High Intensity High Volume Interval Training Improves Endurance Performance and Induces a Nearly Complete Slow-to-Fast Fiber Transformation on the mRNA Level

Impact of Different Training Modalities on Molecular Alterations in Skeletal Muscle of Patients With Heart Failure With Preserved Ejection Fraction: A Substudy of the OptimEx Trial

Background:

Exercise intolerance is a cardinal feature of heart failure with preserved ejection fraction and so far exercise training (ET) is the most effective treatment. Since the improvement in exercise capacity is only weakly associated with changes in diastolic function other mechanisms, like changes in the skeletal muscle, contribute to improvement in peak oxygen consumption. The aim of the present study was to analyze molecular changes in skeletal muscle of patients with heart failure with preserved ejection fraction performing different ET modalities.

Methods:

Skeletal muscle biopsies were taken at study begin and after 3 and 12 months from patients with heart failure with preserved ejection fraction randomized either into a control group (guideline based advice for ET), a high-intensity interval training group (HIIT) or a moderate continuous training group. The first 3 months of ET were supervised in-hospital followed by 9 months home-based ET. Protein and mRNA expression of atrophy-related proteins, enzyme activities of enzymes linked to energy metabolism and satellite cells (SCs) were quantified.

Results:

Exercise capacity improved 3 months after moderate continuous exercise training and HIIT. This beneficial effect was lost after 12 months. HIIT mainly improved markers of energy metabolism and the amount and function of SC, with minor changes in markers for muscle atrophy. Only slight changes were observed after moderate continuous exercise training. The molecular changes were no longer detectable after 12 months.

Conclusions:

Despite similar improvements in exercise capacity by HIIT and moderate continuous exercise training after 3 months, only HIIT altered proteins related to energy metabolism and amount/function of SC. These effects were lost after switching from in-hospital to at-home-based ET.

Registration:

URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02078947.

The circadian clock regulates metabolic responses to physical exercise

It has been proposed for years that physical exercise ameliorates metabolic diseases. Optimal exercise timing in humans and mammals has indicated that circadian clocks play a vital role in exercise and body metabolism. Skeletal muscle metabolism exhibits a robust circadian rhythm under the control of the suprachiasmatic nucleus of the hypothalamus. Clock genes also control the development, differentiation, and function of skeletal muscles. In this review, we aimed to clarify the relationship between exercise, skeletal muscles, and the circadian clock. Health benefits can be attained by the scheduling of exercise at the best circadian time. Exercise therapy for metabolic diseases and cardiovascular health is a key adjuvant method. This review highlights the importance of exercise timing in maintaining healthy metabolism and circadian clocks.

Efficacy of high-intensity interval- or continuous aerobic-training on insulin resistance and muscle function in adults with metabolic syndrome: a clinical trial

PURPOSE

We carried out a randomized, clinical trial in adults of both sexes with metabolic syndrome (MS) to assess the efficacy of high-intensity, low-volume interval training (HIIT) compared to moderate-intensity continuous training (MICT) on insulin resistance (IR), muscle mass, muscle activation, and serum musclin.

METHODS

Fasting glycemia, insulinemia, and glycated haemoglobin were determined by conventional methods, IR by Homeostatic model assessment (HOMA), lean mass by Dual-Energy X-ray Absorptiometry, muscle activation through carnosine by Proton Magnetic Resonance Spectroscopy, and musclin by Enzyme-Linked ImmunoSorbent Assay before and after a supervised, three-times/week, 12-week treadmill programme. HIIT (n = 29) consisted of six intervals with one-minute, high-intensity phases at 90% of peak oxygen consumption (VO_2peak). MICT (n = 31) trained at 60% of VO_2peak for 30 min.

RESULTS

Patients had a mean age of 50.8 ± 6.0 years, body mass index of 30.6 ± 4.0 kg/m², and VO_2peak of 29.0 ± 6.3 mL.kg^-1.min^-1. Compared to MICT, HIIT was not superior at reducing Ln HOMA-IR (adjusted mean difference: 0.083 [95%CI - 0.092 to 0.257]), carnosine or musclin or at increasing thigh lean mass. HIIT increased carnosine by 0.66 mmol/kg.ww (95% CI 0.08-1.24) after intervention. Both interventions reduced IR, body fat percentage and increased total lean mass/height² and VO_2peak. Musclin showed a non-significant reduction with a small effect size after both interventions.

CONCLUSION

Compared to MICT, HIIT is not superior at reducing IR, carnosine or musclin or at increasing skeletal muscle mass in adults with MS. Both training types improved IR, muscle mass and body composition. NCT03087721, March 22nd, 2017.

TRIAL REGISTRATION NUMBER

NCT03087721. Registered March 22nd, 2017.

Individual physiological and mitochondrial responses during 12 weeks of intensified exercise

AIM

Observed effects of exercise are highly variable between individuals, and subject-by-training interaction (i.e., individual response variability) is often not estimated. Here, we measured mitochondrial (citrate synthetase, cytochrome-c oxidase, succinate dehydrogenase, and mitochondrial copy-number), performance markers (Wpeak , lactate threshold [LT], and VO2peak ), and fiber type proportions/expression (type I, type IIa, and type IIx) in multiple time points during 12-week of high-intensity interval training (HIIT) to investigate effects of exercise at the individual level.

METHODS

Sixteen young (age: 33.1 ± 9.0 years), healthy men (VO2peak 35-60 ml/min/kg and BMI: 26.4 ± 4.2) from the Gene SMART study completed 12-week of progressive HIIT. Performance markers and muscle biopsies were collected every 4 weeks. We used mixed-models and bivariate growth models to quantify individual response and to estimate correlations between variables.

RESULTS

All performance markers exhibited significant (Wpeak 0.56 ± 0.33 p = 0.003, LT 0.37 ± 0.35 p = 0.007, VO2peak 3.81 ± 6.13 p = 0.02) increases overtime, with subject-by-training interaction being present (95% CI: Wpeak 0.09-0.24, LT 0.06-0.18, VO2peak 0.27-2.32). All other measurements did not exhibit significant changes. Fiber type IIa proportions at baseline was significantly associated with all physiological variables (p < 0.05), and citrate synthetase and cytochrome-c oxidase levels at baseline and overtime (i.e., intercept and slope) presented significant covariance (p < 0.05). Finally, low correlations between performance and mitochondrial markers were observed.

CONCLUSION

We identified a significant subject-by-training interaction for the performance markers. While for all other measures within-subject variability was too large and interindividual differences in training efficacy could not be verified. Changes in measurements in response to exercise were not correlated, and such disconnection should be further investigated by future studies.

Physiological responses to maximal 4 s sprint interval cycling using inertial loading: the influence of inter-sprint recovery duration

PURPOSE

Interval exercise allows very high-power outputs to be maintained, a key for stimulating training adaptations. The main purpose of this study was to develop a sprint interval protocol that stimulated both anaerobic and aerobic systems while maximizing power output and minimizing fatigue. The secondary goal was to investigate the influence of inter-sprint recovery duration.

METHODS

Sixteen (8 females) participants (age: 23.5 ± 3.4 years, peak oxygen consumption (VO_2peak): 45.6 ± 9.2 ml kg^-1 min^-1) took part in this study. The exercise protocol involved 30 bouts of 4 s maximal cycling sprints using an 'Inertial Load Ergometer'. Recovery durations between sprints of 15, 30 and 45 s were studied in three trials.

RESULTS

Peak power output (PPO) was maintained while taking 45 and 30 s of recovery, although it was 9% higher (p < 0.05) during 45 vs. 30 s. PPO with 15 s recovery declined 18% (p < 0.05) and then stabilized as did oxygen consumption (72±2% VO_2peak) at a level that might reflect the peak rate of ATP-PC resynthesis from oxidative metabolism. The 15-, 30-, and 45 s trials elicited 72, 56, and 49% VO_2peak and 86, 80, and 75% of maximal heart rate (all p<0.001). Perceived exertion increased with shorter recovery periods but remained at 12.6-14.7 and never became 'very hard'.

CONCLUSION

The present study describes the use of an inertial-load ergometer to accommodate repeated 4 s maximal cycling sprints that elicit 72% VO_2peak when the recovery period is 15 s. However, a recovery duration of 15 s was insufficient for the maintenance of power generation.

TRIAL REGISTRATION NUMBER AND DATE

NCT04448925, 26 Jun 2020; retrospectively registered to clinicaltrials.gov.

Delivery of muscle-derived exosomal miRNAs induced by HIIT improves insulin sensitivity through down-regulation of hepatic FoxO1 in mice

Implementation of regular physical activity helps in the maintenance of a healthy metabolic profile both in humans and mice through molecular mechanisms not yet completely defined. Here, we show that high-intensity interval training (HIIT) modifies the microRNA (miRNA) profile of circulating exosomes in mice, including significant increases in miR-133a and miR-133b Importantly, treatment of sedentary mice with exosomes isolated from the plasma of trained mice improves glucose tolerance, insulin sensitivity, and decreases plasma levels of triglycerides. Moreover, exosomes isolated from the muscle of trained mice display similar changes in miRNA content, and their administration to sedentary mice reproduces the improvement of glucose tolerance. Exosomal miRNAs up-regulated by HIIT target insulin-regulated transcription factor forkhead box O1 (FoxO1) and, accordingly, expression of FoxO1 is decreased in the liver of trained and exosome-treated mice. Treatment with exosomes transfected with a miR-133b mimic or with a specific siRNA targeting FoxO1 recapitulates the metabolic effects observed in trained mice. Overall, our data suggest that circulating exosomes released by the muscle carry a specific miRNA signature that is modified by exercise and induce expression changes in the liver that impact whole-body metabolic profile.

Effect of carbohydrate-protein supplementation on endurance training adaptations

Purpose

To examine the influence of post-exercise protein feeding upon the adaptive response to endurance exercise training.

Methods

In a randomised parallel group design, 25 healthy men and women completed 6 weeks of endurance exercise training by running on a treadmill for 30–60 min at 70–75% maximal oxygen uptake (VO_2max) 4 times/week. Participants ingested 1.6 g per kilogram of body mass (g kg BM⁻¹) of carbohydrate (CHO) or an isocaloric carbohydrate–protein solution (CHO-P; 0.8 g carbohydrate kg BM⁻¹ + 0.8 g protein kg BM⁻¹) immediately and 1 h post-exercise. Expired gas, blood and muscle biopsy samples were taken at baseline and follow-up.

Results

Exercise training improved VO_2max in both groups (p ≤ 0.001), but this increment was not different between groups either in absolute terms or relative to body mass (0.2 ± 0.2 L min⁻¹ and 3.0 ± 2 mL kg⁻¹ min⁻¹, respectively). No change occurred in plasma albumin concentration from baseline to follow-up with CHO-P (4.18 ± 0.18 to 4.23 ± 0.17 g dL⁻¹) or CHO (4.17 ± 0.17 to 4.12 ± 0.22 g dL⁻¹; interaction: p > 0.05). Mechanistic target of rapamycin (mTOR) gene expression was up-regulated in CHO-P (+ 46%; p = 0.025) relative to CHO (+ 4%) following exercise training.

Conclusion

Post-exercise protein supplementation up-regulated the expression of mTOR in skeletal muscle over 6 weeks of endurance exercise training. However, the magnitude of improvement in VO_2max was similar between groups.

Energy Metabolism in Continuous, High-Intensity, and Sprint Interval Training Protocols With Matched Mean Intensity

Eigendorf, J, Maassen, M, Apitius, D, and Maassen, N. Energy metabolism in continuous, high-intensity, and sprint interval training protocols with matched mean intensity. J Strength Cond Res XX(X): 000-000, 2019-To evaluate acute physiological reactions and energy metabolism with 3 different training regimes, 7 subjects performed a high-intensity interval training (HIT), a sprint interval training (SIT), and a continuous training (CT) in a cross-over design. All training sessions were matched for relative mean intensity (50% Pmax). Stress-to-pause-ratios were chosen as 6-24 seconds (SIT) and 30-30 seconds (HIT) for interval protocols. No significant differences (significance level p ≤ 0.05) were found for oxygen uptake (V[Combining Dot Above]O2), respiratory exchange ratio (RER), slope of RER (RERslope), and heart rate between the different training regimes. Lactate concentrations ([Lac]) in CT were significantly lower (p < 0.01) compared with HIT and SIT. No significant differences were found for free fatty acids ([FFA], p = 0.41) and glycerol ([GLY], p = 0.26) levels during all 3 training protocols (CT 0.27 mmol·L, SIT 0.22 mmol·L, and HIT 0.22 mmol·L). Ammonia (NH3, p > 0.05) levels did not show significant differences between the 3 training protocols during exercise phase. The comparable physiological reactions of [FFA], [GLY], and RER show that the activation of fat metabolism is not different between training regimes with different stress-to-pause-ratios. Moreover, mean intensity and time of exercise influence activation of fat metabolism. Increases in [NH3] suggest similar sources between the 3 training protocols and the need for further research concerning amino acid deamination. The better understanding of the acute reactions and changing of the energy metabolism during training sessions will help athletes in planning and executing their training sessions more efficiently and more precisely in the context of periodization.

Changes in biomarker levels and myofiber constitution in rat soleus muscle at different exercise intensities

Although exercise affects the function and structure of skeletal muscle, our knowledge regarding the biomedical alterations induced by different intensities of exercise is incomplete. Here we report on the changes in biomarker levels and myofiber constitution in the rat soleus muscle induced by exercise intensity. Male adult rats at 7 weeks of age were divided into 3 groups by exercise intensity, which was set based on the accumulated lactate levels in the blood using a treadmill: stationary control (0 m/min), aerobic exercise (15 m/min), and anaerobic exercise (25 m/min). The rats underwent 30 min/day treadmill training at different exercise intensities for 14 days. Immediately after the last training session, the soleus muscle was dissected out in order to measure the muscle biomarker levels and evaluate the changes in the myofibers. The mRNA expression of citrate synthase, glucose-6-phosphate dehydrogenase, and Myo D increased with aerobic exercise, while the mRNA expression of myosin heavy-chain I and Myo D increased in anaerobic exercise. These results suggest that muscle biomarkers can be used as parameters for the muscle adaptation process in aerobic/anaerobic exercise. Interestingly, by 14 days after the anaerobic exercise, the number of type II (fast-twitch) myofibers had decreased by about 20%. Furthermore, many macrophages and regenerated fibers were observed in addition to the injured fibers 14 days after the anaerobic exercise. Constitutional changes in myofibers due to damage incurred during anaerobic exercise are necessary for at least about 2 weeks. These results indicate that the changes in the biomarker levels and myofiber constitution by exercise intensity are extremely important for understanding the metabolic adaptations of skeletal muscle during physical exercise.

A Multi-Center Comparison of O2peak Trainability Between Interval Training and Moderate Intensity Continuous Training

There is heterogeneity in the observed O_2peak response to similar exercise training, and different exercise approaches produce variable degrees of exercise response (trainability). The aim of this study was to combine data from different laboratories to compare O_2peak trainability between various volumes of interval training and Moderate Intensity Continuous Training (MICT). For interval training, volumes were classified by the duration of total interval time. High-volume High Intensity Interval Training (HIIT) included studies that had participants complete more than 15 min of high intensity efforts per session. Low-volume HIIT/Sprint Interval Training (SIT) included studies using less than 15 min of high intensity efforts per session. In total, 677 participants across 18 aerobic exercise training interventions from eight different universities in five countries were included in the analysis. Participants had completed 3 weeks or more of either high-volume HIIT (n = 299), low-volume HIIT/SIT (n = 116), or MICT (n = 262) and were predominately men (n = 495) with a mix of healthy, elderly and clinical populations. Each training intervention improved mean O_2peak at the group level (P < 0.001). After adjusting for covariates, high-volume HIIT had a significantly greater (P < 0.05) absolute O_2peak increase (0.29 L/min) compared to MICT (0.20 L/min) and low-volume HIIT/SIT (0.18 L/min). Adjusted relative O_2peak increase was also significantly greater (P < 0.01) in high-volume HIIT (3.3 ml/kg/min) than MICT (2.4 ml/kg/min) and insignificantly greater (P = 0.09) than low-volume HIIT/SIT (2.5 mL/kg/min). Based on a high threshold for a likely response (technical error of measurement plus the minimal clinically important difference), high-volume HIIT had significantly more (P < 0.01) likely responders (31%) compared to low-volume HIIT/SIT (16%) and MICT (21%). Covariates such as age, sex, the individual study, population group, sessions per week, study duration and the average between pre and post O_2peak explained only 17.3% of the variance in O_2peak trainability. In conclusion, high-volume HIIT had more likely responders to improvements in O_2peak compared to low-volume HIIT/SIT and MICT.