three circuits of resistance training, where each circuit included 11 exercises at 20% of one-repetition maximum (1RM) and 70% of VO2peak, and with a work-to-rest ratio of 2:1 (40-s exercise and 20-s rest) and 60-s recovery between circuits. The MICT group performed 36 min of exercise at 70% of VO2peak. All measurements were taken 72 h before and after the first and last training sessions.ResultsThere were significant differences between the groups in fat-free mass (FFM), (effect size (ES): 0.78), fat mass (ES: 0.86), VO2peak (ES: 0.59), high-density lipoprotein cholesterol (HDL-C) (ES: 0.83), low-density lipoprotein (LDL-C) (ES: 0.79), total cholesterol (TC) (ES: 0.90), triglyceride (TG) (ES: 0.52) glucose (ES: 0.39), insulin (ES: 0.61), HOM-IR (ES: 0.91) and Nrg4 (ES: 0.98) (p < 0.05). There were no significant changes in very-low-density lipoprotein cholesterol (VLDL-C) (ES: 0.13) levels, or body weights (ES: 0.51) (p > 0.05). Levels of Nrg4 were negatively correlated with LDL-C, TC, TG, VLDL-C, glucose, insulin, HOMA-IR (p < 0.05) and positively with HDL-C (p < 0.05).ConclusionOur results suggest that HIIT and CRT protocols have greater effects than MICT protocol on Nrg4 levels, metabolic and cardiovascular risk factors, and body composition variables in men with obesity.

Changes in Mitochondrial Dynamic Factors (mfn2 and drp1) Following High Intensity Interval Training and Moderate Intensity Continuous Training in Obese Male Rats

Objective: Mitochondrial content and function are important determinants of oxidative capacity and metabolic efficiency of skeletal muscle tissue. The aim of this study was to investigate the changes in mitochondrial dynamic factors (mfn2 and drp1) following high intensity interval training (HIIT) and moderate intensity continuous training (MICT) in obese male rats.&#x0D; Materials and Methods: In this experimental study, 40 male wistar rats after inducing obesity with high fat diet (for 10 weeks), eight rats from the high-fat diet group (O) and eight rats of the standard dietary group (C) were sacrificed and other obese rats were randomly divided into three groups: obesity control (OC), MICT and HIIT groups. The HIIT protocol includes 10 bouts of 4-minute activity with intensity of 85-90% vo2max and 2-minute active rest periods and MICT protocol with intensity of 65-70% VO2max with covered distance was matched to that of HIT protocol for 12 weeks and 5 sessions per week. Protein levels of mfn2 and drp1 soleus muscle were measured by Western blot. For analyzing the data, One-way ANOVA and Tukey post hoc with SPSS–23 and the significance level was P-value≤ 0.05.&#x0D; Results: Induction of obesity was associated with a significant decrease in soleus muscle mfn2 and drp1 (P-value= 0.001). The intervention of HIIT and MICT significantly increased of mfn2 and drp1 compared to control group (P-value= 0.001). Also, mfn2 and drp1 were significantly higher in HIIT compared to MICT group (P-value= 0.001).&#x0D; Conclusion: It seems that HIIT and MICT increase the mitochondrial dynamic factors in skeletal muscle, and the effects of HIIT are significantly higher.

Are the group-based interventions improving the functional exercise capacity and quality of life of frail subjects with chronic heart failure?

Objectives:Frail subjects with chronic heart failure (CHF) often demonstrate limited tolerance of exertion, shortness of breath, and reduced walking capacity resulting poor quality of life (QoL). The aim of this study was to quantify the improvements in functional exercise capacity (FEC) and QoL among Bulgarian frail subjects with CHF performed group-based high-intensity aerobic interval training (HIAIT)/m-Ullevaal intervention and to compare it with moderate intensity continuous training (MICT) protocol.Methods:One hundred and twenty (n=120) frail subjects with mean age of 63.73±6.68 years, in CHF and NYHA class II-IIIB, were enrolled in the single-center, prospective, two-arm randomized controlled clinical trial conducted at the Medical Center for Rehabilitation and Sports Medicine-I-Plovdiv. The baseline assessment included 6-minute walk test (6ΜWT), peak oxygen uptake (VO2peak), modified Borg Perceived Exertion Scale (mBPES), and Minnesota living with the Heart Failure Questionnaire (MLHFQ).Results:The improvement in 6MWT (P<0.001), VO2peak (P<0.001), mBPES (P<0.001), and MLHFQ (P<0.001) observed among frail subjects performed HIAIT/m-Ullevaal intervention was significantly greater compared to the improvement observed in the subjects performed MICT protocol (P<0.001).Conclusions:The group-based HIAIT/m-Ullevaal intervention is a new perspective and challenge for both, Bulgarian cardiac rehabilitation (CR), and frail patients with CHF.

The Effects of Short-Term High-Intensity Interval Training and Moderate Intensity Continuous Training on Body Fat Percentage, Abdominal Circumference, BMI and VO2max in Overweight Subjects.

We aimed to compare the effects of a personalized short-term high-intensity interval training (HIIT) vs. standard moderate intensity continuous training (MICT) on body fat percentage, abdominal circumference, BMI and maximal oxygen uptake (VO2max) in overweight volunteers. Twenty overweight sedentary volunteers (24.9 ± 2.9y; BMI: 26.1 ± 1 kgm−2) were randomly assigned to 2 groups, HIIT or MICT. HIIT trained 6 weeks (3-days/week), 40-min sessions as follows: 6-min warm-up, 20-min resistance training (RT) at 70% 1-RM, 8-min HIIT up to 90% of the predicted Maximal Heart Rate (HRmax), 6-min cool-down. MICT trained 6 weeks (3-days/week) 60-min sessions as follows: 6-min warm-up, 20-min RT at 70% 1-RM, 30-min MICT at 60–70% of the predicted HRmax, 4-min cool-down. Two-way ANOVA was performed in order to compare the efficacy of HIIT and MICT protocols, and no significant interaction between training x time was evidenced (p > 0.05), indicating similar effects of both protocols on all parameters analyzed. Interestingly, the comparison of Δ mean percentage revealed an improvement in VO2max (p = 0.05) together with a positive trend in the reduction of fat mass percentage (p = 0.06) in HIIT compared to MICT protocol. In conclusion, 6 weeks of personalized HIIT, with reduced training time (40 vs. 60 min)/session and volume of training/week, improved VO2max and reduced fat mass percentage more effectively compared to MICT. These positive results encourage us to test this training in a larger population.

Moderate Intensity Continuous Training versus High Intensity Interval Training in Growth Restricted Mice to Improve Cardiac Function: A Pilot Study

IntroductionGrowth‐restriction during postnatal development has been linked to increased cardiovascular disease risk in adulthood, with greater impairment seen in females. Growth‐restricted mice present with thinner left ventricle posterior and anterior walls, compromised diastolic function and reduced stroke volume and cardiac output. Regular aerobic exercise training can promote cardiovascular health and well‐being, with recent evidence suggesting high intensity interval training may be more cardio protective as compared to moderate intensity continuous training. The purpose of this investigation was to determine if high intensity interval training (HIIT) promoted cardiac health in postnatally growth‐restricted female mice as compared to traditional moderate intensity continuous training (MICT).MethodsTo induce postnatal growth‐restriction, FVB mouse dams were fed either a 20% protein control diet or an 8% low‐protein isocaloric diet beginning 2 weeks before mating. Only pups born to control‐fed dams were used and cross‐fostered to either a low‐protein fed dam to induce growth‐restriction (PUN) or a different control fed dam (CON). On postnatal (PN) day 21 all pups were weaned and fed a control diet. At PN33 mice were allocated to MICT (PUN n=4, CON n=3), HIIT (PUN n= 4, CON n= 3) or a corresponding sedentary group (MICT: sedentary PUN n= 5, sedentary CON n=4; or HIIT: sedentary PUN n= 5, sedentary CON n=4). The MICT protocol was defined as treadmill running 3 days/week for 12 weeks at 17 m/min at −16 degree decline for 28 minutes and the HIIT protocol was treadmill running 5 days/week for 8 weeks with alternating intervals of 8 mins at 85% and 2 mins at 55% of maximum workload for 60 minutes. At PN 128 (MICT) and PN 98 (HIIT) echocardiography and Doppler blood flow was utilized to measure cardiac structure and function under 1% isoflurane anesthesia. Statistical analysis was performed using GraphPad Prism 8, utilizing two‐way ANOVAs with an alpha level of .05 set a priori and if significant Tukey’s post hoc for multiple comparisons was conducted.ResultsSedentary PUN groups exhibited cardiac dysfunction as evident by reduced left ventricle (LV) area during systole (p=.0290), LV diameter during diastole (p=.0156) and systole (p=.0003) and LV volume during systole (p=.0191). Systolic function was compromised in the PUN sedentary group by impaired myocardial performance index (MPI) (p=.0049), ejection fraction (EF) (p=.0023), aortic ejection time (AET) (p=.0345) and fractional shortening (FS) (p=.0111). Diastolic impairment manifested as reductions in isovolumic relaxation time (IVRT) (p=.0102) and mitral valve deceleration time (MVDT) (p=&lt;.0001) in the PUN sedentary group. Both MICT and HIIT were able to reverse impairments as no significant differences were noted between exercised PUN groups and their CON counterparts.ConclusionMICT and HIIT both reversed the cardiac impairments caused by growth‐restriction. Impairments caused by growth‐restriction can be mitigated with exercise training. Importantly, exercise professionals have flexibility in prescribing exercise as both MICT and HIIT were shown to be effective.

EFFECTS OF AEROBIC EXERCISE TRAINING ON OXIDATIVE STRESS IN THE SKELETAL MUSCLES OF OBESE RATS

ABSTRACT Introduction Obesity is a complex and multifactorial metabolic disorder characterized by the accumulation of body fat; physical exercise increases energy expenditure and promotes a reparative effect through modulation of endogenous antioxidant defenses. Objective To evaluate the effects of the high-fat diet (HFD) on oxidative stress parameters in skeletal muscles of rats using aerobic exercise training protocols (AETP), moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT). Methods The study was quantitative and experimental. Animals received 8 weeks of HFD or normal diet (ND), followed by 9 weeks of HFD or ND and the two AETPs. Results HFD did not alter the formation of thiobarbituric acid reactive substances (TBA-RS), total sulfhydryl and protein carbonyl content in the soleus and plantaris muscles; in contrast, the protocols caused a decrease in TBA-RS levels in the plantaris muscle and increased the sulfhydryl content in the soleus muscle, while MICT increased the sulfhydryl content in the plantaris muscle and reduced protein carbonyl content in both muscles. HFD reduced SOD activity in the plantaris muscle while the MICT protocol enhanced SOD in the soleus muscle and both protocols reversed the decrease in SOD in the plantaris muscle. HFD increased CAT activity in the soleus muscle, the HIIT protocol prevented this alteration and both protocols increased CAT in the plantaris muscle. HFD reduced GSH-Px activity in both muscles, and the MICT protocol prevented this reduction in the soleus muscle, while the HIIT protocol partially prevented this decrease. The MICT protocol did not prevent the reduction of GSH-Px and the HIIT protocol partially prevented this decrease in the plantaris muscle. Conclusions HFD elicited oxidative stress in the skeletal muscle of rats, and both protocols were able to prevent most of the alterations in oxidative stress parameters caused by the HFD. Level of evidence IV; Investigation of treatment outcomes.

Affective and enjoyment responses to 12 weeks of high intensity interval training and moderate continuous training in adults with Crohn's disease.

The aim was to undertake secondary data analysis from a three-arm randomised feasibility trial of high intensity interval training (HIIT), moderate intensity continuous training (MICT), and usual care control in adults with Crohn’s disease (CD; n = 36), with a primary focus on exploring affective and enjoyment responses. Twenty-five participants with quiescent or mildly-active CD were randomised to one of the two exercise groups: HIIT (n = 13) and MICT (n = 12). Both groups were offered thrice weekly sessions for 12 weeks. MICT consisted of cycling for 30 minutes at 35% peak power (Wpeak), whereas HIIT involved ten 1-minute bouts at 90% Wpeak, interspersed with 1-minute bouts at 15% Wpeak. Heart rate (HR), differentiated ratings of perceived exertion for legs (RPE-L) and central (RPE-C), along with feeling state (Feeling Scale; FS) were measured at 92.5% of each session. Enjoyment was measured at the end of training using the Physical Activity Enjoyment Scale (PACES). Post-hoc exploratory analysis involved a mixed-model two-way ANOVA to compare HR, RPE-L, RPE-C and FS for the exercise sessions in weeks 1, 6 and 12 between groups. Overall, HR was greater (p < 0.01) during HIIT (173 ± 8 bpm) compared with MICT (128 ± 6 bpm). Similarly, RPE-L and RPE-C responses were greater overall (p = 0.03 and p = 0.03, respectively) during HIIT (5.5 ± 1.6 and 5.1 ± 1.7, respectively) compared to MICT (3.3 ± 1.5 and 2.9 ± 1.5, respectively). Overall, FS was 2.2 ± 1.9 for HIIT and 2.1 ± 1.4 for MICT with no effect of treatment group (p = 0.25) or time (p = 0.94). There was also no significant difference in PACES scores between HIIT (99.4 ± 12.9) and MICT (101.3 ± 17.4; p = 0.78). The findings suggest HIIT and MICT protocols elicited similar enjoyment and affect in adults with quiescent or mildly-active CD.

CrossTalk proposal: Exercise training intensity is more important than volume to promote increases in human skeletal muscle mitochondrial content.

CrossTalk proposal: Exercise training intensity is more important than volume to promote increases in human skeletal muscle mitochondrial content.

Enjoyment Responses to High Intensity Interval and Moderate Intensity Continuous Training in Crohn’s Disease Patients

PURPOSE: The aim of this study was to undertake secondary data analysis from a three-arm feasibility trial of high intensity interval training (HIIT), moderate intensity continuous training (MICT), and usual care, in Crohn’s disease (CD) patients (n=36), with a primary focus on exploring affective and enjoyment responses to the two types of exercise training. METHODS: Twenty-five participants with quiescent or mildly-active CD were randomised to one of the two active groups: HIIT (n=13) and MICT (n=12). Both groups were offered three exercise sessions per week for 12 weeks. MICT consisted of cycling for 30 minutes at 35% peak power (Wpeak), whereas HIIT involved ten 1-minute bouts at 90% Wpeak, interspersed with 1-minute bouts at 15% Wpeak. Peak power was determined prior to the intervention and reassessed at weeks 4 and 8 to adjust training load. Heart rate (HR) and differentiated ratings of perceived exertion (RPE) for legs (RPE-L) and central (i.e. ventilatory and circulatory; RPE-C), along with feeling state (Feeling Scale; FS) were measured at regular time intervals during each exercise session. In addition, enjoyment was measured at the end of the training programmes using the Physical Activity Enjoyment Scale (PACES). Post-hoc exploratory analysis involved a mixed-model two-way ANOVA to compare HR, RPE-C, RPE-L and FS at weeks 1, 6 and 12 between groups. An independent t-test was used to assess between-group differences in PACES scores. RESULTS: HR was greater (p < 0.01) during HIIT (168 ± 20 bpm) compared with MICT (124 ± 18 bpm). Similarly, RPE-L and RPE-C responses were greater (p = 0.03 and p = 0.03, respectively) during HIIT (5.5 ± 1.6 and 5.1 ± 1.7 i.e. ‘hard’, respectively) compared to MICT (3.3 ± 1.5 and 2.9 ± 1.5 i.e. ‘moderate’, respectively). Overall, FS recorded was 2.2 ± 1.8 (i.e. ‘fairly good’) for HIIT and 2.1 ± 1.3 (i.e. ‘fairly good’) for MICT with no effect of condition (P=0.25) or time (P=0.94). There was also no statistically significant difference in PACES scores between HIIT (99.4 ± 12.9) and MICT (101.3 ± 17.4; p = 0.78). CONCLUSION: Despite the differences in HR and RPE responses, the findings suggest that the HIIT and MICT protocols elicited similar enjoyment and affective responses in adults with quiescent or mildly-active CD. Support by CCUK Grant SP2015/1.

Affective Adaptation to Repeated SIT and MICT Protocols in Insulin-Resistant Subjects.

The aim of this study was to investigate affective responses to repeated sessions of sprint interval training (SIT) in comparison with moderate-intensity continuous training (MICT) in insulin-resistant subjects. Twenty-six insulin-resistant adults (age, 49 (4) yr; 10 women) were randomized into SIT (n = 13) or MICT (n = 13) groups. Subjects completed six supervised training sessions within 2 wk (SIT session, 4-6 × 30 s all-out cycling/4-min recovery; MICT session, 40-60 min at 60% peak work load). Perceived exertion, stress, and affective state were assessed with questionnaires before, during and after each training session. Perceived exertion, displeasure, and arousal were higher during the SIT compared with MICT sessions (all P < 0.01). These, however, alleviated similarly in response to SIT and MICT over the 6 d of training (all P < 0.05). SIT versus MICT exercise increased perceived stress and decreased positive affect and feeling of satisfaction acutely after exercise especially in the beginning of the intervention (all P < 0.05). These negative responses declined significantly during the training period: perceived stress and positive activation were no longer different between the training groups after the third, and satisfaction after the fifth training session (P > 0.05). The perceptual and affective responses are more negative both during and acutely after SIT compared with MICT in untrained insulin-resistant adults. These responses, however, show significant improvements already within six training sessions, indicating rapid positive affective and physiological adaptations to continual exercise training, both SIT and MICT. These findings suggest that even very intense SIT is mentally tolerable alternative for untrained people with insulin resistance.

Effects of two aerobic exercise training protocols on parameters of oxidative stress in the blood and liver of obese rats.

We evaluated the effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) protocols on the alterations in oxidative stress parameters caused by a high-fat diet (HFD), in the blood and liver of rats. The HFD enhanced thiobarbituric acid reactive substances (TBA-RS) and protein carbonyl content, while reducing total sulfhydryl content and catalase (CAT) and glutathione peroxidase (GSH-Px) activities in the blood. Both trainingprotocols prevented an increase in TBA-RS and protein carbonyl content, and prevented a reduction in CAT. HIIT protocol enhanced SOD activity. In the liver, HFD didn't alter TBA-RS, total sulfhydryl content or SOD, but increased protein carbonyl content and CAT and decreased GSH-Px. The exerciseprotocols prevented the increase in protein carbonyl content and the MICT protocol prevented an alteration in CAT. In conclusion, HFD elicits oxidative stress in the blood and liver and both protocols prevented most of the alterations in the oxidative stress parameters.

Similar Improvements in Cardiorespiratory Fitness after 12 weeks of Sprint Interval and Moderate-Intensity Continuous Training

Sprint interval training (SIT) in the form of repeated Wingate Tests is effective for improving cardiorespiratory fitness similar to traditional moderate-intensity continuous training (MICT) despite a lower time commitment. The potential “time efficiency” of SIT is frequently touted, but Wingate-based protocols nonetheless require ∼25 min per session including warm-up, cool down and recovery intervals. A SIT protocol involving only 3 x 20 sec of all out exercise within a 10 min training session was recently shown to improve VO2peak in sedentary individuals when performed 3x/wk for 6 wk. No studies have directly compared this low-volume SIT protocol to MICT, and the potential changes induced over a longer period of training are unknown. PURPOSE: To compare changes in cardiorespiratory fitness after 6 and 12 wk of low-volume SIT and a MICT protocol requiring a five-fold greater time commitment. METHODS: Sedentary men (27 ± 9 y; BMI = 27 ± 6 kg/m2) performed either SIT or MICT (n=7 each) 3x/wk for 12 wk. SIT consisted of 3 x 20 sec all out cycle sprints against 5% body mass interspersed with 2 min rest, whereas MICT involved 45 min of continuous cycling at ∼70% maximal heart rate (HRmax). A 2 min warm-up and 3 min cool-down at 50 W were included for all sessions in both groups. Training loads were adjusted as appropriate to maintain the desired stimulus. RESULTS: Mean HR elicited during MICT and SIT was 73 ± 5% and 79 ± 3% of HRmax, respectively. VO2peak increased 11% after 6 wk of training in both groups (MICT: 31.9 ± 6.1 to 35.0 ± 6.2; SIT: 30.8 ± 7.2 to 34.2 ± 7.8 ml/kg/min, p<0.001, main effect for time). VO2peak increased further at 12 wk compared to 6 wk in both groups (to 38.0 ± 9.2 in MICT and to 36.6 ± 6.9 ml/kg/min in SIT, p<0.01, main effect for time), corresponding to a 19% improvement overall compared to pre-training in each group. CONCLUSION: A sprint interval training protocol involving 3 x 20 sec bursts of all out cycling within a 10 min training session, performed 3x/wk, improved VO2peak to the same extent as 150 min per week of moderate-intensity continuous exercise. These data attest to the potency of very intense but brief intermittent cycling exercise to improve cardiorespiratory fitness.

Improving Aerobic Power in Primary School Boys: A Comparison of Continuous and Interval Training

The purpose of this study was to assess whether the magnitude of change in aerobic power was different in boys (mean age 10.25 +/- 0.50 y) who followed a high-intensity interval training protocol, compared to those who followed a moderate-intensity continuous training protocol. Boys were assigned to either a control group (n = 15), a continuous training group (n = 10), or an interval training group (n = 10). They completed peak oxygen uptake tests at baseline and following an 8-week training period. The control group continued with normal activity habits, whilst the continuous training group followed a 20-minute steady-state cycle protocol at 80-85 % of the maximal heart rate, and the interval training group completed 30-s sprints on a cycle ergometer, interspersed with active rest periods. The two training protocols were designed to incur similar cardiovascular work over the 20 minutes of each training session. Significant increases (p < 0.05) in peak oxygen uptake were noted for both the interval and continuous training groups. The interval training group showed marked pre- to post-increases in both peak oxygen pulse, oxygen pulse at the ventilatory threshold, and ventilatory threshold that were not apparent in the continuous group boys. It would appear that a high-intensity interval protocol confers a different training effect in comparison to continuous steady-state training in boys. Possible mechanisms that underpin these adaptations may include increased blood volume and a concomitant adjustment in stroke volume.