High intensity interval training alters substrate utilization and reduces oxygen consumption in the heart.
Aims: Although, exercise training induces hypertrophy with improved contractile function, the effect of exercise on myocardial substrate metabolism and cardiac efficiency is less clear. High intensity training has been shown to produce more profound effects on cardiovascular function and aerobic capacity than isocaloric low and moderate intensity training. The aim of the present study was to explore metabolic and mechanoenergetic changes in the heart following endurance exercise training of both high and moderate intensity. Methods and Results: C57BL/6J mice were subjected to 10 weeks treadmill running; either high intensityinterval training (HIT) or distance-matched moderate intensity training (MIT), leading to a more pronounced increase in maximal oxygen uptake following HIT. Although, both modes of exercise were associated with a 10% increase in heart weight to body weight ratio, only HIT altered cardiac substrate utilization, as revealed by a 36% increase in glucose oxidation and a concomitant reduction in fatty acid oxidation. HIT also improved cardiac efficiency by decreasing work-independent myocardial oxygen consumption and increased cardiac maximal mitochondrial respiratory capacity. Conclusion: This study shows that high intensitytraining is required for induction of changes in cardiac substrate utilization and energetics, which may contribute to the superior effect of high to moderate intensity training in terms of increasing aerobic capacity.
Aerobic interval training increases peak oxygen uptake more than usual care exercise training in myocardial infarction patients: a randomised, controlled study.
Objective: Exercise capacity strongly predicts survival and aerobic interval training (AIT) increases peak oxygen uptake effectively in cardiac patients. Usual care in Norway provides exercise training at the hospitals following myocardial infarction (MI), but the effect and actual intensity of these rehabilitation programmes are unknown. Design: Randomised controlled trial. Setting: Hospital cardiac rehabilitation. Subjects: One hundred and seven patients, recruited two to 12 weeks after MI, were randomised to usual care rehabilitation or treadmill AIT. Interventions: Usual care aerobic group exercise training or treadmill AIT as 4 × 4 minutes intervals at 85-95% of peak heart rate. Twice weekly exercise training for 12 weeks. Main measures: The primary outcome measure was peak oxygen uptake. Secondary outcome measures were endothelial function, blood markers of cardiovascular disease, quality of life, resting heart rate, and heart rate recovery. Results: Eighty-nine patients (74 men, 15 women, 57.4 ± 9.5 years) completed the programme. Peak oxygen uptake increased more (P = 0.002) after AIT (from 31.6 ± 5.8 to 36.2 ± 8.6 mL·kg(-1)·min(-1), P < 0.001) than after usual care rehabilitation (from 32.2 ± 6.7 to 34.7 ± 7.9 mL·kg(-1)·min(-1), P < 0.001). The AIT group exercised with significantly higher intensity in the intervals compared to the highest intensity in the usual care group (87.3 ± 3.9% versus 78.7 ± 7.2% of peak heart rate, respectively, P < 0.001). Both programmes increased endothelial function, serum adiponectin, and quality of life, and reduced serum ferritin and resting heart rate. High-density lipoprotein cholesterol increased only after AIT. Conclusions: AIT increased peak oxygen uptake more than the usual care rehabilitation provided to MI patients by Norwegian hospitals.
Aerobic interval training vs. continuous moderate exercise in the metabolic syndrome of rats artificially selected for low aerobic capacity.
The recent development of a rat model that closely resembles the metabolic syndrome allows to study the mechanisms of amelioration of the syndrome by exercise training. Here, we compared the effectiveness for reducing cardiovascular risk factors by exercise training programmes of different exercise intensities.
METHODS AND RESULTS:
Metabolic syndrome rats were subjected to either continuous moderate-intensity exercise (CME) or high-intensity aerobic intervaltraining (AIT). AIT was more effective than CME at reducing cardiovascular disease risk factors linked to the metabolic syndrome. Thus, AIT produced a larger stimulus than CME for increasing maximal oxygen uptake (VO(2max); 45 vs. 10%, P < 0.01), reducing hypertension (20 vs. 6 mmHg, P < 0.01), HDL cholesterol (25 vs. 0%, P < 0.05), and beneficially altering metabolism in fat, liver, and skeletal muscle tissues. Moreover, AIT had a greater beneficial effect than CME on sensitivity of aorta ring segments to acetylcholine (2.7- vs. 2.0-fold, P < 0.01), partly because of intensity-dependent effects on expression levels of nitric oxide synthase and the density of caveolae, and a greater effect than CME on the skeletal muscle Ca2+ handling (50 vs. 0%, P < 0.05). The two exercise trainingprogrammes, however, were equally effective at reducing body weight and fat content.
High-intensity exercise training was more beneficial than moderate-intensity exercise training for reducing cardiovascular risk in rats with the metabolic syndrome. This was linked to more superior effects on VO(2max), endothelial function, blood pressure, and metabolic parameters in several tissues. These results demonstrate that exercise training reduces the impact of the metabolic syndrome and that the magnitude of the effect depends on exercise intensity.
Aerobic interval training versus continuous moderate exercise as a treatment for the metabolic syndrome: a pilot study.
Individuals with the metabolic syndrome are 3 times more likely to die of heart disease than healthy counterparts. Exercise training reduces several of the symptoms of the syndrome, but the exercise intensity that yields the maximal beneficial adaptations is in dispute. We compared moderate and highexercise intensity with regard to variables associated with cardiovascular function and prognosis in patients with the metabolic syndrome.
METHODS AND RESULTS:
Thirty-two metabolic syndrome patients (age, 52.3+/-3.7 years; maximal oxygen uptake [o(2)max], 34 mL x kg(-1) x min(-1)) were randomized to equal volumes of either moderate continuous moderate exercise (CME; 70% of highest measured heart rate [Hfmax]) or aerobic interval training(AIT; 90% of Hfmax) 3 times a week for 16 weeks or to a control group. o(2)max increased more after AIT than CME (35% versus 16%; P<0.01) and was associated with removal of more risk factors that constitute the metabolic syndrome (number of factors: AIT, 5.9 before versus 4.0 after; P<0.01; CME, 5.7 before versus 5.0 after; group difference, P<0.05). AIT was superior to CME in enhancing endothelial function (9% versus 5%; P<0.001), insulin signaling in fat and skeletal muscle, skeletal muscle biogenesis, and excitation-contraction coupling and in reducing blood glucose and lipogenesis in adipose tissue. The 2 exercise programs were equally effective at lowering mean arterial blood pressure and reducing body weight (-2.3 and -3.6 kg in AIT and CME, respectively) and fat.
Exercise intensity was an important factor for improving aerobic capacity and reversing the risk factors of the metabolic syndrome. These findings may have important implications for exercise training in rehabilitation programs and future studies.
High-Intensity Interval Training for Health and Fitness: Can Less be More?
Effect of Aerobic Interval Training on Exercise Capacity and Metabolic Risk Factors in People With Cardiometabolic Disorders: A META-ANALYSIS.
To compare the effectiveness of high-intensity aerobic interval training (AIT) with active recovery and continuous moderate-intensity exercise (CME) on exercise capacity and metabolic risk factors in adults with cardiometabolic disorders through a systematic review and meta-analysis.
Studies were selected from 5 electronic databases (PubMed, MEDLINE, CINAHL, Physiotherapy Evidence Database [PEDro] and Cochrane Library Register of Controlled Trials). Randomized controlled trials (RCTs), published in English, that compared the effects of AIT with CME on exercise capacity and metabolic risk factors in adults with cardiometabolic disorders were included. Aerobic interval training was defined as high-intensity training separated by active recovery periods; CME incurred identical energy expenditure as AIT. Each trial was evaluated using the PEDro scale. Weighted mean difference (WMD) and 95% CIs were used to determine the effect size for each outcome.
Six RCTs with 153 participants (40 overweight/obesity, 19 with metabolic syndrome, and 94 with heart disease) were included. The mean value on the PEDro scale for these studies was 5.0. Aerobic interval training significantly increased peak oxygen consumption (WMD, 3.6 mL·kg·min; 95% CI, 2.3-4.9) with a trend of decreasing fasting glucose (WMD, -0.4 mmol/L; 95% CI, -0.9 to 0.2, P = .18) compared with CME. The effects on other metabolic risk factors were similar between AIT and CME.
Analysis of a limited number of studies with small sample sizes indicates that AIT is superior to CME in terms of improving exercise capacity. Further high quality studies with larger sample size are required to confirm this finding in adults with cardiometabolic disorders.