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The post-acute phase of coronavirus disease 2019 (COVID-19) is often marked by several persistent symptoms and exertional intolerance, which compromise survivors' exercise capacity. This was a cross-sectional study aiming to investigate the impact of COVID-19 on oxygen uptake (V̇o2) kinetics and cardiopulmonary function in survivors of severe COVID-19 about 3-6 mo after intensive care unit (ICU) hospitalization. Thirty-five COVID-19 survivors previously admitted to ICU (5 ± 1 mo after hospital discharge) and 18 controls matched for sex, age, comorbidities, and physical activity level with no prior history of SARS-CoV-2 infection were recruited. Subjects were submitted to a maximum-graded cardiopulmonary exercise test (CPX) with an initial 3-min period of a constant, moderate-intensity walk (i.e., below ventilatory threshold, VT). V̇o2 kinetics was remarkably impaired in COVID-19 survivors as evidenced at the on-transient by an 85% (P = 0.008) and 28% (P = 0.001) greater oxygen deficit and mean response time (MRT), respectively. Furthermore, COVID-19 survivors showed an 11% longer (P = 0.046) half-time of recovery of V̇o2 (T1/2V̇o2) at the off-transient. CPX also revealed cardiopulmonary impairments following COVID-19. Peak oxygen uptake (V̇o2peak), percent-predicted V̇o2peak, and V̇o2 at the ventilatory threshold (V̇o2VT) were reduced by 17%, 17%, and 12% in COVID-19 survivors, respectively (all P < 0.05). None of the ventilatory parameters differed between groups (all P > 0.05). In addition, COVID-19 survivors also presented with blunted chronotropic responses (i.e., chronotropic index, maximum heart rate, and heart rate recovery; all P < 0.05). These findings suggest that COVID-19 negatively affects central (chronotropic) and peripheral (metabolic) factors that impair the rate at which V̇o2 is adjusted to changes in energy demands.NEW & NOTEWORTHY Our findings provide novel data regarding the impact of COVID-19 on submaximal and maximal cardiopulmonary responses to exercise. We showed that V̇o2 kinetics is significantly impaired at both the onset (on-transient) and the recovery phase (off-transient) of exercise in these patients. Furthermore, our results suggest that survivors of severe COVID-19 may have a higher metabolic demand at a walking pace. These findings may partly explain the exertional intolerance frequently observed following COVID-19.

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Abstract Introduction: The Six-Minute Walk Test (6MWT) is widely used to assess functional capacity in children. The measure of work during 6MWT can add important information to the 6MWT assessment in this population as it relates to walking efficiency. Objective: To verify the determinants of work during the Six-Minute Walk Test (6MWTwork) in school-aged children. Method: This is a cross-sectional and exploratory study that included healthy children recruited from the public and private schools of the cities of Belo Horizonte and Uberlândia, Brazil. The inclusion criteria were: children aged 7 to 12 years without diagnosis of chronic cardiorespiratory disease, cognitive, behavioral disorder or physical function impairment (information obtained through self-report of those responsible for children). Exclusion criteria were children who refused to perform the 6MWT; who did not understand the 6MWT or who did not answer the test commands. Three hundred and nineteen school-aged children were included in the study. Correlation analyses and multiple linear regression analysis were used to identify the variables associated with the 6MWTwork. Results: Age, height, nutritional status, physical activity and heart rate showed significant correlation with 6MWTwork (p <0.001) and explained 87% of its variation (p = 0.0001). Conclusion: Age, height, nutritional status and heart rate variation are determinants of 6MWTwork that is able to evaluate functional capacity of school-aged children.

Resumo Introdução: O teste de caminhada de seis minutos (TC6min) é amplamente utilizado para avaliar a capacidade funcional em crianças. A medida do trabalho durante o TC6 poderia adicionar informações importantes à avaliação do TC6 nessa população, no que se refere à eficiência da marcha. Objetivo: Verificar os determinantes do trabalho durante o Teste de Caminhada (TC6min) em crianças em idade escolar. Método: Trata-se de um estudo transversal e exploratório que incluiu crianças saudáveis recrutadas nas escolas públicas e privadas das cidades de Belo Horizonte e Uberlândia, Brasil. Os critérios de inclusão foram: crianças de 7 a 12 anos sem diagnóstico de doença cardiorrespiratória crônica, distúrbio cognitivo, comportamental ou comprometimento da função física (informações obtidas por auto-relato dos responsáveis pelas crianças). Os critérios de exclusão foram: crianças que se recusaram a realizar o TC6; que não entenderam o TC6 ou que não responderam aos comandos de teste. Trezentos e dezenove crianças em idade escolar foram incluídas no estudo. Análises de correlação e análise de regressão linear múltipla foram utilizadas para identificar as variáveis associadas ao trabalho com TC6. Resultados: Idade, altura, estado nutricional, atividade física e frequência cardíaca apresentaram correlação significativa com o trabalho durante o TC6min (p <0,001) e explicaram 87% de sua variação (p = 0,0001). Conclusão: Idade, altura, estado nutricional e variação da frequência cardíaca são determinantes do trabalho no TC6, e portanto, devem ser considerados na avaliação da capacidade funcional de crianças em idade escolar.

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OBJECTIVE: The aim of this study was to evaluate the test-retest reliability, concurrent validity and agreement with peak oxygen uptake (VO2 ) obtained during cardiopulmonary exercise testing (CPX) on a treadmill for the incremental shuttle walking test (ISWT) in obese women. METHODS: Prospective study with a convenient sample of 46 community-dwelling obese women (BMI > 30 kg m(-2) ). The main outcome measures were walking distance on the ISWT and peak VO2 . RESULTS: Test-retest reliability was good to excellent for the exercise tests (ISWT distance ICC: 0.90; and CPX peak VO2 ICC: 0.90). Peak VO2 obtained during CPX correlated significantly with ISWT distance (r = 0.54, P<0.05) and peak VO2 obtained during the ISWT (r = 0.64, P<0.05). Bland and Altman plots demonstrated a high degree of repeatability. CONCLUSION: The ISWT had excellent reliability as well as good concurrent validity and agreement. The ISWT may be a potential tool for monitoring clinical status and intervention efficacy (e.g. programmes for weight loss and rehabilitative strategies) in this population.

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A resposta cardiorrespiratória durante exercícios submáximos, na intensidade da máxima fase estável de lactato (MFELint) até a exaustão, tem sido pouco investigada. O objetivo deste estudo foi investigar a resposta do consumo de oxigênio (VO2), frequência cardíaca (FC) e pulso de oxigênio (pulso O2) em exercício realizado na MFELint até a exaustão, e comparar o gasto energético (GE) estimado pelo VO2 e pela FC. Doze sujeitos treinados realizaram um protocolo incremental em cicloergômetro para determinar parâmetros máximos e submáximos do metabolismo aeróbio. Posteriormente, foram realizados 2 a 4 testes de 30 min com carga constante para identificar a MFELint. Finalmente, os sujeitos realizaram um teste até a exaustão na MFELint. Os parâmetros cardiorrespiratórios foram medidos continuamente durante todos os testes. No teste de exaustão, as respostas fisiológicas foram comparadas entre seis momentos relativos do tempo de exaustão (TTE). O TTE médio foi 55,1±10,2 min. O pulso de O2 apresentou reduções significativas ao longo do tempo, atingindo, no momento da exaustão, um valor ~ 9% inferior comparado ao início do exercício. Este fato ocorreu pelo aumento da FC ao longo do tempo de forma desproporcional ao aumento do VO2, resultando em diferenças significantes entre os GE estimados. Portanto, em exercício realizado na MFELint até a exaustão, parece existir uma perda gradual da eficiência cardiorrespiratória, evidenciada pela redução do pulso O2. Assim, a relação direta entre VO2 e FC com a carga de trabalho é alterada ao longo do exercício, conduzindo a erros de estimativa do GE a partir dos valores da FC.

There has been little research regarding cardiorespiratory responses during submaximal exercise at the maximal lactate steady state intensity (MLSSint) until exhaustion. The objective of this study was to investigate the responses of oxygen consumption (VO2), heart rate (HR) and oxygen pulse (O2 pulse) during exercise to exhaustion at MLSSint, and to compare energy expenditure (EE) estimated by VO2 and HR. Twelve trained athletes followed an incremental protocol on a cycle ergometer to determine maximal and submaximal parameters of aerobic metabolism. On subsequent occasions they performed 2 to 4 30-minute tests with constant load to identify MLSSint. Finally, they underwent a test to exhaustion at MLSSint. Cardiorespiratory parameters were measured continuously during all tests. During the test to exhaustion, physiological responses were compared for six points in time calculated as percentages of the time to exhaustion (TTE). Mean TTE was 55.1±10.2 min. Oxygen pulse presented significant reduction over time, decreasing to a value 9% lower than baseline at the exhaustion point. This fact was the result of increases in HR over time that was disproportional to the increase in VO2, resulting in significant differences between EE estimates. Therefore, there appears to be a gradual loss of cardiorespiratory efficiency during exercise to exhaustion at MLSSint that is shown by the reduction in O2 pulse. The direct relationship between VO2 and HR with workload presents variations over the course of exercise, leading to errors when EE is estimated using HR.

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This study aimed to evaluate if androgenic-anabolic steroids (AAS) abuse may induce cardiac autonomic dysfunction in recreational trained subjects. Twenty-two men were volunteered for the study. The AAS group (n = 11) utilized AAS at mean dosage of 410 ± 78.6 mg/week. All of them were submitted to submaximal exercise testing using an Astrand-Rhyming protocol. Electrocardiogram (ECG) and respired gas analysis were monitored at rest, during, and post-effort. Mean values of VO2 , VCO2 , and VE were higher in AAS group only at rest. The heart rate variability variables were calculated from ECG using MATLAB-based algorithms. At rest, AAS group showed lower values of the standard deviation of R-R intervals, the proportion of adjacent R-R intervals differing by more than 50 ms (pNN50), the root mean square of successive differences (RMSSD), and the total, the low-frequency (LF) and the high-frequency (HF) spectral power, as compared to Control group. After submaximal exercise testing, pNN50, RMSSD, and HF were lower, and the LF/HF ratio was higher in AAS group when compared to control group. Thus, the use of supraphysiological doses of AAS seems to induce dysfunction in tonic cardiac autonomic regulation in recreational trained subjects.

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PURPOSE: The purpose of this study was to investigate the oxidative stress response to a short duration bout of submaximal exercise in a cohort of healthy young adults. METHODS: 15 apparently healthy college age males and females completed a modified Bruce-protocol treadmill test to 75-80% of their heart rate reserve. Blood samples collected immediately before (pre-exercise), immediately after, 30, 60 and 120 minutes post-exercise were assayed for total antioxidant capacity (TAC), superoxide disumutase (SOD), thiobarbituric acid-reactive substances (TBARS), and protein carbonyls (PC). RESULTS: SOD activity was significantly increased from pre-exercise levels at 30 minutes (77%), 60 minutes (33%), and 120 minutes (37%) post-exercise. TAC levels were also significantly increased from pre-exercise levels at 60 minutes (30%) and 120 minutes (33%) post-exercise. There were no significant changes in biomarkers for reactive oxygen/nitrogen species (RONS) mediated damage (TBARS and PC) across all post-exercise time points. CONCLUSIONS: In a cohort of healthy young adults, a short duration bout of submaximal aerobic exercise elicited increases in antioxidant activity/concentration, but did not evoke changes in oxidative stress-induced damage. These results may suggest that: (1) short duration bouts of submaximal aerobic exercise are sufficient to induce RONS generation; and (2) the antioxidant defense system is capable of protecting against enhanced RONS production induced by a short duration, submaximal exercise bout in healthy young adults.

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El objetivo del presente estudio fue de evaluar el efecto del acullico de coca en la capacidad física de consumidores habituales de coca. La población del estudio fueron 22 hombres sanos del Altiplano Boliviano, 14 de los cuales no consumían coca más de 3 veces al año (grupo NC) y 8 acullicaban 3-4 veces por semana (grupo C). La metodología consistió en la medición del consumo máximo de oxígeno y parámetros relacionados así como variables bioquímicas en dos pruebas de esfuerzo en bicicleta ergométrica: La primera fue una prueba de esfuerzo controlado progresivo hasta el máximo y la segunda una prueba de esfuerzo submáximo prolongado a una carga de trabajo de 60-70% de la carga máxima alcanzada en la primera prueba. El grupo C hizo ambas pruebas después de haber acullicado coca durante una hora previa. Se obtuvieron varias muestras de sangre venosa de ambos grupos de sujetos para obtener valores sanguíneos de lactato, adrenalina, noradrenalina, glucosa, insulina y ácidos grasos libres. Los resultados de la prueba máxima evidenciaron un consumo máximo de oxígeno similar en ambos grupos. La única diferencia signifi cativa fue una mayor desaturación de oxígeno en el grupo C que en el grupo NC. Las diferencias entre C y NC se evidenciaron en la prueba submáxima de esfuerzo prolongado donde C mantuvo el consumo de oxígeno estable mientras que NC incremento este parámetro signifi cativamente. Además el grupo C tuvo niveles mayores de adrenalina, noradrenalina y de glucosa y de ácidos grasos circulantes así como niveles menores de insulina. Concluimos que los acullicadores no pueden realizar un trabajo más intenso que los no-acullicadores, pero que pueden tolerar mejor el esfuerzo prolongado como demuestra el consumo de oxígeno estable. El incremento del nivel de glucosa y de los ácidos grasos libres circulantes en C indica que la mejor tolerancia...

The aim of our study was to assess the effects of coca chewing on the exercise capacity of habitual coca chewers. The study population were 22 healthy men from the Bolivian Altiplano, 14 of which did not chew coca more than 3 times per year (group NC) and 8 used coca 3-4 times per week. The methodology consisted in measuring maximal oxygen uptake and related parameters as well as biochemical variables during 2 exercise tests on a bicycle ergometer. The fi rst test was of controlled progressive exercise up to maximal level, and the second consisted of prolonged submaximal exercise during one hour at 60-70% of the maximal level reached in the fi rst test. Group C did both tests after having chewed coca during one hour previously. Various venous blood samples were obtained from both groups for measuring blood levels of lactate, epinephrine, nor-epinephrine, glucose, insulin and free fatty acids. The results of the maximal exercise test showed similar values of maximal oxygen uptake in both groups. The only signifi cant difference was a greater oxygen desaturation in group C than in NC. The differences between C and NC became evident in the prolonged submaximal test, where C maintained the oxygen uptake whereas NC increased the oxygen consumption signifi cantly. Additionally, group C had higher levels of epinephrine, norepinephrine, glucose and free fatty acids and lower levels of insulin. We concluded that coca chewers are not able to do more intensive work than non-chewers, but that they tolerate effort better as shown by their stable oxygen uptake. The increase of glucose levels and circulating free fatty acids indicates that the better tolerance of prolonged effort in C might be due to a belated decrease of the glycogen stores.

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Introdução: Na fibrose cística (FC), o estado nutricional está associado com o crescimento, função pulmonar e índices de sobrevida. Objetivo: Avaliar o estado nutricional em adultos com FC e correlacionar com escore clínico, escore radiológico, pressões respiratórias estáticas máximas, capacidade submáxima de exercício e função pulmonar. Metodologia: O estudo realizado foi transversal e prospectivo, em pacientes (16 anos ou mais), atendidos em um programa para adultos com FC. Os pacientes foram submetidos a uma avaliação nutricional e clínica, ao teste de caminhada de seis minutos (TC6), à medida das pressões respiratórias máximas, a espirometria e exame radiológico do tórax. Resultados: O estudo incluiu 41 pacientes com media de idade de 23,7 ± 6,5 anos e média de índice de massa corporal (IMC) de 20,2 ± 2,2 Kg/m2. Vinte e seis pacientes (63,4%) foram classificados como bem nutridos (IMC =21,7 ± 2,0 Kg/m2), 6 (14,6%) como risco nutricional (IMC = 19,4 ± 0,5 Kg/m2) e 9 (22%) como desnutridos (IMC = 17,6 ± 0,8 Kg/m2). Não houve correlação significativa entre IMC e a idade (r = 0,24; P = 0,13), idade do diagnóstico (r = -0,04; P = 0,81), escore clínico (r = 0,13; P = 0,40) e radiográfico (r = -0,22; P = 0,17), distância percorrida no TC6 (r = 0,20; P = 0,20), VEF1 % (r = 0,11; P = 0,50) e CVF % (r =0,06; P = 0,72). Também não houve associação entre o declínio do estado nutricional e essas variáveis. Conclusão: Este estudo mostrou que a maioria dos pacientes com FC (16 anos ou mais) tem um adequado estado nutricional (63,4%), mas uma porcentagem significante (36,6%) tem depleção nutricional. Não houve associação entre o estado nutricional e a função pulmonar, pressões respiratórias máximas, escore clínico e radiográfico e a capacidade submáxima de exercício

Introduction: In cystic fibrosis (CF) nutritional status is associated with growth, lung function and survival rates. Objective: To evaluated the nutritional status in adults with CF and correlating with clinical score, chest radiographic score, maximal respiratory pressures, submaximal exercise capacity and pulmonary function. Methods: This was a prospective cross-sectional study in patients (16 years and older) attending to an adult CF program. The patients were submitted to a clinical and nutritional evaluation, six minute walk test (6MWT), maximal respiratory pressures, spirometry and chest roentgenograms. Results: The study included 41 patients with a mean age of 23.7 ± 6.5 years and a mean body mass index (BMI) of 20.2 ± 2.2 Kg/m2. Twenty six patients (63.4%) were classified as well nourished (BMI = 21.7 ± 2.0 Kg/m2), six (14.6%) were at nutritional risk (BMI = 19.4 ± 0.50 Kg/m2) and 9 (22%) were malnourished (BMI = 17.6 ± 0.8 Kg/m2). There were no significant correlation between BMI and age (r = 0.24; P = 0.13), age at diagnosis (r = -0.04; P = 0.81), clinical (r = 0.13; P = 0.40) and radiographic (r = -0.22; P = 0.17) scores, distance walked in 6MWT (r = 0.20; P = 0.20), FEV1 % (r = 0.11; P = 0.50) and FVC % (r = 0.06; P = 0.72). Also, there were no significant association between the decline of nutritional status and these variables. Conclusion: This study showed that the majority of patients with CF (16 years and older) have an adequate nutritional status (63.4%), but a significant percentage (36.6%) have a nutritional depletion. There was no significant association between nutritional status and pulmonary function, maximal respiratory pressures, clinical and chest radiographic score and submaximal exercise capacity

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