RESUMO

This study aimed to analyze the agreement between measurements of unloaded oxygen uptake and peak oxygen uptake based on equations proposed by Wasserman and on real measurements directly obtained with the ergospirometry system. We performed an incremental cardiopulmonary exercise test (CPET), which was applied to two groups of sedentary male subjects: one apparently healthy group (HG, n=12) and the other had stable coronary artery disease (n=16). The mean age in the HG was 47±4 years and that in the coronary artery disease group (CG) was 57±8 years. Both groups performed CPET on a cycle ergometer with a ramp-type protocol at an intensity that was calculated according to the Wasserman equation. In the HG, there was no significant difference between measurements predicted by the formula and real measurements obtained in CPET in the unloaded condition. However, at peak effort, a significant difference was observed between oxygen uptake (V˙O2)peak(predicted)and V˙O2peak(real)(nonparametric Wilcoxon test). In the CG, there was a significant difference of 116.26 mL/min between the predicted values by the formula and the real values obtained in the unloaded condition. A significant difference in peak effort was found, where V˙O2peak(real)was 40% lower than V˙O2peak(predicted)(nonparametric Wilcoxon test). There was no agreement between the real and predicted measurements as analyzed by Lin’s coefficient or the Bland and Altman model. The Wasserman formula does not appear to be appropriate for prediction of functional capacity of volunteers. Therefore, this formula cannot precisely predict the increase in power in incremental CPET on a cycle ergometer.

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RESUMO

This study aimed to analyze the agreement between measurements of unloaded oxygen uptake and peak oxygen uptake based on equations proposed by Wasserman and on real measurements directly obtained with the ergospirometry system. We performed an incremental cardiopulmonary exercise test (CPET), which was applied to two groups of sedentary male subjects: one apparently healthy group (HG, n=12) and the other had stable coronary artery disease (n=16). The mean age in the HG was 47±4 years and that in the coronary artery disease group (CG) was 57±8 years. Both groups performed CPET on a cycle ergometer with a ramp-type protocol at an intensity that was calculated according to the Wasserman equation. In the HG, there was no significant difference between measurements predicted by the formula and real measurements obtained in CPET in the unloaded condition. However, at peak effort, a significant difference was observed between oxygen uptake (V˙O2)peak(predicted)and V˙O2peak(real)(nonparametric Wilcoxon test). In the CG, there was a significant difference of 116.26 mL/min between the predicted values by the formula and the real values obtained in the unloaded condition. A significant difference in peak effort was found, where V˙O2peak(real)was 40% lower than V˙O2peak(predicted)(nonparametric Wilcoxon test). There was no agreement between the real and predicted measurements as analyzed by Lin's coefficient or the Bland and Altman model. The Wasserman formula does not appear to be appropriate for prediction of functional capacity of volunteers. Therefore, this formula cannot precisely predict the increase in power in incremental CPET on a cycle ergometer.

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OBJETIVO: Comparar respostas cardiovasculares a Manobra Postural Passiva (Tilt Test) e capacidade cardiorrespiratória em homens e mulheres de meia-idade antes e após treinamento físico aeróbio. MATERIAIS E MÉTODOS: Sete homens - GH (44,6±2,1 anos) e sete mulheres - GM (51,7±4,8 anos), participaram de treinamento físico aeróbio por 12 semanas. Foi realizado protocolo de Tilt Test (cinco minutos supino, dez minutos inclinado 70º, cinco minutos supino), com monitoração da pressão arterial e freqüência cardíaca. Para mensuração da capacidade cardiorrespiratória foi realizado protocolo em cicloergômetro. RESULTADOS: Na condição sedentária, GH mostrou maior influência parassimpática no controle da freqüência cardíaca evidenciada por maior intervalo RR (iRR) durante Tilt Test. Na condição treinada, os valores de iRR de ambos os grupos se assemelham, tendo as mulheres iRR maior em supino, mas na inclinação os homens mantêm iRR mais elevado. Para pressão arterial, as mulheres permanecem com valores superiores após treino, mas a freqüência cardíaca tende a se assemelhar em ambos. Já na capacidade cardiorrespiratória, homens e mulheres têm um padrão de comportamento semelhante após treino. Com exceção dos valores absolutos da freqüência cardíaca, sem diferenças entre os grupos, para todas as outras variáveis os homens obtiveram valores superiores aos das mulheres. Observa-se ainda que, após o treinamento, houve redução significativa dos valores de pressão arterial no GM, mesmo continuando superiores aos dos homens. CONCLUSÃO: O treinamento parece ter reduzido os níveis pressóricos nas mulheres, além de serem observadas melhorias na capacidade cardiorrespiratória de ambos os grupos, permanecendo os homens com melhor desempenho do que as mulheres.

OBJECTIVE: To compare the cardiovascular responses to passive postural maneuvers (tilt test) and the cardiorespiratory capacity in middle-aged men and women, before and after aerobic physical training. METHODS: Seven men (44.6±2.1 years old) and seven women (51.7±4.8 years old) participated in aerobic physical training for 12 weeks. The tilt test protocol (five minutes supine, ten minutes tilted at 70º and five minutes supine) was followed, with arterial blood pressure and heart rate monitoring. A cycle ergometer protocol was used to measure cardiorespiratory capacity. RESULTS: In the sedentary condition, men showed greater parasympathetic influence in heart rate control, as demonstrated by their higher RR interval (iRR) during the tilt test. After training, the iRR values became more similar in the two groups, although the women had higher iRR in the supine position and the men continued to present higher iRR under tilted conditions. The women's blood pressures continued to be higher after training, but heart rate tended to become similar in the two groups. The cardiorespiratory capacity patterns in the two groups were similar after training. Except for absolute heart rate values, for which there were no differences between the groups, the men's values were higher than those of the women for all other variables. It was also observed that, after the training, the women's blood pressures were significantly lower, even though their pressures remained higher than the men's. CONCLUSIONS: The training seemed to reduce the women's arterial blood pressure levels and improve both groups' cardiorespiratory capacity, but the men continued to present better performance than the women.

RESUMO

OBJECTIVE: To evaluate the influence of joint angle on heart rate (HR) responses induced by isometric exercise. METHODS: Ten healthy men (23.8 ± 2.5 years old) underwent isometric maximum voluntary contraction (MVC) tests lasting 10 sec using an electronic dynamometer under the following experimental conditions: knee extension at angles of 60º and 90º and knee flexion at angles of 30º and 90º angles. Their HR was recorded at rest (65 sec), during MVC (10 sec) and during the recovery period (120 sec). The data on mean maximum torque (MMT) and HR variation (deltaHR) were analyzed using the Friedman test with the Dunn post-hoc test, and their correlation was analyzed using the Spearman test (alpha= 0.05). RESULTS: 1) MMT was significantly higher at 60º and 90º knee extension than at 30º and 90º knee flexion (p< 0.05), while no significant differences were found between the two extension angles or between the two flexion angles; 2) deltaHR was similar under all the experimental conditions; 3) No correlation was found between MMT and deltaHR. CONCLUSION: The data suggest that the rapid increase in HR during the 10 sec of isometric MVC does not depend on the joint angle or the morphofunctional differences between the two muscle groups studied.

OBJETIVO: Avaliar a influência do ângulo articular nas respostas da freqüência cardíaca (FC) induzida pelo exercício isométrico. MÉTODOS: Dez homens saudáveis (23,8 ± 2,5 anos) foram submetidos a testes de contração voluntária máxima (CVM) isométrica, durante 10s, em um dinamômetro eletrônico, nas seguintes condições experimentais: extensão do joelho nos ângulos de 60º e 90º e flexão do joelho nos ângulos de 30º e 90º. A freqüência cardíaca foi registrada durante o repouso (65s), durante a CVM (10s) e durante o período de recuperação (120s). Os dados de torque médio máximo (TMM) e de variação da FC (deltaFC) foram analisados usando teste de Friedman, com pós-teste de Dunn, e sua correlação foi analisada usando o teste de Spearman (alfa= 0,05). RESULTADOS: 1) TMM foi significativamente maior nos ângulos de 60º e 90º de extensão em relação aos ângulos de 30º e 90º de flexão (p< 0,05), enquanto entre os dois ângulos de flexão e entre os dois de extensão não foram encontradas diferenças significativas; 2) deltaFC foi similar em todas as condições experimentais; 3) Não foi encontrada correlação entre TMM e deltaFC. CONCLUSÕES: Os dados sugerem que a elevação rápida da FC, durante os 10 s de CVM isométrica, independe do ângulo articular e das diferenças morfofuncionais entre os dois grupos musculares estudados.

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The aim of the present study was to determine whether estrogen therapy (ET) reduces alterations of the autonomic control of heart rate (HR) due to hypoestrogenism and aging. Thirteen young (24 ± 2.6 years), 10 postmenopausal (53 ± 4.6 years) undergoing ET (PM-ET), and 14 postmenopausal (56 ± 2.6 years) women not undergoing ET (PM) were studied. ET consisted of 0.625 mg/day conjugated equine estrogen. HR was recorded continuously for 8 min at rest in the supine and sitting positions. HR variability (HRV) was analyzed by time (SDNN and rMSSD indices) and frequency domain methods. Power spectral components are reported as normalized units (nu) at low (LF) and high (HF) frequencies, and as LF/HF ratio. Intergroup comparisons: SDNN index was higher in young (median: supine, 47 ms; sitting, 42 ms) than in PM-ET (33; 29 ms) and PM (31; 29 ms) women (P < 0.05). PM showed lower HFnu, higher LFnu and higher LF/HF ratio (supine: 44, 56, 1.29; sitting: 38, 62, 1.60) than the young group in the supine position (61, 39, 0.63) and the PM-ET group in the sitting position (57, 43, 0.75; P < 0.05). Intragroup comparisons: HR was lower in the supine than in the sitting position for all groups (P < 0.05). The HRV decrease from the supine to the sitting position was significant only in the young group. These results suggest that HRV decreases during aging. ET seems to attenuate this process, promoting a reduction in sympathetic activity on the heart and contributing to the cardioprotective effect of estrogen hormones.

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Several methods are used to estimate anaerobic threshold (AT) during exercise. The aim of the present study was to compare AT obtained by a graphic visual method for the estimate of ventilatory and metabolic variables (gold standard), to a bi-segmental linear regression mathematical model of Hinkley's algorithm applied to heart rate (HR) and carbon dioxide output (VCO2) data. Thirteen young (24 ± 2.63 years old) and 16 postmenopausal (57 ± 4.79 years old) healthy and sedentary women were submitted to a continuous ergospirometric incremental test on an electromagnetic braking cycloergometer with 10 to 20 W/min increases until physical exhaustion. The ventilatory variables were recorded breath-to-breath and HR was obtained beat-to-beat over real time. Data were analyzed by the nonparametric Friedman test and Spearman correlation test with the level of significance set at 5 percent. Power output (W), HR (bpm), oxygen uptake (VO2; mL kg-1 min-1), VO2 (mL/min), VCO2 (mL/min), and minute ventilation (VE; L/min) data observed at the AT level were similar for both methods and groups studied (P > 0.05). The VO2 (mL kg-1 min-1) data showed significant correlation (P < 0.05) between the gold standard method and the mathematical model when applied to HR (r s = 0.75) and VCO2 (r s = 0.78) data for the subjects as a whole (N = 29). The proposed mathematical method for the detection of changes in response patterns of VCO2 and HR was adequate and promising for AT detection in young and middle-aged women, representing a semi-automatic, non-invasive and objective AT measurement.

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OBJETIVO: Analisar e comparar a variabilidade da freqüência cardíaca (VFC), em repouso, de homens e mulheres de meia-idade. MÉTODOS: Foram estudados 10 homens (54 ± 3,2 anos) e 14 mulheres na pós-menopausa (56 ± 2,6 anos) que não faziam uso de terapia hormonal. A freqüência cardíaca (FC) e os intervalos R-R foram obtidos a partir do eletrocardiograma, batimento a batimento, durante 8 minutos em repouso, nas posições supina e sentada. A VFC foi analisada no domínio da freqüência, usando a transformada rápida de Fourier, por meio da qual foram obtidas as bandas de baixa (BF) e alta freqüência (AF), as quais foram expressas em unidades normalizadas (AFun) e (BFun) e na razão BF/AF. Foram utilizados os testes estatísticos não-paramétricos de Mann-Whitney e de Wilcoxon, com nível de significância de alfa= 5 por cento. RESULTADOS: Na comparação intergrupo, as mulheres apresentaram maiores valores da banda AFun e menores valores da banda BFun e da razão BF/AF em relação aos homens, diferenças essas significativas (p<0,05). Na comparação intragrupo, não foram observadas diferenças significativas nos índices de VFC entre as posições supina e sentada para os 2 grupos estudados. CONCLUSÃO: Nossos resultados mostram uma maior modulação vagal e menor simpática no controle autonômico da FC para as mulheres em comparação aos homens de mesma idade, o que sugere que as diferenças autonômicas relacionadas ao gênero não se devem unicamente aos níveis hormonais de estrogênio, uma vez que as mulheres estudadas já se encontravam na fase pós-menopausa. Outros fatores podem estar contribuindo para essas diferenças.

OBJECTIVE: To analyze and compare heart rate variability (HRV) in middle-aged men and women under resting conditions. METHOD: Ten men (54 ± 3.2 years) and fourteen postmenopausal women (56 ± 2.6 years) who were not using hormonal therapy were studied. Heart rates (HR) and R-R intervals (iR-R) on a beat-to-beat basis were obtained from electrocardiograms over an eight-minute period under resting conditions, in the supine and sitting positions. The HRV was analyzed in the frequency domain by means of fast Fourier transforms and the low (LF) and high (HF) frequency bands were obtained and presented as normalized units (LFnu and HFnu) and the LF/HF ratio. Wilcoxon and Mann-Whitney non-parametric statistical tests were used, with the significance level set at 5 percent. RESULTS: Comparing between the groups, the women presented significantly higher HFnu and lower LFnu and LF/HF ratios than did the men (p<0.05). Comparing within the groups, no significant differences (p>0.05) were found in the HRV indexes between the supine and sitting positions for either study group. CONCLUSION: Our results show greater vagal modulation and lower sympathetic activity in autonomic heart rate control among women than among men of similar age. This suggests that the gender-related autonomic differences are not solely dependent on estrogen levels, since the women studied were already postmenopausal. Other factors may be contributing towards these differences.

RESUMO

OBJETIVO: Aplicar diferentes metodologias de análise aos dados dos testes contínuo em rampa (TCR) e descontínuo em degrau (TDD) e comparar as respostas das variáveis cardiorrespiratórias. MÉTODOS: 8 homens realizaram teste ergoespirométrico em bicicleta: TCR com incremento de 20 a 25W.min-1 e TDD em degraus de 15min cada baseado no limiar de anaerobiose ventilatório (LAV) do TCR, sendo degrau 1 (70 por centoLAV), degrau 2 (100 por centoLAV) e degrau 3 (130 por centoLAV). O LAV foi determinado pela perda do paralelismo entre consumo de oxigênio (VO2) e produção de dióxido de carbono (VCO2). A freqüência cardíaca (FC bpm),VCO2, VO2, (ml.min-1), VO2, (ml.kg-1.min-1), ventilação (VE L.min-1) do TCR foram analisadas em médias móveis de 8 ciclos respiratórios, respiração-a-respiração e pela regressão linear. No TDD, a média foi aplicada do 3° ao 15°min dos degraus. Na análise estatística foram utilizados o teste de Kolmogorov-Smirnov, ANOVA, post hoc de Tukey-Kramer e regressão linear, p<0,05. RESULTADOS: No pico do exercício houve diferença estatisticamente significante entre respiração-a-respiração e demais metodologias. Na comparação de protocolos: VO2, VCO2, V E foram similares entre LAV e degrau 1 (p>0,05), porém VO2 relativo foi diferente (p<0,05) entre LAV e todos os degraus; a FC mostrou diferença (p<0,05) entre LAV e degrau 3, e na análise entre os três degraus houve diferença (p<0,05). CONCLUSÃO: Os resultados indicam que a regressão linear foi eficaz para estimar as variáveis cardiorrespiratórias. Em relação aos protocolos, verificou-se que para a obtenção no TDD de valores cardiorrespiratórios similares ao LAV do TCR foi necessário diminuir a potência em 30 por cento.

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The effects of the aging process and an active life-style on the autonomic control of heart rate (HR) were investigated in nine young sedentary (YS, 23 +/- 2.4 years), 16 young active (YA, 22 +/- 2.1 years), 8 older sedentary (OS, 63 +/- 2.4 years) and 8 older active (OA, 61 +/- 1.1 years) healthy men. Electrocardiogram was continuously recorded for 15 min at rest and for 4 min in the deep breathing test, with a breath rate of 5 to 6 cycles/min in the supine position. Resting HR and RR intervals were analyzed by time (RMSSD index) and frequency domain methods. The power spectral components are reported in normalized units (nu) at low (LF) and high (HF) frequency, and as the LF/HF ratio. The deep breathing test was analyzed by the respiratory sinus arrhythmia indices: expiration/inspiration ratio (E/I) and inspiration-expiration difference (deltaIE). The active groups had lower HR and higher RMSSD index than the sedentary groups (life-style condition: sedentary vs active, P < 0.05). The older groups showed lower HFnu, higher LFnu and higher LF/HF ratio than the young groups (aging effect: young vs older, P < 0.05). The OS group had a lower E/I ratio (1.16) and deltaIE (9.7 bpm) than the other groups studied (YS: 1.38, 22.4 bpm; YA: 1.40, 21.3 bpm; OA: 1.38, 18.5 bpm). The interaction between aging and life-style effects had a P < 0.05. These results suggest that aging reduces HR variability. However, regular physical activity positively affects vagal activity on the heart and consequently attenuates the effects of aging in the autonomic control of HR.

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The effects of the aging process and an active life-style on the autonomic control of heart rate (HR) were investigated in nine young sedentary (YS, 23 ± 2.4 years), 16 young active (YA, 22 ± 2.1 years), 8 older sedentary (OS, 63 ± 2.4 years) and 8 older active (OA, 61 ± 1.1 years) healthy men. Electrocardiogram was continuously recorded for 15 min at rest and for 4 min in the deep breathing test, with a breath rate of 5 to 6 cycles/min in the supine position. Resting HR and RR intervals were analyzed by time (RMSSD index) and frequency domain methods. The power spectral components are reported in normalized units (nu) at low (LF) and high (HF) frequency, and as the LF/HF ratio. The deep breathing test was analyzed by the respiratory sinus arrhythmia indices: expiration/inspiration ratio (E/I) and inspiration-expiration difference (deltaIE). The active groups had lower HR and higher RMSSD index than the sedentary groups (life-style condition: sedentary vs active, P < 0.05). The older groups showed lower HFnu, higher LFnu and higher LF/HF ratio than the young groups (aging effect: young vs older, P < 0.05). The OS group had a lower E/I ratio (1.16) and deltaIE (9.7 bpm) than the other groups studied (YS: 1.38, 22.4 bpm; YA: 1.40, 21.3 bpm; OA: 1.38, 18.5 bpm). The interaction between aging and life-style effects had a P < 0.05. These results suggest that aging reduces HR variability. However, regular physical activity positively affects vagal activity on the heart and consequently attenuates the effects of aging in the autonomic control of HR.

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