Familial aggregation of VO(2max) response to exercise training: results from the HERITAGE Family Study

A Systematic Review and Meta-analysis Highlights a Link Between Aerobic Fitness and Telomere Maintenance

Cardiorespiratory fitness declines with aging and is a major risk factor of cardiometabolic diseases and early death. Although the benefits of regular exercise are well established, whether maximal oxygen uptake (VO2max) is associated with biological aging remains unclear. Given that telomere shortening is a hallmark of aging, the purpose of this systematic review and meta-analysis was to determine the association between VO2max and telomere length. Articles were retrieved from PubMed, Scopus, and ScienceDirect and deemed eligible if they: (i) involved human participants with relatively low and high VO2max values objectively assessed by pulmonary analysis; (ii) quantified telomere length using an established technique; and (iii) were peer-reviewed journal articles written in English. Relative to individuals with below-average VO2max based on age- and sex-adjusted norms, fit participants with relative VO2max values in the 70th percentile or higher possessed longer telomeres (standardized mean difference [95% confidence interval {CI}]: 0.36 [0.14-0.59], p = .002). A similar difference was observed between individuals with below-average VO2max and those above the 90th percentile (0.28 [0.03-0.53], p = .03). However, no statistically significant telomere length differences were observed between individuals in the 70th to 90th percentile compared to those above the 90th (-0.08 [-0.40 to 0.24], p = .62). The findings provide evidence linking metabolism to telomere biology. They encourage individuals to regularly engage in endurance exercise to attenuate telomere attrition and promote healthy biological aging. Importantly, the results suggest that extensive endurance training may not be required to protect the telomeres, rather moderate amounts of training may be sufficient to reach more achievable VO2max targets.

The MDM2 SNP309 differentially impacts cardiorespiratory fitness in young healthy women and men

PURPOSE

Maximal oxygen consumption (VO2max), the predominant index of cardiorespiratory fitness (CRF), is a predictor of whole-body function and longevity in humans. The central cardiac function and the skeletal muscle's capacity to use oxygen are key determinants of VO2max. Murine Double Minute 2 (MDM2), mainly known as an oncogene, could regulate myocardial hypertrophy, skeletal muscle angiogenesis, and oxidative phosphorylation. A prevalent single nucleotide polymorphism in the MDM2 promoter (SNP309) substitutes a T for a G, supporting a greater transcriptional activity. We aim to assess whether SNP309 impacts intrinsic CRF.

METHODS

82 young healthy nonathletic male and female adults aged 23 ± 2 years performed cardiorespiratory exercise testing to determine their VO2max (mL kg-1 min-1). The genomic DNAs isolated from saliva were genotyped using Taqman-based qPCR.

RESULTS

A one-way ANOVA showed that SNP309 influenced relative VO2max in the whole cohort (p = 0.044) and in men (p = 0.009), remaining non-significant in women (p = 0.133). VO2max was higher in TT homozygotes than in GT heterozygotes (whole cohort, 47 ± 12 vs. 42 ± 6 mL kg-1 min-1, p = 0.030; men, 53 ± 8 vs. 45 ± 6 mL kg-1 min-1, p = 0.011). A contingency analysis revealed a positive association between SNP309 in men in which the TT genotype was more frequent in the high VO2max group (p = 0.006). When considering G as the dominant allele, men bearing a G allele had lower relative VO2max than TT homozygotes (47 ± 7 vs. 53 ± 8, GG/GT vs. TT, p = 0.010). Conversely, women bearing a G allele had a higher relative VO2max than TT homozygotes (39 ± 5 vs. 34 ± 7, GG/GT vs. TT, p = 0.047).

CONCLUSION

SNP309 impacts VO2max in a sex-dependent manner in our cohort.

Cardiorespiratory Fitness and Mortality in Patients With Chronic Kidney Disease: A Prospective Cohort Study

OBJECTIVE

To assess the association between objectively measured cardiorespiratory fitness (CRF) and mortality in patients with chronic kidney disease (CKD).

PATIENTS AND METHODS

From a large cohort of US veterans (n=750,302) based on the ETHOS (Exercise Testing and Health Outcomes) study, we identified 45,674 men and women aged 30 to 95 years (mean, 65.1 ± 8.8 years) who completed an exercise treadmill test (ETT) within the Veterans Affairs hospitals across the United States. All were diagnosed with CKD before the ETT by International Classification of Diseases 9th and 10th revision codes. Age- and-sex-specific CRF categories (quintiles) were established based on peak metabolic equivalents (METs) achieved during the ETT. We computed HRs and 95% CIs with Cox regression analyses adjusted for comorbidities and medications.

RESULTS

During 15.9 years of follow-up, 24,310 individuals (53.2%) died. The adjusted association between CRF and mortality risk was inverse and graded. For each 1-MET increase in CRF, the adjusted HR for mortality was 12% lower (HR, 0.88; 95% CI, 0.875 to 0.885; P<.001). When risk was assessed across CRF categories using the least-fit CRF category as the referent, the adjusted HRs and CIs were 0.76 (95% CI, 0.73 to 0.78), 0.63 (95% CI, 0.61 to 0.66), 0.49 (95% CI, 0.47 to 0.51), and 0.33 (95% CI, 0.30 to 0.35), for low-fit, moderate-fit, fit, and high-fit individuals, respectively. The pattern of the CRF mortality risk association was similar regardless of age, race, or sex.

CONCLUSION

In this large multiethnic study, we found an independent, inverse, and graded association between CRF and mortality in CKD patients. These findings underscore the importance of increasing CRF in CKD patients to lower the risk of mortality.

Genomics May Be the Key to Understanding Endurance Training Pillars

Endurance performance is primarily determined by three key physiological pillars: maximal oxygen uptake (VO2max), anaerobic threshold, and economy of movement. Recent research has suggested physiological resilience as a potential fourth dimension, referring to an athlete's ability to sustain performance despite accumulating fatigue. While the role of genetic factors in endurance has been widely studied, their influence on these pillars, particularly on fatigue resistance and long-term adaptation, remains an area of growing interest. This narrative review explores the genomic basis of endurance performance, analyzing genetic contributions to oxygen transport, metabolic efficiency, muscle composition, and recovery. Additionally, it discusses how genetic variability may modulate an athlete's response to training, including aspects of physiological adaptation, injury susceptibility, sleep, and nutrition. The review highlights physiological resilience in the context of endurance sports, discussing its connection to neuromuscular and metabolic regulation. By integrating genetic insights with established physiological principles, this review provides a comprehensive perspective on endurance adaptation. Future research directions are outlined to enhance our understanding of the genetic underpinnings of endurance, with implications for personalized training and performance optimization.

Cognitive-Motor Coupling in Multiple Sclerosis: Do Chronological Age and Physical Activity Matter?

Background: People with multiple sclerosis (MS) often demonstrate both cognitive and physical dysfunctions, particularly with greater age and lower physical activity levels, and there is evidence of a relationship between these outcomes (i.e., cognitive-motor coupling) in MS. To date, little is known about cognitive-motor coupling when controlling for chronological age and levels of physical activity. Objectives: We examined cognitive-motor coupling in people with MS while accounting for chronological age and physical activity. Methods: The sample included 290 people with MS between the ages of 22 and 77 years. Participants underwent the Symbol Digit Modalities Test (SDMT) for cognitive processing speed and the California Verbal Learning and Memory Test-Second Edition (CVLT-II) for verbal learning and memory. Participants completed the 6-Minute Walk and the Timed 25-Foot Walk tests for walking endurance and speed, respectively. Participants wore an accelerometer for a 7-day period to measure moderate-to-vigorous physical activity (MVPA). Results: The bivariate correlation analyses indicated that cognitive function had moderate-to-strong associations with motor function (range of rs between 0.433 and 0.459). The linear regression analyses indicated cognitive-motor coupling between SDMT and motor function (with a range of β between 0.139 and 0.145) when controlling for demographic and clinical characteristics. The regression analyses further indicated that the CVLT-II was associated with motor function (with a range of β between 0.125 and 0.135) when controlling for demographic and clinical characteristics. When age and MVPA were entered into the regression analyses, SDMT was still associated with the motor function of individuals (β = 0.119), and CVLT-II was still associated with the motor function of individuals (with a range of β between 0.115 and 0.124). Conclusions: Cognitive-motor coupling is present in people with MS independent of chronological age and levels of physical activity. This warrants further investigation of the underlying mechanism and potential approaches for the management of co-occurring MS-related dysfunction.

Charting the Molecular Terrain of Exercise: Energetics, Exerkines, and the Future of Multiomic Mapping

Physical activity plays a fundamental role in human health and disease. Exercise has been shown to improve a wide variety of disease states, and the scientific community is committed to understanding the precise molecular mechanisms that underlie the exquisite benefits. This review provides an overview of molecular responses to acute exercise and chronic training, particularly energy mobilization and generation, structural adaptation, inflammation, and immune regulation. Furthermore, it offers a detailed discussion of known molecular signals and systemic regulators activated during various forms of exercise and their role in orchestrating health benefits. Critically, the increasing use of multiomic technologies is explored with an emphasis on how multiomic and multitissue studies contribute to a more profound understanding of exercise biology. These data inform anticipated future advancement in the field and highlight the prospect of integrating exercise with pharmacology for personalized disease prevention and treatment.

Genetics, Fitness, and Left Ventricular Remodelling: The Current State of Play

Cardiorespiratory fitness (CRF) exists on a spectrum and is driven by a constellation of factors, including genetic and environmental differences. This results in wide interindividual variation in baseline CRF and the ability to improve CRF with regular endurance exercise training. As opposed to monogenic conditions, CRF is described as a complex genetic trait as it is believed to be influenced by multiple common genetic variants in addition to exogenous factors. Importantly, CRF is an independent predictor of morbidity and mortality, and so understanding the impact of genetic variation on CRF may provide insights into both human athletic performance and personalized risk assessment and prevention. Despite rapidly advancing technology, progress in this field has been restricted by small sample sizes and the limited number of genetic studies using the "gold standard" objective measure of peak oxygen consumption (VO2peak) for CRF assessment. In recent years, there has been increasing interest in the heritability of numerous parameters of cardiac structure and function and how this may relate to both normal cardiac physiology and disease pathology. Regular endurance training can result in exercise-induced cardiac remodelling, which manifests as balanced dilation of cardiac chambers and is associated with superior CRF. This results in a complex relationship between CRF, cardiac size, and exercise, and whether shared genetic pathways may influence this remains unknown. In this review we highlight recent and relevant studies into the genomic predictors of CRF with a unique emphasis on how this may relate to cardiac remodelling and human adaptation to endurance exercise.

Circulating microRNAs and physical activity: Impact in diabetes

The term "ci-miRNAs," or "circulating microRNAs," refers to extracellular microRNAs (miRNAs) that exist outside of cells and can be detected in various bodily fluids, including blood, saliva, urine, and breast milk. These ci-miRNAs play a role in regulating gene expression and are mainly recognized for their functions beyond the cell, serving as signaling molecules in the blood. Researchers have thoroughly investigated the roles of these circulating miRNAs in various diseases. The capacity to detect and quantify ci-miRNAs in bodily fluids suggests their potential as biomarkers for monitoring several health conditions, including cancer, heart disease, brain disorders, and metabolic disorders, where fluctuations in miRNA levels may correlate with different physiological and pathological states. Current methods enable researchers to identify and measure miRNAs in these fluids, facilitating the exploration of their roles in health maintenance and disease resistance. Although research on ci-miRNAs is ongoing, recent studies focus on uncovering their significance, assessing their viability as biomarkers, and clarifying their functions. However, our understanding of how various types, intensities, and durations of exercise influence the levels of these miRNAs in the bloodstream is still limited. This section seeks to provide an overview of the changes in ci-miRNAs in response to exercise.

Association of cardiorespiratory fitness with the incidence and progression trajectory of cardiometabolic multimorbidity

OBJECTIVES

This study examined the relationship of cardiorespiratory fitness (CRF) in the transition from healthy status to first cardiometabolic disease, subsequent cardiometabolic multimorbidity and further to death.

METHODS

We used data from the UK Biobank of 47 484 participants without cardiometabolic diseases at baseline. CRF was assessed via a 6 min incremental ramp cycle ergometer test and expressed in metabolic equivalent of tasks (METs, 1 MET=3.5 mL/kg/min). Cardiometabolic multimorbidity was defined as at least two diseases among diabetes, hypertension, coronary heart disease and stroke.

RESULTS

Over 12.5 years median follow-up, 8123 participants developed first cardiometabolic disease, 1958 developed cardiometabolic multimorbidity and 2177 died. CRF was associated with different transition stages in cardiometabolic multimorbidity development. The HRs (95% CIs) per MET increase in CRF were 0.94 (0.93 to 0.95) and 0.97 (0.96 to 0.99) for transitions from healthy baseline to first cardiometabolic disease and subsequent cardiometabolic multimorbidity. Per MET increase in CRF was associated with reduced risk of transition from healthy baseline to death (HR: 0.97, 95% CI 0.95 to 0.99), but not for the transition from first cardiometabolic disease and cardiometabolic multimorbidity to death. When first cardiometabolic disease was divided into specific cardiometabolic diseases, there were comparable trends of CRF on the disease-specific transitions from healthy baseline to first cardiometabolic disease and subsequent cardiometabolic multimorbidity.

CONCLUSION

Higher CRF was associated with a lower risk of progression from a healthy state to first cardiometabolic disease and subsequently to cardiometabolic multimorbidity. These findings suggest that improving CRF is a potential strategy for preventing cardiometabolic multimorbidity development.

Changes in Cardiorespiratory Fitness Following Exercise Training Prescribed Relative to Traditional Intensity Anchors and Physiological Thresholds: A Systematic Review with Meta-analysis of Individual Participant Data

BACKGROUND

It is unknown whether there are differences in maximal oxygen uptake ( V O2max) response when prescribing intensity relative to traditional (TRAD) anchors or to physiological thresholds (THR).

OBJECTIVES

The present meta-analysis sought to compare: (a) mean change in V O2max, (b) proportion of individuals increasing V O2max beyond a minimum important difference (MID) and (c) response variability in V O2max between TRAD and THR.

METHODS

Electronic databases were searched, yielding data for 1544 individuals from 42 studies. Two datasets were created, comprising studies with a control group ('controlled' studies), and without a control group ('non-controlled' studies). A Bayesian approach with multi-level distributional models was used to separately analyse V O2max change scores from the two datasets and inferences were made using Bayes factors (BF). The MID was predefined as one metabolic equivalent (MET; 3.5 mL kg-1 min-1).

RESULTS

In controlled studies, mean V O2max change was greater in the THR group compared with TRAD (4.1 versus 1.8 mL kg-1 min-1, BF > 100), with 64% of individuals in the THR group experiencing an increase in V O2max > MID, compared with 16% of individuals taking part in TRAD. Evidence indicated no difference in standard deviation of change between THR and TRAD (1.5 versus 1.7 mL kg-1 min-1, BF = 0.55), and greater variation in exercise groups relative to non-exercising controls (1.9 versus 1.3 mL kg-1 min-1, BF = 12.4). In non-controlled studies, mean V O2max change was greater in the THR group versus the TRAD group (4.4 versus 3.4 mL kg-1 min-1, BF = 35.1), with no difference in standard deviation of change (3.0 versus 3.2 mL kg-1 min-1, BF = 0.41).

CONCLUSION

Prescribing exercise intensity using THR approaches elicited superior mean changes in V O2max and increased the likelihood of increasing V O2max beyond the MID compared with TRAD. Researchers designing future exercise training studies should thus consider the use of THR approaches to prescribe exercise intensity where possible. Analysis comparing interventions with controls suggested the existence of intervention response heterogeneity; however, evidence was not obtained for a difference in response variability between THR and TRAD. Future primary research should be conducted with adequate power to investigate the scope of inter-individual differences in V O2max trainability, and if meaningful, the causative factors.

Effects of the Birthplace Altitude and Training Volume on Hematological Characteristics in Youth and Junior Male Colombian Cyclists

PURPOSE

The long-term development of talent in endurance sports is a topic of interest. Among various factors, the importance of total hemoglobin mass (tHbmass) and the potential benefits of being an altitude-native athlete remain unclear, particularly in young categories. This study aimed to investigate the impact of altitude and training content on hematological characteristics by comparing young male cyclists age 15-16 and 17-18 years who were born and trained at a moderate altitude (ie, greater than or equal to 2500 m; MA) and cyclists who were born and trained at low altitude (below 1000 m; LA).

METHODS

tHbmass (in grams and grams per kilogram), measured by using the optimized carbon monoxide rebreathing method during an incremental test on a cycle ergometer; hematocrit percentage, hemoglobin concentration; and erythrocyte, blood, and plasma volume were measured in youth male cyclists age 15-16 years and junior cyclists age 17-18 years who were born and trained at MA versus LA. All variables were analyzed with a 2-way (age [youth cyclist vs junior cyclist] × altitude level [MA vs LA]) analysis of variance with subsequent Tuckey post hoc test.

RESULTS AND CONCLUSION

Some altitude-induced benefits were reported in cyclists at age 15-16 years in the MA group with higher values in hematocrit percentage, hemoglobin concentration, and tHbmass (grams per kilogram) (P < .05) than their LA counterparts. This was also observed at age 17-18 years (P < .001), except for tHbmass, wherein no significant difference was found between MA and LA groups. In contrast, plasma volume was lower in MA than LA junior cyclists.

NEW FINDINGS

(1) The altitude of birth and residence could generate an advantage in tHbmass in young male cyclists age 15-16 and 17-18 years who train at MA compared with cyclists who are born and train at LA. (2) Altitude-induced benefits in physiological variables (hematocrit percentage, hemoglobin concentration, tHbmass in g·kg-1) were reported in cyclists at age 15-16 years and partially at age 17-18 years. In contrast, plasma volume was lower in MA than in LA junior cyclists. This may impact the strategies for identifying and developing talent in cycling.

A partial loss-of-function variant (Ile191Val) of the TAS1R2 glucose receptor is associated with enhanced responses to exercise training in older adults with obesity: A translational study

BACKGROUND

The TAS1R2 receptor, known for its role in taste perception, has also emerged as a key regulator of muscle physiology. Previous studies have shown that genetic ablation of TAS1R2 in mice enhances muscle fitness mimicking responses to endurance exercise training. However, the translational relevance of these findings to humans remains uncertain.

METHODS

We explored responses to endurance exercise training in mice and humans with genetic deficiency of TAS1R2. First, we assessed the effects of muscle-specific deletion of TAS1R2 in mice (mKO) or wild type controls (mWT) following 4 weeks of voluntary wheel running (VWR). Next, we investigated the effects of the TAS1R2-Ile191Val (rs35874116) partial loss-of-function variant on responses to a 6-month diet-induced weight loss with exercise training (WLEX), weight loss alone (WL), or education control (CON) interventions in older individuals with obesity. Participants were retrospectively genotyped for the TAS1R2-Ile191Val polymorphism and classified as conventional function (Ile/Ile) or partial loss-of-function (Val carriers: Ile/Val and Val/Val). Body composition, cardiorespiratory fitness, and skeletal muscle mitochondrial function were assessed before and after the intervention.

RESULTS

In response to VWR, mKO mice demonstrated enhanced running endurance and mitochondrial protein content. Similarly, TAS1R2 Val carriers exhibited distinctive improvements in body composition, including increased muscle mass, along with enhanced cardiorespiratory fitness and mitochondrial function in skeletal muscle following the WLEX intervention compared to Ile/Ile counterparts. Notably, every Val carrier demonstrated substantial responses to exercise training and weight loss, surpassing all Ile/Ile participants in overall performance metrics.

CONCLUSIONS

Our findings suggest that TAS1R2 partial loss-of-function confers beneficial effects on muscle function and metabolism in humans in response to exercise training, akin to observations in TAS1R2 muscle-deficient mice. Targeting TAS1R2 may help enhancing exercise training adaptations in individuals with compromised exercise tolerance or metabolic disorders, presenting a potential avenue for personalized exercise interventions.

Global consensus on optimal exercise recommendations for enhancing healthy longevity in older adults (ICFSR)

Aging, a universal and inevitable process, is characterized by a progressive accumulation of physiological alterations and functional decline over time, leading to increased vulnerability to diseases and ultimately mortality as age advances. Lifestyle factors, notably physical activity (PA) and exercise, significantly modulate aging phenotypes. Physical activity and exercise can prevent or ameliorate lifestyle-related diseases, extend health span, enhance physical function, and reduce the burden of non-communicable chronic diseases including cardiometabolic disease, cancer, musculoskeletal and neurological conditions, and chronic respiratory diseases as well as premature mortality. Physical activity influences the cellular and molecular drivers of biological aging, slowing aging rates-a foundational aspect of geroscience. Thus, PA serves both as preventive medicine and therapeutic agent in pathological states. Sub-optimal PA levels correlate with increased disease prevalence in aging populations. Structured exercise prescriptions should therefore be customized and monitored like any other medical treatment, considering the dose-response relationships and specific adaptations necessary for intended outcomes. Current guidelines recommend a multifaceted exercise regimen that includes aerobic, resistance, balance, and flexibility training through structured and incidental (integrated lifestyle) activities. Tailored exercise programs have proven effective in helping older adults maintain their functional capacities, extending their health span, and enhancing their quality of life. Particularly important are anabolic exercises, such as Progressive resistance training (PRT), which are indispensable for maintaining or improving functional capacity in older adults, particularly those with frailty, sarcopenia or osteoporosis, or those hospitalized or in residential aged care. Multicomponent exercise interventions that include cognitive tasks significantly enhance the hallmarks of frailty (low body mass, strength, mobility, PA level, and energy) and cognitive function, thus preventing falls and optimizing functional capacity during aging. Importantly, PA/exercise displays dose-response characteristics and varies between individuals, necessitating personalized modalities tailored to specific medical conditions. Precision in exercise prescriptions remains a significant area of further research, given the global impact of aging and broad effects of PA. Economic analyses underscore the cost benefits of exercise programs, justifying broader integration into health care for older adults. However, despite these benefits, exercise is far from fully integrated into medical practice for older people. Many healthcare professionals, including geriatricians, need more training to incorporate exercise directly into patient care, whether in settings including hospitals, outpatient clinics, or residential care. Education about the use of exercise as isolated or adjunctive treatment for geriatric syndromes and chronic diseases would do much to ease the problems of polypharmacy and widespread prescription of potentially inappropriate medications. This intersection of prescriptive practices and PA/exercise offers a promising approach to enhance the well-being of older adults. An integrated strategy that combines exercise prescriptions with pharmacotherapy would optimize the vitality and functional independence of older people whilst minimizing adverse drug reactions. This consensus provides the rationale for the integration of PA into health promotion, disease prevention, and management strategies for older adults. Guidelines are included for specific modalities and dosages of exercise with proven efficacy in randomized controlled trials. Descriptions of the beneficial physiological changes, attenuation of aging phenotypes, and role of exercise in chronic disease and disability management in older adults are provided. The use of exercise in cardiometabolic disease, cancer, musculoskeletal conditions, frailty, sarcopenia, and neuropsychological health is emphasized. Recommendations to bridge existing knowledge and implementation gaps and fully integrate PA into the mainstream of geriatric care are provided. Particular attention is paid to the need for personalized medicine as it applies to exercise and geroscience, given the inter-individual variability in adaptation to exercise demonstrated in older adult cohorts. Overall, this consensus provides a foundation for applying and extending the current knowledge base of exercise as medicine for an aging population to optimize health span and quality of life.

History and perspectives on interval training in sport, health, and disease

Exercise can be conducted as low-intensity continuous training (LICT) or a variety of higher intensity work/rest formats, collectively called interval training. Interval training was developed for athletes in the early 20th century. It was systemized in Sweden as Fartlek, and in Germany as die interval Method, in the 1930s. Most contemporary forms of interval training evolved from these progenitors. In essence, interval training allows a large volume of high-intensity or race specific training to be performed while controlling the development of fatigue. Adding interval training to LICT done by athletes adds about 2%-4% to performance achievable with LICT, which represents a competitively meaningful difference in performance (e.g., 4:25 vs. 4:00 over 1 mile). More recently, interval training has been applied to health- fitness participants and even to patients with health conditions. Studies indicate that a comparatively low volume of interval training can produce substantial improvement in physiologic capacity, in as little as 20% of training time versus LICT. There are data indicating that interval training can be reasonably pleasant, have good adherence, and is safe, even in patients. Although interval training was originally designed for athletics, the fundamental patterns of work versus recovery are remarkably similar in healthy adults and patients. Although the total volume of training and both absolute and relative intensity and magnitude of homeostatic disturbance are larger in athletes, the overall pattern of effort is the same in fitness participants and patients. Interval training can thus be characterized as an important step in the evolution of exercise training.

Clinical and physiological effects of high-intensity aerobic training on metabolic syndrome: understanding the individual exercise response variability

We analyzed the interindividual heterogeneity in health responses to a supervised high-intensity interval training (HIIT) program in individuals with metabolic syndrome (MetS). Two hundred and sixty-four adults with overweight/obesity (56.3 ± 7.3 yr, body mass index: 32.3 ± 4.7 kg/m2) and MetS were randomized to a standard health care nonexercise group (CONT group, N = 58) or standard health care plus HIIT (EXER group, N = 206). HIIT intervention was performed on a cycloergometer thrice a week (43 min/session). MetS components (i.e., MetS z score), cardiorespiratory fitness (V̇o2peak), maximal cycling power (WPEAK), and body weight/composition was assessed in both groups before (0 wk) and after the intervention (16 wk). Individual responses in the EXER group were considered attributable to HIIT when the improvements were larger than twice the typical error (>2TE). TE was calculated using pre- and postintervention data from the time-matched CONT group. The percentage of participants who improved MetS z score beyond 2TE was 51% driven by reductions in blood pressure (45%) and waist circumference (48%). Blood lipids and glucose response were only 21% and 16%, respectively (participants improving beyond 2TE). Sixty percent of individuals who improved MetS z score also improved V̇o2peak (r = -0.013; P = 0.86), whereas 85% of individuals improving MetS z score also improved WPEAK (r = 0.151; P = 0.03). In summary, health providers can expect that a 16-wk HIIT program would indisputably improve MetS in approximately 50% of individuals completing the program. Finally, WPEAK better predicts which individuals would improve MetS than V̇o2peak when the direct assessment of the five MetS factors is not feasible.NEW & NOTEWORTHY Our study offers healthcare providers the expected percentage of individuals who would improve their metabolic syndrome condition after completing a standardized HIIT program (16 wk, 43 min/session, 3 days/wk). Only half of the subjects achieved indisputable improvement in their MetS z score when we accounted for biological variability and instrument errors. Detection of individuals with a positive response in MetS z score could be inferred from gains in maximal cycling power (i.e., exercise functionality).

Diabetes and obesity: leveraging heterogeneity for precision medicine

The increasing prevalence of diabetes, obesity, and their cardiometabolic sequelae present major global health challenges and highlight shortfalls of current approaches to the prevention and treatment of these conditions. Representing the largest global burden of morbidity and mortality, the pathobiological processes underlying cardiometabolic diseases are in principle preventable and, even when disease is manifest, sometimes reversable. Nevertheless, with current clinical and public health strategies, goals of widespread prevention and remission remain largely aspirational. Application of precision medicine approaches that reduce errors and improve accuracy in medical and health recommendations has potential to accelerate progress towards these goals. Precision medicine must also maintain safety and ideally be cost-effective, as well as being compatible with an individual's preferences, capabilities, and needs. Initial progress in precision medicine was made in the context of rare diseases, with much focus on pharmacogenetic studies, owing to the cause of these diseases often being attributable to highly penetrant single gene mutations. By contrast, most obesity and type 2 diabetes are heterogeneous in aetiology and clinical presentation, underpinned by complex interactions between genetic and non-genetic factors. The heterogeneity of these conditions can be leveraged for development of approaches for precision therapies. Adequate characterization of the heterogeneity in cardiometabolic disease necessitates diversity of and synthesis across data types and research methods, ideally culminating in precision trials and real-world application of precision medicine approaches. This State-of-the-Art Review provides an overview of the current state of the science of precision medicine, as well as outlining a roadmap for study designs that maximise opportunities and address challenges to clinical implementation of precision medicine approaches in obesity and diabetes.

Genetic Determinants of Endurance: A Narrative Review on Elite Athlete Status and Performance

This narrative review explores the relationship between genetics and elite endurance athletes, summarizes the current literature, highlights some novel findings, and provides a physiological basis for understanding the mechanistic effects of genetics in sport. Key genetic markers include ACTN3 R577X (muscle fiber composition), ACE I/D (cardiovascular efficiency), and polymorphisms in PPARA, VEGFA, and ADRB2, influencing energy metabolism, angiogenesis, and cardiovascular function. This review underscores the benefits of a multi-omics approach to better understand the complex interactions between genetic polymorphisms and physiological traits. It also addresses long-standing issues such as small sample sizes in studies and the heterogeneity in heritability estimates influenced by factors like sex. Understanding the mechanistic relationship between genetics and endurance performance can lead to personalized training strategies, injury prevention, and improved health outcomes. Future studies should focus on standardized classification of sports, replication studies involving diverse populations, and establishing solid physiological associations between polymorphisms and endurance traits to advance the field of sports genetics.

Mechanical efficiency: associations with body composition and glycemic profile in healthy adults

The aim of this study was to assess the association between net mechanical efficiency (NME) and body composition and glycemic profile, in middle-aged (38.3 ± 14.3 years) participants from the Quebec Family Study (QFS). Analyses were completed on a sample of 605 participants (271 males and 334 females) who performed a submaximal exercise test on an ergometer consisting of three consecutive 6-min workloads at increasing intensity during which respiratory gas exchange was assessed. The calculation of NME [power output/ (vO2-vO2seated before exercise)] was based on the values of the last 3 min of the first workload at a targeted power output of 30 W. Correlations between NME and dependent variables were computed separately in males and females. Associations between NME and body composition and glucose-insulin variables were assessed by comparing groups of subjects categorized in sex-specific tertiles of NME after adjustments for age. Significant negative correlations were observed between NME and body composition and glycemic profile in both sexes. Comparison across tertiles showed that individuals with high NME displayed more favorable adiposity and glycemic profiles. These differences remained significant after further adjustments for participation in vigorous physical activity, cardiorespiratory fitness, and mean exercise respiratory exchange ratio whereas most differences in glucose-insulin variables became non-significant after further adjustment for percent body fat. QFS familial data indicate that the heritability of NME reaches about 30%. In conclusion, the results of this study show that beyond aerobic fitness and physical activity-participation, mechanical efficiency is an additional activity-related variable that is independently associated with variations in body composition and glycemic profile.

Unraveling the link between cardiorespiratory fitness and cancer: a state-of-the-art review

Cardiorespiratory fitness (CRF) not only reflects an individual's capacity to perform physical activities but also encapsulates broader effects on the basic biology of aging. This review aims to summarize the evidence on the influence of CRF on overall and site-specific cancer risks. It delves into the biological mechanisms through which CRF may exert its effects, explores the clinical implications of these findings, identifies gaps in the current evidence base, and suggests directions for future research. The synthesis of findings reveals that higher CRF levels (general threshold of > 7 METs) are consistently associated with a reduced risk of a range of cancers, including head and neck, lung, breast, gastrointestinal, particularly pancreatic and colorectal, bladder, overall cancer incidence and mortality, and potentially stomach and liver, bile duct, and gall bladder cancers. These inverse associations between CRF and cancer risk do not generally differ across age groups, sex, race, or adiposity, suggesting a universal protective effect of CRF. Nonetheless, evidence linking CRF with skin, mouth and pharynx, kidney, and endometrial cancers is limited and inconclusive. Conversely, higher CRF levels may be potentially linked to an increased risk of prostate cancer and hematological malignancies, such as leukemia and myeloma, although the evidence is still not conclusive. CRF appears to play a significant role in reducing the risk of several cancers through various biological mechanisms, including inflammation reduction, immune system enhancement, hormonal regulation, and metabolic improvements. Overall, enhancing CRF through regular physical activity offers a vital, accessible strategy for reducing cancer risk and extending the health span. Future research should aim to fill the existing evidence gaps regarding specific cancers and elucidate the detailed dose-response relationships between CRF levels and cancer risk. Studies are also needed to elucidate the causal relationships and mechanistic pathways linking CRF to cancer outcomes.

Observational and genetic associations between cardiorespiratory fitness and age-related diseases: longitudinal analyses in the UK Biobank study

Background

Observational studies have indicated that increased cardiorespiratory fitness is associated with a decreased risk of cardiovascular disease (CVD), Alzheimer's disease (AD), and Parkinson's disease (PD). However, the causal mechanisms remain unclear. The objective of this study was to assess the role of fitness in the early detection and reduction of disease risk within the framework of predictive, preventive, and personalized medicine (PPPM/3PM).

Methods

The associations of fitness with CVD, AD, and PD were explored in a large cohort of up to 502,486 individuals between the ages of 40 and 69 years from the UK Biobank. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the risk of CVD, AD, and PD among participants who completed a submaximal fitness test. Causality relationships were assessed via two-sample Mendelian randomization (MR).

Results

After a median of 11 years of follow-up, each 3.5 ml of O2⋅min-1⋅kg-1 increase in total body mass (equivalent to 1 metabolic equivalent of task (MET), approximately 0.5 standard deviations (SDs)) was associated with decreased risks of CVD (20.0%, 95% CI 17.6-22.3%), AD (31.9%, 95% CI 26.7-33.6%), and PD (21.2%, 95% CI 11.2-31.8%). After adjusting for obesity, the observational associations were attenuated. According to the MR analyses, fitness was associated with PD (OR IVW 0.937, 95% CI 0.897-0.978) and small vessel stroke (OR IVW 0.964, 95% CI 0.933-0.995).

Conclusion

Our results indicate that fitness has an effect on age-related diseases. Protective associations of higher fitness levels with the risk of CVD, AD, and PD were validated in this cohort study. These findings might be valuable for predicting, preventing, and reducing disease morbidity and mortality through primary prevention and healthcare in the context of PPPM.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-024-00382-4.

Cerebral blood flow and arterial transit time responses to exercise training in older adults

Brain vascular health worsens with age, as is made evident by resting grey matter cerebral blood flow (CBFGM) reductions and lengthening arterial transit time (ATTGM). Exercise training can improve aspects of brain health in older adults, yet its effects on CBFGM and ATTGM remain unclear. This randomised controlled trial assessed responses of CBFGM and ATTGM to a 26 week exercise intervention in 65 healthy older adults (control: n = 33, exercise: n = 32, aged 60-81 years), including whether changes in CBFGM or ATTGM were associated with changes in cognitive functions. Multiple-delay pseudo-continuous arterial spin labelling data were used to estimate resting global and regional CBFGM and ATTGM. Results showed no between-group differences in CBFGM or ATTGM following the intervention. However, exercise participants with the greatest cardiorespiratory gains (n = 17; ∆V̇O2peak >2 mL/kg/min) experienced global CBFGM reductions (-4.0 [-7.3, -0.8] mL/100 g/min). Cognitive functions did not change in either group and changes were not associated with changes in CBFGM or ATTGM. Our findings indicate that exercise training in older adults may induce global CBFGM reductions when high cardiorespiratory fitness gains are induced, but this does not appear to affect cognitive functions.

Changes in muscle cross-sectional area during two menstrual cycles may not be exclusively attributed to resistance training

This study investigated the impact of menstrual cycle (MC) phases and resistance training (RT) on muscle cross-sectional area (CSA) in two MCs utilizing a within-subject design. Twenty women with regular MCs had their legs randomly allocated to either the control (CON) or RT condition, which included 16 training sessions over two MCs. CSA, estradiol (E2), and progesterone (P4) were assessed during the menstruation (M), ovulation (O), and luteal (L) phases in the first (M1, O1, L1) and second (M2, O2, L2) MCs and at the beginning of the third MC (M3). P4 values were significantly higher during the luteal phase than during menstruation (P < 0.0001) and ovulation (P < 0.0001). No significant differences in E2 concentrations were observed between the MC phases (P = 0.08). For the RT condition, the CSA showed significant increases at O2, L2, and M3 compared to baseline (M1) (all P < 0.0001). No significant changes were observed for the CON condition during the two MCs (P > 0.05). However, RT condition showed a significant change in average CSA across two MCs. Additionally, individual analyses revealed that 19 participants showed variation in CSA above or below the minimum detectable difference during the two MCs. These findings suggest that changes in muscle CSA observed during two MCs may not be exclusively attributed to RT.

Testing in Football: A Narrative Review

Football clubs regularly test and monitor players, with different approaches reflecting player age and competitive level. This narrative review aims to summarise justifications for testing and commonly used testing protocols. We also aim to discuss the validity and reliability of specific tests used to assess football players and provide a holistic overview of protocols currently used in football or those demonstrating potential utility. The PubMed, SportDiscus, and Google Scholar databases were screened for relevant articles from inception to September 2024. Articles that met our inclusion criteria documented tests for several purposes, including talent identification or the assessment of growth/maturation, physiological capacity, sport-specific skill, health status, monitoring fatigue/recovery, training adaptation, and injury risk factors. We provide information on specific tests of anthropometry, physical capacity, biochemical markers, psychological indices, injury risk screening, sport-specific skills, and genetic profile and highlight where certain tests may require further evidence to support their use. The available evidence suggests that test selection and implementation are influenced by financial resources, coach perceptions, and playing schedules. The ability to conduct field-based testing at low cost and to test multiple players simultaneously appear to be key drivers of test development and implementation among practitioners working in elite football environments.

Hamstrings Hypertrophy Is Specific to the Training Exercise: Nordic Hamstring versus Lengthened State Eccentric Training

INTRODUCTION

The hamstring muscles play a crucial role in sprint running but are also highly susceptible to strain injuries, particularly within the biceps femoris long head (BFlh). This study compared the adaptations in muscle size and strength of the knee flexors, as well as BFlh muscle and aponeurosis size, after two eccentrically focused knee flexion training regimes: Nordic hamstring training (NHT) vs lengthened state eccentric training (LSET, isoinertial weight stack resistance in an accentuated hip-flexed position) vs habitual activity (no training controls: CON).

METHODS

Forty-two healthy young males completed 34 sessions of NHT or LSET over 12 wk or served as CON ( n = 14/group). Magnetic resonance imaging-measured muscle volume of seven individual knee flexors and BFlh aponeurosis area, and maximum knee flexion torque during eccentric, concentric, and isometric contractions were assessed pre- and post-training.

RESULTS

LSET induced greater increases in hamstrings (+18% vs +11%) and BFlh (+19% vs +5%) muscle volumes and BFlh aponeurosis area (+9% vs +3%) than NHT (all P ≤ 0.001), with no changes after CON. There were distinctly different patterns of hypertrophy between the two training regimes, largely due to the functional role of the muscles; LSET was more effective for increasing the size of knee flexors that also extend the hip (2.2-fold vs NHT), whereas NHT increased the size of knee flexors that do not extend the hip (1.9-fold vs LSET; both P ≤ 0.001). Changes in maximum eccentric torque differed only between LSET and CON (+17% vs +4%; P = 0.009), with NHT (+11%) inbetween.

CONCLUSIONS

These results suggest that LSET is superior to NHT in inducing overall hamstrings and BFlh hypertrophy, potentially contributing to better sprint performance improvements and protection against hamstring strain injuries than NHT.

Determinants of cerebral blood flow and arterial transit time in healthy older adults

Cerebral blood flow (CBF) and arterial transit time (ATT), markers of brain vascular health, worsen with age. The primary aim of this cross-sectional study was to identify modifiable determinants of CBF and ATT in healthy older adults (n = 78, aged 60-81 years). Associations between cardiorespiratory fitness and CBF or ATT were of particular interest because the impact of cardiorespiratory fitness is not clear within existing literature. Secondly, this study assessed whether CBF or ATT relate to cognitive function in older adults. Multiple post-labelling delay pseudo-continuous arterial spin labelling estimated resting CBF and ATT in grey matter. Results from multiple linear regressions found higher BMI was associated with lower global CBF (β = -0.35, P = 0.008) and a longer global ATT (β = 0.30, P = 0.017), global ATT lengthened with increasing age (β = 0.43, P = 0.004), and higher cardiorespiratory fitness was associated with longer ATT in parietal (β = 0.44, P = 0.004) and occipital (β = 0.45, P = 0.003) regions. Global or regional CBF or ATT were not associated with processing speed, working memory, or attention. In conclusion, preventing excessive weight gain may help attenuate age-related declines in brain vascular health. ATT may be more sensitive to age-related decline than CBF, and therefore useful for early detection and management of cerebrovascular impairment. Finally, cardiorespiratory fitness appears to have little effect on CBF but may induce longer ATT in specific regions.

Cardiorespiratory fitness, atrial fibrillation and stroke: a review of the evidence in 2024

INTRODUCTION

The body of evidence linking cardiorespiratory fitness (CRF) levels with the risk of atrial fibrillation (AF) and stroke - two interconnected cardiovascular conditions - is not entirely consistent. Furthermore, specific CRF thresholds beyond which the risk of AF or stroke might not decrease are not well defined.

AREAS COVERED

This review summarizes research evidence on the role of CRF in the development of AF and stroke including dose-response relationships in general population participants, explores the biological mechanisms through which CRF may exert its effects, assesses the potential implications for clinical care and population health, identifies gaps in the current evidence, and suggest directions for future research. MEDLINE and Embase were searched from inception until July 2024 to identify observational longitudinal and interventional studies as well as systematic reviews and meta-analyses related to these study designs.

EXPERT OPINION

In the general population, increasing levels of CRF, achieved through consistent physical activity, can significantly reduce the likelihood of developing AF and stroke. The findings also advocate for a tailored approach to exercise prescriptions, acknowledging the plateau in benefits for AF risk beyond certain CRF levels, while advocating for higher intensity or prolonged activity to further reduce stroke risk.

Circulating miRNA Signaling for Fatty Acid Metabolism in Response to a Maximum Endurance Test in Elite Long-Distance Runners

Maximal oxygen uptake (VO2max) is a determining indicator for cardiorespiratory capacity in endurance athletes, and epigenetics is crucial in its levels and variability. This initial study examined a broad plasma miRNA profile of twenty-three trained elite endurance athletes with similar training volumes but different VO2max in response to an acute maximal graded endurance test. Six were clustered as higher/lower levels based on their VO2max (75.4 ± 0.9 and 60.1 ± 5.0 mL.kg-1.min-1). Plasma was obtained from athletes before and after the test and 15 ng of total RNA was extracted and detected using an SYBR-based 1113 miRNA RT-qPCR panel. A total of 51 miRNAs were differentially expressed among group comparisons. Relative amounts of miRNA showed a clustering behavior among groups regarding distinct performance/time points. Significantly expressed miRNAs were used to perform functional bioinformatic analysis (DIANA tools). Fatty acid metabolism pathways were strongly targeted for the significantly different miRNAs in all performance groups and time points (p < 0.001). Although this pathway does not solely determine endurance performance, their significant contribution is certainly achieved through the involvement of miRNAs. A highly genetically dependent gold standard variable for performance evaluation in a homogeneous group of elite athletes allowed genetic/epigenetic aspects related to fatty acid pathways to emerge.

Mechanisms of exercise intervention in type 2 diabetes: a bibliometric and visualization analysis based on CiteSpace

Objective

Type 2 diabetes (T2D) is a common chronic metabolic disease, and its prevalence is increasing globally. Exercise is crucial for T2D management, yet many aspects of its mechanisms remain unclear. This study employs CiteSpace to reveal research hotspots and frontier issues in exercise intervention for T2D.

Method

A literature review spanning from January 1, 2013 to December 31, 2022, was conducted using the Web of Science Core Collection (WoSCC), with keywords including "exercise," "type 2 diabetes," and "mechanisms." We analyzed network diagrams generated by CiteSpace, which depicted relationships among countries, authors, and keywords.

Results

This study includes 1,210 English papers from 555 journals, affiliated with 348 institutions across 80 countries/regions. Notably, the United States, China, and the United Kingdom account for nearly half of all publications. The University of Copenhagen leads in publication volume, followed by Harvard Medical School and the University of Colorado. Key authors include Kirwan, John P (Case Western Reserve University), Malin, Steven K (Rutgers University), and Pedersen, Bente Klarlund (University of Copenhagen). Based on co-occurrence analysis of keywords, it is evident that terms such as "disease," "glucagon-like peptide 1," and "cardiovascular risk factor" exhibit high intermediary centrality.

Conclusion

The analysis highlights ongoing investigations into molecular mechanisms, such as β-cell function enhancement, exerkines, and epigenetic mechanisms. Emerging areas include exercise response heterogeneity, circadian rhythm regulation, transcription factors, neurotrophic factors, and mitochondrial function. Future studies should prioritize understanding interactions between different exercise mechanisms and optimizing exercise prescriptions for T2D. Exercise prescriptions are crucial for effective interventions. Collaboration between countries and institutions is essential to understand the influences of different genetic backgrounds and environmental factors. Currently, a combination of aerobic and resistance training is considered the optimal form of exercise. However, considering time efficiency, high-intensity interval training (HIIT) has gained widespread attention and research due to its ability to achieve similar exercise effects in a shorter duration. Additionally, circadian rhythm regulation may affect the exercise outcomes of diabetic individuals at different times of the day, particularly concerning the specific types, doses, and intensities used for precision intervention in T2D.

Matrisome proteomics reveals novel mediators of muscle remodeling with aerobic exercise training

Skeletal muscle has a unique ability to remodel in response to stimuli such as contraction and aerobic exercise training. Phenotypic changes in muscle that occur with training such as a switch to a more oxidative fiber type, and increased capillary density contribute to the well-known health benefits of aerobic exercise. The muscle matrisome likely plays an important role in muscle remodeling with exercise. However, due to technical limitations in studying muscle ECM proteins, which are highly insoluble, little is known about the muscle matrisome and how it contributes to muscle remodeling. Here, we utilized two-fraction methodology to extract muscle proteins, combined with multiplexed tandem mass tag proteomic technology to identify 161 unique ECM proteins in mouse skeletal muscle. In addition, we demonstrate that aerobic exercise training induces remodeling of a significant proportion of the muscle matrisome. We performed follow-up experiments to validate exercise-regulated ECM targets in a separate cohort of mice using Western blotting and immunofluorescence imaging. Our data demonstrate that changes in several key ECM targets are strongly associated with muscle remodeling processes such as increased capillary density in mice. We also identify LOXL1 as a novel muscle ECM target associated with aerobic capacity in humans. In addition, publically available data and databases were used for in silico modeling to determine the likely cellular sources of exercise-induced ECM remodeling targets and identify ECM interaction networks. This work greatly enhances our understanding of ECM content and function in skeletal muscle and demonstrates an important role for ECM remodeling in the adaptive response to exercise. The raw MS data have been deposited to the ProteomeXchange with identifier PXD053003.

Lifestyle factors as determinants of atherosclerotic cardiovascular health

A sedentary lifestyle, low levels of physical activity and fitness, poor dietary patterns, and psychosocial stress are strongly associated with increased morbidity and mortality from atherosclerotic cardiovascular disease (ASCVD). Conversely, engaging in regular physical activity, maintaining optimal fitness levels, adhering to a heart-healthy dietary pattern, effectively managing body weight, ensuring adequate sleep, implementing stress-reduction strategies, and addressing psychosocial risk factors are associated with a reduced risk of ASCVD. This comprehensive review synthesizes current evidence from large observational studies and randomized controlled trials on lifestyle factors as determinants of ASCVD health. It also briefly reviews mechanistic insights into how factors such as low shear stress, increased reactive oxygen species production, chronic inflammation, platelets and coagulation activation, endothelial dysfunction, and sympathetic hyperactivity contribute to the initiation and exacerbation of ASCVD risk factors. These include obesity, hyperglycemia, type 2 diabetes, hypertension, and dyslipidemia, subsequently leading to the development and progression of atherosclerosis, ultimately resulting in chronic ASCVD or acute cardiovascular events. To bridge the translational gap between epidemiologic and trial-based evidence and clinical practice, practical recommendations are summarized to facilitate the translation of scientific knowledge into actionable interventions to promote ASCVD health. Acknowledged is the gap between the evidence-based knowledge and adoption within healthcare systems, which remains a crucial objective in advancing cardiovascular health at the population level.

Standing on the Shoulders of Giants: Essential Papers in Sports and Exercise Physiology

PURPOSE

The purpose of this survey was to create a list of essential historical and contemporary readings for undergraduate and graduate students in the field of exercise physiology.

METHODS

Fifty-two exercise physiologists/sport scientists served as referees, and each nominated ∼25 papers for inclusion in the list. In total, 396 papers were nominated by the referees. This list was then sent back to the referees, with the instructions to nominate the "100 essential papers in sports and exercise physiology."

RESULTS

The referees cast 4722 votes. The 100 papers with the highest number of votes received 51% (2406) of the total number of votes. A total of 37 papers in the list of "100 essential papers" were published >50 years ago, and 63 papers were published since 1973.

CONCLUSIONS

This list of essential studies will provide a perspective on contemporary studies, the "giant's shoulders" to enable young scholars to "see further" or to understand where they have "come from." This compilation is also meant to impress on students that, given the (lack of) technology available in the past, some of the early science required enormous intuitive leaps on the part of historical scientists.

The delta concept does not effectively normalise exercise responses to exhaustive interval training

OBJECTIVES

This study was designed to quantify inter- and intra-individual variability in performance, physiological, and perceptual responses to high-intensity interval training prescribed using the percentage of delta (%Δ) method, in which the gas exchange threshold and maximal oxygen uptake (V̇O2max) are taken into account to normalise relative exercise intensity.

DESIGN

Repeated-measures, within-subjects design with mixed-effects modelling.

METHODS

Eighteen male and four female cyclists (age: 36 ± 12 years, height: 178 ± 10 cm, body mass: 75.2 ± 13.7 kg, V̇O2max: 51.6 ± 5.3 ml·kg-1·min-1) undertook an incremental test to exhaustion to determine the gas exchange threshold and V̇O2max as prescription benchmarks. On separate occasions, participants then completed four high-intensity interval training sessions of identical intensity (70 %Δ) and format (4-min on, 2-min off); all performed to exhaustion. Acute high-intensity interval training responses were modelled with participant as a random effect to provide estimates of inter- and intra-individual variability.

RESULTS

Greater variability was generally observed at the between- compared with the within-individual level, ranging from 50 % to 89 % and from 11 % to 50 % of the total variability, respectively. For the group mean time to exhaustion of 20.3 min, inter- and intra-individual standard deviations reached 9.3 min (coefficient of variation = 46 %) and 4.5 min (coefficient of variation = 22 %), respectively.

CONCLUSIONS

Due to the high variability observed, the %Δ method does not effectively normalise the relative intensity of exhaustive high-intensity interval training across individuals. The generally larger inter- versus intra-individual variability suggests that day-to-day biological fluctuations and/or measurement errors cannot explain the identified shortcoming of the method.

The effects of exercise on epigenetic modifications: focus on DNA methylation, histone modifications and non-coding RNAs

Physical activity on a regular basis has been shown to bolster the overall wellness of an individual; research is now revealing that these changes are accompanied by epigenetic modifications. Regular exercise has been proven to make intervention plans more successful and prolong adherence to them. When it comes to epigenetic changes, there are four primary components. This includes changes to the DNA, histones, expression of particular non-coding RNAs and DNA methylation. External triggers, such as physical activity, can lead to modifications in the epigenetic components, resulting in changes in the transcription process. This report pays attention to the current knowledge that pertains to the epigenetic alterations that occur after exercise, the genes affected and the resulting characteristics.

Heavy-, Severe-, and Extreme-, but Not Moderate-Intensity Exercise Increase V̇o 2max and Thresholds after 6 wk of Training

INTRODUCTION

This study assessed the effect of individualized, domain-based exercise intensity prescription on changes in maximal oxygen uptake (V̇O 2max ) and submaximal thresholds.

METHODS

Eighty-four young healthy participants (42 females, 42 males) were randomly assigned to six age, sex, and V̇O 2max -matched groups (14 participants each). Groups performed continuous cycling in the 1) moderate (MOD), 2) lower heavy (HVY1), and 3) upper heavy-intensity (HVY2) domain; interval cycling in the form of 4) high-intensity interval training (HIIT) in the severe-intensity domain, or 5) sprint-interval training (SIT) in the extreme-intensity domain; or no exercise for 6) control (CON). All training groups, except SIT, were work-matched. Training participants completed three sessions per week for 6 wk with physiological evaluations performed at PRE, MID, and POST intervention.

RESULTS

Compared with the change in V̇O 2max (∆V̇O 2max ) in CON (0.1 ± 1.2 mL·kg -1 ·min -1 ), all training groups, except MOD (1.8 ± 2.7 mL·kg -1 ·min -1 ), demonstrated a significant increase ( P < 0.05). HIIT produced the highest increase (6.2 ± 2.8 mL·kg -1 ·min -1 ) followed by HVY2 (5.4 ± 2.3 mL·kg -1 ·min -1 ), SIT (4.7 ± 2.3 mL·kg -1 ·min -1 ), and HVY1 (3.3 ± 2.4 mL·kg -1 ·min -1 ), respectively. The ΔPO at the estimated lactate threshold ( θLT ) was similar across HVY1, HVY2, HIIT, and SIT, which were all greater than CON ( P < 0.05). The ΔV̇O 2 and ΔPO at θLT for MOD was not different from CON ( P > 0.05). HIIT produced the highest ΔPO at maximal metabolic steady state, which was greater than CON, MOD, and SIT ( P < 0.05).

CONCLUSIONS

This study demonstrated that i) exercise intensity is a key component determining changes in V̇O 2max and submaximal thresholds and ii) exercise intensity domain-based prescription allows for a homogenous metabolic stimulus across individuals.

Intra-Individual Variations in How Insulin Sensitivity Responds to Long-Term Exercise: Predictions by Machine Learning Based on Large-Scale Serum Proteomics

Physical activity is effective for preventing and treating type 2 diabetes, but some individuals do not achieve metabolic benefits from exercise ("non-responders"). We investigated non-responders in terms of insulin sensitivity changes following a 12-week supervised strength and endurance exercise program. We used a hyperinsulinaemic euglycaemic clamp to measure insulin sensitivity among 26 men aged 40-65, categorizing them into non-responders or responders based on their insulin sensitivity change scores. The exercise regimen included VO2max, muscle strength, whole-body MRI scans, muscle and fat biopsies, and serum samples. mRNA sequencing was performed on biopsies and Olink proteomics on serum samples. Non-responders showed more visceral and intramuscular fat and signs of dyslipidaemia and low-grade inflammation at baseline and did not improve in insulin sensitivity following exercise, although they showed gains in VO2max and muscle strength. Impaired IL6-JAK-STAT3 signalling in non-responders was suggested by serum proteomics analysis, and a baseline serum proteomic machine learning (ML) algorithm predicted insulin sensitivity responses with high accuracy, validated across two independent exercise cohorts. The ML model identified 30 serum proteins that could forecast exercise-induced insulin sensitivity changes.

Understanding the variation in exercise responses to guide personalized physical activity prescriptions

Understanding the factors that contribute to exercise response variation is the first step in achieving the goal of developing personalized exercise prescriptions. This review discusses the key molecular and other mechanistic factors, both extrinsic and intrinsic, that influence exercise responses and health outcomes. Extrinsic characteristics include the timing and dose of exercise, circadian rhythms, sleep habits, dietary interactions, and medication use, whereas intrinsic factors such as sex, age, hormonal status, race/ethnicity, and genetics are also integral. The molecular transducers of exercise (i.e., genomic/epigenomic, proteomic/post-translational, transcriptomic, metabolic/metabolomic, and lipidomic elements) are considered with respect to variability in physiological and health outcomes. Finally, this review highlights the current challenges that impede our ability to develop effective personalized exercise prescriptions. The Molecular Transducers of Physical Activity Consortium (MoTrPAC) aims to fill significant gaps in the understanding of exercise response variability, yet further investigations are needed to address additional health outcomes across all populations.

Low Response to Aerobic Training in Metabolic Disease: Role of Skeletal Muscle

Aerobic exercise is established to increase cardiorespiratory fitness (CRF), which is linked to reduced morbidity and mortality. However, people with metabolic diseases such as type 1 and type 2 diabetes may be more likely to display blunted improvements in CRF with training. Here, we present evidence supporting the hypothesis that altered skeletal muscle signaling and remodeling may contribute to low CRF with metabolic disease.

Cardiac hemodynamics phenotypes and individual responses to training in coronary heart disease patients

BACKGROUND

In patients with coronary heart disease (CHD), individualized exercise training (ET) programs are strongly recommended to optimize peak oxygen uptake (V ̇ $$ \dot{\mathrm{V}} $$ O2peak) improvement and prognosis. However, the cardiac hemodynamic factors responsible for a positive response to training remain unclear. The aim of this study was to compare cardiac hemodynamic changes after an ET program in responder (R) versus non-responder (NR) CHD patients.

METHODS

A total of 72 CHD patients completed a 3-month ET program and were assessed by cycle ergometer cardiopulmonary exercise test (CPET:V ̇ $$ \dot{\mathrm{V}} $$ O2peak assessment) with impedance cardiography (ICG) for hemodynamic measurements before and after training. Cardiac hemodynamics (e.g., CO, CI, SV, ESV, EDV, and SVR) were measured by ICG during CPET. The R and NR groups were classified using the median change inV ̇ $$ \dot{\mathrm{V}} $$ O2peak (>the median for R and ≤the median for NR).

RESULTS

In the R group,V ̇ $$ \dot{\mathrm{V}} $$ O2peak (+17%, p < 0.001), CO, CI, SV, and HR increased by 17%, 17%, 13%, and 5%, respectively (p < 0.05) after the training program. In the NR group,V ̇ $$ \dot{\mathrm{V}} $$ O2peak, CO, CI, and SV increased by 0.5%, 5%, 8%, and 6%, respectively (p < 0.01). The SVR decreased in both groups (-19% in R and -11% in NR, p < 0.001).

CONCLUSION

Among CHD patients, the R group showed a better improvement in peak cardiac output via an increase in peak stroke volume and heart rate and a reduced systemic vascular resistance than the NR group. Different cardiac phenotype adaptations and clinical individual responses were identified in CHD patients according to the aerobic fitness responder's status.

Inherited physical capacity: Widening divergence from young to adult to old

Cardiorespiratory performance segregates into rat strains of inherited low- and high-capacity runners (LCRs and HCRs); during adulthood, this segregation remains stable, but widens in senescence and is followed by segregated function, health, and mortality. However, this segregation has not been investigated prior to adulthood. We, therefore, assessed cardiorespiratory performance and cardiac cell (cardiomyocyte) structure-function in 1- and 4-month-old LCRs and HCRs. Maximal oxygen uptake was 23% less in LCRs at 1-month compared to HCRs at 1-month, and 72% less at 4 months. Cardiomyocyte contractility was 37-56% decreased, and Ca2+ release was 34-62% decreased, in 1- and 4-month LCRs versus HCRs. This occurred because HCRs had improved contractility and Ca2+ release during maturation, whereas LCRs did not. In quiescent cardiomyocytes, LCRs displayed 180% and 297% more Ca2+ sparks and 91% and 38% more Ca2+ waves at 1 and 4 months versus HCRs. Cell sizes were not different between LCRs and HCRs, but LCRs showed reduced transverse-tubules versus HCRs, though no discrepant transverse-tubule generation occurred during maturation. In conclusion, LCRs show reduced scores for aerobic capacity and cardiomyocyte structure-function compared to HCRs and there is a widening divergence between LCRs and HCRs during juvenile to near-adult maturation.

Modelling inter-individual variability in acute and adaptive responses to interval training: insights into exercise intensity normalisation

PURPOSE

To investigate the influence of exercise intensity normalisation on intra- and inter-individual acute and adaptive responses to an interval training programme.

METHODS

Nineteen cyclists were split in two groups differing (only) in how exercise intensity was normalised: 80% of the maximal work rate achieved in an incremental test (% W ˙ max) vs. maximal sustainable work rate in a self-paced interval training session (% W ˙ max-SP). Testing duplicates were conducted before and after an initial control phase, during the training intervention, and at the end, enabling the estimation of inter-individual variability in adaptive responses devoid of intra-individual variability.

RESULTS

Due to premature exhaustion, the median training completion rate was 88.8% for the % W ˙ max group, but 100% for the % W ˙ max-SP the group. Ratings of perceived exertion and heart rates were not sensitive to how intensity was normalised, manifesting similar inter-individual variability, although intra-individual variability was minimised for the % W ˙ max-SP group. Amongst six adaptive response variables, there was evidence of individual response for only maximal oxygen uptake (standard deviation: 0.027 L·min-1·week-1) and self-paced interval training performance (standard deviation: 1.451 W·week-1). However, inter-individual variability magnitudes were similar between groups. Average adaptive responses were also similar between groups across all variables.

CONCLUSIONS

To normalise completion rates of interval training, % W ˙ max-SP should be used to prescribe relative intensity. However, the variability in adaptive responses to training may not reflect how exercise intensity is normalised, underlining the complexity of the exercise dose-adaptation relationship. True inter-individual variability in adaptive responses cannot always be identified when intra-individual variability is accounted for.

Genetics of Exercise and Diet-Induced Fat Loss Efficiency: A Systematic Review

Physical exercise and dieting are well-known and effective methods for fat loss and improving cardiovascular health. However, different individuals often react differently to the same exercise regimen or dietary plan. While specific individuals may undergo substantial fat loss, others may observe only limited effects. A wide range of inter-individual variability in weight gain and changes in body composition induced by physical exercises and diets led to an investigation into the genetic factors that may contribute to the individual variations in such responses. This systematic review aimed at identifying the genetic markers associated with fat loss resulting from diet or exercise. A search of the current literature was performed using the PubMed database. Forty-seven articles met the inclusion criteria when assessing genetic markers associated with weight loss efficiency in response to different types of exercises and diets. Overall, we identified 30 genetic markers of fat-loss efficiency in response to different kinds of diets and 24 in response to exercise. Most studies (n = 46) used the candidate gene approach. We should aspire to the customized selection of exercise and dietary plans for each individual to prevent and treat obesity.

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.

Serum factors mediate changes in mitochondrial bioenergetics associated with diet and exercise interventions

Mitochondrial improvements resulting from behavioral interventions, such as diet and exercise, are systemic and apparent across multiple tissues. Here, we test the hypothesis that factors present in serum, and therefore circulating throughout the body, can mediate changes in mitochondrial function in response to intervention. To investigate this, we used stored serum from a clinical trial comparing resistance training (RT) and RT plus caloric restriction (RT + CR) to examine effects of blood borne circulating factors on myoblasts in vitro. We report that exposure to dilute serum is sufficient to mediate bioenergetic benefits of these interventions. Additionally, serum-mediated bioenergetic changes can differentiate between interventions, recapitulate sex differences in bioenergetic responses, and is linked to improvements in physical function and inflammation. Using metabolomics, we identified circulating factors associated with changes in mitochondrial bioenergetics and the effects of interventions. This study provides new evidence that circulating factors play a role in the beneficial effects of interventions that improve healthspan among older adults. Understanding the factors that drive improvements in mitochondrial function is a key step towards predicting intervention outcomes and developing strategies to countermand systemic age-related bioenergetic decline.

Hemodynamic Response to Exercise Training in Heart Failure With Reduced Ejection Fraction Patients

Background

Supervised exercise training decreases total and cardiac mortality and increases quality of life of heart failure with reduced ejection fraction (HFrEF) patients. However, response to training is variable from one patient to another and factors responsible for a positive response to training remain unclear. The aims of the study were to compare cardiac hemodynamic changes after an exercise training program in responders (R) versus non-responders (NR) HFrEF patients, and to compare different discriminators used to assess response to training.

Methods

Seventy-six HFrEF patients (86% males, 57 ± 12 years) completed an exercise training program for 4 weeks. Patients underwent cardiopulmonary exercise testing (CPET) on a cycle ergometer before and after training. Cardiac hemodynamics were measured by impedance cardiography during CPET. The R and NR groups were classified using the median change in peak oxygen uptake (V̇O2peak).

Results

There were statistically significant differences in V̇O2peak (+35% vs. -1%, P < 0.0001) and in peaks of ventilation (+30% vs. +2%, P < 0.0001), cardiac output (COpeak) (+25% vs. +4%, P < 0.01), systolic blood pressure (+12% vs. +2%, P < 0.05), diastolic blood pressure (+9% vs. +4%, P < 0.05) and heart rate (+8% vs. +1%, P < 0.01) between R and NR after the training program. V̇O2peak was the best discriminator between R and NR (receiver operating characteristic (ROC) area under the curve (AUC) = 0.83, P < 0.0001), followed by COpeak (ROC AUC = 0.77, P < 0.0001).

Conclusion

V̇O2peak is the best discriminator between HFrEF R and NR patients after the training program. Responders showed improvements in peak hemodynamic parameters. These results pave the way for other studies to determine how the individualization of exercise training programs and peak hemodynamic parameters potentially linked to a better positive response status.

Observational and genetic associations between cardiorespiratory fitness and cancer: a UK Biobank and international consortia study

BACKGROUND

The association of fitness with cancer risk is not clear.

METHODS

We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of lung, colorectal, endometrial, breast, and prostate cancer in a subset of UK Biobank participants who completed a submaximal fitness test in 2009-12 (N = 72,572). We also investigated relationships using two-sample Mendelian randomisation (MR), odds ratios (ORs) were estimated using the inverse-variance weighted method.

RESULTS

After a median of 11 years of follow-up, 4290 cancers of interest were diagnosed. A 3.5 ml O2⋅min-1⋅kg-1 total-body mass increase in fitness (equivalent to 1 metabolic equivalent of task (MET), approximately 0.5 standard deviation (SD)) was associated with lower risks of endometrial (HR = 0.81, 95% CI: 0.73-0.89), colorectal (0.94, 0.90-0.99), and breast cancer (0.96, 0.92-0.99). In MR analyses, a 0.5 SD increase in genetically predicted O2⋅min-1⋅kg-1 fat-free mass was associated with a lower risk of breast cancer (OR = 0.92, 95% CI: 0.86-0.98). After adjusting for adiposity, both the observational and genetic associations were attenuated.

DISCUSSION

Higher fitness levels may reduce risks of endometrial, colorectal, and breast cancer, though relationships with adiposity are complex and may mediate these relationships. Increasing fitness, including via changes in body composition, may be an effective strategy for cancer prevention.

Biological sex does not influence the peak cardiac output response to twelve weeks of sprint interval training

Sprint interval training (SIT) increases peak oxygen uptake (V̇O2peak) but the mechanistic basis is unclear. We have reported that 12 wk of SIT increased V̇O2peak and peak cardiac output (Q̇peak) and the changes in these variables were correlated. An exploratory analysis suggested that Q̇peak increased in males but not females. The present study incorporated best practices to examine the potential influence of biological sex on the Q̇peak response to SIT. Male and female participants (n = 10 each; 21 ± 4 y) performed 33 ± 2 sessions of SIT over 12 wk. Each 10-min session involved 3 × 20-s 'all-out' sprints on an ergometer. V̇O2peak increased after SIT (3.16 ± 1.0 vs. 2.89 ± 1.0 L/min, η2p = 0.53, p < 0.001) with no sex × time interaction (p = 0.61). Q̇peak was unchanged after training (15.2 ± 3.3 vs. 15.1 ± 3.0 L/min, p = 0.85), in contrast to our previous study. The peak estimated arteriovenous oxygen difference increased after training (204 ± 30 vs. 187 ± 36 ml/L, p = 0.006). There was no effect of training or sex on measures of endothelial function. We conclude that 12 wk of SIT increases V̇O2peak but the mechanistic basis remains unclear. The capacity of inert gas rebreathing to assess changes in Q̇peak may be limited and invasive studies that use more direct measures are needed.

Effects of Time-Efficient Occupational Exercise on Cardiorespiratory Fitness in Firefighters

OBJECTIVE

For a cohort of operational firefighters, we assessed the effects of workplace-based high-intensity interval training (HIIT) on cardiorespiratory fitness.

METHODS

Fifteen firefighters performed HIIT or moderate-intensity continuous training for 4 weeks. Outcomes were peak oxygen uptake, time trial performance, and affective (pleasure/displeasure) responses to exercise.

RESULTS

There was an increase in peak oxygen uptake for both conditions, although this did not reach statistical significance ( P = 0.06, η2 = 0.26) and time trial performance improved for both groups (2%, P < 0.01, η2 = 0.51). Affective responses were more favorable for HIIT, but both conditions avoided excessive sensations of displeasure.

CONCLUSION

Results suggest that workplace-based HIIT improved fitness and performance to a similar magnitude to moderate-intensity continuous training while avoiding overly negative affective responses and could improve occupational health of firefighters, despite reduced time commitment.

The Genetic Association with Athlete Status, Physical Performance, and Injury Risk in Soccer

The aim of this review was to critically appraise the literature concerning the genetic association with athlete status, physical performance, and injury risk in soccer. The objectives were to provide guidance on which genetic markers could potentially be used as part of future practice in soccer and to provide direction for future research in this area. The most compelling evidence identified six genetic polymorphisms to be associated with soccer athlete status (ACE I/D; ACTN3 rs1815739; AGT rs699; MCT1 rs1049434; NOS3 rs2070744; PPARA rs4253778), six with physical performance (ACTN3 rs1815739; AMPD1 rs17602729; BDNF rs6265; COL2A1 rs2070739; COL5A1 rs12722; NOS3 rs2070744), and seven with injury risk (ACTN3 rs1815739; CCL2 rs2857656; COL1A1 rs1800012; COL5A1 rs12722; EMILIN1 rs2289360; IL6 rs1800795; MMP3 rs679620). As well as replication by independent groups, large-scale genome-wide association studies are required to identify new genetic markers. Future research should also investigate the physiological mechanisms associating these polymorphisms with specific phenotypes. Further, researchers should investigate the above associations in female and non-Caucasian soccer players, as almost all published studies have recruited male participants of European ancestry. Only after robust, independently replicated genetic data have been generated, can genetic testing be considered an additional tool to potentially inform future practice in soccer.

Expression of mitochondrial oxidative stress response genes in muscle is associated with mitochondrial respiration, physical performance, and muscle mass in the Study of Muscle, Mobility and Aging (SOMMA)

Gene expression in skeletal muscle of older individuals may reflect compensatory adaptations in response to oxidative damage that preserve tissue integrity and maintain function. Identifying associations between oxidative stress response gene expression patterns and mitochondrial function, physical performance, and muscle mass in older individuals would further our knowledge of mechanisms related to managing molecular damage that may be targeted to preserve physical resilience. To characterize expression patterns of genes responsible for the oxidative stress response, RNA was extracted and sequenced from skeletal muscle biopsies collected from 575 participants (≥70 years old) from the Study of Muscle, Mobility and Aging. Expression levels of twenty-one protein coding RNAs related to the oxidative stress response were analyzed in relation to six phenotypic measures, including: maximal mitochondrial respiration from muscle biopsies (Max OXPHOS), physical performance (VO2 peak, 400m walking speed, and leg strength), and muscle size (thigh muscle volume and whole-body D3Cr muscle mass). The mRNA level of the oxidative stress response genes most consistently associated across outcomes are preferentially expressed within the mitochondria. Higher expression of mRNAs that encode generally mitochondria located proteins SOD2, TRX2, PRX3, PRX5, and GRX2 were associated with higher levels of mitochondrial respiration and VO2 peak. In addition, greater SOD2, PRX3, and GRX2 expression was associated with higher physical performance and muscle size. Identifying specific mechanisms associated with high functioning across multiple performance and physical domains may lead to targeted antioxidant interventions with greater impacts on mobility and independence.

Understanding Exercise Capacity: From Elite Athlete to HFpEF

Exercise capacity is a spectrum that reflects an individual's functional capacity and the dynamic nature of cardiac remodelling along with respiratory and skeletal muscle systems. The relationship of increasing physical activity, increased cardiac mass and volumes, and improved cardiorespiratory fitness (CRF) is well established in the endurance athlete. However, less emphasis has been placed on the other end of the spectrum, which includes individuals with a more sedentary lifestyle and small hearts who are at increased risk of functional disability and poor clinical outcomes. Reduced CRF is an independent predictor of all-cause mortality and cardiovascular events determined by multiple inter-related exogenous and endogenous factors. In this review, we explore the relationship of physical activity, cardiac remodelling, and CRF across the exercise spectrum, emphasising the critical role of cardiac size in determining exercise capacity. In contrast to the large compliant left ventricle of the endurance athlete, an individual with a lifetime of physical inactivity is likely to have a small, stiff heart with reduced cardiac reserve. We propose that this might contribute to the development of heart failure with preserved ejection fraction in certain individuals, and is key to understanding the link between low CRF and increased risk of heart failure.