High-intensity aerobic, but not resistance or combined, exercise training improves both cardiometabolic health and skeletal muscle mitochondrial dynamics

Effect of high-intensity interval training on clinical parameters in patients with metabolic dysfunction-associated steatotic liver disease: a systematic review and meta-analysis of randomized controlled trials

High-intensity interval training (HIIT) has potential health benefits in the treatment of many chronic diseases. However, the efficacy of HIIT in patients with metabolic dysfunction-associated steatotic liver disease (MASLD) remains unclear. This systematic review and meta-analysis aimed to assess the impact of HIIT on intrahepatic lipids (IHLs) , liver enzymes, and metabolic profiles in individuals with MASLD. All randomized-controlled trials (RCT) that evaluated and compared the effects of HIIT on clinical parameters in patients with MASLD were searched using the PubMed, EMBASE, WOS, and Cochrane databases. Data analysis and integration were performed using RevMan 5.3 (Cochrane Collaboration, Copenhagen, Denmark) and Stata version 18 software (StataCorp LLC, College Station, Texas, USA), and outcomes were assessed using the standardized mean difference (SMD). Our results showed that compared with other types of exercise or no exercise, HIIT could reduce the levels of IHL [SMD: -0.56%, 95% confidence interval (CI): -0.99 to -0.13, P = 0.01], BMI (SMD: -0.31, 95% CI: -0.62 to -0.01, P = 0.04), alanine aminotransferase (ALT) (SMD: -0.61, 95% CI: -0.95 to -0.26, P = 0.0006), and aspartate aminotransaminase (AST) (SMD: -0.43, 95% CI: -0.81 to -0.05, P = 0.03) in patients with MASLD. In addition, subgroup analyses showed that HIIT had a positive impact on clinical indicators in patients with MASLD with an intervention duration of less than equal to 8 weeks. This study supports the idea that HIIT can significantly reduce IHL, BMI, ALT, and AST levels, and further studies are needed to assess the long-term adherence and treatment effects of HIIT.

The role of skeletal muscle respiratory capacity in exercise performance

The connection between the respiratory capacity of skeletal muscle mitochondria and athletic performance is widely acknowledged in contemporary research. Building on a solid foundation of prior studies, current research has fostered an environment where scientists can effectively demonstrate how a tailored regimen of exercise intensity, duration, and frequency significantly boosts mitochondrial function within skeletal muscles. The range of exercise modalities is broad, spanning from endurance and high-intensity interval training to resistance-based exercises, allowing for an in-depth exploration of effective strategies to enhance mitochondrial respiratory capacity-a key factor in improving exercise performance, in other words offering a better skeletal muscle capacity to cope with exercise demands. By identifying optimal training strategies, individuals can significantly improve their performance, leading to better outcomes in their fitness and athletic endeavours. This review provides the prevailing insights on skeletal muscle mitochondrial respiratory capacity and its role in exercise performance, covering essential instrumental and methodological aspects, findings from animal studies, potential sex differences, a review of existing human studies, and considerations for future research directions.

The acute and chronic influence of exercise on mitochondrial dynamics in skeletal muscle

Exercise and nutritional modulation are potent stimuli for eliciting increases in mitochondrial mass and function. Collectively, these beneficial adaptations are increasingly recognized to coincide with improvements in skeletal muscle health. Mitochondrial dynamics of fission and fusion are increasingly implicated as having a central role in mediating aspects of key organelle adaptations that are seen with exercise. Exercise-induced mitochondrial adaptation dynamics that have been implicated are 1) increases to mitochondrial turnover, resulting from elevated rates of mitochondrial synthesis (biogenesis) and degradative (mitophagy) processes and 2) morphological changes to the three-dimensional (3-D) tubular network, known as the mitochondrial reticulum, that mitochondria form in skeletal muscle. Notably, mitochondrial fission has also been implicated in coordinating increases in mitophagy, following acute exercise. Furthermore, increased fusion following exercise training promotes increased connectivity of the mitochondrial reticulum and is associated with improved metabolism and mitochondrial function. However, the molecular basis and fashion in which exercise infers beneficial mitochondrial adaptations through mitochondrial dynamics remains to be fully elucidated. This review attempts to highlight recent developments investigating the effects of exercise on mitochondrial dynamics, while attempting to offer a perspective of the methodological refinements and potential variables, such as substrate/glycogen availability, which should be considered going forward.

Time to Elicit Physiological and Exertional Vigorous Responses from Daily Living Activities: Setting Foundations of an Empirical Definition of VILPA

PURPOSE

Vigorous intermittent lifestyle physical activity (VILPA) are bursts of incidental vigorous activity that occur during day-to-day activities outside of the exercise-domain. Vigorous intermittent lifestyle physical activity has shown promise in lowering risk of mortality and chronic disease. However, there is an absence of an empirically derived definition. Using physiological and effort-based metrics commonly used to define vigorous intensity, we investigated the minimum time needed to elicit physiological and perceived exertion responses to standardized activities of daily living.

METHODS

Seventy adults (age = 58.0 ± 9.6 yr; 35 female) completed 9 VILPA activities of daily living in a randomized order, which included fast walking, fast incline walking, stair climbing, stationary cycling, and carrying external weight equal to 5% and 10% of body weight. Metabolic rate (by continuous indirect calorimetry), heart rate (telemetry) and perceived effort (Borg Scale) were measured during exercise. Time to reach VILPA was assessed using %V̇O 2max , %HRmax, and rating of perceived exertion thresholds.

RESULTS

The mean time to elicit VILPA ranged from 65 to 95 s (mean ± sd = 76.7 ± 3.8 s) for %V̇O 2max , 68 to 105 s (mean ± sd = 82.8 ± 6.8 s) for %HRmax, and 20 to 60 s (mean ± sd = 44.6 ± 6.7 s) for rating of perceived exertion. For each of the three indices, there was no difference in the time to elicit VILPA responses by sex or age ( P > 0.08), and times were also consistent between activities of daily living tasks. For example, for females and males, the average time to elicit vigorous responses while walking on a flat surface was 85.8 s (±16.9 s) and 80 s (±13.9 s), respectively, and for stair climbing while carrying 10% of body weight the duration was 78.4 s (±17.6 s) and 76.9 (±17.7 s).

CONCLUSIONS

When participants undertook activities of daily living, VILPA elicited a physiological response at an average of 77 to 83 s for %V̇O 2max and %HRmax, and 45 s for perceived exertion. The absence of a difference in the time to reach VILPA between sex and age suggests that a consistent behavioral VILPA translation can be used in interventions and population-based studies designed to assess the health effects of incidental physical activity.

Unlocking the biochemical secrets of longevity: balancing healthspan and lifespan

In an era of rising global life expectancies, research focuses on enhancing the quality of extended years. This review examines the link between mitochondrial function and aging, highlighting the importance of healthspan alongside lifespan. This involves significant human and economic challenges, with longer lifespans often accompanied by reduced well-being. Addressing mitochondrial decline, exploring targeted interventions, and understanding the complexities of research models are vital for advancing our knowledge in this field. Additionally, promoting physical exercise and adopting personalized supplementation strategies based on individual needs can contribute to healthy aging. The insights from this Perspective article offer a hopeful outlook for future advances in extending both lifespan and healthspan, aiming to improve the overall quality of life in aging populations.

The role of mitochondrial dynamics and mitophagy in skeletal muscle atrophy: from molecular mechanisms to therapeutic insights

Skeletal muscle is the largest metabolic organ of the human body. Maintaining the best quality control and functional integrity of mitochondria is essential for the health of skeletal muscle. However, mitochondrial dysfunction characterized by mitochondrial dynamic imbalance and mitophagy disruption can lead to varying degrees of muscle atrophy, but the underlying mechanism of action is still unclear. Although mitochondrial dynamics and mitophagy are two different mitochondrial quality control mechanisms, a large amount of evidence has indicated that they are interrelated and mutually regulated. The former maintains the balance of the mitochondrial network, eliminates damaged or aged mitochondria, and enables cells to survive normally. The latter degrades damaged or aged mitochondria through the lysosomal pathway, ensuring cellular functional health and metabolic homeostasis. Skeletal muscle atrophy is considered an urgent global health issue. Understanding and gaining knowledge about muscle atrophy caused by mitochondrial dysfunction, particularly focusing on mitochondrial dynamics and mitochondrial autophagy, can greatly contribute to the prevention and treatment of muscle atrophy. In this review, we critically summarize the recent research progress on mitochondrial dynamics and mitophagy in skeletal muscle atrophy, and expound on the intrinsic molecular mechanism of skeletal muscle atrophy caused by mitochondrial dynamics and mitophagy. Importantly, we emphasize the potential of targeting mitochondrial dynamics and mitophagy as therapeutic strategies for the prevention and treatment of muscle atrophy, including pharmacological treatment and exercise therapy, and summarize effective methods for the treatment of skeletal muscle atrophy.

Exercise induces tissue-specific adaptations to enhance cardiometabolic health

The risk associated with multiple cancers, cardiovascular disease, diabetes, and all-cause mortality is decreased in individuals who meet the current recommendations for physical activity. Therefore, regular exercise remains a cornerstone in the prevention and treatment of non-communicable diseases. An acute bout of exercise results in the coordinated interaction between multiple tissues to meet the increased energy demand of exercise. Over time, the associated metabolic stress of each individual exercise bout provides the basis for long-term adaptations across tissues, including the cardiovascular system, skeletal muscle, adipose tissue, liver, pancreas, gut, and brain. Therefore, regular exercise is associated with a plethora of benefits throughout the whole body, including improved cardiorespiratory fitness, physical function, and glycemic control. Overall, we summarize the exercise-induced adaptations that occur within multiple tissues and how they converge to ultimately improve cardiometabolic health.

Mitophagy-dependent cardioprotection of resistance training on heart failure

Resistance exercise is an indispensable mode of exercise rehabilitation for heart failure. Here we elucidate the cardiac effects of resistance training alone or combined with different aerobic trainings on heart failure and explore the critical regulation of mitophagy. The chronic heart failure model was constructed by transverse aortic constriction surgery, followed by 8 wk of resistance training (RT), moderate-intensity continuous training combined with resistance training (MRT), and high-intensity interval training combined with resistance training (HRT), and subsequently analyzed the changes of maximum load, cardiac structure and function, and myocardial mitophagic activity. The role and signaling of mitophagy in exercise protection of heart failure were investigated by knockdown of Hif1α and Parkin genes in primary neonatal cardiomyocytes. RT and especially MRT improved maximum load (P < 0.0001), myocardial morphology and fibrosis (P < 0.0001), reduced left ventricular diameter and enhanced left ventricular systolic function (P < 0.01), and enhanced myocardial mitophagic activity and HIF1α expression (P < 0.05) in heart failure mice. However, HRT had no obvious protective effect on ventricular diameter and function or mitophagy. The abilities of exercise stimulation to regulate reactive oxygen species, adenosine triphosphate, and brain natriuretic peptide were impaired after knockdown of Hif1α and Parkin genes inhibited mitophagy in failing cardiomyocytes (P < 0.05). Different exercise modalities provide discrepant cardiovascular effects on heart failure, and MRT exhibits optimal protection. The HIF1α-Parkin-mitophagy pathway is involved in the protection and regulation of exercise on heart failure.NEW & NOTEWORTHY Impaired myocardial mitophagy is implicated in the pathogenesis of heart failure. Resistance training alone or combined with different aerobic trainings provide discrepant cardiovascular effects on heart failure, and the cardioprotective function depends on HIF1α-Parkin-mitophagy pathway.