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Print version ISSN 1517-8692
Rev Bras Med Esporte vol.12 no.6 Niterói Nov./Dec. 2006
Heart rate and blood pressure behavior throughout pregnancy, with training in water medium*
Comportamiento de la frecuencia cardiaca y la presión arterial, a lo largo de la gestación, con entrenamiento en medio líquido
Ilana FinkelsteinI; Roberta BgeginskiII; Marcus Peikriszwili TartarugaIII; Cristine Lima AlbertonIV; Luiz Fernando Martins KruelV
IMestre em Ciências do Movimento
Humano pela Escola de Educação Física (EsEF) da Universidade
Federal do Rio Grande do Sul (UFRGS), Porto Alegre
IIAcadêmica, EsEF, UFRGS
IIIMestrando do Programa de Ciências do Movimento Humano, EsEF, UFRGS
IVMestranda do Programa de Ciências do Movimento Humano, EsEF, UFRGS
VDoutor em Ciências do Movimento Humano, Professor, EsEF, UFRGS.
PURPOSE: The aim of the present study
was to evaluate the behavior of heart rate (HR) throughout gestation, before,
during, and after the exercise in water, as well as the behavior of blood pressure
(BP) before and after the same exercise.
METHODS: The sample was composed of seven pregnant women. The HR was measured in three moments: 1) in radial artery, in 15 seconds, with the women sitting; 2) after 20 to 30 minutes the beginning of exercise, which was performed varying from 13 to 14 based on the subject's perceived exertion (Borg's 6-20 scale), with women standing in a pool, with water at the level of their xiphoid process; 3) approximately 20 minutes after the end of the session, with women sitting. The measurement of BP was performed before and after exercise in the same conditions described above. Measurements were taken once a week throughout the gestational period. Descriptive statistics, ANOVA for repeated measures and the Bonferroni test were used, with p < 0.05 (SPSS version 11.0).
RESULTS: No statistically significant differences were found between the end of gestational trimesters and measurement conditions of variables evaluated.
CONCLUSION: We conclude that pregnants that practice water exercises presented a constant behavior of HR and BP during the gestational period. That can probably evidence a water training effect in this population.
Keywords: Physiological adaptation. Pregnancy. Water exercises.
OBJETIVO: El objetivo de este estudio
ha sido el de evaluar el comportamiento de la Frecuencia Cardiaca (FC) a lo
largo de la gestación, antes, durante y después de las clases
de hidrogimnasia, y el de la Presión Arterial (PA) antes y después
del mismo ejercicio.
MÉTODOS: La muestra fue compuesta por siete gestantes. La lectura de FC fue realizada en tres momentos: 1) en la arteria radial, 15 segundos antes del ejercicio, en posición sentada; 2) después de 20 a 30 minutos de iniciado el ejercicio, realizada entre 13-14 en la escala de percepción subjetiva de esfuerzo (Escala de Borg 6-20) de pie, con agua hasta la altura del apéndice xifoide; 3) después, aproximadamente, de 20 minutos de acabada la clase, en posición sentada. La medición de PA fue verificada antes y después del ejercicio en las condiciones descritas anteriormente. Las medidas fueron realizadas una vez por semana durante el transcurso de la gestación. Se utilizó la estadística descriptiva, ANOVA para medidas repetidas y test post hoc de Bonferroni con p < 0,05 (SPSS versión 11.0).
RESULTADOS: No encontramos diferencias estadísticas significativas entre los finales de los trimestres de gestación y entre las condiciones de medición en las variables evaluadas.
CONCLUSIONES: Nuestro estudio concluyó que la FC y PA presenta comportamiento constante a lo largo de los tres trimestres de gestación.
Palabras-clave: Adaptación fisiológica. Embarazo. Hidrogimnasia.
Pregnancy, as other growth processes, is followed by deep alterations in women's structure, metabolism and endocrine and cardiovascular function(1-2). In pregnant women clinically healthy, the Blood Pressure (BP) decreases until the middle of pregnancy, and then increases until the day of delivery, with final indices similar to the ones found in the beginning of pregnancy(3,16-20). The Resting Heart Rate (RHR) abruptly increases in the first trimester of pregnancy, followed by a moderate increase until the end(4).
Arterial Hypertension in pregnant women constitutes in one of the main problems of contemporary obstetrics, being one of the main causes of perinatal mortality and morbidity(5). The isolated measurement of BP is still the main diagnosis device of pre-eclampsia/eclampsia(3), condition which may develop and lead to several problems, among them, brain hemorrhage in the pregnant woman; prematurity and fetal hypoxia(6). The control of this variable during physical activity is crucial in order to obtain an early diagnosis.
Physical activity during pregnancy is recommended, provided that the woman is considered totally healthy, after specialized medical evaluation and prescription performed by a Physical education Professional. During a normal pregnancy, women practitioners of exercise may continue to exercise, with adequate prescription for each gestational period(7). Among the suitable activities, is water gymnastics, since it has as characteristics low articular impact(8); increase of venous return due to hydrostatic pressure(9) and lower HR and BP behavior(10) also avoiding the supine position which after the first trimester may result in a relative obstruction of venous return(11).
The literature presents studies with monthly measurements of BP during pregnancy; however, the number of studies which weekly verified this behavior is scarce. The lack of papers which mention physical activity in the water environment, such as water gymnastics, and which mention the effects of this kind of training in the cardiorespiratory variables of pregnant women, justify the conduction of this study. The deep understanding of this behavior may help in future studies concerning treatment and prevention of hypertensive disturbs during pregnancy.
The following questioning guided our study: How do heart rate and blood pressure of pregnant women who practice water gymnastics during pregnancy behave?
Therefore, this work had as objective to evaluate the HR behavior throughout pregnancy; before, during and after water gymnastics classes, as well as the BP behavior before and after the same exercise.
The sample of this study consisted of seven pregnant women voluntarily chosen, with ages between 26 and 34 years. All women began the water gymnastics program between the 11th and 13th gestational week and followed with it until the 38th week, with a total of approximately 28 weeks of training, with a frequency of two to three weekly sessions, according to table 1. None of them had physical problems or were under medication, besides not having exercised in the last three months. The volunteers signed an Informed Consent Form in two copies, after explanation about all the phases of the research.
The data concerning age, initial body weight and height of the women who characterized the sample were obtained from questionnaires about medical evaluations of each woman, collected before entering the program. The baby's weight was obtained through the baby's card data, with measurements conducted in the hospital immediately after birth. The value of the estimated Mean Blood Pressure (MBP) (MBP = DBP + [0,333 x (PAS PAD)])(12) was calculated from the Systolic Blood pressure (SBP) and the Diastolic Blood Pressure (DBP) for the resting experimental situations (PAMR) and post-exercise (PMBP). The Body Mass Index (BMI) was calculated from the weight and height data (weight/height2).
For the collection beginning, each pregnant woman would be sitting, in resting situation for two minutes, with arm extended at the heart level and rested. At the end of it, the RBP was measured in the radial artery, in 15 seconds. The Resting Systolic BP (RSBP) and the Resting Diastolic Blood Pressure (RDBP) were also conducted at that moment, with an aneroid sphygmometer and a stethoscope.
The entire procedure was repeated once a week, from the first class of the pregnant woman until the last one before delivery.
The collected data were divided in three time periods: end of the 1st trimester mean of the measurements conducted between the 11th and 13th gestational weeks; end of 2nd trimester mean of the measurements conducted between the 25th and 27th gestational weeks; and end of the 3rd trimester mean of the measurements conducted between the 36th and 38th gestational weeks.
The water gymnastics classes were conducted in a swimming pool with immersion depth ranging from the umbilical scar and xiphoid appendix; with water temperature kept between 30 and 32ºC. The class consisted of a cefalo-tail articular warm-up with duration of five minutes, followed by organic warm-up of five minutes. The main part was basically aerobic, with duration of 20 to 30 minutes and another part of localized muscular endurance consisting of upper limbs; lower limbs and abdominal exercises, with duration of five to ten minutes. The intensity was controlled through the Borg's Scale of Perceived Exertion(13), keeping exertion between indices 13 and 14.
In the ten final minutes of the aerobic part, the exercise HR (EHR) was measured in the radial artery, for 15 seconds. For this measurement, the pregnant woman remained standing on a step, with arm extended at the heart level and rested, with water between the umbilical scar and the xiphoid appendix(10).
The final part of the class consisted of stretching and relaxing, with duration of 10 to 15 minutes. After 20 minutes of the class end, the post-exercise measurements of HR (PHR); the Systolic BP (PSBP) and the Diastolic BP (PDBP) were taken, with the pregnant woman at the same conditions of the initial resting measurements.
Descriptive statistics was used for the analysis of the collected data. Shapiro-Wilk test was used for normality. ANOVA for repeated measurements and the Bonferroni post-hoc test were used for comparison of the dependent variables in the different time periods. The significance level adopted in this study was p < 0,05. All statistical tests were performed in the statistical program SPSS, version 11.0.
The data presented normal and homogeneous distribution, allowing hence, the utilization of parametrical tests.
Analyzing the RHR responses, no statistically significant differences (p < 0,05) were observed in the different gestational trimesters, nor in the exercise and post-exercise situations, as shown in table 2.
Table 3 presents the BP indices. The RSBP; the RDBP; the RMBP; the PSBP; the PDBP and the PMBP did not present statistically significant differences (p < 0,05) in the different gestational trimesters for the resting and post-exercise results.
Several authors found a dramatic increase of HR in the first four weeks of pregnancy; followed by a gradual increase; reaching a plateau of approximately 15 beats per minute above the RHR indices in the non-pregnant state(1,14-15). Such increase may be caused by vascular and hemodynamic adjustments derived from pregnancy(16). Nevertheless, in this research no significant increases were found in the RHR indices throughout pregnancy. A relevant fact is that we did not measure the pre-pregnancy HR in order to compare with the measurement of the end of the 1st trimester and to be able to verify an initial sudden increase or not, limiting thus, that this analysis was conducted in the present study. During the 2nd and 3rd trimesters we did not find gradual increase, according to studies previously mentioned, what probably may be caused by the training effects, which may have induced maintenance of the HR indices during the water gymnastics program.
Such finding agrees with the study by Pivarnik et al.(17) who compared a group of pregnant women who practiced exercise throughout pregnancy with a group of sedentary pregnant women. In the 25th and 36th weeks of pregnancy and in the 12th week post-delivery, the two groups were tested in cycle ergometer, with HR set at 140 bpm. The results showed that the trained pregnant women reached higher loads for the same given HR than the sedentary ones. Moreover, they presented a resting systolic volume higher during exercise. Although the group of trained pregnant women has presented an increase in HR, this increase was lower than the one of the non-trained women.
Beller and Dolny(18) when compared pregnant women who walked three times a week with sedentary pregnant women, verified a a decrease of HR of seven bpm in the 2nd gestational trimester and, of four bpm in the 3rd gestational trimester when tested the pregnant women in cycle ergometer for 20 minutes, in the same exercise intensity.
South-Paul et al.(19) also compared pregnant women who practiced exercise three times a week and who began training with ten pregnancy weeks, with sedentary pregnant women during ten weeks. An increase of O2peak of 9% was verified in the active pregnant women and of 2% in the control group (sedentary pregnant women), while no alterations in the HR during exercise at 75 W in cycle ergometer was verified Corroborating these findings, Santos et al.(20) verified increase of physical capacity in sedentary pregnant women with overweight.
There is still a certain divergence in the literature concerning the BP behavior throughout pregnancy. In clinically healthy pregnant women, the BP decreases until the middle of the pregnancy, then it increases until delivery day, with final values similar to those found in the beginning of pregnancy(3,21-25). Mooney et al.(25) checked the BP of 68 healthy pregnant women and concluded that both the SBP and the DBP were lower in the 18th gestational week. Moreover, these values slowly increased after that, in a proportion of 0,4 mmHg for the DBP per week. It is important to mention that none of these studies applied a physical training for evaluation of the chronic effect of it over the physiological parameters analyzed.
Nevertheless, the study by Sá et al.(5), which did not evaluate the physical conditioning degree either, nor the exercise practice among the pregnant women, found a different result. The authors concluded that the BP presented steady behavior during pregnancy, with no statistically significant variation in the trimesters. However, the authors did not discuss the possible causes for these findings. The present study did not find significant differences in the BP during the gestational trimesters either with the application of water gymnastics training. Both our results and the ones by Sá et al.(5) diverge from the international literature which show a distinct behavior of BP; however, in our study a training intervention occurred, which may have caused these results.
The BP decrease during immersion in rest in pregnant women is described in the literature(9-10,26-27). It can be explained by the vagal tone increase(28-29) and by the hydrostatic pressure action which acts in the edema of pregnant women. The blood redirection produces high diuresis through the stimulation of the receptors which leads to hormonal and neural reflex adjustments and cause diuresis as well as natriuresis. Such signal is immediate to the receptors and consequently leads to a decrease in the systolic and diastolic blood pressure(30).
Hartmann et al.(30) compared the BP responses in pregnant women in rest and during exercise in water and on land and verified that the immersion did not significantly affect the blood pressure in the water during rest and exercise. However, both the SBP and the DBP decreased more in the water post-exercise than in land post-exercise.
McMurray et al.(31) tested 12 pregnant women, with the aim to determine the pregnancy effect on the cardiovascular responses during water exercise and during immersion. The sample remained immersed, in rest, for 20 minutes and other 20 minutes pedaling in cycle ergometer at 60% of the predicted O2max. The water temperature was 30ºC and the pregnant women were tested in the 15, 25 and 35 gestational weeks and 8-10 weeks after delivery. The results showed that the HR at the same metabolic demand is lower in the exercise in water than on land. The combination of exercise in water and pregnancy results in a more expressive increase of the cardiac debt than the one expected on land. This study demonstrates that the HR and BP response during exercise in water is different from the one on land; therefore, it suggests that it is not recommended to use the same training HR zones of the exercise on land.
Some authors(32) did not evidence a crucial role of regular aerobic exercise during pregnancy in the prevention of gestational hypertension. Nonetheless, Tomoda et al.(33) evaluated two groups of pregnant women: one that walked 25 minutes, three times a week, with HR around 120 bpm, and another group that did not practice physical exercise. After having tested the groups in the 12th, 22nd, 29th and 36th gestational weeks and 1 month after delivery, the authors concluded that the moderate exercise was able to prevent gestational hypertension, once 22,5% of the group which did not exercise developed gestational hypertension, while in the group which practiced exercise there was not any case.
Sorensen et al.(34) verified in their study that women who engaged in any regular physical activity in the beginning of pregnancy, when compared with inactive women, presented a decrease of 35% of the risk to develop pre-eclampsia. Besides that, they concluded that regular physical activity, especially when 'performed' during the year before pregnancy and during the beginning of pregnancy, is associated with a reduced risk of pre-eclampsia.
Weissgerber et al.(35) studying the role of regular physical activity in the pre-eclampsia prevention suggest that pre-natal regular exercise may prevent or even avoid the progression of this disease.
The authors previously mentioned evaluated the acute effects of immersion in the HR and BP response. Tomoda et al.(33); Sorensen et al.(34) and Weissgerber et al.(35) studied the chronic effect of exercise in the prevention of gestational hypertension and concluded that it plays an important role in the cardiorespiratory adaptations. Our study presents evidence that pregnant women exposed to the training and immersion effects may present chronic adaptations in physiological parameters, such as HR and BP.
The role of physical training role in pregnant women is little known yet, due to the few number of quality studies available. Although the present study does not present control group, we believe that future investigations should be conducted in order to better establish the role of physical exercise in the hemodynamic behavior throughout pregnancy.
Our study concluded that pregnant women submitted to water gymnastics classes presented steady behavior of HR and BP throughout the three gestational trimesters, which showed a probable chronic effect of training in water environment for this population.
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Received in 29/4/05. Final version received in 15/3/06. Approved in 15/5/06.
All the authors declared there is not any
potential conflict of interests regarding this article.
* Grupo de Pesquisa em Atividades Aquáticas e Terrestres, Laboratório de Pesquisa do Exercício, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul.