Familial resemblance for VO2max in the sedentary state: the HERITAGE family study

Connections among family socioeconomic status, aerobic fitness, executive function, and the positive experiences of childhood physical activity

A family's socioeconomic status (SES) can be linked to a child's physical and cognitive health, with children from low-SES families often experiencing poor developmental outcomes. Early positive childhood experiences that include structured and unstructured physical activities (SUPAs) offer a potential avenue to promote positive health and cognitive development during early childhood. However, prior to school entry, it is not well-understood whether SES is related to participation in SUPAs or how SUPAs relate to early health and cognitive indicators such as aerobic fitnessand executive function (EF). Children (N = 99) aged 3 to 5 years were recruited from 17 classrooms in seven center-based pre-kindergartens. In fall and spring, children were assessed on EF using the Head-Toes-Knees-Shoulders task and aerobic fitness was assessed with the 20-m shuttle run test. Family SES significantly predicted SUPAs and fall and spring fitness, with SUPAs and spring fitness significantly predicting spring EF. Partial support for an indirect relationship between SES and EF through SUPAs was also found. Results suggest that family SES could play a role in predicting participation in SUPAs and aerobic fitness, with SUPAs and aerobic fitness linked to EF during pre-kindergarten.

Movement behaviors and cardiorespiratory fitness - a cross-sectional compositional data analysis among German adults

BACKGROUND

We investigated associations of movement behaviors (moderate-vigorous physical activity, light physical activity, and stationary time) with various parameters measured during cardiopulmonary exercise testing. We applied compositional data analysis to account for the relative contributions of different movement behaviors to the overall time budget of the waking day.

METHODS

We used data from 1,396 participants of the cross-sectional population-based Study of Health in Pomerania (SHIP-TREND-1), who provided valid accelerometer data worn on the hip for seven days during waking hours and participated in cardiopulmonary exercise testing on a cycle ergometer (n = 1,396 participants with a mean age of 57.1 (SD 13.2, 51% men). Linear regression models applying compositional data analysis were used to examine associations of proportions of movement behaviors (exposure) with parameters derived during cardiopulmonary exercise testing (outcome) normalized for body weight and stratified by sex. Models were adjusted for age, education, smoking, and partnership, except the %predicted VO2peak model, where age was omitted, as it is part of the calculation of the %predicted VO2peak. In models examining O2pulse or HRmax, individuals using beta blockers were excluded.

RESULTS

In males and females, more time spent in moderate-to-vigorous physical activity was associated with greater VO2VT1, VO2peak, and VO2 recovery after 60 s (all p < 0.01). Greater moderate-to-vigorous physical activity was also related to higher %predicted VO2peak and maximum heart rate in males and to higher VO2/work in females (all p < 0.01). In both sexes, more time in stationary time was associated with less %predicted VO2peak (p < 0.01). More light intensity physical activity was associated to higher %predicted VO2peak in both sexes and with lower VO2/work in women (all p < 0.01). Greater stationary time was related to less VO2/work, VO2VT1, and VO2peak in males and to less VO2 recovery after 60 s and O2pulse in females (p values < 0.05).

CONCLUSION

Moderate-to-vigorous physical activity (positive) and stationary time (inverse) influence parameters derived during cardiopulmonary exercise testing irrespective of age, smoking, and living in a relationship. The sex specific effects were rather small. Hence, promoting physical activity should be encouraged to increase cardiorespiratory fitness.

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.

Cardiopulmonary Fitness and Physical Activity Among Children and Adolescents With Inherited Cardiac Disease

Importance

Historical restrictions on children with inherited cardiac arrhythmia or cardiomyopathy have been implemented to mitigate the potential risk of sudden death, but these limitations can be detrimental to overall health and cardiopulmonary fitness.

Objectives

To evaluate cardiopulmonary fitness and physical activity among children with inherited cardiac disease and identify the factors associated with maximum oxygen uptake (V̇o2max) in this population.

Design, Setting, and Participants

This cross-sectional, multicenter, prospective controlled study was conducted in 7 tertiary care expert centers for inherited cardiac disease in France from February 1, 2021, to June 20, 2023, with a 2-week follow-up. Participants included 100 children and adolescents aged 6 to 17 years with inherited cardiac arrhythmia or cardiomyopathy who were compared with 107 sex- and age-matched controls.

Main Outcomes and Measures

Maximum oxygen uptake was assessed using cardiopulmonary exercise testing, and results were expressed using pediatric reference z score values. The main determinants of V̇o2max included clinical (New York Heart Association [NYHA] functional class, treatment, echocardiographic, and electrocardiogram variables), functional (cardiopulmonary exercise test parameters), sociodemographic (sex, schooling, and parents' education), and behavioral (physical activity and motivation) characteristics.

Results

A total of 100 patients (mean [SD] age, 12.7 [3.1] years; 52 boys [52.0%]) and 107 controls (mean [SD] age, 11.7 [3.3] years; 54 boys [50.5%]) were included. The V̇o2max was lower in patients than controls, expressed as z scores (mean [SD] score, -1.49 [1.48] vs -0.16 [0.97]; P < .001) or raw values (mean [SD] value, 32.2 [7.9] vs 40.2 [8.5] mL/kg/min; P < .001). Moderate to vigorous physical activity levels were lower in patients than in controls (mean [SD] level, 42.0 [23.6] vs 48.2 [20.4] min/d; P = .009). The final multivariable model explained 80% of the V̇o2max by integrating clinical (lower NYHA functional class, absence of ventricular dilatation, and absence of implantable cardioverter-defibrillator), functional (higher forced vital capacity and ventilatory anaerobic threshold), sociodemographic (male sex, normal progression of schooling, and higher maternal educational level), and behavioral (higher self-reported physical activity and motivation toward physical activity) parameters.

Conclusions and Relevance

This cross-sectional study suggests that levels of cardiopulmonary fitness and physical activity were lower in children and adolescents with inherited cardiac disease than in healthy controls, even after adjusting for use of β-blockers and using modern pediatric reference models. Assessing cardiopulmonary fitness among children with inherited cardiac disease can contribute to engaging in a shared decision-making process for sports participation and preventive interventions, such as early cardiac rehabilitation programs.

Longitudinal Associations of Aerobic Activity, Muscle-Strengthening Activity, and Adiposity with Cardiorespiratory Fitness

PURPOSE

Cardiorespiratory fitness (CRF) declines with age, and greater declines increase the risk for adverse health outcomes. Understanding factors that attenuate age-related decreases in CRF can help extend healthy life. We sought to determine the longitudinal associations of aerobic physical activity, muscle-strengthening activity (MSA), and adiposity with CRF.

METHODS

Study participants were enrolled in the Cooper Center Longitudinal Study and had three or more preventive medical examinations at the Cooper Clinic (Dallas, Texas) during 1987-2019. Aerobic activity and MSA were self-reported, and three measures of adiposity were clinically assessed: body mass index (BMI), body fat percentage, and waist circumference. CRF, expressed as metabolic equivalents (METs), was estimated by a maximal treadmill test. The longitudinal associations of aerobic activity, MSA, and adiposity with CRF were estimated using multivariable mixed linear regression models.

RESULTS

The study included 6105 participants who were followed for a median of 7.1 yr. Most participants were men (83.6%), and their average age at baseline was 47.0 (SD = 8.7) yr. Mean CRF at baseline was 12.2 (SD = 2.3) METs. Increasing aerobic activity (per 500 MET·min·wk -1 , β = 0.069, 95% confidence interval = 0.064-0.074 METs) or MSA (per days per week, β = 0.066, 95% confidence interval = 0.058-0.073 METs) was associated with increased CRF over time. Increasing BMI, body fat percentage, or waist circumference were each associated with decreased CRF over time.

CONCLUSIONS

These data offer longitudinal evidence on how changes in aerobic activity, MSA, and various measures of adiposity (beyond BMI) independently correlate with CRF over time. Healthy lifestyle behaviors that include increasing aerobic and MSA and limiting adiposity may positively influence the retention of fitness with age and improve downstream health outcomes.

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.

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.

Indicators of Obesity and Cardiorespiratory Fitness in Croatian Children

BACKGROUND/OBJECTIVES

The aim of this study is to investigate the relationship between CRF (cardiorespiratory fitness) and body composition, specifically obesity indicators, in a sample of schoolchildren from the continental and Adriatic regions of the Republic of Croatia. Given that Croatia ranks among the leading countries in Europe in terms of obesity, it is believed that there is a need to combat this condition starting from school age. The usefulness of cardiorespiratory fitness (CRF) lies in the fact that it is one of the indicators of children's overall health and is considered a measure of general health status. The findings will emphasize the need to determine CRF and BMI as important factors that should be addressed from early school years in order to prevent future cardiovascular diseases.

METHODS

The total sample consisted of 423 students, including 212 girls and 211 boys, from the continental and Adriatic regions of the Republic of Croatia, with an average age of 10.32 years. Body height was measured using a portable stadiometer, while body weight, body mass index (BMI), and body fat percentage were measured using a dual-frequency body composition analyzer (TANITA DC-360P) based on the principles of bioelectrical impedance. The WHR index was calculated as the ratio of waist to hips, while the WHtR index was calculated as the ratio of waist circumference to height. Cardiorespiratory fitness was assessed using the 20-meter multistage shuttle run test.

RESULTS

The results show that 25% of the participants were overweight, and 9% were obese. The ANOVA results indicate that the boys had significantly higher values for BMI, WC, HC, WHtR, and WHR, while the girls had a significantly higher body fat percentage (BF%). Additionally, the boys had better CRF, as they ran more meters in the 20-meter shuttle run test. The variance analysis revealed that the participants with normal body weight had significantly higher cardiorespiratory capacity values compared to overweight or obese students. Regression analysis showed statistical significance for the set of predictor variables, which were BMI indicators, on the criterion variable predicting cardiorespiratory fitness (CRF) in both genders. The coefficient of determination (R2) explained almost 22% of the shared variability in boys and 19% in girls. Statistically significant beta coefficients were found for body fat percentage (-0.60) in boys and (-0.98) in girls.

CONCLUSIONS

Body fat percentage (BF%) was shown to be a significant and useful predictor of cardiorespiratory fitness in school-aged boys and girls. Maintaining an optimal body weight along with high levels of CRF should be an important goal in promoting health among children and adolescents.

Genotypic Influences on Actuators of Aerobic Performance in Tactical Athletes

BACKGROUND

This study examines genetic variations in the systemic oxygen transport cascade during exhaustive exercise in physically trained tactical athletes. Research goal: To update the information on the distribution of influence of eleven polymorphisms in ten genes, namely ACE (rs1799752), AGT (rs699), MCT1 (rs1049434), HIF1A (rs11549465), COMT (rs4680), CKM (rs8111989), TNC (rs2104772), PTK2 (rs7460 and rs7843014), ACTN3 (rs1815739), and MSTN (rs1805086)-on the connected steps of oxygen transport during aerobic muscle work.

METHODS

251 young, healthy tactical athletes (including 12 females) with a systematic physical training history underwent exercise tests, including standardized endurance running with a 12.6 kg vest. Key endurance performance metrics were assessed using ergospirometry, blood sampling, and near-infrared spectroscopy of knee and ankle extensor muscles. The influence of gene polymorphisms on the above performance metrics was analyzed using Bayesian analysis of variance.

RESULTS

Subjects exhibited good aerobic fitness (maximal oxygen uptake (VO2max): 4.3 ± 0.6 L min-1, peak aerobic power: 3.6 W ± 0.7 W kg-1). Energy supply-related gene polymorphisms rs1799752, rs4680, rs1049434, rs7843014, rs11549465, and rs8111989 did not follow the Hardy-Weinberg equilibrium. Polymorphisms in genes that regulate metabolic and contractile features were strongly associated with variability in oxygen transport and metabolism, such as body mass-related VO2 (rs7843014, rs2104772), cardiac output (rs7460), total muscle hemoglobin content (rs7460, rs4680), oxygen saturation in exercised muscle (rs1049434), and respiration exchange ratio (rs7843014, rs11549465) at first or secondary ventilatory thresholds or VO2max. Moderate influences were found for mass-related power output.

CONCLUSIONS

The posterior distribution of effects from genetic modulators of aerobic metabolism and muscle contractility mostly confirmed prior opinions in the direction of association. The observed genetic effects of rs4680 and rs1049434 indicate a crucial role of dopamine- and lactate-modulated muscle perfusion and oxygen metabolism during running, suggesting self-selection in Swiss tactical athletes.

Lifelong physiology of a former marathon world-record holder: the pros and cons of extreme cardiac remodeling

In a 77-year-old former world-record-holding male marathoner (2:08:33.6), this study sought to investigate the impact of lifelong intensive endurance exercise on cardiac structure, function, and the trajectory of functional capacity (determined by maximal oxygen consumption, V̇o2max) throughout the adult lifespan. As a competitive runner, our athlete (DC) reported performing up to 150-300 miles/wk of moderate-to-vigorous exercise and sustained 10-15 h/wk of endurance exercise after retirement from competition. DC underwent maximal cardiopulmonary exercise testing in 1970 (aged 27 yr), 1991 (aged 49 yr), and 2020 (aged 77 yr) to determine V̇o2max. At his evaluation in 2020, DC also underwent comprehensive cardiac assessments including resting echocardiography, and resting and exercise cardiac magnetic resonance to quantify cardiac structure and function at rest and during peak supine exercise. DC's V̇o2max showed minimal change from 27 yr (69.7 mL/kg/min) to 49 yr (68.1 mL/kg/min), although it eventually declined by 36% by the age of 77 yr (43.6 mL/kg/min). DC's V̇o2max at 77 yr, was equivalent to the 50th percentile for healthy 20- to 29-yr-old males and 2.4 times the requirement for maintaining functional independence. This was partly due to marked ventricular dilatation (left-ventricular end-diastolic volume: 273 mL), which facilitates a large peak supine exercise stroke volume (200 mL) and cardiac output (22.2 L/min). However, at the age of 78 yr, DC developed palpitations and fatigue and was found to be in atrial fibrillation requiring ablation procedures to revert his heart to sinus rhythm. Overall, this life study of a world champion marathon runner exemplifies the substantial benefits and potential side effects of many decades of intense endurance exercise.NEW & NOTEWORTHY This life study of a 77-yr-old former world champion marathon runner exemplifies the impact of lifelong high-volume endurance exercise on functional capacity (V̇o2max equivalent to a 20- to 29-yr-old), partly due to extreme ventricular remodeling that facilitates a large cardiac output during exercise despite reduced maximal heart rate. Although it is possible that this extreme remodeling may contribute to developing atrial fibrillation, the net benefits of extreme exercise throughout this athlete's lifespan favor increased health span and expected longevity.

Insulin sensitivity and skeletal muscle mitochondrial respiration in Black and White women with obesity

OBJECTIVES

Non-Hispanic black women (BW) have a greater risk of type 2 diabetes (T2D) and insulin resistance (IR) compared to non-Hispanic white women (WW). The mechanisms leading to these differences are not understood, and it is unclear whether synergistic effects of race and obesity impact disease risk. To understand the interaction of race and weight, hepatic and peripheral IR were compared in WW and BW with and without obesity.

METHODS

Hepatic and peripheral IR was measured by a labeled, hyperinsulinemic-euglycemic clamp in BW (n=32) and WW (n=32) with and without obesity. Measurements of body composition, cardiorespiratory fitness, and skeletal muscle (SM) respiration were completed. Data were analyzed by mixed model ANOVA.

RESULTS

Subjects with obesity had greater hepatic and peripheral IR and lower SM respiration (P<0.001). Despite 14% greater insulin (P=0.066), BW tended to have lower peripheral glucose disposal (Rd; P=0.062), which was driven by women without obesity (P=0.002). BW had significantly lower glucose production (P=0.005), hepatic IR (P=0.024), and maximal coupled and uncoupled respiration (P<0.001) than WW. Maximal coupled and uncoupled SM mitochondrial respiration was strongly correlated with peripheral and hepatic IR (P<0.01).

CONCLUSION

While BW without obesity had lower Rd than WW, race and obesity did not synergistically impact peripheral IR. Paradoxically, WW with obesity had greater hepatic IR compared to BW. Relationships between SM respiration and IR persisted across a range of body weight. These data provide support for therapies in BW, like exercise, that improve SM mitochondrial respiration to reduce IR and T2D risk.

Outrunning the grim reaper: longevity of the first 200 sub-4 min mile male runners

OBJECTIVES

To determine the impact of running a sub-4 min mile on longevity. It was hypothesised that there would be an increase in longevity for runners who successfully completed a sub-4 min mile compared with the general population.

METHODS

As part of this retrospective cohort study, the Sub-4 Alphabetic Register was used to extract the first 200 athletes to run a sub-4 min mile. Each runner's date of birth, date of their first successful mile attempt, current age (if alive) or age at death was compared with the United Nations Life Tables to determine the difference in each runner's current age or age at death with their country of origin-specific life expectancy.

RESULTS

Of the first 200 sub-4 min mile runners (100% male), 60 were dead (30%) and 140 were still alive. Sub-4 min mile runners lived an average of 4.7 years beyond their predicted life expectancy (95% CI 4.7 to 4.8). When accounting for the decade of completion (1950s, 1960s or 1970s), the longevity benefits were 9.2 years (n=22; 95% CI 8.3 to 10.1), 5.5 years (n=88; 95% CI 5.3 to 5.7) and 2.9 years (n=90; 95% CI 2.7 to 3.1), respectively.

CONCLUSION

Sub-4 min mile runners have increased longevity compared with the general population, thereby challenging the notion that extreme endurance exercise may be detrimental to longevity.

Cardiorespiratory fitness is a strong and consistent predictor of morbidity and mortality among adults: an overview of meta-analyses representing over 20.9 million observations from 199 unique cohort studies

OBJECTIVE

To examine and summarise evidence from meta-analyses of cohort studies that evaluated the predictive associations between baseline cardiorespiratory fitness (CRF) and health outcomes among adults.

DESIGN

Overview of systematic reviews.

DATA SOURCE

Five bibliographic databases were searched from January 2002 to March 2024.

RESULTS

From the 9062 papers identified, we included 26 systematic reviews. We found eight meta-analyses that described five unique mortality outcomes among general populations. CRF had the largest risk reduction for all-cause mortality when comparing high versus low CRF (HR=0.47; 95% CI 0.39 to 0.56). A dose-response relationship for every 1-metabolic equivalent of task (MET) higher level of CRF was associated with a 11%-17% reduction in all-cause mortality (HR=0.89; 95% CI 0.86 to 0.92, and HR=0.83; 95% CI 0.78 to 0.88). For incident outcomes, nine meta-analyses described 12 unique outcomes. CRF was associated with the largest risk reduction in incident heart failure when comparing high versus low CRF (HR=0.31; 95% CI 0.19 to 0.49). A dose-response relationship for every 1-MET higher level of CRF was associated with a 18% reduction in heart failure (HR=0.82; 95% CI 0.79 to 0.84). Among those living with chronic conditions, nine meta-analyses described four unique outcomes in nine patient groups. CRF was associated with the largest risk reduction for cardiovascular mortality among those living with cardiovascular disease when comparing high versus low CRF (HR=0.27; 95% CI 0.16 to 0.48). The certainty of the evidence across all studies ranged from very low-to-moderate according to Grading of Recommendations, Assessment, Development and Evaluations.

CONCLUSION

We found consistent evidence that high CRF is strongly associated with lower risk for a variety of mortality and incident chronic conditions in general and clinical populations.

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.

Parental cardiorespiratory fitness influences early life energetics and metabolic health

High cardiorespiratory fitness (CRF) is associated with a reduced risk of metabolic disease and is linked to superior mitochondrial respiratory function. This study investigated how intrinsic CRF affects bioenergetics and metabolic health in adulthood and early life. Adult rats selectively bred for low and high running capacity [low capacity runners (LCR) and high capacity runners (HCR), respectively] underwent metabolic phenotyping before mating. Weanlings were evaluated at 4-6 wk of age, and whole body energetics and behavior were assessed using metabolic cages. Mitochondrial respiratory function was assessed in permeabilized tissues through high-resolution respirometry. Proteomic signatures of adult and weanling tissues were determined using mass spectrometry. The adult HCR group exhibited lower body mass, improved glucose tolerance, and greater physical activity compared with the LCR group. The adult HCR group demonstrated higher mitochondrial respiratory capacities in the soleus and heart compared with the adult LCR group, which coincided with a greater abundance of proteins involved in lipid catabolism. HCR and LCR weanlings had similar body mass, but HCR weanlings displayed reduced adiposity. In addition, HCR weanlings exhibited better glucose tolerance and higher physical activity levels than LCR weanlings. Higher respiratory capacities were observed in the soleus, heart, and liver tissues of HCR weanlings compared with LCR weanlings, which were not owed to greater mitochondrial content. Proteomic analyses indicated a greater potential for lipid oxidation in the contractile muscles of HCR weanlings. In conclusion, offspring born to parents with high CRF possess an enhanced capacity for lipid catabolism and oxidative phosphorylation, thereby influencing metabolic health. These findings highlight that intrinsic CRF shapes the bioenergetic phenotype with implications for metabolic resilience in early life.NEW & NOTEWORTHY Inherited cardiorespiratory fitness (CRF) influences early life bioenergetics and metabolic health. Higher intrinsic CRF was associated with reduced adiposity and improved glucose tolerance in early life. This metabolic phenotype was accompanied by greater mitochondrial respiratory capacity in skeletal muscle, heart, and liver tissue. Proteomic profiling of these three tissues further revealed potential mechanisms linking inherited CRF to early life metabolism.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 2: physiological measurements

In this, the second of four historical reviews on human thermoregulation during exercise, we examine the research techniques developed by our forebears. We emphasise calorimetry and thermometry, and measurements of vasomotor and sudomotor function. Since its first human use (1899), direct calorimetry has provided the foundation for modern respirometric methods for quantifying metabolic rate, and remains the most precise index of whole-body heat exchange and storage. Its alternative, biophysical modelling, relies upon many, often dubious assumptions. Thermometry, used for >300 y to assess deep-body temperatures, provides only an instantaneous snapshot of the thermal status of tissues in contact with any thermometer. Seemingly unbeknownst to some, thermal time delays at some surrogate sites preclude valid measurements during non-steady state conditions. To assess cutaneous blood flow, immersion plethysmography was introduced (1875), followed by strain-gauge plethysmography (1949) and then laser-Doppler velocimetry (1964). Those techniques allow only local flow measurements, which may not reflect whole-body blood flows. Sudomotor function has been estimated from body-mass losses since the 1600s, but using mass losses to assess evaporation rates requires precise measures of non-evaporated sweat, which are rarely obtained. Hygrometric methods provide data for local sweat rates, but not local evaporation rates, and most local sweat rates cannot be extrapolated to reflect whole-body sweating. The objective of these methodological overviews and critiques is to provide a deeper understanding of how modern measurement techniques were developed, their underlying assumptions, and the strengths and weaknesses of the measurements used for humans exercising and working in thermally challenging conditions.

The Effect of Downhill Running on Quadriceps Muscle in Growth-Restricted Mice

INTRODUCTION

Growth restriction (GR) reduces ribosome abundance and skeletal muscle mass in mice. A reduction in skeletal muscle mass increases the risk of frailty and is associated with high morbidity and mortality rates. As eccentric type exercise increases muscle mass, this investigation aimed to determine if eccentric loading of skeletal muscle via downhill running (DHR) increased muscle mass in GR mice.

METHODS

Mice were growth-restricted either gestational undernutrition (GUN, n = 8 litters), postnatal undernutrition (PUN, n = 8 litters), or were not restricted (CON, n = 8 litters) via a validated cross-fostering nutritive model. On postnatal day (PN) 21, all mice were weaned to a healthy diet, isolating the period of GR to early life as seen in humans. At PN45, mice were assigned to either a DHR (CON, n = 4 litters; GUN, n = 4 litters; PUN, n = 4 litters) or sedentary (SED: CON, n = 4 litters; GUN, n = 4 litters; PUN, n = 4 litters) group. Downhill running (16% decline: 18 m·min -1 ) was performed in 30-min bouts, three times per week, for 12 wk on a rodent treadmill. At PN129, the quadriceps femoris was dissected and evaluated for mass, myofiber size and type, and molecular markers of growth.

RESULTS

Following training, CON-DHR mice having larger cells than CON-SED, GUN-SED, PUN-SED, and PUN-DHR mice ( P < 0.05). The PUN group (as compared with CON) had reduced body mass ( P < 0.001), upstream binding factor abundance ( P = 0.012), phosphor-mTOR ( P < 0.001), and quadriceps mass ( P = 0.02). The GUN and PUN groups had increased MuRF1 abundance ( P < 0.001) compared with CON ( P < 0.001).

CONCLUSIONS

The blunted response to training suggests GR mice may have anabolic resistance when exposed to eccentric type exercise.

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.

Comparison of ventilatory and oxygen consumption measurements of yearling Thoroughbred colts and fillies exercising unridden on an all-weather track

Sex effects on ventilatory and oxygen consumption (V̇O2) measurements during exercise have been identified in humans. This study's aim was to evaluate the hypothesis that there are sex effects on ventilatory and V̇O2 measurements in exercising, untrained yearling Thoroughbreds (Tb). Forty-one Tbs (16 colts, 25 fillies; 19.8 ± 1.4 months old) were recruited. Physiological, ventilatory and exercise data were gathered from horses exercising unridden at high intensity on an all-weather track from a global positioning-heart rate unit and a portable ergospirometry system. Data were analysed with an unpaired Student's t-test and the Benjamini-Hochberg correction for multiple testing (P ≤ 0.05 significant). Mean bodyweight (BW, P = 0.002) and wither height (P = 0.04) were greater for colts than fillies. There were no differences in physiological and exercise data and absolute peak V̇O2 between groups. However, fillies had a higher mass specific peak V̇O2 (P = 0.03) than colts (121.5 ± 21.6 mL/kg.min vs. 111.9 ± 27.4 mL/kg.min). The peak breathing frequency was greater for fillies (P < 0.001) while the peak inspiratory (P < 0.001) and expiratory air flow (P < 0.001), peak expiratory tidal volume (VTE; P < 0.001) and peak minute ventilation (V̇E; P = 0.01) were greater for colts; there were no differences for peak VTE and V̇E when adjusted for BW. Differences in BW explain the differences in mass specific peak V̇O2 between groups. Given their morphological differences, it is likely that lung volumes and airway diameters are smaller for fillies, resulting in greater resistance and lower air flows and volumes. Further research is required to investigate the ventilatory differences and how they may change with maturation and impact performance.

Association of ACTN3 R577X Polymorphism with Elite Basketball Player Status and Training Responses

The α-actinin-3 (ACTN3) gene rs1815739 (C/T, R577X) polymorphism is a variant frequently associated with athletic performance among different populations. However, there is limited research on the impact of this variant on athlete status and physical performance in basketball players. Therefore, the aim of this study was twofold: (1) to determine the association of ACTN3 rs1815739 polymorphism with changes in physical performance in response to six weeks of training in elite basketball players using 30 m sprint and Yo-Yo Intermittent Recovery Test Level 2 (IR 2) tests, and (2) to compare ACTN3 genotype and allelic frequencies between elite basketball players and controls. The study included a total of 363 individuals, comprising 101 elite basketball players and 262 sedentary individuals. Genomic DNA was isolated from oral epithelial cells or leukocytes, and genotyping was performed by real-time PCR using KASP genotyping method or by microarray analysis. We found that the frequency of the ACTN3 rs1815739 XX genotype was significantly lower in basketball players compared to controls (10.9 vs. 21.4%, p = 0.023), suggesting that RR/RX genotypes were more favorable for playing basketball. Statistically significant (p = 0.045) changes were observed in Yo-Yo IRT 2 performance measurement tests in basketball players with the RR genotype only. In conclusion, our findings suggest that the carriage of the ACTN3 rs1815739 R allele may confer an advantage in basketball.

Epigenetic Analysis of the Dopamine Transporter Gene DAT1 with a Focus on Personality Traits in Athletes

Human phenotypes (traits) are determined by the selective use of a person's unique genotype (DNA sequence), following exposure to environmental stimuli, such as exercise. Inducing profound changes in epigenetics may be an underlying factor of the beneficial effects of exercise. This study aimed to investigate the association between methylation in the promoter region of the DAT1 gene and personality traits measured by the NEO-FFI questionnaire in a group of athletes. The study group included 163 athletes, and the control group consisted of 232 non-athletes. The obtained results show several significant differences between the studied groups of subjects. The Extraversion scale and the Conscientiousness scale results of the NEO-FFI are significantly higher in the group of athletes compared to controls. The total methylation and the number of methylated islands in the promoter region of the DAT1 gene are higher in the study group. Pearson's linear correlation between the total methylation, the number of methylated islands and the NEO-FFI shows significant results for the Extraversion and Agreeability scales. The total methylation and the number of methylated islands in the promoter region of the DAT1 gene are higher in the study group. Pearson's linear correlation between the total methylation, the number of methylated islands and the NEO-FFI shows significant results for the Extraversion and Agreeability scales. Our analysis of the methylation status of individual CpG sites revealed a new direction of research into the biological aspects of regulating dopamine release and personality traits in people practicing sports.

The PPARGC1A Gly482Ser polymorphism is associated with elite long-distance running performance

Success in long-distance running relies on multiple factors including oxygen utilisation and lactate metabolism, and genetic associations with athlete status suggest elite competitors are heritably predisposed to superior performance. The Gly allele of the PPARGC1A Gly482Ser rs8192678 polymorphism has been associated with endurance athlete status and favourable aerobic training adaptations. However, the association of this polymorphism with performance amongst long-distance runners remains unclear. Accordingly, this study investigated whether rs8192678 was associated with elite status and competitive performance of long-distance runners. Genomic DNA from 656 Caucasian participants including 288 long-distance runners (201 men, 87 women) and 368 non-athletes (285 men, 83 women) was analysed. Medians of the 10 best UK times (Top10) for 10 km, half-marathon and marathon races were calculated, with all included athletes having personal best (PB) performances within 20% of Top10 (this study's definition of "elite"). Genotype and allele frequencies were compared between athletes and non-athletes, and athlete PB compared between genotypes. There were no differences in genotype frequency between athletes and non-athletes, but athlete Ser allele carriers were 2.5% faster than Gly/Gly homozygotes (p = 0.030). This study demonstrates that performance differences between elite long-distance runners are associated with rs8192678 genotype, with the Ser allele appearing to enhance performance.

Changes in Cardiorespiratory Fitness and Survival in Patients With or Without Cardiovascular Disease

BACKGROUND

The association between cardiorespiratory fitness (CRF) and mortality risk is based mostly on 1 CRF assessment. The impact of CRF change on mortality risk is not well-defined.

OBJECTIVES

This study sought to evaluate changes in CRF and all-cause mortality.

METHODS

We assessed 93,060 participants aged 30-95 years (mean 61.3 ± 9.8 years). All completed 2 symptom-limited exercise treadmill tests, 1 or more years apart (mean 5.8 ± 3.7 years) with no evidence of overt cardiovascular disease. Participants were assigned to age-specific fitness quartiles based on peak METS achieved on the baseline exercise treadmill test. Additionally, each CRF quartile was stratified based on CRF changes (increase, decrease, no change) observed on the final exercise treadmill test. Multivariable Cox models were used to estimate HRs and 95% CIs for all-cause mortality.

RESULTS

During a median follow-up of 6.3 years (IQR: 3.7-9.9 years), 18,302 participants died with an average yearly mortality rate of 27.6 events per 1,000 person-years. In general, changes in CRF ≥1.0 MET were associated with inverse and proportionate changes in mortality risk regardless of baseline CRF status. For example, a decline in CRF of >2.0 METS was associated with a 74% increase in risk (HR: 1.74; 95% CI: 1.59-1.91) for low-fit individuals with CVD, and 69% increase (HR: 1.69; 95% CI: 1.45-1.96) for those without CVD.

CONCLUSIONS

Changes in CRF reflected inverse and proportional changes in mortality risk for those with and without CVD. The impact of relatively small CRF changes on mortality risk has considerable clinical and public health significance.

The association between rheumatoid arthritis and reduced estimated cardiorespiratory fitness is mediated by physical symptoms and negative emotions: a cross-sectional study

OBJECTIVES

Persons with rheumatoid arthritis (RA) have lower cardiorespiratory fitness (CRF) than healthy individuals. We sought to identify variables explaining the association between RA status and reduced CRF.

METHODS

RA patients recruited from two Norwegian hospitals and blood donors recruited as controls filled in questionnaires about physical activity, physical symptoms, and psychological factors. Estimated CRF (eCRF) was calculated from non-exercise models. The relationship between RA status and reduced eCRF was explored with structural equation modelling. The latent variables physical symptoms (based on morning stiffness, joint pain, and pain in neck, back, or hips) and negative emotions (based on Hospital Anxiety and Depression Scale's Depression score and Cohen's perceived stress scale) were included as possible mediators between RA status and eCRF in separate and combined models adjusted for age and sex.

RESULTS

Two-hundred-and-twenty-seven RA patients and 300 controls participated. The patients were older and had lower eCRF than controls (age- and sex-adjusted mean difference: 1.7 mL/kg/min, p=0.002). Both latent variables were significant mediators of the association between RA and reduced eCRF when included in separate models. The latent variables mediated 74% of the total effect of RA on eCRF in the combined model. Standardized coefficients: direct effect of RA -0.024 (p=0.46), indirect effect through physical symptoms -0.034 (p=0.051), and indirect effect through negative emotions -0.034 (p=0.039).

CONCLUSION

Both physical symptoms and negative emotions mediated the association between RA and reduced eCRF with similar effect sizes. To successfully increase CRF in RA patients, both physical and psychological factors should be addressed. Key Points • The RA patients in the present study had 1.7 mL/kg/min lower mean estimated cardiorespiratory fitness (CRF) compared to healthy controls. • Mediation analysis demonstrated that physical symptoms and negative emotions mediated 74% of the total negative effect of RA on estimated CRF in a combined, adjusted model. • This suggests that both physical and psychological factors should be addressed when supporting RA patients in improving their CRF.

Utility of a Physical Fitness Score in Screening for Chronic Diseases

We developed a new Physical Score (PS) consisting of comprehensive physical fitness indicators and elucidated the association between the resultant PS and metabolic diseases, i.e., diabetes, hypertension, dyslipidemia, fatty liver, and metabolic syndrome (MetS), among Japanese. Analyzed were 49,850 persons (30,039 men) aged 30 to 69 y who underwent physical fitness tests. Principal component analysis was performed on the correlation matrix of the physical fitness test results (relative grip strength, single-leg balance with eyes closed, and forward bending) according to sex and age. We defined the PS as the first principal component score. A formula was developed for various age groups comprised of men and women from 30 to 69 years of age from which the PS for each age and sex was calculated. The PS for both men and women was normally distributed with a value of 0 ± 1.15-1.16. Multivariate logistic regression analysis showed that the risk of metabolic diseases increased approximately 1.1-1.6 times per each 1-point reduction in the PS. The association between PS and MetS was particularly strong in that a 1-point reduction in the PS increased the risk of MetS by 1.54 times (95% confidence interval 1.46 to 1.62) in men and by 1.21 times (1.15 to 1.28) in women. The association between a lower PS and disease risk was stronger in younger men for fatty liver and in older men for MetS. Conversely, in women, the association between a lower PS and disease risk was stronger in older women for fatty liver and in younger women for MetS. For diabetes, hypertension, and dyslipidemia, the change in the impact of PS reductions across age groups was small. The PS is a useful and simple non-invasive tool for screening Japanese people for metabolic diseases.

A Nonexercise Prediction of Peak Oxygen Uptake for Patients With Cardiovascular Disease: DATA FROM THE FITNESS REGISTRY AND THE IMPORTANCE OF EXERCISE INTERNATIONAL DATABASE (FRIEND)

PURPOSE

Nonexercise predictions of peak oxygen uptake (V˙ o2peak ) are used clinically, yet current equations were developed from cohorts of apparently healthy individuals and may not be applicable to individuals with cardiovascular disease (CVD). Our purpose was to develop a CVD-specific nonexercise prediction equation for V˙ o2peak .

METHODS

Participants were from the Fitness Registry and Importance of Exercise International Database (FRIEND) with a diagnosis of coronary artery bypass surgery (CABG), myocardial infarction (MI), percutaneous coronary intervention (PCI), or heart failure (HF) who met maximal effort criteria during a cardiopulmonary exercise test (n = 15 997; 83% male; age 63.1 ± 10.4 yr). The cohort was split into development (n = 12 798) and validation groups (n = 3199). The prediction equation was developed using regression analysis and compared with a previous equation developed on a healthy cohort.

RESULTS

Age, sex, height, weight, exercise mode, and CVD diagnosis were all significant predictors of V˙ o2peak . The regression equation was:V˙ o2peak (mL · kg -1 · min -1 ) = 16.18 - (0.22 × age [yr]) + (3.63 × sex [male = 1; female = 0]) + (0.14 × height [cm]) - (0.12 × weight [kg]) + (3.62 × mode [treadmill = 1; cycle = 0]) - (2.70 × CABG [yes = 1, no = 0]) - (0.31 × MI [yes = 1, no = 0]) + (0.37 × PCI [yes = 1, no = 0]) - (4.47 × HF [yes = 1, no = 0]). Adjusted R 2 = 0.43; SEE = 4.75 mL · kg -1 · min -1 .Compared with measured V˙ o2peak in the validation group, percent predicted V˙ o2peak was 141% for the healthy cohort equation and 100% for the CVD-specific equation.

CONCLUSIONS

The new equation for individuals with CVD had lower error between measured and predicted V˙ o2peak than the healthy cohort equation, suggesting population-specific equations are needed for predicting V˙ o2peak ; however, errors associated with nonexercise prediction equations suggest V˙ o2peak should be directly measured whenever feasible.

Percentage of Age-Predicted Cardiorespiratory Fitness May Be a Stronger Risk Indicator for Incident Type 2 Diabetes Than Absolute Levels of Cardiorespiratory Fitness

PURPOSE

There are inverse and independent associations between cardiorespiratory fitness (CRF) and several adverse cardiometabolic outcomes. The percentage of age-predicted CRF (%age-predicted CRF) is comparable to absolute CRF as a risk indicator for some of these outcomes, but the association between %age-predicted CRF and risk of type 2 diabetes (T2D) has not been previously investigated. We aimed to assess the association between %age-predicted CRF and T2D in a prospective cohort study.

METHODS

Cardiorespiratory fitness, as measured directly by peak oxygen uptake, was assessed in 1901 men aged 42-60 yr who underwent cardiopulmonary exercise testing. The age-predicted CRF estimated from a regression equation for age was converted to %age-predicted CRF using (achieved CRF/age-predicted CRF) × 100. Hazard ratios (95% CI) were estimated for T2D.

RESULTS

During a median follow-up of 26.8 yr, 227 T2D cases were recorded. The risk of T2D decreased continuously with increasing %age-predicted CRF ( P value for nonlinearity = .30). A 1-SD increase in %age-predicted CRF was associated with a decreased risk of T2D in analysis adjusted for established risk factors (HR = 0.68: 95% CI, 0.59-0.79). The corresponding adjusted risk was (HR = 0.51: 95% CI, 0.35-0.75) comparing extreme tertiles of %age-predicted CRF. The respective estimates for the association between absolute CRF and T2D were-HR (95% CI)-0.71 (0.60-0.83) and 0.64 (0.44-0.95).

CONCLUSIONS

Percentage of age-predicted CRF is linearly, inversely, and independently associated with the risk of incident T2D and may be a stronger risk indicator for T2D compared to absolute CRF in a general population of middle-aged and older men.

Cardiorespiratory fitness as a vital sign of CVD risk in the COVID-19 era

The severe health consequences of the corona virus disease 2019 (COVID-19) pandemic have been exacerbated by the prevalence of cardiovascular disease (CVD) risk factors, such as physical inactivity, obesity, hypertension, and diabetes. Further, policy decisions during the pandemic augmented unhealthy lifestyle behaviors and health inequalities, likely increasing the global disease burden. Cardiorespiratory fitness (CRF) is a well-established biomarker associated with CVD risk. Emerging data demonstrate that high CRF offers some protection against severe outcomes from COVID-19 infection, highlighting the importance of CRF for population health and the potential for limiting the severity of future pandemics. CRF is best assessed by cardiopulmonary exercise testing (CPET), which will be an important tool for understanding the prolonged pathophysiology of COVID-19, the emergence of long-COVID, and the lasting effects of COVID-19 on CVD risk. Utilization of CRF and CPET within clinical settings should become commonplace because of lessons learned from the COVID-19 pandemic.

Body surface scan anthropometrics are related to cardiorespiratory fitness in the general population

The assessment of cardiorespiratory fitness (CRF) is an important tool for prognosis evaluation of cardiovascular events. The gold standard to measure CRF is cardiopulmonary exercise testing (CPET) to determine peak oxygen uptake (VO2peak). However, CPET is not only time consuming but also expensive and is therefore not widely applicable in daily practice. The aim of our study was to analyze, whether and which anthropometric markers derived from a 3D body scanner were related to VO2peak in a general population-based study. We analyzed data (SHIP-START-3) from 3D body scanner and CPET of 1035 subjects (529 women; 51.1%, age range 36-93). A total of 164 anthropometric markers were detected with the 3D body scanner VITUS Smart XXL using the software AnthroScan Professional. Anthropometric measurements were standardized and associated with CRF by sex-stratified linear regression models adjusted for age and height. Anthropometric markers were ranked according to the  - log- p values derived from these regression models. In men a greater left and right thigh-knee-ratio, a longer forearm-fingertip length, a greater left thigh circumference and greater left upper arm circumference were most strongly associated with a higher VO2peak. In women a greater left and right thigh circumference, left calf circumference, thigh thickness and right calf circumference were most strongly associated with a higher VO2peak. The detected VO2peak-related anthropometric markers could be helpful in assessing CRF in clinical routine. Commonly used anthropometric markers, e.g. waist and hip circumference, were not among the markers associated with VO2peak.

Cardiorespiratory Fitness and the Risk of All-Cause, Cardiovascular and Cancer Mortality in Men with Hypercholesterolemia

Background: Whether higher cardiorespiratory fitness (CRF) confers protection against cardiovascular disease (CVD) in individuals with manifest hypercholesterolemia is poorly understood. Methods: Participants were 8920 men aged 20−82 years with hypercholesterolemia but no history of CVD and/or cancer and who received a preventive examination at the Cooper Clinic in Dallas, TX, USA, during 1974−2001. CRF was quantified as maximal treadmill test duration and was grouped for analysis as low, moderate, or high based on the traditional Aerobics Center Longitudinal Study cutpoints. Using Cox regression analyses, we computed hazard ratios and 95% confidence intervals for risk of mortality based on CRF. Results: During an average of 17 years of follow-up, 329 CVD and 290 cancer deaths occurred. After control for baseline age, examination year, body mass index, total cholesterol, smoking, alcohol intake, physical activity, hypertension, diabetes, and parental history of CVD, hazard ratios (95% confidence interval) for CVD deaths across moderate and high categories of CRF (with low fit as referent) were: 0.66 (0.50−0.87) and 0.55 (0.39−0.79), respectively. There was an inverse association between CRF and CVD death among normal-weight (trend p < 0.0001), younger (<60 y, trend p = 0.01), and inactive men (trend p = 0.002). However, no significant association was found between CRF and cancer mortality. Conclusions: Among men with hypercholesterolemia, higher CRF was associated with a lower risk of dying from CVD independent of other clinical risk factors. Our findings underscored the importance of promoting CRF in the primary prevention of CVD in patients with hypercholesterolemia.

The association of cardiorespiratory fitness and the risk of hypertension: a systematic review and dose-response meta-analysis

Established evidence has indicated a negative correlation between cardiorespiratory fitness (CRF) and hypertension risk. In this study, we performed a meta-analysis to investigate the categorical and dose-response relationship between CRF and hypertension risk and the effects of CRF changes on hypertension risk reduction. The PubMed, Web of Science, and Embase databases were searched for relevant studies. The summarized relative risk (RR) and 95% confidence interval (95% CI) were estimated using the DerSimonian and Laird random effect model, and the dose-response relationship between CRF and hypertension risk was characterized using generalized least-squares regression and restricted cubic splines. Nine cohorts describing 110,638 incident hypertension events among 1,618,067 participants were included in this study. Compared with the lowest category of CRF, the RR of hypertension was 0.63 (95% CI: 0.56-0.70) for the highest CRF category and 0.85 (95% CI: 0.80-0.91) for the moderate category of CRF. For a 1-metabolic equivalent increment in CRF, the pooled RR of hypertension was 0.92 (95% CI: 0.90-0.94) in the total population. The RR of hypertension was 0.71 (95% CI: 0.64-0.79) for participants with CRF increased compared with those whose CRF was decreased over time. In conclusion, our meta-analysis supports the widely held notion of a negative dose-dependent relationship between CRF and hypertension risk.

Getting Fit to Counteract Cognitive Aging: Evidence and Future Directions

Physical activity has shown tremendous promise for counteracting cognitive aging, but also tremendous variability in cognitive benefits. We describe evidence for how exercise affects cognitive and brain aging, and whether cardiorespiratory fitness is a key factor. We highlight a brain network framework as a valuable paradigm for the mechanistic insight needed to tailor physical activity for cognitive benefits.

Interindividual variation in maximum aerobic metabolism varies with gill morphology and myocardial bioenergetics

This study asked whether interindividual variation in maximum and standard aerobic metabolic rates of the Gulf killifish, Fundulus grandis, correlate with gill morphology and cardiac mitochondrial bioenergetics, traits reflecting critical steps in the O2 transport cascade from the environment to the tissues. Maximum metabolic rate (MMR) was positively related to body mass, total gill filament length, and myocardial oxygen consumption during maximum oxidative phosphorylation (multiple R2=0.836). Standard metabolic rate (SMR) was positively related to body mass, total gill filament length, and myocardial oxygen consumption during maximum electron transport system activity (multiple R2=0.717). After controlling for body mass, individuals with longer gill filaments, summed over all gill arches, or greater cardiac respiratory capacity had higher whole-animal metabolic rates. The overall model fit and the explanatory power of individual predictor variables were better for MMR than for SMR, suggesting that gill morphology and myocardial bioenergetics are more important in determining active rather than resting metabolism. After accounting for body mass, heart ventricle mass was not related to variation in MMR or SMR, indicating that the quality of the heart (i.e., the capacity for mitochondrial metabolism) was more influential than heart size. Finally, the myocardial oxygen consumption required to offset the dissipation of the transmembrane proton gradient in the absence of ATP synthesis was not correlated with either MMR or SMR. The results support the idea that interindividual variation in aerobic metabolism, particularly maximum metabolic rate, is associated with variation in specific steps in the O2 transport cascade.

Fitness and arterial stiffness in healthy aging: Modifiable cardiovascular risk factors contribute to altered default mode network patterns during executive function

Increases in cardiovascular risks such as high blood pressure and low physical fitness have been independently associated with altered default mode network (DMN) activation patterns in healthy aging. However, cardiovascular risk is a multidimensional health problem. Therefore, we need to investigate multiple cardiovascular risk factors and their contributions to cognition and DMN activations in older adults, which has not yet been done. The current fMRI study examined contributions of two common modifiable cardiovascular risk factors (arterial stiffness and physical fitness) on DMN activations involved during random n-back, a task of executive functioning and working memory, in older adults. The results how that high cardiovascular risk of either increased arterial stiffness or decreased fitness independently contributed to worse task performance and reduced deactivations in two DMN regions: the anterior and posterior cingulate cortices. We then examined not only the potential interaction between the two risk factors, but also their additive (i.e., combined) effect on performance and DMN deactivations. A significant interaction between the two cardiovascular risk factors was observed on performance, with arterial stiffness moderating the relationship between physical fitness and random n-back accuracy. The additive effect of the two factors on task performance was driven by arterial stiffness. Arterial stiffness was also found to be the driving factor when the additive effect of the two risk factors was examined on DMN deactivations. However, in posterior cingulate cortex, a hub region of the DMN, the additive effect on its deactivation was significantly higher than the effect of each risk factor alone. These results suggest that the effects of cardiovascular risks on the aging brain are complicated and multi-dimensional, with arterial stiffness moderating or driving the combined effects on performance and anterior DMN deactivations, but physical fitness contributing additional effect to posterior DMN deactivation during executive functioning.

The HERITAGE Family Study: A Review of the Effects of Exercise Training on Cardiometabolic Health, with Insights into Molecular Transducers

The aim of the HERITAGE Family Study was to investigate individual differences in response to a standardized endurance exercise program, the role of familial aggregation, and the genetics of response levels of cardiorespiratory fitness and cardiovascular disease and diabetes risk factors. Here we summarize the findings and their potential implications for cardiometabolic health and cardiorespiratory fitness. It begins with overviews of background and planning, recruitment, testing and exercise program protocol, quality control measures, and other relevant organizational issues. A summary of findings is then provided on cardiorespiratory fitness, exercise hemodynamics, insulin and glucose metabolism, lipid and lipoprotein profiles, adiposity and abdominal visceral fat, blood levels of steroids and other hormones, markers of oxidative stress, skeletal muscle morphology and metabolic indicators, and resting metabolic rate. These summaries document the extent of the individual differences in response to a standardized and fully monitored endurance exercise program and document the importance of familial aggregation and heritability level for exercise response traits. Findings from genomic markers, muscle gene expression studies, and proteomic and metabolomics explorations are reviewed, along with lessons learned from a bioinformatics-driven analysis pipeline. The new opportunities being pursued in integrative -omics and physiology have extended considerably the expected life of HERITAGE and are being discussed in relation to the original conceptual model of the study.

Amaral S, Buzalaf MAR. Effect of Physical Exercise and Genetic Background on Glucose Homeostasis and Liver/Muscle Proteomes in Mice

We compared the parameters related to glucose homeostasis, and liver and muscle proteomes in fluorosis-susceptible (A/J; S) and fluorosis-resistant (129P3/J; R) mice in response to fluoride (F) exposure and exercise. Ninety male mice (45 R-mice and 45 S-mice) were randomized into three groups: (SI; RI) No-F, No-Exercise, (SII; RII) 50 ppm F, No-Exercise, (SIII; RIII) 50 ppm F, Exercise. Overall, mean F concentrations in the plasma and femur were significantly higher in R-mice compared with S-mice. In R-mice, exercise resulted in an increase in F accumulation in the femur. In S-mice, the mean plasma glucose level was significantly higher in Group II compared with Groups I and III. There was an increase in liver proteins involved in energy flux and antioxidant enzymes in non-exercise groups (I, II) of S-mice in comparison with the corresponding groups of R-mice. The results also showed a decrease in muscle protein expression in Group I S-mice compared with their R-mice counterparts. In conclusion, the findings suggest an increased state of oxidative stress in fluorosis-susceptible mice that might be exacerbated by the treatment with F. In addition, fluorosis-susceptible mice have plasma glucose levels higher than fluorosis-resistant mice on exposure to F, and this is not affected by exercise.

A novel perspective suggesting high sustained energy expenditure may be net protective against cancer

Energy expenditure (EE) is generally viewed as tumorigenic, due to production of reactive oxygen species (ROS) that can damage cells and DNA. On this basis, individuals within a species that sustain high EE should be more likely to develop cancer. Here, we argue the opposite, that high EE may be net protective effect against cancer, despite high ROS production. This is possible because individuals that sustain high EE have a greater energetic capacity (=greater energy acquisition, expenditure and ability to up-regulate output), and can therefore allocate energy to multiple cancer-fighting mechanisms with minimal energetic trade-offs. Our review finds that individuals sustaining high EE have greater antioxidant production, lower oxidative stress, greater immune function and lower cancer incidence. Our hypothesis and literature review suggest that EE may indeed be net protective against cancer, and that individual variation in energetic capacity may be a key mechanism to understand the highly individual nature of cancer risk in contemporary human populations and laboratory animals.

Lay summary The process of expending energy generates reactive oxygen species that can lead to oxidative stress, cell and DNA damage, and the accumulation of this damage is thought to be a major contributor to many ageing related diseases that include cancer. Here, we challenge this view, proposing how and why high energy expenditure (EE) may actually be net protective against cancer, and provide literature support for our hypothesis. We find individuals with high sustained EE have greater energetic capacity and thus can invest more in repair to counter oxidative stress, and more in immune function, both of which reduce cancer risk. Our hypothesis provides a novel mechanism to understand the highly individual nature of cancer, why taller individuals are more at risk, why physically active individuals have lower cancer risk, and why regular exercise can reduce cancer risk.

Influence of Intrinsic Aerobic Exercise Capacity and Sex on Cardiac Injury Following Acute Myocardial Ischemia and Reperfusion

Purpose: Previous reports have suggested that active exercise aside, intrinsic aerobic running capacity (Low = LCR, high = HCR) in otherwise sedentary animals may influence several cardiovascular health-related indicators. Relative to the HCR phenotype, the LCR phenotype is characterized by decreased endothelial reactivity, increased susceptibility to reperfusion-induced arrhythmias following short, non-infarction ischemia, and increased diet-induced insulin resistance. More broadly, the LCR phenotype has come to be characterized as a "disease prone" model, with the HCRs as "disease resistant." Whether these effects extend to injury outcomes in an overt infarction or whether the effects are gender specific is not known. This study was designed to determine whether HCR/LCR phenotypic differences would be evident in injury responses to acute myocardial ischemia-reperfusion injury (AIR), measured as infarct size and to determine whether sex differences in infarction size were preserved with phenotypic selection. Methods: Regional myocardial AIR was induced in vivo by either 15 or 30 min ligation of the left anterior descending coronary artery, followed by 2 h of reperfusion. Global ischemia was induced in isolated hearts ex vivo using a Langendorff perfusion system and cessation of perfusion for either 15 or 30 min followed by 2 h of reperfusion. Infarct size was determined using 2, 3, 5-triphenyltetrazolium chloride (TTC) staining, and normalized to area at risk in the regional model, or whole heart in the global model. Portions of the tissue were paraffin embedded for H&E staining and histology analysis. Results: Phenotype dependent differences in infarct size were seen with 15 min occlusion/2 h reperfusion (LCR > HCR, p < 0.05) in both regional and global models. In both models, longer occlusion times (30 min/2 h) produced significantly larger infarctions in both phenotypes, but phenotypic differences were no longer present (LCR vs. HCR, p = n.s.). Sex differences in infarct size were present in each phenotype (LCR male > LCR female, p < 0.05; HCR male > HCR female, p < 0.05 regardless of length of occlusion, or ischemia model. Conclusions: There is cardioprotection afforded by high intrinsic aerobic capacity, but it is not infinite/continuous, and may be overcome with sufficient injury burden. Phenotypic selection based on endurance running capacity preserved sex differences in response to both short and longer term coronary occlusive challenges. Outcomes could not be associated with differences in system characteristics such as circulating inflammatory mediators or autonomic nervous system influences, as similar phenotypic injury patterns were seen in vivo, and in isolated crystalloid perfused heart ex vivo.

The Metabolic Signature of Cardiorespiratory Fitness: A Systematic Review

Background

Cardiorespiratory fitness (CRF) is a potent health marker, the improvement of which is associated with a reduced incidence of non-communicable diseases and all-cause mortality. Identifying metabolic signatures associated with CRF could reveal how CRF fosters human health and lead to the development of novel health-monitoring strategies.

Objective

This article systematically reviewed reported associations between CRF and metabolites measured in human tissues and body fluids.

Methods

PubMed, EMBASE, and Web of Science were searched from database inception to 3 June, 2021. Metabolomics studies reporting metabolites associated with CRF, measured by means of cardiopulmonary exercise test, were deemed eligible. Backward and forward citation tracking on eligible records were used to complement the results of database searching. Risk of bias at the study level was assessed using QUADOMICS.

Results

Twenty-two studies were included and 667 metabolites, measured in plasma (n = 619), serum (n = 18), skeletal muscle (n = 16), urine (n = 11), or sweat (n = 3), were identified. Lipids were the metabolites most commonly positively (n = 174) and negatively (n = 274) associated with CRF. Specific circulating glycerophospholipids (n = 85) and cholesterol esters (n = 17) were positively associated with CRF, while circulating glycerolipids (n = 152), glycerophospholipids (n = 42), acylcarnitines (n = 14), and ceramides (n = 12) were negatively associated with CRF. Interestingly, muscle acylcarnitines were positively correlated with CRF (n = 15).

Conclusions

Cardiorespiratory fitness was associated with circulating and muscle lipidome composition. Causality of the revealed associations at the molecular species level remains to be investigated further. Finally, included studies were heterogeneous in terms of participants’ characteristics and analytical and statistical approaches.

PROSPERO Registration Number

CRD42020214375.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40279-021-01590-y.

Physical Activity in De Novo Parkinson Disease: Daily Step Recommendation and Effects of Treadmill Exercise on Physical Activity

OBJECTIVE

People with Parkinson disease (PD) have low physical activity (PA) levels and are at risk for cardiovascular events. The 3 purposes of this study were to determine a step threshold that corresponds to meeting aerobic PA guidelines, determine effects of treadmill exercise on PA, and quantify the relationship between changes in daily steps and fitness.

METHODS

This was a secondary analysis of the Study in Parkinson's Disease of Exercise trial, which randomized participants to high-intensity treadmill exercise, moderate-intensity treadmill exercise, or usual care for 6 months. Daily steps and moderate- to vigorous-intensity PA (MVPA) were assessed at baseline and once each month using an activity monitor. Fitness was assessed via graded exercise test at baseline and at 6 months. A step threshold that corresponds to meeting PA guidelines was determined by receiver operating characteristic curves. The effect of treadmill exercise on PA was examined in those below the step threshold (ie, the least active participants). Pearson r correlations determined the relationship between daily steps and fitness.

RESULTS

Individuals with de novo PD (n = 110) were included. Those with ≥4200 steps were 23 times more likely (95% CI = 7.72 to 68) to meet PA guidelines than those with <4200 steps. For those with <4200 steps at baseline (n = 33), only those in the high-intensity exercise group increased daily steps (median of differences = 1250 steps, z = -2.35) and MVPA (median of differences = 12.5 minutes, z = -2.67) at 6 months. For those with <4200 steps, changes in daily steps were not associated with changes in fitness (r = .183).

CONCLUSION

In people with PD and <4200 daily steps at baseline, high-intensity treadmill exercise increased daily steps and MVPA, but these changes were not associated with changes in fitness.

IMPACT

People with PD should be encouraged to take ≥4200 daily steps to meet PA guidelines through walking.

The genetics of human performance

Human physiology is likely to have been selected for endurance physical activity. However, modern humans have become largely sedentary, with physical activity becoming a leisure-time pursuit for most. Whereas inactivity is a strong risk factor for disease, regular physical activity reduces the risk of chronic disease and mortality. Although substantial epidemiological evidence supports the beneficial effects of exercise, comparatively little is known about the molecular mechanisms through which these effects operate. Genetic and genomic analyses have identified genetic variation associated with human performance and, together with recent proteomic, metabolomic and multi-omic analyses, are beginning to elucidate the molecular genetic mechanisms underlying the beneficial effects of physical activity on human health.

Effects and dose-response relationship of high-intensity interval training on cardiorespiratory fitness in overweight and obese adults: a systematic review and meta-analysis

This study aims to quantify the effects of high-intensity interval training (HIIT) on cardiorespiratory fitness (CRF) by considering potential moderators and to characterise dose-response relationships of HIIT variables that could maximise CRF improvements in overweight and obese adults. Following a comprehensive search through four electronic databases, 19 studies met eligibility criteria. Random-effects models were applied to weight all included studies and to compute the weighted mean standardised mean differences (SMD_wm). Meta-analysis showed that HIIT was a highly effective approach for improving CRF in overweight and obese adults (SMD_wm = 1.13). Effects were modified by sex and baseline CRF level. Dose-response relationship analysis provided some preliminary data regarding the training period, training intensity, and session duration. However, it is still not possible to provide accurate recommendations currently. Further studies are still needed to identify the most appropriate training variables to prescribe effective HIIT programmes for improving CRF in overweight and obese adults.

Is estimated cardiorespiratory fitness an effective predictor for cardiovascular and all-cause mortality? A meta-analysis

BACKGROUND AND AIMS

Estimated cardiorespiratory fitness (eCRF) derived from algorithm correlates well with exercise testing-measured CRF, yet its clinical use for mortality risk stratification has not been systematically evaluated. This meta-analysis with dose-response analysis was conducted to quantify its association with risk of cardiovascular and all-cause mortality.

METHODS

Electronic databases were searched for prospective cohort studies that investigated the association of eCRF with risk of cardiovascular and all-cause mortality. Study-specific multivariate-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) per 1-metabolic equivalent (MET) higher of eCRF were pooled using a random-effects model.

RESULTS

Twenty-five datasets from 8 cohort studies that enrolled more than 170,000 participants were included. The summary HR per 1-MET higher of eCRF was 0.83 (95% CI 0.80 to 0.86) for cardiovascular mortality (11 datasets) and 0.83 (95% CI 0.78 to 0.88) for all-cause mortality (14 datasets) in the general population. These associations showed no sex-difference and were all linearly shaped (all p_nonlinearity ≥ 0.27). The performance of eCRF (assessed by the area under the curve) in discriminating future risk of cardiovascular and all-cause mortality was higher than all its components (such as physical activity, resting heart rate, and body mass index, all p < 0.05), but slightly lower than exercise testing-measured CRF.

CONCLUSIONS

Higher eCRF was independently associated with lower risk of cardiovascular and all-cause mortality in the general population, indicating that eCRF might hold the potential as an effective and practical risk prediction tool in epidemiological or population research.

Genetic Polymorphisms Related to VO2max Adaptation Are Associated With Elite Rugby Union Status and Competitive Marathon Performance

PURPOSE

Genetic polymorphisms have been associated with the adaptation to training in maximal oxygen uptake (V˙O2max). However, the genotype distribution of selected polymorphisms in athletic cohorts is unknown, with their influence on performance characteristics also undetermined. This study investigated whether the genotype distributions of 3 polymorphisms previously associated with V˙O2max training adaptation are associated with elite athlete status and performance characteristics in runners and rugby athletes, competitors for whom aerobic metabolism is important.

METHODS

Genomic DNA was collected from 732 men including 165 long-distance runners, 212 elite rugby union athletes, and 355 nonathletes. Genotype and allele frequencies of PRDM1 rs10499043 C/T, GRIN3A rs1535628 G/A, and KCNH8 rs4973706 T/C were compared between athletes and nonathletes. Personal-best marathon times in runners, as well as in-game performance variables and playing position, of rugby athletes were analyzed according to genotype.

RESULTS

Runners with PRDM1 T alleles recorded marathon times ∼3 minutes faster than CC homozygotes (02:27:55 [00:07:32] h vs 02:31:03 [00:08:24] h, P = .023). Rugby athletes had 1.57 times greater odds of possessing the KCNH8 TT genotype than nonathletes (65.5% vs 54.7%, χ2 = 6.494, P = .013). No other associations were identified.

CONCLUSIONS

This study is the first to demonstrate that polymorphisms previously associated with V˙O2max training adaptations in nonathletes are also associated with marathon performance (PRDM1) and elite rugby union status (KCNH8). The genotypes and alleles previously associated with superior endurance-training adaptation appear to be advantageous in long-distance running and achieving elite status in rugby union.

Human plasma proteomic profiles indicative of cardiorespiratory fitness

Maximal oxygen uptake (VO₂max) is a direct measure of human cardiorespiratory fitness and is associated with health. However, the molecular determinants of interindividual differences in baseline (intrinsic) VO₂max, and of increases of VO₂max in response to exercise training (ΔVO₂max), are largely unknown. Here, we measure ~5,000 plasma proteins using an affinity-based platform in over 650 sedentary adults before and after a 20-week endurance-exercise intervention and identify 147 proteins and 102 proteins whose plasma levels are associated with baseline VO₂max and ΔVO₂max, respectively. Addition of a protein biomarker score derived from these proteins to a score based on clinical traits improves the prediction of an individual's ΔVO₂max. We validate findings in a separate exercise cohort, further link 21 proteins to incident all-cause mortality in a community-based cohort and reproduce the specificity of ~75% of our key findings using antibody-based assays. Taken together, our data shed light on biological pathways relevant to cardiorespiratory fitness and highlight the potential additive value of protein biomarkers in identifying exercise responsiveness in humans.

Longitudinal changes in maximal oxygen uptake in adolescent girls and boys with different training backgrounds

The purpose of this study was to investigate the effects of high-volume endurance training on the development of maximal oxygen uptake (VO_2max ) in physically active boys and girls between the ages of 12 and 15 years, using a longitudinal design. The children participated in organized training in sports clubs for an average of 7-10 hours per week, with one group undertaking a high volume of endurance training (~7 hours per week; End boys, n = 23 and End girls, n = 17) and the other group having a primary focus on technical and tactical skill development, undertaking low volumes of endurance training (~1.6 hours per week; non-End boys, n = 29 and non-End girls, n = 9). VO_2max and anthropometrics were assessed at age 12, 13, and 15. At age 12, VO_2max was 58.9 (5.6), 65.5 (7.2), 56.5 (6.5), and 58.8 (7.9) mL·kg^-1 ·min^-1 in End girls, End boys, non-End girls, and non-End boys, respectively. Over the three years, there was no difference between the training groups in the development of VO_2max independent of scaling. In boys, VO_2max relative to body mass (BM) did not change from age 12 to 15, while VO_2max tended to decrease relative to fat-free mass (FFM). In girls, VO_2max relative to BM decreased slightly from age 12 to 15, with no changes over the years relative to FFM. The present longitudinal study suggests that in growing active children during puberty, high volumes of systematic endurance training do not have an additional effect on VO_2max compared with similar volume of training mainly aiming at developing motor skills.

Understanding the Relationship between Intrinsic Cardiorespiratory Fitness and Serum and Skeletal Muscle Metabolomics Profile

Intrinsic cardiorespiratory fitness (iCRF) indicates the CRF level in the sedentary state. However, even among sedentary individuals, a wide interindividual variability is observed in the iCRF levels, whose associated molecular characteristics are little understood. This study aimed to investigate whether serum and skeletal muscle metabolomics profiles are associated with iCRF, measured by maximal power output (MPO). Seventy sedentary young adults were submitted to venous blood sampling, a biopsy of the vastus lateralis muscle and iCRF assessment. Blood serum and muscle tissue samples were analyzed by proton nuclear magnetic resonance (¹H NMR) spectroscopy. Metabolites related to iCRF were those supported by three levels of evidence: (1) correlation with iCRF, (2) significant difference between individuals with low and high iCRF, and (3) metabolite contribution to significant pathways associated with iCRF. From 43 serum and 70 skeletal muscle analyzed metabolites, iCRF was positively associated with levels of betaine, threonine, proline, ornithine, and glutamine in serum and lactate, fumarate, NADP+, and formate in skeletal muscle. Serum betaine and ornithine and skeletal muscle lactate metabolites explained 31.2 and 16.8%, respectively, of the iCRF variability in addition to body mass. The results suggest that iCRF in young adults is positively associated with serum and skeletal muscle metabolic levels, indicative of the amino acid and carbohydrate metabolism.

Intrinsic exercise capacity induces divergent vascular plasticity via arachidonic acid-mediated inflammatory pathways in female rats

Metabolic syndrome prevalence has increased among US adults, particularly among non-hispanic white and black women. Sedentary behavior often leads to chronic inflammation, a triggering factor of metabolic syndrome. Given that intrinsic exercise capacity is genetically inherited, we questioned if low-grade chronic inflammation would be present in a female rat model of low intrinsic exercise capacity-induced metabolic syndrome, while beneficial increase of resolution of inflammation would be present in a female rat model of high intrinsic exercise capacity. In the vascular system, two primary markers for inflammation and resolution of inflammation are cyclooxygenase (COX) and lipoxygenase (LOX), respectively. Our study focused on the novel hypothesis that untrained, inherited exercise capacity induces divergent vascular plasticity via changes in the delicate balance between COX and LOX inflammatory mediators. We used divergent rat strains with low (LCR) and high (HCR) aerobic running capacity. By using animals with contrasting intrinsic exercise capacities, it is possible to determine the exact triggers that lead to inherited vascular plasticity in female rats. We observed that female LCR displayed increased periovarian fat pad and body weight, which is congruent with their obesity-presenting phenotype. Furthermore, LCR presented with vascular hypocontractility and increased COX and LOX-derived pro-inflammatory factors. On the other hand, HCR presented with a "shutdown" of COX-induced vasoconstriction and enhanced resolution of inflammation to maintain vascular tone and homeostasis. In conclusion, LCR display low-grade chronic inflammation via increased COX activity. These results provide mechanistic clues as to why lower intrinsic aerobic capacity correlates with a predisposition to risk of vascular disease. Conversely, being born with higher intrinsic aerobic capacity is a significant factor for improved vascular physiology in female rats.