Determinants of Work in the Six-Minute Walk Test in School-Age Children / Determinantes do trabalho no Teste de Caminhada de Seis Minutos em escolares

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.

The evaluation of intraocular pressure fluctuation in glaucoma subjects during submaximal exercise using an ocular telemetry sensor

Purpose: To evaluate the effect of acute submaximal exercise on intraocular pressure (IOP) fluctuations in open-angle glaucoma (OAG) subjects using an ocular telemetry sensor (OTS, Sensimed TriggerFish®). Methods: Twelve OAG subjects aged 45–65 years with no medical limitation for exercise were included in this prospective study. A submaximal exercise test was performed using a cycle ergometer for 20 min during which OTS voltages and metabolic parameters were recorded continuously. IOP voltages taken before, during, and after exercise were compared using the Friedman test and correlations with the metabolic parameters were evaluated using the Spearman analysis. Results: In two subjects, the OTS stopped functioning after a few hours. Median OTS measurements were 37.60 mVeq 10 min before exercise [interquartile range (IQR) 137.27], 51.75 (IQR 121.2), 62.35 (IQR 123.72), 54.6 (IQR 141.3), and 59.7 mVeq (IQR 196.7) during exercise (4 time points, 5 min apart), and 50.7 (IQR 147.35) and 64.2 mVeq (IQR 103.25) 10 and 30 min after exercise and the change was statistically non-significant (P = 0.66). No correlations were found between OTS and metabolic parameters measured at the same time points (P > 0.05). Nocturnal acrophase pattern was detected in five subjects (50%), diurnal acrophase in two patients, and double-hump in two patients. Median IOP voltages in the morning, afternoon/evening, and night were 335.84, 149.15, and 341.38 mVeq, respectively (P < 0.001). Conclusion: Continuous IOP monitoring did not reveal a remarkable voltage change in OAG patients during or immediately after exercise, but nocturnal IOP peaks in half of the patients.

Resposta cardiorrespiratoria e gasto energetico em exercicio na maxima fase estavel de lactato / Cardiorespiratory response and energy expenditure during exercise at maximal lactate steady state

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.

Cardiopulmonary fitness test among Nepalese students

Background and Objectives: Maximum Oxygen uptake (VO2 max) is a good predictor of cardiopulmonary and muscle fitness. Maximum oxygen uptake is defined as the highest rate at which oxygen can be taken up and utilize by body during severe exercise. The present study aims to find out the level of VO2 max using Mc Ardle equation and to compare obtained values from Chatterjee’s equation in Nepalese population. Methodology: Maximum oxygen uptake was determined by using the Queen’s college step-stool of 16.25 inches and popular Mc Ardle equation. Stepping was done for a total duration of 3 minutes at the rate of 24 cycles per minute for males and 22 cycles per minute for females. After completion of the exercise, subjects remained standing while the carotid pulse rate was taken as heart rate. Maximum oxygen uptake was calculated using obtained heart rate. Results: Queen’s college step test (QCT) was used as a submaximal exercise and the estimated VO2 max in boys and girls was 48.8± 7.3 ml/kg/min and 37.4± 2.7 ml/kg/min respectively with Mc Ardle equation and the value was higher when compared with Chatterjee’s equations. The value of VO2 max was observed and found to be less in smokers and sedentary individuals. Conclusion: As the values of VO2 max obtained from different equations are different, this research strongly argues the need of developing a prediction equation specifically for the Nepalese population.

Sobre la influencia del acullico de coca en la capacidad física / On the influence of coca acullico in the physical ability

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.

Validity of the Prediction Equation of the Maximal OxygenConsumption in Submaximal Exercise Test

OBJECTIVE: To explore accuracy and validity of a VO2max prediction equation of the multistage model using by modified Bruce protocol submaximal exercise test in healthy subjects. METHOD: Thirty three healthy subjects (age: 44.0+/-12.9) were recruited. VO2max was measured during treadmill by direct gas analysis from a maximal incremental test. VO2max was then predicted from multistage model equation with age, measured oxygen consumption and heart rate during a maximal incremental treadmill test. And the predicted VO2max values from equation were compared with the measured VO2max values. RESULTS: The predicted VO2max values and the measured VO2max values were highly correlated (r=0.9, p<0.001). The predicted VO2max values (2,285.3+/-536.0 ml/min) were not significantly different from the measured VO2max values (2,285.5+/-598.5 ml/min). CONCLUSION: In healthy subjects, the multistage model equation offers a fairly accurate VO2max prediction. Therefore the equation can be used in the estimation of VO2max at modified Bruce protocol in an aerobic exercise program.

Usefulness of the Oxygen Uptake Efficiency Slope in the Evaluation of Cardiorespiratory Fitness of the Stroke Patients

OBJECTIVE: To investigate the usefulness of the oxygen uptake efficiency slope (OUES) in the evaluation of cardiorespiratory fitness of the stroke patients. METHOD: 25 stroke patients who could walk independently were included in this syudy. The symptom-limited graded treadmill test was performed to assess cardiovascular fitness. During the test, minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory exchange ratio (RER) and anaerobic threshold (AT) were measured through respiratory gas analysis. A linear relationship was established between the oxygen consumption and the logarithmic transformation of minute ventilation. From this linear relationship, we obtained a slope that represented the OUES. OUES values were obtained from data corresponding to 75% (OUES75), 90% (OUES90) and 100% (OUES100) of the exercise duration. RESULTS: The differences among OUES75, OUES90 and OUES100 groups were not statistically significant and these three groups were highly correlated to each other. Maximal oxygen consumption (VO2max) was positively correlated with OUES75 (r=0.723), OUES90 (r=0.762), OUES100 (r=0.809) and AT (r=0.696), respectively (p<0.01). CONCLUSION: OUES is considered to be the valuable submaximal index to evaluate the cardiorespiratory fitness of stroke patients who can not reach maximal exercise.

Estado nutricional em pacientes atendidos por um programa de adultos para fibrose cística / Nutritional status in patients seen at an adult program for cystic fibrosis patients

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

Breathing Reserve Index at Anaerobic Threshold of Cardiopulmonary Exercise Test in Chronic Obstructive Pulmonary Disease / 결핵

OBJECTIVE: Cardiopulmonary exercise test is a useful tool to evaluate the operative risk and to plan exercise treatment for the patients with chronic obstructive pulmonary disease(COPD). In cardiopulmonary exercise test, most of the measured parameters are recorded at the time of peak exercise, which are hard to attain in COPD patients. So we evaluated the usefulness of the parameter, breathing reserve index(BRI=minute ventilation [VE]/maximal voluntary ventilation[MVV]) at the time of anaerobic threshold(BRIAT) for the differentiation of COPD patients with normal controls. METHODS: Thirty-six COPD patients and forty-two healthy subjects underwent progressive, incremental exercise test with bicycle ergometer upto possible maximal exercise. All the parameters was measured by breath by breath method. RESULTS: The maximal oxygen uptake in COPD patients (mean+/-SE) was 1061.2+/-65.6ml/min which was significantly lower than 2137.6+/-1.4ml/min of normal subjects(p or =1.09) was accomplished in 7 of 36 COPD patients(19.4%) and in 18 of 42 normal subjects(42.9%). The BRIAT of COPD patients was higher(0.50+/-0.03) than that of control subject(0.28+/-0.02, p<0.01), reflecting early hyperventilation in COPD patient during exercise. The correlation between BRIAT and BRI at maximal exercise in COPD patients was good(r=0.9687, p<0.01). CONCLUSION: The BRIAT could be a useful parameter for the differentiation of COPD patients with normal controls in the submaximal cardiopulmonary exercise test.

Validity analysis of for exercise tests in assessing aerobic capacity of young men

BACKGROUND: Assessment of aerobic capacity (VO2max) is one of the essential components in exercise prescription for health promotion and maintenance. This study was conducted to compare the validity of four exercise tests to assess aerobic capacity in young adult male subjects by comparing them to the values measured from maximal ergometer exercise test (criterion VO2max). METHODS: Twenty young healthy adult males (M+/-SD=21.1+/-1.5 years) volunteered as subjects. Criterion VO2max was calculated and printed out automatically by computerized analysis system of expired air samples collected during maximal ergometer exercise test. VO2max was estimated for each subject from heart rate at submaximal workloads on the cycle ergometer using the Astrand-Rhyming nomogram(A/R) and Fox protocol(FOX) and the computerized multiple extrapolation method (XTP). The score got from Havard step test(H/S) was used to compare the validity. The validity of the procedures was based on the evaluation of the predicted VO2max (from A/R, FOX, XTP, and H/S) versus the criterion VO2max via the calculation of constant error (CE=mean difference for predicted minus criterion VO2max), r value, standard error of the estimate[SEE=SD(1-r2)(1/2)], total error [TE=(sigma(predicted VO2max - criterion VO2max)(2)/n)(1/2)]. RESULTS: In relation to criterion VO2max, the XTP and A.R underpredicted (XTP: 40.8 ml/kg/min SD=4.1; A/R: 37.3 ml/kg/min SD=5.0) and the H/S and FOX overpredicted (H/S: 48.0 ml/kg/min SD=5.9: FOX 46.3 ml/kg/min SD=5.5). Dunnett post-hoc procedures revealed that there were significant (P<0.05) mean differences (CE) for VO2max from A/R versus criterion. The validity coefficients for VO2max derived from XTP, H/S, A/R, and FOX were 0.68, 0.53, 0.50, and 0.49, respectively. TE of the XTP, FOX, H/S and A/R, which accounts for the effects of both the CE and SEE, were 5.73, 6.13, 6.75, and 8.87, respectively. CONCLUSIONS: These results suggest that the XTP is recommended first for estimation VO2max in young adult males. It is also considered that further studies about female and other age groups are necessary.

The effects of alcohol ingestion on temperature regulation during submaximal exercise / 体力科学

The purpose of this study was undertaken to examine the effects of alcohol ingestion on temperature regulation during submaximal exercise. Five healthy male students participated in this study. Forty minutes of supine exercise using a bicycle ergometer was done following and without alcohol ingestion of 0.44 m<I>l</I>/kg. Respiratory gas exchange, rectal temperature, skin temperatures at 6 sites, finger blood flow, and heart rate were measured before and during the exercise. Respiratory gas exchange was measured by the Douglas bag method during 8-10, 1820, 28-30 min periods of exercise. Thermistor sensors were applied to measure rectal and skin temperatures, and finger blood flow was measured by venous occlusion plethysmography using a mercury rubber strain gauge. After low doses of alcohol, marked increase in finger blood flow and heart rate were observed in all subjects at rest. During exercise, VE, VO<SUB>2</SUB>, VCO<SUB>2</SUB>, and RQ were not different between the experiments with and without alcohol ingestion except only VE during the 8-10 min period. The rises in rectal temperature during exercise were the same between the two conditions. Heart rate was significantly higher after alcohol ingestion during the period of 20 to 40 min of exercise. Finger blood flow tended to be higher with alcohol ingestion, but not significant. It was suggested that low doses of alcohol (0.44 m<I>l</I>/kg) did not affect thermoregulatory or respiratory responses during submaximal exercise.