Validity of a new portable indirect calorimeter: the AeroSport TEEM 100

Nitrate-rich beet juice intake on cardiovascular performance in response to exercise in postmenopausal women with arterial hypertension: study protocol for a randomized controlled trial

BACKGROUND

There is no evidence of the use of beetroot juice with a previously recommended dose of nitrate (NO3) (> 300 mg) on the cardiovascular performance during and recovery following exercise in postmenopausal women with systemic arterial hypertension (SAH).

METHODS

We will investigate the effects of beetroot juice rich in NO3 acutely (800 mg) and during a week with daily doses (400 mg) on blood pressure, heart rate (HR), cardiac autonomic control, endothelial function, inflammatory, hormonal, and stress biomarkers oxidative stress and enzymes involved in nitric oxide synthesis and mitochondrial regulation, under resting conditions, as well as mediated by submaximal aerobic exercise sessions. Through a randomized, crossover, triple-blind, placebo-controlled clinical trial, 25 physically inactive women with SAH will undergo an acute and 1-week trial, each with two intervention protocols: (1) placebo and (2) beetroot, in which will ingest beet juice with or without NO3 in its composition with a 7-day washout interval. On collection days, exercise will be performed on a treadmill for 40 min at a speed corresponding to 65-70% of VO2peak. The collection of variables (cardiovascular, autonomic, and blood samples for molecular analyses) of the study will take place at rest (135 min after ingestion of the intervention), during exercise (40 min), and in the effort recovery stage (during 60 min) based on previously validated protocols. The collections were arranged so that the measurement of one variable does not interfere with the other and that they have adequate intervals between them.

DISCUSSION

The results of this research may help in the real understanding of the nutritional compounds capable of generating safety to the cardiovascular system during physical exercise, especially for women who are aging and who have cardiovascular limitations (e.g., arterial hypertension) to perform physical exercise. Therefore, our results will be able to help specific nutritional recommendations to optimize cardiovascular health.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05384340. Registered on May 20, 2022.

Acute Effects of Energy Drink on Autonomic and Cardiovascular Parameters Recovery in Individuals with Different Cardiorespiratory Fitness: A Randomized, Crossover, Double-Blind and Placebo-Controlled Trial

Fundamento

Tem-se sugerido que o consumo de bebidas energéticas (BEs) possa afetar a atividade cardiovascular.

Objetivos

Investigar os efeitos agudos da ingestão de BE sobre a variabilidade da frequência cardíaca (VFC) recuperação cardiovascular após exercício aeróbico moderado em homens de diferentes capacidades cardiorrespiratórias.

Métodos

Este é um estudo randomizado, duplo cego, crossover, controlado por placebo. Vinte e oito jovens adultos foram divididos em dois grupos de acordo com o pico de consumo de oxigênio (pico de VO2): (1) pico de VO2 alto (AO) – pico de VO2 > 52,15 mL/Kg/min, e (2) pico de VO2 baixo (BO) - pico de VO2 <52,15 mL/Kg/min. Os indivíduos de ambos os grupos foram submetidos a dois protocolos de exercícios em ordem aleatória: exercício moderado aeróbico (60% de pico de VO2) após a ingestão de 250 mL de água (protocolo placebo) ou 250 mL de BE (protocolo BE). Durante os testes de exercício, foram registrados valores de parâmetros cardiorrespiratórios e de VFC.

Resultados

Foram observadas diferenças significativas para o índice de LF (unidades normalizadas) entre “repouso” e “Rec1” nos grupos de AO e BO durante o protocolo BE. Para a razão LF/HF, foram observadas diferenças significativas entre “repouso” e Rec1 nos grupos AO e BO nos protocolos BE.

Conclusão

A ingestão aguda de BE retardou a recuperação da frequência cardíaca após o exercício em indivíduos com capacidade cardiorrespiratória baixa e indivíduos com capacidade cardiorrespiratória alta.

Energy Drink before Exercise Did Not Affect Autonomic Recovery Following Moderate Aerobic Exercise: A Crossover, Randomized and Controlled Trial

Introduction: Energy drink (ED) intake could initiate physiological changes owing to its stimulant characteristics and, it improves endurance and athletic performance. We evaluated the acute effects of ED on autonomic heart rate (HR) control during recovery after a session of submaximal aerobic exercise.Method: The study was completed by submitting 29 healthy males between 18 and 30 years old to three conventions: (A) Maximum exercise test by the adapted Bruce protocol; (B) Placebo protocol (PP) - water intake 15 minutes prior to exercise, rest in dorsal decubitus for 15 minutes followed by 5 minutes of treadmill running at 1% inclination, initial speed of 5 km/h for 5 minutes 25 minutes with 60% of the velocity consistent to the maximum oxygen consumption (VO2max), and finally 60 minutes of recovery at rest in the supine position; (C) Experimental protocol (PE) - similar to PP previously, but with ED intake 15 minutes before physical exercise. The time, frequency and geometric indexes of HR variability (HRV) were inspected before and after exercise.Results: There was a significant (p < 0.05, <5%) effect on the HRV index (HR-nu and ms², LF-nu and ms², LF/HF, SD1, SDNN and RMSSD), indicating a reduction in HRV in the first 5 minutes after exercise in both protocols (PP and PE). Yet, no protocol interaction was detected, suggesting no effect of ED on HRV throughout recovery after submaximal aerobic exercise.Conclusion: There was no significant effect of ED on the autonomic control of HR in the recovery phase after submaximal aerobic exercise.

Reliable Breathing Tracking with Wearable Mask Device

Breathing tracking is critical for the assessment of lung functions, exercise physiologies, and energy expenditure. Conventional methods require using a face mask or mouthpiece that is connected to a stationary equipment through a tube, restricting the location, movement, or even the posture. To obtain accurate breathing physiology parameters that represent the true state of the patient during different scenarios, a wearable technology that has less intervention to patient's activities in free-living conditions is highly preferred. Here, we propose a miniaturized, reliable, and wide-dynamic ranged flow sensing technology that is immune to orientation, movement, and noise. As far as we know, this is the first work of introducing a fully integrated mask device focusing on breath tracking in free-living conditions. There are two key challenges for achieving this goal: miniaturized flow sensing and motion-induced artifacts elimination. To address these challenges, we come up with two technical innovations: 1) in hardware wise, we have designed an integrated flow sensing technique based on differential pressure Pneumotach approach and motion sensing; 2) in software wise, we have developed comprehensive algorithms based baseline tracking and orientation and motion compensation. The effectiveness of the proposed technology has been proven by the experiments. Experimental results from simulator and real breath conditions show high correlation (R² = 0.9994 and 0.9964 respectively) and mean error within 2.5% for Minute Volume (VE), when compared to values computed from reference methods. These results show that the proposed method is accurate and reliable to track the key breath parameters in free-living conditions.

Validity and Reliability of the New Portable Metabolic Analyzer PNOE

Assessment of the oxygen and carbon dioxide content of expired air during exercise is critical for determining cardiorespiratory status. The purpose of this study was to compare the new portable metabolic analyzer PNOE with COSMED – Quark CPET, a previously validated stationary metabolic cart.

Methods: A total of 22 subjects (17 male and 5 female) aged 32.3 ± 11.1 years took part in the study. Breath by breath gas exchange was measured by both devices during a four-stage incremental protocol on a cycle ergometer. On a separate day, 10 participants repeated the trial to assess the reliability of the PNOE metabolic cart.

Results: Strong correlations were obtained in VO₂ (r = 0.98, p < 0.001), VCO₂ (r = 0.98, p < 0.001), VE (r = 0.98, p < 0.001), and RQ (r = 0.91, p < 0.001), between the two devices. Bland-Altman plots revealed a mean difference of 34.0 ± 118 ml/min and 36.4 ± 110 ml/min in VO₂ and VCO₂ analysis, respectively. There were no significant differences in VO₂, VCO₂, VE, or RQ between the two devices. Intraclass correlation coefficient was high between the two trials for VO₂ (r = 0.98, p < 0.001), VCO₂ (r = 0.98, p < 0.001), VE (r = 0.99, p < 0.001), and RQ (r = 0.93, p < 0.001).

Conclusions: Our data indicate that the portable metabolic cart PNOE can accurately determine respiratory gases over a wide range of exercise intensities, in healthy individuals, in a controlled laboratory setting.

Yoga and breathing technique training in patients with heart failure and preserved ejection fraction: study protocol for a randomized clinical trial

Background

Current therapies for heart failure (HF) are followed by strategies to improve quality of life and exercise tolerance, besides reducing morbidity and mortality. Some HF patients present changes in the musculoskeletal system and inspiratory muscle weakness, which may be restored by inspiratory muscle training, thus increasing respiratory muscle strength and endurance, maximal oxygen uptake (VO₂), functional capacity, respiratory responses to exercise, and quality of life. Yoga therapies have been shown to improve quality of life, inflammatory markers, and peak VO₂ mostly in HF patients with a reduced ejection fraction. However, the effect of different yoga breathing techniques in patients showing HF with a preserved ejection fraction (HFpEF) remain to be assessed.

Methods/design

A PROBE (prospective randomized open blinded end-point) parallel-group trial will be conducted at two specialized HF clinics. Adult patients previously diagnosed with HFpEF will be included. After signing informed consent and performing a pre-test intervention, patients will be randomized into three groups and provided with either (1) active yoga breathing techniques; (2) passive yoga breathing techniques (pranayama); or and (3) control (standard pharmacological treatment). Follow-up will last 8 weeks (16 sessions). The post-intervention tests will be performed at the end of the intervention period for analysis of outcomes. Interventions will occur continuously according to patients’ enrollment. The main outcome is respiratory muscular resistance. A total of 33 enrolled patients are expected. The present protocol followed the SPIRIT guidelines and fulfilled the SPIRIT checklist.

Discussion

This trial is probably the first to assess the effects of a non-pharmacological intervention, namely yoga and specific breathing techniques, to improve cardiorespiratory function, autonomic system, and quality of life in patients with HFpEF.

Trial registration

REBEC Identifier: RBR-64mbnx (August 19, 2012).

Clinical Trials Register: NCT03028168. Registered on 16 January 2017).

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2802-5) contains supplementary material, which is available to authorized users.

Aerobic capacity and health-related quality of life in adults HIV-infected patients with and without lipodystrophy

INTRODUCTION

HIV infection and its therapy which can affect their aerobic capacity and health-related quality of life of patients.

OBJECTIVE

We conducted a cross-sectional study to determine if aerobic capacity and health related quality of life was decreased in HIV-infected patients receiving highly active antiretroviral therapy and comparing patients with and without lipodystrophy.

RESEARCH DESIGN AND METHODS

HIV-infected patients older than 18 years, and in current use of highly active antiretroviral therapy drugs, were evaluated for blood count, fasting total cholesterol, high density lipoprotein, triglycerides, glucose, HIV viral load and CD4/CD8 counts, body composition, peak oxygen consumption (peak VO2) and metabolic equivalent. Health related quality of life was assessed by using Short Form-36 (SF-36). Statistical analysis was carried out using SPSS version 20.0.

RESULTS

A total of 63 patients with mean age of 43.1±6.4 years were evaluated, of these 34 (54%) had lipodystrophy. The average peak VO2 (31.4±7.6mLkg(-1)min(-1)) was significantly lower (p<0.01) than expected values (37.9±5.6mLkg(-1)min(-1)) according to the characteristics of the patients. The lipodystrophy group presented with a significant difference in muscle mass, body fat, peak VO2 and metabolic equivalent and in functional capacity domains of SF-36.

CONCLUSION

Aerobic capacity values were reduced in HIV-infected patients under highly active antiretroviral therapy when compared to predicted values. Lipodystrophy was associated with reduced aerobic capacity and higher frequency of metabolic syndrome. Lifestyle modification should be a priority in the management of chronic HIV disease.

Efeito do treinamento sobre a eficiência ventilatória de indivíduos saudáveis

Introdução: Diversos índices de eficiência ventilatória (EV) têm fornecido uma medida extra para avaliação do condicionamento cardiorrespiratório em adição ao consumo de oxigênio (VO2) no pico do exercício e no nível do limiar ventilatório (VO2LV). Em indivíduos com insuficiência cardíaca já foi demonstrado que há aumento da EV após treinamento. No entanto, a sensibilidade dessa medida para avaliar o efeito do treinamento em indivíduos saudáveis foi pouco estudada.Objetivo: Testar a hipótese de que um programa de treinamento delineado para melhorar a condição aeróbia, também exerça alterações na eficiência ventilatória em indivíduos saudáveis.Métodos: 48 homens, aparentemente saudáveis e ativos (24±5 anos), foram submetidos a um teste cardiopulmonar de exercício (TCPE), antes e após 13 semanas de treinamento aeróbio, realizado três vezes por semana, durante 30 minutos com a intensidade inicial de 60-65% da FCmáx, gradualmente aumentada até o fim do programa para 85-90% da FCmax. Os parâmetros avaliados incluíram: VO2pico, VO2 no LV e EV determinada através do cálculo do slope da relação entre a ventilação e a produção de dióxido de carbono, por meio de regressão linear.Resultados: Houve um aumento de 12,5% no VO2LV (30,4±4,5 vs. 34,2±4,9 ml.kg-1.min-1, p<0,05) e de 10,9% no VO2pico (53,2±8,3 vs. 59±9,9 ml.kg-1.min-1, p<0,05), acompanhado de uma redução de 4,1% no slopeVE-VCO2 (25,2±3,3 vs. 24,2±3,7, p<0,05).Conclusão: A EV aumenta após o treinamento em homens saudáveis sugerindo que o slope da relação VE-VCO2 pode ser utilizado de forma adicional na monitoração dos efeitos do treinamento, complementando a interpretação da integração cardiorrespiratória do TCPE.

The influence of active and passive smoking on the cardiorespiratory fitness of adults

BACKGROUND

The aim of this study was to analyze the influence of active and passive smoking on cardiorespiratory responses in asymptomatic adults during a sub-maximal-exertion incremental test.

METHODS

The participants (n = 43) were divided into three different groups: active smokers (n = 14; aged 36.5 ± 8 years), passive smokers (n = 14; aged 34.6 ± 11.9 years) and non-smokers (n = 15; aged 30 ± 8.1 years). They all answered the Test for Nicotine Dependence and underwent anthropometric evaluation, spirometry and ergospirometry according to the Bruce Treadmill Protocol.

RESULTS

VO2max differed statistically between active and non-smokers groups (p < 0.001) and between non-smokers and passive group (p=0.022). However, there was no difference between the passive and active smokers groups (p=0.053). Negative and significant correlations occurred between VO2max and age (r = - 0.401, p = 0.044), percentage of body fat (r = - 0.429, p = 0.011), and waist circumference (WC) (r = - 0.382, p = 0.025).

CONCLUSION

VO2max was significantly higher in non-smokers compared to active smokers and passive smokers. However, the VO2max of passive smokers did not differ from active smokers.

Examination of the Moxus Modular Metabolic System by the Douglas-bag technique

The purpose of this study was to examine the performance of the Moxus Modular Metabolic System from AEI Technologies, Inc. using the Douglas-bag method as reference. To achieve this, eight moderately trained subjects cycled for 5 min at constant powers from 50 to 300 W in increments of 50 W. The O2 uptake was measured simultaneously by both systems during the last minute of each stage. The O2 uptake reported by the Moxus system was 83 ± 78 mL·min–1 higher (mean ± SD; ≈3%, +62 µmol·s–1, P < 0.001) than that reported by the Douglas-bag method; the bias varied by ≈2% between the subjects. The higher O2 uptake of the Moxus system was a consequence of 1.4% ± 3.0% higher reported ventilation and 2% ± 3% higher reported O2 extraction per volume of air breathed. The respiratory exchange ratio (R value) reported by the Moxus system rose proportionally to that of the Douglas-bag method and was 1% ± 2% higher for the range examined (0.75–1.10). Repeated tests of the maximal O2 uptake showed a variability (coefficient of variation) of 2.5%. The study concluded that measurements by the Moxus system showed some bias and residual variation and, in addition, some systematic differences between the subjects in the O2 uptake. The R value was reported quite accurately with moderate random error. Although there were some computer software and hardware instability problems that need to be solved, the Moxus system worked quite well and provided data more reliable than those of most commercial instruments.

Measurement of human energy expenditure, with particular reference to field studies: an historical perspective

Over the years, techniques for the study of human movement have ranged in complexity and precision from direct observation of the subject through activity diaries, questionnaires, and recordings of body movement, to the measurement of physiological responses, studies of metabolism and indirect and direct calorimetry. This article reviews developments in each of these domains. Particular reference is made to their impact upon the continuing search for valid field estimates of activity patterns and energy expenditures, as required by the applied physiologist, ergonomist, sports scientist, nutritionist and epidemiologist. Early observers sought to improve productivity in demanding employment. Direct observation and filming of workers were supplemented by monitoring of heart rates, ventilation and oxygen consumption. Such methods still find application in ergonomics and sport, but many investigators are now interested in relationships between habitual physical activity and chronic disease. Even sophisticated questionnaires still do not provide valid information on the absolute energy expenditures associated with good health. Emphasis has thus shifted to use of sophisticated pedometer/accelerometers, sometimes combining their output with GPS and other data. Some modern pedometer/accelerometers perform well in the laboratory, but show substantial systematic errors relative to laboratory reference criteria such as the metabolism of doubly labeled water when assessing the varied activities of daily life. The challenge remains to develop activity monitors that are sufficiently inexpensive for field use, yet meet required accuracy standards. Possibly, measurements of oxygen consumption by portable respirometers may soon satisfy part of this need, although a need for valid longer term monitoring will remain.

A randomized, clinical trial to evaluate the impact of regular physical activity on the quality of life, body morphology and metabolic parameters of patients with AIDS in Salvador, Brazil

Patients with AIDS under antiretroviral therapy often present with metabolic problems associated with HIV infection and its therapy, which can affect their quality of life. The knowledge on the potential benefits of regular physical exercises for HIV-infected patients is limited.

OBJECTIVE

We conducted a clinical trial to evaluate the impact of regular physical activity on quality of life, anatomic disturbances, and/or metabolic changes in patients with AIDS in the city of Salvador, Brazil.

METHODS

Patients were randomly assigned in monthly workshops (1-hour duration) to discuss the importance of physical activity and receive nutritional counseling (control group) or to receive a 1-hour supervised gym class three times a week plus monthly nutritional counseling (intervention group). Before and after intervention, body composition, maximum oxygen consumption, metabolic equivalent, blood count, fasting total cholesterol, high-density lipoprotein, triglycerides, glucose, HIV viral load and CD4/CD8 counts, and resting heart rate were measured. Quality of life was evaluated at baseline and after 24 weeks.

RESULTS

The domains of quality of life, general health, vitality and mental health increased in the exercise group (P < 0.05) compared with the control group. In the exercise group, fat mass (P = 0.04), the resting heart rate (P = 0.001), waist circumference (P = 0.002), and glucose (P = 0.003) decreased. Muscle mass (P = 0.002), CD4 T cells (P = 0.002), metabolic equivalent (P = 0.014), and maximum oxygen consumption (P = 0.05) increased.

CONCLUSION

The practice of regular exercise, coupled with nutritional guidance, in individuals with HIV/AIDS significantly improves the quality of life.

Resposta da cinética de consumo de oxigênio e da eficiência mecânica delta de homens e mulheres em diferentes intensidades de esforço

INTRODUÇÃO:A eficiência mecânica delta (EMΔ ) e a cinética do consumo de oxigênio (K<img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2) são influenciadas por parâmetros metabólicos musculares e pelo transporte de <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2. O objetivo do presente estudo foi determinar a diferença na K<img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 e na EMΔ em três intensidades de esforço nos dois gêneros. MÉTODOS: 56 sujeitos (26 mulheres) foram submetidos ao protocolo de esforço escalonado, contínuo e máximo (GxT) no cicloergômetro mecânico para determinação da potência aeróbia máxima (<img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2máx), carga máxima (Wmax), limiar anaeróbio (AT) e ponto de compensação respiratória (PCR). O AT foi determinado através dos métodos V-slope e E <img src="/img/revistas/rbme/v17n4/a13cr02.jpg" align="absmiddle" /><img src="/img/revistas/rbme/v17n4/a13cr02.jpg" align="absmiddle" />E / <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2; o PCR através da relação <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 versus <img src="/img/revistas/rbme/v17n4/a13cr02.jpg" align="absmiddle" />E ; ambos por dois avaliadores. A EMΔ e a K <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 foram consideradas como a inclinação entre <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 versus Watts e <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 versus tempo (s), respectivamente, do começo do teste até o AT (S1), do AT ao PCR (S2) e do PCR ao <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2máx (S3), determinada por análise de regressão linear. RESULTADOS: Para a EMΔ, diferenças significativas foram observadas entre S1 versus S2 (p = 0,001), S1 versus S3 (p = 0,001) e S2 versus S3 (p = 0,006). Não foi observada diferença (p = 0,060) ou interação significativa (p = 0,062) entre homens versus mulheres. Para a K <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 diferenças significativas foram observadas entre S1 versus S3 (p = 0,001) e S2 versus S3 (p = 0,001) em ambos gêneros. Diferenças (p = 0,001) e interação significativa (p = 0,006) foram observadas entre homens versus mulheres, no último parâmetro. CONCLUSÕES: A EMΔ decresce com o incremento da intensidade de trabalho, porém, não há diferenças quando se compara homens e mulheres. Por outro lado, as mulheres apresentam K <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 mais rápida do que os homens.

Influência do protocolo ergométrico na ocorrência de diferentes critérios de esforço máximo

INTRODUÇÃO E OBJETIVO: Neste estudo investigamos a influência de diferentes protocolos ergométricos na ocorrência dos critérios de esforço máximo. MÉTODOS: Nove sujeitos fisicamente ativos (23 ± 4 anos, 177 ± 10cm, e 77,1 ± 16kg) realizaram três testes de esforço (PR1 - 15W·min-1, PR2 - 50W·3 min-1, e PR3 - 50W·5 min-1) no cicloergômetro. O consumo de oxigênio foi medido em circuito aberto e integrado a cada 20s. Adotaram-se como critérios de esforço máximo: o platô no consumo de oxigênio < 150 mL·min-1; frequência cardíaca máxima (FCmáx) > 95% prevista pela idade; lactato > 8,0 mM; e RER > 1,1. RESULTADOS: O VO2máx não apresentou diferenças entre os protocolos (2,68 ± 1,0; 2,58 ± 1,0 e 2,99 ± 1,3L·min-1 para PR1, PR2 e PR3, p = 0,72). A maior ocorrência do platô foi observada em PR1 (cinco sujeitos). O critério da frequência cardíaca máxima foi satisfeito em três sujeitos em PR3, e o critério do lactato em seis sujeitos, no mesmo protocolo (PR3). O RER > 1,1 foi observado em seis sujeitos em PR1. CONCLUSÃO: Concluímos que a ocorrência de diferentes critérios de esforço máximo é influenciada pela escolha do protocolo ergométrico, não indicando, contudo, valores distintos de VO2máx

Inspiratory muscle training improves oxygen uptake efficiency slope in patients with chronic heart failure

PURPOSE

Inspiratory muscle training (IMT) improves exercise capacity and ventilatory responses to exercise in patients with chronic heart failure (CHF) with inspiratory muscle weakness (IMW). We analyzed the effects of IMT on the oxygen uptake efficiency slope (OUES) in this patient population.

METHODS

Thirty-two CHF patients with IMW (maximal inspiratory pressure [PImax] < 70% of predicted) were randomly assigned to either a 12-week program of IMT (IMT, n = 16) or placebo-IMT (P-IMT, n = 16). PImax and OUES were obtained before and after the intervention.

RESULTS

Inspiratory muscle training resulted in 115% increment in PImax (5.9 +/- 0.9 vs 12.7 +/- 0.9 kPa; P < .001) and in significant improvement in OUES (1,554 +/- 617 to 2,037 +/- 747 mL min O2/L min of minute ventilation; P = .001). There were no significant changes in the P-IMT group. There was a significant association between the changes in PImax and OUES (r = 0.82, P < .01).

CONCLUSION

In CHF patients with IMW, IMT results in a significant increase in OUES.

Inspiratory muscle strength as a determinant of functional capacity early after coronary artery bypass graft surgery

Stein R, Maia CP, Silveira AD, Chiappa GR, Myers J, Ribeiro JP. Inspiratory muscle strength as a determinant of functional capacity early after coronary artery bypass graft surgery.

OBJECTIVE

To evaluate the effects of a 6-day postoperative in-hospital cardiopulmonary rehabilitation program on inspiratory muscle strength and its potential association with improved functional capacity after coronary artery bypass graft (CABG) surgery.

DESIGN

Prospective, randomized controlled trial.

SETTING

Tertiary public hospital in Brazil.

PARTICIPANTS

Men (N=20) after CABG were randomized to cardiopulmonary rehabilitation (n=10; age, 64+/-8y) or to usual care (n=10; age, 63+/-7y).

INTERVENTIONS

Ten subjects underwent a 6-day postoperative in-hospital program, which included the use of expiratory positive airway pressure mask and bronchial hygiene techniques, coupled with progressive distance walking and calisthenics as well as cardiopulmonary training. Ten controls were followed by their own physicians and received routine nursing assistance but were not exposed to any specific respiratory or motor physical intervention.

MAIN OUTCOME MEASURES

Maximal inspiratory and expiratory pressure were measured by a pressure transducer, and the highest pressure obtained in 6 measurements was used for analysis (before surgery, and 7 and 30d after surgery). The six-minute walk test (6MWT) was performed 7 days after surgery, and maximal cardiopulmonary exercise testing was performed 30 days after CABG.

RESULTS

After randomization, clinical and functional characteristics were similar in the 2 groups. Rehabilitation resulted in maintenance of maximal inspiratory pressure (PImax) measured at 7 and 30 days postoperatively, respectively (from 68+/-19% at baseline to 58+/-22% and to 61+/-22% predicted), while it was significantly reduced in the control group. 6MWT distance was longer 7 days after CABG in rehabilitation subjects (416+/-78m) than controls (323+/-67m). Peak oxygen uptake (Vo(2)peak) at day 30 was also higher (28%) in the rehabilitation group and was correlated with PImax (r=.90).

CONCLUSIONS

A 6-day rehabilitation program attenuated the postoperative reduction in respiratory muscle strength and also improved the recovery of functional capacity after CABG. The correlation between PImax and Vo(2)peak during the late postoperative period suggests that inspiratory muscle strength is an important determinant of functional capacity after CABG.

Cardiorespiratory responses to maximal arm and leg exercise in national-class marathon runners

Marathon runners (MR) are among the most aerobically fit athletes in the world. Although aerobic capacity (VO(2)max) during arm exercise generally varies between 64% and 80% of leg VO(2)max (mean 70%) in healthy men, few data are available regarding the comparative arm fitness of MR. To clarify the relationship between arm and leg fitness in MR, we studied 10 national-class MR (mean + or - standard deviation age 30 + or - 4 years) whose best marathon times averaged < 2 hours and 40 minutes. Each MR underwent lower and upper body maximal exercise evaluations with measurement of cardiorespiratory variables using indirect calorimetry during treadmill testing (standard Bruce protocol) and arm-crank ergometry, respectively. Our subjects achieved VO(2)max levels equaling 75.8 + or - 7.1 mL/kg/min (5.2 + or - 0.6 L/min) during treadmill testing, which was significantly higher than the level of cardiorespiratory fitness achieved during maximal arm exercise (45.4 + or - 12.4 mL/kg/min [3.1 + or - 0.9 L/min]; P < 0.01). In addition, maximal heart rate (183.2 + or - 8.2 vs 163.7 + or - 10 bpm) and systolic blood pressure (201.8 + or - 10.1 vs 186.6 + or - 12.1 mm Hg) were significantly higher (P < 0.01 and P < 0.05, respectively) during maximal leg versus arm exercise. Relative arm fitness (arm VO(2)max/leg VO(2)max) was extremely variable (41%-76%), averaging 60% + or - 13%. Although MR are able to achieve significantly higher VO(2)max values during treadmill testing than those observed in the general population, their relative arm fitness appears to be slightly reduced. These findings add to and strongly support the specificity of measurement and training concept.

Comparação entre as modalidades de caminhada e corrida na predição do consumo máximo de oxigênio

Os testes ergométricos de exercício realizados em esteira podem ser desempenhados a partir das modalidades de caminhada e corrida, contudo, sem haver grandes elucidações ao comparar resultados de VO2máx obtidos nessas possibilidades de teste. Com o intuito de responder a essa questão, o presente estudo objetivou comparar a predição do VO2máx entre um protocolo escalonado máximo de caminhada e um de corrida, ambos elaborados de modo a proporcionar demandas metabólicas idênticas em cada estágio. Foram voluntários para o presente estudo 23 indivíduos (15 masculinos e oito femininos) com 27,7 ± 7,6 anos de idade, 73,0 ± 14,9kg de massa corporal, 170,0 ± 1,0cm de estatura, 19,3 ± 8,6% de gordura corporal, 24,7 ± 3,3kg×m-2 de índice de massa corporal e 44,1 ± 6,0mL×kg-1×min-1 de potência aeróbia máxima. Um teste t pareado não demonstrou diferenças significativas (p = 0,364; IC 95 % = -2,2 a 0,85) entre o protocolo de caminhada e o de corrida, apesar de a média dos valores do VO2máx na corrida ter sido 2,4% superior (42,4 vs. 43,4mL×kg-1×min-1). Com base nos resultados encontrados, conclui-se que a administração de diferentes estratégias de protocolos em esteira (caminhada ou corrida) não influenciou significativamente a estimativa do VO2max, não interferindo na posterior tomada de decisão para a prescrição do treinamento cardiorrespiratório.

Detection of ventilatory threshold by an automatic parabolic model

This work aims at presenting a method for automatic detection of the ventilatory threshold by modeling ventilatory equivalent of oxygen by a parabolic function. Thirty healthy male subjects were submitted to a single maximal oxygen uptake test, being monitored the ventilatory gas exchange signals. Ventilatory threshold by visual inspection, automatic v-slope and parabolic function methods was compared. The automatic methods showed no significant differences with visual inspection, but the parabolic technique presented higher consistence than v-slope. Since the parabolic method have low computation cost and is a simple method, it can be recommended as an alternative choice to v-slope method.

Validation of the VO2000 calorimeter for measuring resting metabolic rate

BACKGROUND & AIMS

Metabolic carts used in laboratory settings for the measurement of resting metabolism are cumbersome limiting their use in the field. The validity of a newly developed portable calorimeter (Medical Graphics VO2000) under resting conditions was assessed in comparison to a well-established reference system, the DELTATRAC.

METHODS

Gas exchange and energy expenditure were measured for 25 min consecutively using the two devices. Values of the last 20 min were averaged and used in the analysis. The order of device for the first subject was randomly chosen and the calorimeters were alternated thereafter.

RESULTS

Among 33 subjects, acceptable measures of resting metabolism were obtained in 25 (11 men) aged 20-78 years because eight subjects (three men) either hyperventilated or did not adapt well enough to the facemask. VO(2), VCO(2), and RQ were not significantly different between devices. Small (2.8%) non-clinically relevant mean differences (-0.145+/-0.341 MJ day(-1)) were found. Results of the two devices were highly correlated (r=0.95) yielding a more accurate estimate than predictive equations.

CONCLUSIONS

The VO2000 calorimeter is a valid system to measure resting metabolism but the facemask may not be suitable for some people.

Exercise training in HIV-1-infected individuals with dyslipidemia and lipodystrophy

PURPOSE

Highly active antiretroviral therapy has improved the prognosis of human immuno deficiency virus type 1 (HIV-1)-infected individuals, but it has been associated with the development of metabolic and fat distribution abnormalities known as the lipodystrophy syndrome. This study tested the hypothesis that aerobic exercise training added to a low-lipid diet may have favorable effects in HIV-1-infected individuals with dyslipidemia and lipodystrophy.

METHODS

Thirty healthy subjects, carriers of HIV-1, with dyslipidemia and lipodystrophy, all of whom were using protease inhibitors and/or non-nucleoside reverse transcriptase inhibitors, were randomly assigned to participate in either a 12-wk program of aerobic exercise or a 12-wk stretching and relaxation program. All subjects received recommendations for a low-lipid diet. Before and after intervention, peak oxygen uptake, body composition, CD4, viral load, lipid profile, and plasma endothelin-1 levels were measured.

RESULTS

Peak oxygen uptake increased significantly in the diet and exercise group (mean +/- SD: 32 +/- 5 mL x kg(-1) x min(-1) before; 40 +/- 8 mL x kg(-1) x min(-1) after) but not in the diet only group (34 +/- 7 mL x kg(-1) x min(-1) before; 35 +/- 8 mL x kg(-1) x min(-1) after). Body weight, body fat, and waist-to-hip ratio decreased significantly and similarly in the two groups. There were no significant changes in immunologic variables in either group. Likewise, plasma triglycerides, total cholesterol, and HDL cholesterol levels did not change significantly in either group. Plasma endothelin-1 levels were elevated in both groups and presented no significant changes during the study.

CONCLUSION

HIV-seropositive individuals with lipodystrophy and dyslipidemia submitted to a short-term intervention of low-lipid diet and aerobic exercise training are able to increase their functional capacity without any consistent changes in plasma lipid levels.

Challenges in measuring energy expenditure in companion animals: a clinician's perspective

Standard recommendations as to how much to feed dogs and cats are based on the average requirements of unstressed healthy laboratory dogs and cats of normal body condition undertaking modest amounts of exercise in a thermoneutral environment, but most clinical patients do not conform to these norms. Most clinicians estimate the energy expenditure of patients using a factorial calculation that adjusts for any differences from the norm, but little information exists upon which to base these adjustments. Furthermore, individual variation in energy expenditure is substantial even in dogs and cats under closely defined physiological conditions, and the estimate of energy expenditure obtained by using a factorial calculation can differ by a substantial margin from the energy expenditure of an individual. Detailed dietary histories provide an estimate of individual energy requirements but are time consuming to perform and rely on several assumptions. There are also no readily available point-of-care methods for measuring the energy expenditure of dogs and cats. There is a need, therefore, for further research concerning factors that affect energy expenditure of dogs and cats and methods of measuring energy expenditure in individual patients.

Inspiratory muscle training in patients with heart failure and inspiratory muscle weakness: a randomized trial

OBJECTIVES

This study sought to evaluate the effects of inspiratory muscle training in inspiratory muscle strength, as well as in functional capacity, ventilatory responses to exercise, recovery oxygen uptake kinetics, and quality of life in patients with chronic heart failure (CHF) and inspiratory muscle weakness.

BACKGROUND

Patients with CHF may have reduced strength and endurance in inspiratory muscles, which may contribute to exercise intolerance and is associated with a poor prognosis.

METHODS

Thirty-two patients with CHF and weakness of inspiratory muscles (maximal inspiratory pressure [Pi(max)] <70% of predicted) were randomly assigned to a 12-week program of inspiratory muscle training (IMT, 16 patients) or to a placebo-inspiratory muscle training (P-IMT, 16 patients). The following measures were obtained before and after the program: Pi(max) at rest and 10 min after maximal exercise; peak oxygen uptake, circulatory power, ventilatory oscillations, and oxygen kinetics during early recovery (VO2/t-slope); 6-min walk test; and quality of life scores.

RESULTS

The IMT resulted in a 115% increment Pi(max), 17% increase in peak oxygen uptake, and 19% increase in the 6-min walk distance. Likewise, circulatory power increased and ventilatory oscillations were reduced. The VO2/t-slope was improved during the recovery period, and quality of life scores improved.

CONCLUSIONS

In patients with CHF and inspiratory muscle weakness, IMT results in marked improvement in inspiratory muscle strength, as well as improvement in functional capacity, ventilatory response to exercise, recovery oxygen uptake kinetics, and quality of life.

Aerobic Exercise and Submaximal Functional Capacity in Overweight Pregnant Women

OBJECTIVE

To evaluate the effects of aerobic training on submaximal cardiorespiratory capacity in overweight pregnant women.

METHODS

We conducted a randomized clinical trial in a referral center prenatal clinic during the period 2000-2002. Of 132 overweight (body mass index 26-31 kg/m2) but otherwise healthy volunteers, at 20 years of age or older, with gestational age of 20 weeks or less, and without diabetes or hypertension, 92 consented to participate and were randomized. Intervention consisted of 3 one-hour aerobic exercise sessions per week; the control group received weekly relaxation and focus group discussions. The main outcome measure was submaximal exercise capacity evaluated by oxygen uptake at the anaerobic (first ventilatory) threshold during cardiopulmonary treadmill testing 12 weeks after randomization.

RESULTS

Oxygen uptake at the anaerobic threshold increased 18% (15.9 +/- 2.6 to 18.1 +/- 3.1 mL . min(-1) . kg(-1)) in the exercise group but decreased 16% (16.9 +/- 3.0 to 15.8 +/- 2.6 mL . min(-1) . kg(-1)) among the control group. Oxygen consumption at the anaerobic threshold, adjusted through analysis of covariance for baseline oxygen uptake, was 2.68 (95% confidence interval 1.23 to 4.12) mL . min(-1) . kg(-1) greater in the exercise group. Women in the exercise group were approximately 5 times more likely than those in the control group to have regular or good cardiorespiratory capacity (12/38 versus 2/38; relative risk 5.2, 95% confidence interval 1.2 to 22.0, number needed to treat 5).

CONCLUSION

Aerobic training in overweight pregnant women substantially increases submaximal exercise capacity, overcoming the otherwise negative effects of pregnancy in this regard. Additional studies are required to evaluate its effect on major clinical outcomes.

Aerobic endurance, energy expenditure, and serum leptin response in obese, sedentary, prepubertal children and adolescents participating in a short-term treadmill protocol

OBJECTIVE

We analyzed aerobic endurance, energy expenditure, and serum leptin concentrations during programmed, short-term exercise in a group of untrained, obese children and adolescents.

METHODS

This was a prospective, controlled study of prepubertal males and females ages 6 to 11 y. Group 1 (n = 40) comprised obese children, and group 2 comprised similarly aged non-obese children (n = 16). The children completed a stepwise maximal aerobic endurance test (Bruce protocol) on a treadmill. The variables measured included anthropometric indexes, serum leptin, and physiologic indexes.

RESULTS

Maximal oxygen consumption (corrected for body weight) values were 29.9 +/- 6.7 mL x kg(-1) x min(-1) in group 1 and 47.2 +/- 5.3 mL x kg(-1) x min(-1) in group 2 (P < 0.05). The number of exercise steps was smaller in group 1 (3.7 +/- 0.7 versus 5.3 +/- 0.4, P < 0.05), as was time to exhaustion (9.3 +/- 1.9 min versus 15.1 +/- 1.9 min, P < 0.05). However, the energy cost of the exercise did not differ significantly between groups (57.7 +/- 17.8 kcal versus 65.2 +/- 17.6 kcal), indicating greater energy expenditure for less performance in the obese children. Initial leptin concentrations were higher in group 1 (24.0 +/- 13.1 ng/mL versus 1.6 +/- 1.7 ng/mL, P < 0.001), and exercise did not significantly modify these findings.

CONCLUSIONS

Obese children were seriously unfit and paid a high energy price for the treadmill test. Initial leptin concentrations were very high in the obese children, in the range of concentrations found in obese adults. No significant change in leptin concentration was observed at the end of the test, probably because of the short duration of the activity.

Intrinsic sinus and atrioventricular node electrophysiologic adaptations in endurance athletes

OBJECTIVES

In the present study, we evaluated sinus and atrioventricular (AV) node electrophysiology of endurance athletes and untrained individuals before and after autonomic pharmacologic blockade.

BACKGROUND

Endurance athletes present a higher prevalence of sinus bradycardia and AV conduction abnormalities, as compared with untrained individuals. Previous data from our laboratory suggest that nonautonomic factors may be responsible for the longer AV node refractory period found in well-trained athletes.

METHODS

Six aerobically trained male athletes and six healthy male individuals with similar ages and normal rest electrocardiograms were studied. Maximal oxygen uptake (O(2)max) was measured by cardiopulmonary testing. The sinus cycle length (SCL), AV conduction intervals, sinus node recovery time (SNRT), Wenckebach cycle (WC) and anterograde effective refractory period (ERP) of the AV node were evaluated by invasive electrophysiologic studies at baseline, after intravenous atropine (0.04 mg/kg) and after addition of intravenous propranolol (0.2 mg/kg).

RESULTS

Athletes had a significantly higher O(2)max as compared with untrained individuals. The SCL was longer in athletes at baseline, after atropine and after the addition of propranolol for double-autonomic blockade. The mean maximal SNRT/SCL was longer in athletes after atropine and after propranolol. The WC and anterograde ERP of the AV node were longer in athletes at baseline, after atropine and after propranolol.

CONCLUSIONS

Under double-pharmacologic blockade, we demonstrated that sinus automaticity and AV node conduction changes of endurance athletes are related to intrinsic physiology and not to autonomic influences.

Automated metabolic gas analysis systems: a review

The use of automated metabolic gas analysis systems or metabolic measurement carts (MMC) in exercise studies is common throughout the industrialised world. They have become essential tools for diagnosing many hospital patients, especially those with cardiorespiratory disease. Moreover, the measurement of maximal oxygen uptake (VO2max) is routine for many athletes in fitness laboratories and has become a defacto standard in spite of its limitations. The development of metabolic carts has also facilitated the noninvasive determination of the lactate threshold and cardiac output, respiratory gas exchange kinetics, as well as studies of outdoor activities via small portable systems that often use telemetry. Although the fundamental principles behind the measurement of oxygen uptake (VO2) and carbon dioxide production (VCO2) have not changed, the techniques used have, and indeed, some have almost turned through a full circle. Early scientists often employed a manual Douglas bag method together with separate chemical analyses, but the need for faster and more efficient techniques fuelled the development of semi- and full-automated systems by private and commercial institutions. Yet, recently some scientists are returning back to the traditional Douglas bag or Tissot-spirometer methods, or are using less complex automated systems to not only save capital costs, but also to have greater control over the measurement process. Over the last 40 years, a considerable number of automated systems have been developed, with over a dozen commercial manufacturers producing in excess of 20 different automated systems. The validity and reliability of all these different systems is not well known, with relatively few independent studies having been published in this area. For comparative studies to be possible and to facilitate greater consistency of measurements in test-retest or longitudinal studies of individuals, further knowledge about the performance characteristics of these systems is needed. Such information, along with the costs and the common features associated with these systems, may aid physicians and scientists to select a system that is best suited to their requirements and may also improve the quality of these frequently-reported physiological measures.

Velocidade de corrida associada ao consumo máximo de oxigênio em meninos de 10 a 15 anos

O objetivo deste estudo foi determinar a influência da idade cronológica e da maturação biológica sobre o consumo máximo de oxigênio (VO2max) e a velocidade de corrida correspondente ao VO2max em crianças e adolescentes brasileiros, do sexo masculino, com idade entre 10 e 15 anos, não praticantes de atividade física sistemática. Participaram do estudo 40 voluntários, divididos em dois grupos, segundo a idade cronológica (GC1 - n = 20; 11,4 ± 0,6 anos; 38,8 ± 8,6kg; 143,6 ± 8,2cm e GC2 - n = 20; 14,1 ± 0,6 anos; 55,9 ± 14,2kg; 163,3 ± 10,2cm) e maturação biológica (GB1 - n = 20; estágios 1, 2 e 3; e GB2 - n = 20; estágios 4 e 5). O VO2max foi mensurado em um teste progressivo e intermitente de corrida em esteira rolante, com estágios de três minutos e pausa de 20 segundos, incrementos de 1km/h a começar com 9km/h, até a exaustão voluntária. A velocidade correspondente ao VO2max (vVO2max) foi considerada como a menor velocidade em que se observou o maior valor de VO2. A máxima velocidade aeróbia (Va max) foi calculada pela fórmula proposta por di Prampero (1986). Houve diferença significante para os valores de VO2max(l/min), Va max(km/h)e vVO2max(km/h) entre os grupos GC1 e GC2 (1,84 ± 0,41 / 2,81 ± 0,61; 11,8 ± 1,2 / 12,6 ± 1,2; 12,1 ± 1,2 / 12,9 ± 1,1, respectivamente), GB1 e GB2 (1,80 ± 0,37 / 2,87 ± 0,56; 12,1 ± 1,2 / 12,9 ± 1,1; 11,8 ± 1,2 / 12,5 ± 1,1, respectivamente), mas não para os valores de VO2max em ml.kg-1.min-1 para todos os grupos (GC1 e GC2: 47,9 ± 6,8 / 50,4 ± 5,5; GB1 e GB2: 47,9 ± 6,8 / 50,3 ± 5,5, respectivamente). Com base nos resultados obtidos, pode-se concluir que o VO2max (l/min), aVa max e a vVO2max têm seus valores aumentados como um provável efeito do crescimento e desenvolvimento, podendo, ainda, expressar melhora da economia de movimento, mesmo em indivíduos não praticantes de atividade física sistemática.

Determination of metabolic monitor errors and precision under clinical conditions

BACKGROUND & AIMS

Metabolic monitoring devices used in the critical care setting are subject to a range of conditions that may compromise their accuracy. We sought to investigate the error and precision of the Deltatrac metabolic monitor under these conditions.

METHODS

A modified version of the funnel burner, described by Miodownik et al. (8), was ventilated by a mechanical ventilator. This was used to examine the performance of the Deltatrac metabolic monitor over a wide range of inspired oxygen concentrations, minute ventilation, and positive end expiratory pressure at different levels of oxygen consumption and carbon dioxide production.

RESULTS

The Deltatrac measured V(O(2)) with a mean error+/-precision of 9.4%+/-19.5% (range, 9.3%+/-1.9%-72.6%+/-13.6%). The mean V(CO(2)) error+/-precision was 1.2%+/-3.1% (range-2.0%+/-1.2%-5.4%+/-3.1%). Error was significantly affected by oxygen concentration and minute ventilation but was largely independent of positive and expiratory pressure.

CONCLUSIONS

The methodology of Miodownik et al. permits the expression of metabolic device errors over a wide range of simulated clinical conditions.

Validity of inspiratory and expiratory methods of measuring gas exchange with a computerized system

The accuracy of a computerized metabolic system, using inspiratory and expiratory methods of measuring ventilation, was assessed in eight male subjects. Gas exchange was measured at rest and during five stages on a cycle ergometer. Pneumotachometers were placed on the inspired and expired side to measure inspired (VI) and expired ventilation (VE). The devices were connected to two systems sampling expired O(2) and CO(2) from a single mixing chamber. Simultaneously, the criterion (Douglas bag, or DB) method assessed VE and fractions of O(2) and CO(2) in expired gas (FE(O(2)) and FE(CO(2))) for subsequent calculation of O(2) uptake (VO(2)), CO(2) production (VCO(2)), and respiratory exchange ratio. Both systems accurately measured metabolic variables over a wide range of intensities. Though differences were found between the DB and computerized systems for FE(O(2)) (both inspired and expired systems), FE(CO(2)) (expired system only), and VO(2) (inspired system only), the differences were extremely small (FE(O(2)) = 0.0004, FE(CO(2)) = -0.0003, VO(2) = -0.018 l/min). Thus a computerized system, using inspiratory or expiratory configurations, permits extremely precise measurements to be made in a less time-consuming manner than the DB technique.

Effects of front and dual suspension mountain bike systems on uphill cycling performance

PURPOSE

The purpose of this study was to evaluate the effects of front suspension (FS) and dual suspension (DS) mountain bike designs on time-trial performance and physiological responses during uphill cycling on a paved- and off-road course.

METHODS

Six trained male cyclists (35.6 +/- 9 yr, 76.9 +/- 8.8 kg, VO2 peak 58.4 +/- 5.6 mL x kg(-1) x min-1)) were timed using both suspension systems on an uphill paved course (1.62 km, 183-m elevation gain) and an uphill off-road course (1.38 km, 123-m elevation gain). During the field trials, VO2 was monitored continuously with a KB1-C portable gas analyzer, and power output with an SRM training system.

RESULTS

On the paved course, total ride time on FS (10.4 +/- 0.7 min) and DS (10.4 +/- 0.8 min) was not different (P > 0.05). Similarly, total ride time on the off-road course was not significantly different on the FS bike (8.3 +/- 0.7 min) versus the DS bike (8.4 +/- 1.1 min). For each of the course conditions, there was no significant difference between FS and DS in average minute-by-minute VO2, whether expressed in absolute (ABS; L x min(-1)) or relative (REL; mL x [kg body wt +/- kg bike wt(-1)] x min(-1) values. Average power output (W) was significantly lower for ABS FS versus DS (266.1 +/- 61.6 W vs 341.9 +/- 61.1 W, P < 0.001) and REL FS versus DS (2.90 +/- 0.55 W x kg(-1) vs 3.65 +/- 0.53 W x kg(-1), P < 0.001) during the off-road trials. Power output on the paved course was also significantly different for ABS FS versus DS (266.6 +/- 52 W vs 345.4 +/- 53.4 W, P < 0.001) and REL FS versus DS (2.99 +/- 0.55 W x kg(-1) vs 3.84 +/- 0.54 W x kg(-1), P < 0.001).

CONCLUSION

We conclude that despite significant differences in power output between FS and DS mountain bike systems during uphill cycling, these differences do not translate into significant differences in oxygen cost or time to complete either a paved- or off-road course.

Comparing physical activity assessment methods in the Seasonal Variation of Blood Cholesterol Study

PURPOSE

This paper evaluated three measures of physical activity employed in the Seasonal Variation of Blood Cholesterol Study (Seasons), and it had two objectives: 1) To examine the laboratory validity of the Actillume activity monitor, and 2) To examine the relative validity of three 24-h physical activity recalls (24HR) in quantifying short-term physical activity behaviors.

METHODS

Nineteen healthy middle-age adults completed seven activity trials (reading, typing, box moving, stepping, and walking (3.5, 4.25, 5.0 km x h(-1))) while oxygen consumption and Actillume measures were obtained. ANOVA, linear regression, and a scatter plot were employed to examine the validity of the Actillume. In relative validity analyses of the 24HR in the Seasons study, participants (N = 481) completed two or three 24HR (MET-h x d(-1)) and a modified Baecke Questionnaire. A subset of the cohort (N = 41) wore the Actillume for 3-8 d (counts x min(-1) x d(-1)). The relative validity of the 24HR method was examined by comparison to these criterion measures.

RESULTS

In laboratory validation analyses, the monitor was found to discriminate between sedentary and moderate intensity activities, changes in walking speed, and to account for 79% of the variance in oxygen consumption across sedentary and walking trials. In relative validity analyses, correlations between the 24HR and the modified Baecke ranged from 0.29 to 0.52 (P < 0.01) across total, household, occupational, and leisure-time activities.

CONCLUSIONS

In laboratory testing, the Actillume monitor discriminated between sedentary and moderate intensity activities and was highly correlated with oxygen consumption. Three 24HR of physical activity were observed to have a relative validity that was comparable to published data from other short-term activity assessments that also employed the Baecke Questionnaire and activity monitors as criterion measures.

Efeito do tempo de intervalo da amostra ventilatória na variabilidade do consumo máximo de oxigênio (VO2 máx) em jogadores de futebol profissional

O propósito deste estudo foi verificar, em futebolistas profissionais, o impacto de sete intervalos de tempo sobre a variável fisiológica consumo máximo de oxigênio (VO2 máx). Dezoito jogadores de futebol com média de idade de 24 ± 4 anos (18-31), peso de 72,5 ± 5,9kg (62-83) e estatura de 176,5 ± 7,0cm (164-188) foram submetidos a teste ergométrico máximo em esteira rolante, utilizando-se protocolo escalonado contínuo. A resposta de freqüência cardíaca (FC) foi registrada por meio de um eletrocardiógrafo computadorizado de 12 derivações simultâneas. A ventilação pulmonar (V E), o consumo de oxigênio (VO2), a produção de dióxido de carbono (VCO2) e a razão de troca respiratória (RER) foram calculadas a partir de valores medidos por um sistema espirométrico computadorizado. Os resultados deste estudo demonstraram que houve variabilidade significante do VO2 máx (p < 0,05) somente quando se comparou a resposta instantânea respiração-a-respiração (breath-by-breath) em relação aos outros intervalos de tempos analisados (10, 20, 30, 40, 50 e 60 segundos), respectivamente. Concluindo, durante o exercício de intensidade progressiva, observou-se que o aumento do VO2 foi proporcional à diminuição do intervalo de tempo da coleta ventilatória. O tempo de intervalo maior subestimou esse aumento. Assim, sugere-se que o avaliador utilize intervalos médios na faixa de tempo entre 10 e 60 segundos, pois não foi verificada diferença estatística significante entre esses intervalos.

Caloric expenditure during cardiac rehabilitation

PURPOSE

The purpose of this study was to describe estimated caloric expenditure among patients in a maintenance cardiac rehabilitation program relative to a stated goal of approximately 300 kcal/session or 1,000 kcal/week. Additionally, we assessed the validity of several different methods for estimating caloric expenditure.

METHODS

The caloric expenditure for an exercise session was evaluated in 30 of 65 patients exercising in a maintenance cardiac rehabilitation program. Patients exercised using a treadmill, dual-action ergometer, upright stepper, or reclining stepper. The kilocalorie expenditure was assessed by three different techniques. The first used liquid crystal display (LCD) readings from the equipment (LCD method), the second combined both the American College of Sports Medicine metabolic equations for treadmill walking and the LCD values from the other equipment (Combined method), and the third measured oxygen consumption (VO2 method).

RESULTS

The caloric expenditure for the LCD, Combined, and VO2 methods were 247 +/- 83, 245 +/- 80, and 230 +/- 88 kcal, respectively. Agreement between methods using intraclass correlation analysis was r = 0.84 (0.68 to 0.92, 95% confidence intervals) for LCD versus VO2 and r = 0.88 (0.77 to 0.94, 95% confidence intervals) for Combined versus VO2 method.

CONCLUSIONS

Most patients (83%) in a maintenance cardiac rehabilitation program exercise below 300 kcal per session, a level believed to be necessary to illicit favorable changes in cardiovascular health. Additionally, the Combined method provides a reasonable estimate of kilocalorie expenditure. Use of kilocalorie expenditure should be considered in the cardiac rehabilitation setting as a fourth component in the exercise prescription.

Aerobic and myocardial demands of lawn mowing in patients with coronary artery disease

Lawn mowing approximates 4 to 6 METs and may evoke heart rate and systolic blood pressure responses that approach and exceed those attained during maximal exercise testing. The excessive cardiac demands may be deceptively camouflaged by the moderate aerobic requirements and perceived effort.

Automated VO2max calibrator for open-circuit indirect calorimetry systems

The complete calibration of indirect calorimetry systems involves simultaneous checks of gas analyzers, volume device, and software, and this requires a machine that can mimic accurately and precisely the ventilation and expired gases of an athlete. While previous calibrators have been built successfully, none have matched the ventilatory flows produced by athletes during high intensity exercise. A calibrator able to simulate high aerobic power (VO2max calibrator) was fabricated and tested against conventional indirect calorimetry systems that use chain-compensated gasometers to measure expired volume (VE systems) and calibrated electronic gas analyzers. The calibrator was also checked against a system that measures inspired volume (VI system) with a turbine ventilometer. The pooled data from both VE and VI systems for predicted VO2 ranging from 2.9 to 7.9 L.min-1 and ventilation ranging from 89 to 246 L.min-1 how that the absolute accuracy (bias) of values measured by conventional indirect calorimetry systems compared with those predicted by the calibrator was excellent. The bias was < 35 mL.min-1 for VO2 and carbon dioxide production, < 0.50 L.min-1 for ventilator (VE BTPS), -0.02% absolute for the percentage of expired O2 and +0.02% absolute for the percentage of expired CO2. Overall, the precision of the measured VO2, VCO2, and VE BTPS was approximately 1%. This VO2max calibrator is a versatile device that can be used for routine calibration of most indirect calorimetry systems that assess the ventilation and aerobic power of athletes.

Reliability and validity of a portable metabolic measurement system

The purpose of this study was to assess the reliability and validity of a portable metabolic system (TEEM 100) during submaximal and maximal (VO2max) exercise using a computer-based metabolic system as the reference system (REF). Between repeated trials of submaximal exercise at three constant loads, differences in ventilation (Ve) and oxygen consumption (VO2) were 0.2 +/- 4.9 L . min-1 and 0.03 +/- 0.10 L . min-1 for REF, and 1.9 +/- 0.7 L . min-1 and 0.00 +/- 0.17 L . min-1 for TEEM 100. Pooled intraclass reliability coefficients for Ve and VO2 calculated from the repeated submaximal trials were r = .89 and r = .94 for REF, and r = .86 and r = .94 for the TEEM 100. Respiratory exchange ratio (RER) measured by the TEEM 100 was significantly higher (p = .01) at only the lowest workload. At VO2max, the TEEM 100 recorded significantly higher values for FeO2 (p = .01) and RER (p < .001). These results suggest that the TEEM 100 provides reliable and valid measurements of VO2 during submaximal and maximal exercise.