Cardiorespiratory Fitness and Cardiometabolic Risk Factors in Children and Adolescents From Southwest Colombia: Association Patterns Considering Adiposity.

BACKGROUND: Little is known about the cardiorespiratory fitness (CRF)-cardiometabolic risk relationship in Latin American pediatric populations across different age/sex groups, especially when considering the potential effects of adiposity on the association. We evaluated cross-sectional associations between VO2max and cardiometabolic risk variables (CMRV), and verified whether the associations were independent of adiposity markers in school-aged children and adolescents from Cali, Colombia. METHODS: The sample consisted of 1206 children aged 5-17 years. CMRV were fasting glucose, HDL and LDL cholesterol, triglycerides, systolic, and diastolic pressure. Logistic regressions were conducted for associations of age/sex-specific tertiles of VO2max with age/sex-specific highest tertiles of CMRV (except HDL-C, lowest tertile) and a CMR cluster (> 2 CMRV in extreme tertiles), adjusting for socioeconomic stratum, and adiposity markers (BMI, body fat percentage, and waist circumference). RESULTS: Overweight/obesity ranged from 15% to 18% with no difference by sex. In children aged 5-11 years, high VO2max (highest tertile vs. lowest) was inversely associated with the CMR cluster [Odds ratio (95% confidence interval): 0.18 (0.06-0.47), p < 0.05] independently of adjustment for any adiposity marker in boys but not in girls. In the age group of 12-17 years, there were initially significant VO2max- CMR cluster and VO2max- CMRV associations but attenuated by adiposity adjustment. In girls, high VO2max was inversely associated with high systolic blood pressure regardless of adjustment for adiposity markers. CONCLUSION: VO2max is inversely associated with cardiometabolic risk, but adiposity influences the association. The adiposity-independent association among younger boys requires further research. Interventions to tackle cardiometabolic risk in childhood may primarily focus on reducing excess adiposity, and secondarily on improvement of CRF.

Adiponectin concentration and cardiometabolic risk factors: the moderator role of cardiorespiratory fitness in adolescents.

The aim of this study was to examine the moderating role of cardiorespiratory fitness (CRF) between the relationship of cardiometabolic risk factors and adiponectin in adolescents. This is a cross-sectional study conducted with 255 adolescents of both sexes, aged 11 to 17 years. Anthropometric and biochemical parameters such as body mass, height, fat mass (FM), fat-free mass, high-density lipoprotein, low-density lipoprotein, triglycerides, glucose, insulin, adiponectin, systolic blood pressure, diastolic blood pressure, and peak oxygen consumption (VO2peak) were measured. Body mass index z-score (BMI-z), tri-ponderal mass index (TMI), homeostasis model assessment insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), and age peak height velocity were calculated. The moderation analyses were tested using linear regression models. Interaction was observed with low CRF, indicating that those who achieved more than 2.27 (BMI-z), 2.18 (TMI), 2.10 (FM), 2.57 (insulin), 2.65 (HOMA-IR), and 2.81 (QUICKI) in L·min-1 on the CRF test may experience reduced risks in cardiometabolic risk factors. CONCLUSION: The deleterious effects attributed to excess adiposity and unfavorable changes related to insulin resistance and sensitivity may be attenuated by CRF. WHAT IS KNOWN: • Adiponectin, a protein derived from adipose tissue, may play a role as a potential marker of protection and predictor of cardiometabolic disorders and its relationship with cardiorespiratory fitness is controversial. WHAT IS NEW: • The deleterious effects attributed to overweight and unfavorable changes related to insulin resistance and sensitivity may be attenuated by high cardiorespiratory fitness in adolescents.

Treinamento Físico Reduz a Inflamação e a Fibrose e Preserva a Função e a Perfusão Miocárdica em um Modelo de Cardiomiopatia Chagásica Crônica / Exercise Training Reduces Inflammation and Fibrosis and Preserves Myocardial Function and Perfusion in a Model of Chronic Chagas Cardiomyopathy

Resumo Fundamento: A Cardiomiopatia Chagásica Crônica (CCC) é causada por um processo inflamatório induzido pelo Trypanosoma cruzi, que leva à miocardite com fibrose reativa e reparativa. A CCC progride com alterações de perfusão miocárdica e eventos histopatológicos que afetam a Aptidão Cardiorrespiratória (ACR). Objetivos: Avaliamos os efeitos do Treinamento Físico Aeróbico (TFA) na perfusão miocárdica e nos comprometimentos morfológicos e funcionais relacionados à inflamação e fibrose em hamsters sírios com CCC. Como objetivo secundário, analisamos as áreas de secção transversa do músculo esquelético. Métodos: Hamsters com CCC e seus respectivos controles foram divididos em quatro grupos: CCC sedentário, CCC-TFA, controle sedentário e controle TFA. Sete meses após a infecção, os animais foram submetidos à ecocardiografia, à cintilografia de perfusão miocárdica e ao teste de esforço cardiopulmonar. TFA de intensidade moderada foi realizado durante cinquenta minutos, cinco vezes por semana, por oito semanas. Posteriormente, os animais foram reavaliados. A análise histopatológica foi realizada após os procedimentos acima mencionados. O nível de significância foi estabelecido em 5% em todas as análises (p<0,05). Resultados: Animais com CCC sedentários apresentaram piores Defeitos de Perfusão Miocárdica (DPM) ao longo do tempo, Fração de Ejeção do Ventrículo Esquerdo (FEVE) reduzida, e apresentaram mais inflamação e fibrose quando comparados aos demais grupos (análise ANOVA mista). Por outro lado, o TFA foi capaz de mitigar a progressão do DPM, atenuar a inflamação e a fibrose e melhorar a eficiência da ACR em animais CCC-TFA. Conclusão: Nosso estudo demonstrou que o TFA melhorou a disfunção cardíaca, DPM e reduziu a inflamação e a fibrose em modelos de hamster com CCC. Além disso, os animais CCC-SED apresentaram atrofia do músculo esquelético, enquanto os animais CCC-TFA apresentaram a AST do músculo esquelético preservada. Compreender os efeitos da TFA nas dimensões fisiopatológicas da CCC é crucial para futuras pesquisas e intervenções terapêuticas.

Abstract Background: Chronic Chagas cardiomyopathy (CCC) is caused by an inflammatory process induced by Trypanosoma cruzi, which leads to myocarditis with reactive and reparative fibrosis. CCC progresses with myocardial perfusion abnormalities and histopathological events that affect cardiorespiratory fitness (CRF). Objectives: We evaluated the effects of aerobic physical training (APT) on myocardial perfusion and on morphological and functional impairments related with inflammation and fibrosis in Syrian hamsters with CCC. As a secondary objective, we analyzed the cross-sectional areas of the skeletal muscle. Methods: Hamsters with CCC and their respective controls were divided into four groups: CCC sedentary, CCC-APT, sedentary control and APT control. Seven months after infection, the animals underwent echocardiography, myocardial perfusion scintigraphy and cardiopulmonary exercise testing. Moderate-intensity APT was performed for fifty minutes, five times a week, for eight weeks. Subsequently, the animals were reassessed. Histopathological analysis was conducted after the above-mentioned procedures. The level of significance was set at 5% in all analyses (p<0.05). Results: CCC sedentary animals presented worse myocardial perfusion defects (MPD) over time, reduced left ventricle ejection fraction (LVEF) and showed more inflammation and fibrosis when compared to other groups (mixed ANOVA analysis). Conversely, APT was able to mitigate the progression of MPD, ameliorate inflammation and fibrosis and improve CRF efficiency in CCC-APT animals. Conclusions: Our study demonstrated that APT ameliorated cardiac dysfunction, MPD, and reduced inflammation and fibrosis in CCC hamster models. Additionally, CCC-SED animals presented skeletal muscle atrophy while CCC-APT animals showed preserved skeletal muscle CSA. Understanding APT's effects on CCC's pathophysiological dimensions is crucial for future research and therapeutic interventions.

Cardiorespiratory fitness and socioeconomic influences in Chilean schoolchildren: a cross-sectional study.

OBJECTIVE: To compare the cardiovascular risk and physical fitness, according to type of school in a national sample of Chilean school students. METHODS: A total of 7,218 students participated, who completed all the national tests of the National System for Measuring the Quality of Education, which included physical fitness and anthropometric tests. The results were compared according to the type of educational establishment and anthropometric indicators were considered. Physical fitness was measured by lower extremity strength, abdominal strength, upper extremity strength, trunk flexibility, exertional heart rate, and cardiorespiratory fitness. Body mass index, heart rate, and waist-to-height ratio were analyzed as predictors of cardiovascular risk. RESULTS: There were differences according to the type of establishment in the predictors of cardiovascular risk (p < 0.05). Differences were also found in the physical fitness tests evaluated (p < 0.01). Students in private schools (PSC) and subsidized schools (SC) had lower levels of cardiovascular risk and higher levels of physical fitness than public schools (PS) and schools with delegated administration (DA). CONCLUSIONS: In conclusion, students in educational establishments with a higher socioeconomic level have lower levels of cardiovascular risk and better physical fitness than students in public establishments. The authors suggest considering specific school interventions to mitigate cardiovascular risk and improve physical fitness among this vulnerable population. To this end, future studies should analyze the characteristics of physical activity and nutritional habits in schools to determine the factors that affect the results.

The prognostic role of cardiopulmonary exercise testing in obesity.

AIM: Poor cardiorespiratory fitness has been suggested to increase the risk of chronic diseases in obesity. We investigated the ability of key variables from cardiopulmonary exercise testing (CPET) to predict all-cause mortality in an obese cohort. METHODS: The sample included 469 participants of both sexes (mean age 40 ± 13 years) who underwent a CPET for clinical reasons between 1 March 2009 and 1 December 2023. All-cause mortality was the prognostic endpoint. A receiver operating characteristic analysis was performed to establish optimal cut-points for CPET variables. Kaplan-Meier and Cox regression analyses were used to determine the association between CPET variables and all-cause mortality. RESULTS: There were 46 deaths during a mean follow-up period of 69 ± 48 months, resulting in an annual mortality rate of 2%. Despite the sample being made up of mostly women (70%), there were more deaths in men (18 vs. 6%, p < 0.001).The optimal thresholds for discrimination of survival were as follows: (a) peak oxygen uptake (pVO2) ≤16 mL/kg/min; (b) minute ventilation/carbon dioxide production (VE/VCO2) slope ≥31; (c) ventilatory power ≤5.8 mmHg; and (d) circulatory power ≤2980 mmHg/mL O2/min. Kaplan-Meier survival plots revealed a significant positive association between lower pVO2, circulatory power and ventilatory power values and survival (log-rank, p < 0.001) and higher mortality for men than women. Adjusted Cox regression models showed that a pVO2 ≤16 mL/kg/min had a 20-fold higher risk of mortality when compared with >16 mL/kg/min. CONCLUSION: Given the strong association of VO2, ventilatory efficiency, circulatory and ventilatory power with all-cause mortality, our findings support the notion that poorer cardiorespiratory fitness is associated with a poor prognosis in patients with obesity.

Association of statins with peak oxygen consumption in 4,941 adults: A cross-sectional study.

Background and aims: Cardiovascular disease remains a leading cause of mortality, with statins widely used to reduce its risk. Despite extensive research, the nuanced impact of statin therapy on cardiorespiratory fitness, particularly the reduction in peak oxygen consumption (VO2), is still an open question. This study aims to contribute fresh insights to the ongoing discussion, highlighting the unresolved nature of this clinical matter. Methods: We retrospectively analyzed maximal cardiopulmonary exercise test (CPET) in male and female participants over 18 years of age who were under statins treatment. They were categorized as physically active or inactive according to self-report of physical activity. From 33,804 CPET, 4,941 participants (76 % men, age 42 ± 13 years; and 24 % women, age 41 ± 13 years) were included in the study. Results: The multivariate linear regression model showed that statins were associated with a significant reduction in VO2 peak (-4.2 [-4.8, -3.5] mL/kg/min, p < 0.01) after adjusting for age, sex, use of beta-blockers, antiarrhythmics, presence of diabetes, and weekly level of physical activity. This reduction in VO2 peak was attenuated in participants with higher weekly physical activity volume (150 to 300 min/week: 3.2 [2.7; 3.7] mL/kg/min; 301 to 600 min/week: 4.5 [3.7; 5.3] mL/kg/min; and > 600 min/week: 6.9 [5.4; 8.4] mL/kg/min, all p < 0.01). Conclusions: Statin use is associated with a lower VO2 peak in adults. However, this adverse effect appears to be mitigated by engaging in regular physical activity (>150 min/week). Future research should explore the mechanisms behind this interaction and identify optimal exercise regimens for individuals on statin therapy.

Detraining's Effects on Cardiorespiratory Fitness and Maximal and Explosive Strength in Army Soldiers: Does Age Matter?

PURPOSE: This study investigated the impact of four weeks of age-dependent detraining on army soldiers' cardiorespiratory fitness and maximal and explosive strength. METHODS: Fourteen volunteer tactical athletes participated, divided into two age groups (20 to 29 and 30 to 40 years). Before and after the detraining period, we assessed their anthropometric measurements (weight, height, body mass index, fat mass, and fat-free mass), cardiorespiratory fitness (maximal oxygen uptake [VO2max] and ventilatory thresholds [VT1 and VT2]), and kinematic properties during a single-leg counter-moving jump (CMJ) test for both the dominant and non-dominant legs. Two-way ANOVA followed by the Holm-Sidak post hoc test was used. RESULTS: The anthropometric and cardiovascular variables did not show significant differences between the groups. However, both groups exhibited a significantly reduced maximum time and speed at the VO2max. Furthermore, the flight time and maximum height during the CMJ significantly decreased in the non-dominant leg for both age groups. Notably, the dominant leg's concentric impulse (CI) significantly reduced during the CMJ, but this effect was observed only in the 30-40 age group. There were significant differences between the two age groups. CONCLUSIONS: Our findings suggest that four weeks of detraining negatively impacts aerobic fitness and muscular strength, independently of age. However, the dominant leg may be more susceptible to detraining effects in army soldiers aged 30-40. Furthermore, as a perspective, our results strongly suggest that a detraining period could affect successful missions (aerobic performance deterioration), as well as promote a muscle imbalance between the legs, which could encourage muscle injuries and endanger combat missions.

The Mediating Role of Cardiorespiratory Fitness in the Association between a Negative Lifestyle and Poor Mental Health in Chilean Schoolchildren.

BACKGROUND: A negative lifestyle has a reported relationship with psychological problems and deteriorated well-being. However, there is little information regarding the mediating role of cardiorespiratory fitness (CRF) in this relationship. OBJECTIVES: The objectives of the present study are twofold: first, to investigate the association between negative lifestyle, physical self-concept (PSC), and depression, and second, to assess the potential mediating role of CRF in this complex relationship. METHODS: This cross-sectional study included 612 schoolchildren aged between 9 and 14 years from the Araucanía region (southern Chile). CRF was measured using the Leger test, and lifestyle, depression, and PSC were measured using validated questionnaires. RESULTS: A negative lifestyle reported an inverse association with PSC (p < 0.001) and a positive association with depression levels (p < 0.001). The mediation analysis showed that CRF was positively related to PSC (p < 0.001) and inversely related to depression (p = 0.001); besides, the indirect effect CRF acted as a partial mediator in the association between a negative lifestyle and PSC (indirect effect = -1.15; SE = 0.01; 95% CI, -1.87, -0.55) and depression levels (indirect effect = 0.22; SE = 0.08; 95% CI, 0.08, 0.38). CONCLUSION: In conclusion, CRF in schoolchildren played a potential mediating role in the association between a negative lifestyle and depression and PSC.

Phase angle and its determinants among adolescents: influence of body composition and physical fitness level.

To examine the association between levels of physical fitness, parameters of body composition and phase angle (PhA) amongst adolescents. A total of 152 adolescents (84 girls) aged 11-16 years were included in this study. Weight and height were measured and the body mass index (BMI) was calculated. Bioelectrical impedance analysis (BIA) provided resistance and reactance parameters to calculate fat-free mass (FFM), PhA and fat mass (%FM). The following physical fitness variables were analysed: flexibility, abdominal muscular endurance, upper and lower limb explosive strength, agility, speed and cardiorespiratory fitness. Generalized Linear Models were applied to verify differences across sexes. Stepwise linear regression was used to establish an association between the variables studied. The study established an association between PhA and weight, FFM, BMI, FM, %FM and medicine ball throw (MBT) for girls. As for the boys, an association was verified between PhA and weight, FFM, BMI, standing long jump (SLJ), MBT and the three allometric VO2peak variables analyzed. An association was found between PhA and the boys' 4-m shuttle run test (4SRT) and 20-m sprint test (20SRT). Boys showed a greater phase angle than girls; In girls, BMI and %FM, were determinant of 32.4% (r = 0.57). PhA variability which is influenced by physical fitness, body composition and, therefore, the tissues electrical conductivity. Furthermore, boys' height, FFM, upper limb strength, and agility account for 58.4% (r = 0.76) PhA variability. There was a positive correlation between the physical fitness tests and the PhA.

Determinants of cardiorespiratory fitness measured by cardiopulmonary exercise testing in COVID-19 survivors: a systematic review with meta-analysis and meta­regression.

BACKGROUND: The relationship between cardiorespiratory fitness and its possible determinants in post-COVID-19 survivors has not been systematically assessed. OBJECTIVES: To identify and summarize studies comparing cardiorespiratory fitness measured by cardiopulmonary exercise testing in COVID-19 survivors versus non-COVID-19 controls, as well as to determine the influence of potential moderating factors. METHODS: We conducted a systematic search of MEDLINE/PubMed, Cochrane Library, EMBASE, Google Scholar, and SciELO since their inceptions until June 2022. Mean differences (MD), standard mean differences (SMD), and 95% confidence intervals (CI) were calculated. Subgroup and meta-regression analyses were used to evaluate potential moderating factors. RESULTS: 48 studies (3372 participants, mean age 42 years, and with a mean testing time of 4 months post-COVID-19) were included, comprising a total of 1823 COVID-19 survivors and 1549 non-COVID-19 controls. After data pooling, VO2 peak (SMD=1.0 95% CI: 0.5, 1.5; 17 studies; N = 1273) was impaired in COVID-19 survivors. In 15 studies that reported VO2 peak values in mL/min/kg, non-COVID-19 controls had higher peak VO2 values than COVID-19 survivors (MD=6.2, 95% CI: 3.5, 8.8; N = 905; I2=84%). In addition, VO2 peak was associated with age, time post-COVID-19, disease severity, presence of dyspnea, and reduced exercise capacity. CONCLUSION: This systematic review provides evidence that cardiorespiratory fitness may be impaired in COVID-19 survivors, especially for those with severe disease, presence of dyspnea, and reduced exercise capacity. Furthermore, the degree of reduction of VO2 peak is inversely associated with age and time post-COVID.

Association between Gross Motor Competence and Physical Fitness in Chilean Children Aged 4 to 6 Years.

The preschool period is considered critical for the development of motor competence, but as far as we know, no studies have investigated the association between motor competence and physical fitness in Chilean children. The aim of this study was to analyse the association between gross motor competence and physical fitness, controlling for possible confounding factors. A cross-sectional study was conducted with a sample of 144 preschool children (56.25% girls) with an average age of 5.3 years (4 to 6 years) from the Araucanía region, Chile. Motor competence was measured using the Children's Movement Assessment Battery, 2nd Edition (MABC-2). Regarding physical fitness, the components of cardiorespiratory fitness, lower body muscle strength and speed/agility were evaluated using the Battery to Assess FITness in PREschool (PREFIT). Partial correlation models and analysis of variance (ANCOVA) were used to assess differences in physical fitness between motor competence categories, controlling for age and body mass index. The mean fitness scores for cardiorespiratory fitness, lower body muscle strength and speed/agility components were significantly higher in children with higher gross motor competence. In terms of effect size, large values were found for the lower body strength component in model 1 for boys and in model 2 for the total samples of girls and boys. The results of this study suggest that good levels of gross motor competence are associated with better physical fitness levels.

A Dynamic Fitting Strategy for Physiological Models: A Case Study of a Cardiorespiratory Model for the Simulation of Incremental Aerobic Exercise.

Using mathematical models of physiological systems in medicine has allowed for the development of diagnostic, treatment, and medical educational tools. However, their complexity restricts, in most cases, their application for predictive, preventive, and personalized purposes. Although there are strategies that reduce the complexity of applying models based on fitting techniques, most of them are focused on a single instant of time, neglecting the effect of the system's temporal evolution. The objective of this research was to introduce a dynamic fitting strategy for physiological models with an extensive array of parameters and a constrained amount of experimental data. The proposed strategy focused on obtaining better predictions based on the temporal trends in the system's parameters and being capable of predicting future states. The study utilized a cardiorespiratory model as a case study. Experimental data from a longitudinal study of healthy adult subjects undergoing aerobic exercise were used for fitting and validation. The model predictions obtained in a steady state using the proposed strategy and the traditional single-fit approach were compared. The most successful outcomes were primarily linked to the proposed strategy, exhibiting better overall results regarding accuracy and behavior than the traditional population fitting approach at a single instant in time. The results evidenced the usefulness of the dynamic fitting strategy, highlighting its use for predictive, preventive, and personalized applications.

Fitness and fatness in children and adolescents: investigating their role in the association between physical activity and cardiometabolic health.

To verify the role of the combination of fitness and fatness in the relationship between physical activity (PA) and cardiometabolic risk in children and adolescents. This is a cross-sectional study performed with 2786 children and adolescents (6 to 17 years). Fitness was determined by the cardiorespiratory fitness (CRF) six-minute walking and running test. Waist circumference (WC) was considered a fatness indicator. A selfreported questionnaire was used to determine PA practice, whereas the clustered cardiometabolic risk score (cMetS) was calculated by summing z-scores of triglycerides, total cholesterol/HDL-C ratio, systolic blood pressure, glucose, and WC. Considering the combination of CRF (fitness) and WC (fatness), the following phenotypes were created: Fit/Unfat, Fit/Fat, Unfit/Unfat and Unfit/Fat. Moderation analyses were tested using linear regression models. Significant interactions were found between PA and Unfit/Fat category (ß = -0.001; p = 0.001) only for adolescents. The interaction observed in the Unfit/Fat phenotype indicated that adolescents who practise PA for 330 minutes per week presented lower cMetS compared to those who do not practise or practise for 60 minutes respectively. The combination of fitness and fatness moderates the relationship between PA and cardiometabolic risk, suggesting that adolescents, particularly those who are less fit and present high adiposity, should be encouraged to engage in regular PA to improve their metabolic health.

Cardiorespiratory fitness and mortality risk in patients receiving hemodialysis: a prospective cohort / Aptidão cardiorrespiratória e risco de mortalidade em pacientes em hemodiálise: uma coorte prospectiva

ABSTRACT Background: Kidney failure reduces life expectancy by one-third compared with the general population, and cardiovascular complications and poor cardiorespiratory fitness (CRF) are the main causes. We aimed to evaluate the association between severely low CRF and all-cause mortality risk in HD patients. Methods: This observational prospective cohort study followed-up patients receiving HD from August 2015 until March 2022. Cardiorespiratory fitness was evaluated through the cardiopulmonary exercise test, and the peak oxygen uptake (VO2peak) value was used to determine severely low CRF (< 15 mL∙kg−1∙min−1). Cox regression and univariate Kaplan-Meier analysis were used to evaluate the association of severely low CRF with mortality risk and survival rate. Results: Forty-eight patients were followed-up for a median of 33.0 [14.3 - 49.3] months. A total of 26 patients had severely low CRF. During the follow-up period, 11 patients (22.92%) died from all causes. From these, eight (30.8%) had severely low CRF. Even so, severely low CRF was not associated with crude death rates for patients stratified by CRF levels (p = 0.189), neither in unadjusted (HR 2.18; CI 95% 0.58−8.23) nor in adjusted (HR 1.32; CI 95% 0.31−5.59) Cox proportional hazard models. As a continuous variable, VO2peak was not associated with mortality risk (HR 1.01; CI 95% 0.84−1.21). Univariate Kaplan-Meier analysis showed that patients with severely low CRF did not have significantly worse survival rates than those with mild-moderate CRF (p = 0.186). Conclusion: Our findings indicated that severely low CRF was not associated with all-cause mortality in patients on HD. Despite severely low CRF being prevalent, larger cohort studies are needed to establish strong conclusions on its association with all-cause mortality.

RESUMO Introdução A insuficiência renal reduz a expectativa de vida em um terço comparada à população em geral. Complicações cardiovasculares e baixa aptidão cardiorrespiratória (ACR) são as principais causas. Avaliamos a associação entre ACR muito baixa e risco de mortalidade por todas as causas em pacientes em HD. Métodos Este estudo de coorte prospectivo observacional acompanhou pacientes em HD de agosto/2015 a março/2022. Avaliou-se a aptidão cardiorrespiratória pelo teste de exercício cardiopulmonar, e o valor do pico do consumo de oxigênio (VO2pico) foi usado para determinar ACR muito baixa (< 15 mL∙kg−1∙min−1). Utilizamos regressão de Cox e análise univariada de Kaplan-Meier para avaliar associação da ACR muito baixa com o risco de mortalidade e taxa de sobrevida. Resultados Acompanhamos 48 pacientes por uma média de 33,0 [14,3 - 49,3] meses. Um total de 26 pacientes apresentaram ACR muito baixa. No período de acompanhamento, 11 pacientes (22,92%) foram a óbito por todas as causas. Destes, oito (30,8%) apresentavam ACR muito baixa. Mesmo assim, ACR muito baixa não foi associada a taxas brutas de mortalidade para pacientes estratificados por níveis de ACR (p = 0,189), nem em modelos de risco proporcional de Cox não ajustados (HR 2,18; IC 95% 0,58-8,23) ou ajustados (HR 1,32; IC 95% 0,31-5,59). Como variável contínua, VO2pico não foi associado ao risco de mortalidade (HR 1,01; IC 95% 0,84-1,21). A análise univariada de Kaplan-Meier mostrou que pacientes com ACR muito baixa não apresentaram taxas de sobrevida significativamente piores do que aqueles com ACR leve-moderada (p = 0,186). Conclusão Nossos achados indicaram que a ACR muito baixa não foi associada à mortalidade por todas as causas em pacientes em HD. Apesar de ACR muito baixa ser prevalente, são necessários estudos de coorte maiores para estabelecer conclusões sólidas sobre sua associação com mortalidade por todas as causas.

Cardiorespiratory patterns of male South American sea lions (Otaria flavescens) resting on land.

The goal of this study was to characterize the cardiorespiratory patterns of male South American sea lions (SASLs, Otaria flavescens) resting on land. We recorded respiratory and heart rate (n = 360 individuals studied) by observing the nostrils, chest movements and the impact of the heart on the thoracic wall. The sea lions breathe apneustically with a pause on inspiration, representing 74% of the respiratory cycle. The mean breathing frequency was 3.2 ± 1.0 breaths min-1, with a breathing cycle presenting periods of bradypneas, tachypneas, and long-term post-inspiratory pauses. The normal heart rate (nHR) was 73.4 ± 14.5 beats min-1 and no significant differences were observed between age classes. All animals showed variability in HR in relation to respiratory phases (Inspiration: 101.2 ± 18.4 beats min-1; post-inspiratory pause: 73.4 ± 14.5 beats min-1; expiration: 64.6 ± 17.7 beats min-1), consistent with respiratory sinus arrhythmia (RSA). The mean HR (measured during all respiratory phases) was 79.9 ± 22.7 beats min-1, and was significantly different between age classes. The total duration of respiratory cycle, and duration of both inspiration and expiration, decreased with an increment in ambient temperature, with no variation in the pause duration. Heart rate during pause and expiration was significantly higher during high temperatures. Similar changes in cardiorespiratory patterns have been reported in other pinnipeds. Our results showed ontogenetic differences in development and typical variations with environmental and behavioral variables.

Peak oxygen uptake after the 80s as a survival predictor.

PURPOSE: Peak oxygen uptake (VO2peak) is a crucial health marker, extensively studied in adults for its prognostic value. However, its significance in the older persons, especially octogenarians, remains underexplored due to limited representation in research. This study aims to assess the predictive power of VO2peak for survival in individuals aged 80 and above. METHODS: We included individuals aged 80 or older who underwent cardiopulmonary exercise tests at a single center. Mortality rates were compared based on VO2peak relative to 80% of predicted values (%VO2peak). We employed three multivariate Cox regression models: Model 1 (unadjusted), Model 2 (adjusted for age) and Model 3 (adjusted for age and stroke). RESULTS: Among 188 participants (mean age 83.3 ± 3 years, 68.9% male), 22 (11.7%) passed away during a median follow-up of 494 days. Non-survivors tended to be older with lower VO2peak and %VO2peak. All models demonstrated associations between %VO2peak ≤ 80% and mortality: HR = 3.19 (95% CI: 1.30-7.86, p = 0.011) for M1; HR = 3.12 (95% CI: 1.26-7.74, p = 0.013) for M2 and HR = 2.80 (95% CI: 1.11-7.06, p = 0.028) for M3. CONCLUSION: In the context of an aging population, this study underscores the enduring significance of VO2peak as a survival predictor among the older person, including octogenarians. These findings carry profound implications for tailoring healthcare strategies to address the evolving demographic landscape.

Longitudinal strain and myocardial work in symptomatic patients having recovered from COVID-19 and possible associations with the severity of the disease.

COVID-19 may have residual consequences in multiple organs, including the cardiovascular system. The purpose of the present investigation is to quantify myocardial function in symptomatic individuals with long COVID and investigate the association between illness severity and myocardial function. A retrospective cross-sectional study was conducted in which symptomatic individuals with previous COVID-19 underwent echocardiographic analysis of left ventricle global longitudinal strain (LVGLS) and myocardial work (MW). Individuals also performed cardiopulmonary testing (CPX) to assess peak oxygen uptake (VO2peak). Differences between illness severity subgroups were analyzed by the Mann-Whitney test. Correlations were calculated using the Spearman correlation test. Multilinear regressions were performed to evaluate the influences of COVID-19 severity, body mass index, age, and sex on MW. Fifty-six individuals were included (critical subgroup: 17; moderate/severe subgroup: 39), 59% females; median age: 56 years (IQR: 43-63). CPX revealed a substantial reduction in VO2peak (median of 53% of predicted values). LVGLS were not statistically different between subgroups. Global wasted work (GWW) was higher in the critical subgroup [146 (104-212) versus 121 (74-163) mmHg%, p = 0.01], and global work efficiency (GWE) was lower in this subgroup [93 (91-95) versus 94 (93-96), p = 0.03]. Illness severity was the only independent predictor of GWW and GWE (GWW: r2 = 0.167; p = 0.009; GWE: r2 = 0.172; p = 0.005) in multilinear regressions. In our study with long COVID-19 individuals, despite having a similar LVGLS, patients had subclinical LV dysfunction, demonstrated only by an increase in GWW and a decrease in GWE.

The Effects of a Physical Activity Intervention on Adiposity, Physical Fitness and Motor Competence: A School-Based, Non-Randomized Controlled Trial.

Evidence suggests that early physical activity interventions are a means of preventing childhood obesity and are more effective when delivered in a school setting and based on the ecological model. Therefore, the present study aims to determine the effect of a multicomponent intervention based on the ecological model on adiposity, physical fitness and motor competence in children aged 4 to 5 years. METHODS: This study is a non-randomized controlled trial involving 173 children from Chile. The intervention was based on an ecological model and consisted of a physical activity program with three simultaneous parts, affecting intra- and interpersonal dimensions. The adiposity index, body mass index and waist circumference were measured. For physical fitness, muscle strength in the lower part, speed/agility and cardiorespiratory fitness were measured. Motor competence was assessed using catching, aiming and dynamic and static balance tests. RESULTS: After the intervention, there was no reduction in adiposity indices; in the intervention group, body mass index increased significantly with a high effect size. The intervention group showed significant differences in physical fitness in the components of muscle strength in the lower part (p = 0.000) and speed/agility (p = 0.002). For motor competence, the intervention group showed significant improvements in most components. CONCLUSIONS: The multicomponent intervention did not reduce adiposity indices; however, it caused significant improvements in the physical fitness and motor competence components, so it seems prudent to continue implementing it, given the benefits that adequate levels of motor competence and physical fitness bring to children's health, both in the short and long term.

Validity of the two-minute walk test to assess exercise capacity and estimate cardiorespiratory fitness in individuals after stroke: a cross-sectional study.

OBJECTIVES: The purpose of this study was to investigate the construct validity of the 2-minute walk test (2MWT) to assess the exercise capacity and the criterion-concurrent validity of the 2MWT and the 6-minute walk test (6MWT) to estimate the cardiorespiratory fitness of ambulatory individuals with chronic stroke. In addition, to provide an equation to predict the distance covered in the 6MWT and another to predict the peak oxygen consumption (VO2peak) for these individuals. METHODS: This is a cross-sectional and prospective study. A convenience sample with 57 individuals with chronic stroke was recruited. The 2MWT, the 6MWT and the cardiopulmonary exercise test (CPET) were performed in a laboratory. The Spearman's correlation coefficient was used to investigate the validity. To develop the equations, stepwise multiple linear regression analysis was used. RESULTS: A significant correlation of very high magnitude between the distance covered in the 2MWT and the 6MWT was found (rs = 0.93; p < 0.001). A significant correlation of moderate magnitude between the distance covered in the 2MWT and the VO2peak (rs = 0.53; p < 0.001) similar to the correlation between the 6MWT and the VO2peak (rs = 0.55; p < 0,001) were found. Furthermore, an equation was developed to predict the VO2peak (R2 = 0.690; p < 0.001; VO2peak = 13.532 + 0.078*distance walked in the 2MWT +4.509*sex-0.172*age), and another to predict the distance covered in the 6MWT (R2 = 0.827; p < 0.001; MWT = -1.867 + 3.008*distance walked in the 2MWT). CONCLUSION: 2MWT showed adequate construct and concurrent validity. Furthermore, it is possible to use the prediction equations developed to estimate the VO2peak or the distance covered in the 6MWT.

Reference Values for Cardiorespiratory Fitness in Patients Aged 6 to 18 Years.

OBJECTIVE: To develop reference values for cardiorespiratory fitness, as quantified by peak oxygen uptake (VO2peak) and treadmill time, in patients aged 6 through 18 years referred for cardiopulmonary exercise testing (CPET). STUDY DESIGN: We reviewed a clinical pediatric CPET database for fitness data in children aged 6-18 years with no underlying heart disease. CPET was obtained via the Bruce protocol utilizing objectively confirmed maximal effort via respiratory exchange ratio. Fitness data (VO2peak and treadmill test duration) were analyzed to determine age- and sex-specific reference values for this pediatric cohort. RESULTS: Data from 2025 pediatric CPETs (53.2% female) were included in the analyses. VO2peak increased with age in males, but not females. Treadmill test duration increased with age in both males and females. Fitness was generally higher in males when compared with females in the same age groups. CONCLUSIONS: Our study provides extensive reference values for both VO2peak and total treadmill test time via the Bruce protocol for a pediatric population without known cardiac disease. Furthermore, the inclusion of objectively confirmed maximal exercise effort increases confidence in these findings compared with prior studies in this area. Clinicians performing CPET in pediatric populations can utilize these reference values to characterize test results according to representative peer data.