ORIGINAL ARTICLE Effectiveness of aquatic exercise on reduction B-type natriuretic peptide values in postmenopausal hypertensive women: a randomized clinical trial Eduardo Aguilar Arca1,2 • Rodrigo Leal de Paiva Carvalho1,2 • Silvia Regina Barrile1,2 • Camila Gimenes1,2 • Bruno Martinelli2 • Roberto Jorge da Silva Franco3 • Luis Cuadrado Martin3 Received: 4 March 2016 / Accepted: 12 May 2016 / Published online: 23 May 2016 � Springer-Verlag Italia 2016 Abstract Purpose To compare the responses of aquatic exercise with dry land training and control inactive group on B-type natriuretic peptide and plasma renin activity levels in postmenopausal hypertensive women. Methods Forty postmenopausal hypertensive women were randomly assigned to 3 groups: water group, dry land group and a non-intervention control group. The exercises programs consisted of consisted of 50-min sessions, three- times a week and was performed for 12 weeks. Samples of B-type natriuretic peptide and plasma renin activity levels were collected pre- and post-intervention. In the dry land exercise program, heart rate was maintained at around 50–60 % of the heart rate reserve, deducting 17 heart beats for aquatic exercise. Results There was a statistically significant reduction in B-type natriuretic peptide in the water group (37 ± 11.1 ng/L) to (22 ± 9.4 ng/L), pre and post inter- vention, respectively. There was no difference in plasma renin activity levels between groups and moments. Conclusion This study demonstrated the effectiveness of aquatic exercise in reducing B-type natriuretic peptide values in postmenopausal hypertensive women. Plasma renin activity levels values were not influenced by either of the interventions. Keywords Hydrotherapy � Exercise � B-type natriuretic peptide � Hypertension Abbreviations ANP Atrial natriuretic peptide BNP B-type natriuretic peptide BP Blood pressure CG Non-intervention control group HR Heart rate LG Dry land group NT-proBNP N-terminal of the prohormone brain natriuretic peptide PRA Plasma renin activity RAAS Renin–angiotensin–aldosterone system WG Water group Introduction The renin–angiotensin–aldosterone system (RAAS) is a central control mechanism of the salt and water home- ostasis of the body and of blood pressure [1]. The physi- ological effects of the RAAS that result in the conservation of extracellular volume and stabilization of blood pressure are counterbalanced by the natriuretic peptides: atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) [1, 2]. Higher serum concentrations of BNP is a robust marker of pressure-induced cardiac damage, left atrial enlargement and left ventricular hypertrophy, in patients with hyper- tension [3]. & Rodrigo Leal de Paiva Carvalho rodrigo.carvalho@usc.br 1 Post-graduate Program in Physiotherapy, Sagrado Coração University, USC, Rua Irmã Arminda, 10-50, Jardim Brasil, Bauru, SP CEP 17011-160, Brazil 2 Department of Physiotherapy, Sagrado Coração University, USC, Bauru, SP, Brazil 3 Department of Clinical Medicine, Paulista State University, UNESP, Botucatu, SP, Brazil 123 Sport Sci Health (2016) 12:255–260 DOI 10.1007/s11332-016-0284-y http://crossmark.crossref.org/dialog/?doi=10.1007/s11332-016-0284-y&domain=pdf http://crossmark.crossref.org/dialog/?doi=10.1007/s11332-016-0284-y&domain=pdf Studies comparing changes in the levels of BNP fol- lowing dry land exercise training have demonstrated vari- able results [4–8]. Passino et al. [4] presented a 34 % reduction in BNP levels with a 9-month cycling program, which was performed 3 days a week for 30 min, compared to the group which maintained their usual life style, who presented a 7 % increase in BNP levels in heart failure patients. Accordingly Parrinello et al. [6], reported a 19 % reduction in BNP levels in heart failure patients trained with a 10-week walking program for 30 min a day, 5 days a week, compared to a 14 % rise in the control group. Nevertheless, no studies have researched the effects of aquatic exercise on BNP levels in hypertensive individuals. Regarding PRA levels in hypertensive patients, there were no changes in dry land exercise training [9, 10]. It is known that the acute effect of water immersion may elevate natri- uretic peptide values and decrease plasma concentration of rennin [11, 12]. The effect of aquatic exercise on blood pressure in hypertensive women showed a decrease in blood pressure as demonstrated previously in the study [13–15]. The hypothesis of the present study was that aquatic exercise could to affect the BNP and PRA levels in hyper- tensive women. Currently, there is no study available com- paring the chronic effect of aquatic exercise on BNP and PRA. Thus, the objective of this study was to compare the responses of aquatic exercise with dry land training and control inactive group on B-type natriuretic peptide and plasma renin activity levels in postmenopausal hypertensive women. Methods Ethical considerations This study was performed according to the National Health Council resolution 196/96 and was approved by the local Research Ethics Committee (protocol: 041/05) and have been performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. Written informed consent was obtained from all volunteers. Subjects Study participants were postmenopausal hypertensive women who were on the waiting list of the Physical Therapy Clinic of the Sagrado Coração University, located in Bauru, São Paulo, Brazil. Study design An interventional controlled randomized trial was per- formed. Seventy-eight hypertensive female volunteers were enrolled to participate in the study. Of the 78 par- ticipants, 18 were excluded due to positive coronary insufficiency in the treadmill test. The 60 remaining par- ticipants were randomly assigned into three groups: water group (WG: n = 20), dry land group (LG: n = 20) and control group (CG: n = 20). During the study, there was a loss of 20 participants from the 3 groups. There were 20 losses during the period of intervention and review, and analyzed data from 40 volun- teers. The methodological sequence of selection and ran- domization of the study participants can be seen in Fig. 1. Outcome measures Table 1 shows the baseline characteristics of the study participants. The sample consisted of postmenopausal hypertensive women with overweight and obesity. Indi- vidual height and body weight were measured with the subjects wearing bathing suits. Body mass index and waist to hip ratio were calculated as previously described by Lohman et al. [16]. Blood pressure (BP) and heart rate (HR) were measured according to VI DBH [17]. Blood sample were collected for BNP and PRA mea- surements in the morning, pre and post intervention period, initially with the patients in a fasting state and then 2 h later with the patients in the standing position. Regular antihypertensive drug treatment and habitual diet were maintained by all patients groups. This procedure was performed in the Clinical Analysis Laboratory at Sagrado Coração University. Blood sample for BNP analysis was stored in pre chilled tubes containing ethylene diamine tetra-acetic and the plasma was immediately separated after collection in a refrigerated centrifuge at 4 �C. BNP plasma concentrations were determined using an automated equipment method- ology for microparticle enzyme testing, developed by AxSym analyzer ABBOTT� (Minnesota, USA) and the results were expressed in ng/L. PRA measurements were performed by angiotensin I generation in vitro using a commercially available radioimmunoassay kit Renin� Mayan (Codolet, France), with results expressed in ng/mL/h. PRA and BNP were evaluated before and after exercise treatment. Materials The aquatic exercises were performed with the aid of a swim support ring from the manufacturer Nautika� (Guarulhos, Brazil) in a heated pool with a water temper- ature of between 33 and 33.5 �C. The dry land exercises were performed at an ambient temperature on a stationary exercise cycle ergometer Caloi� (São Paulo, Brazil). 256 Sport Sci Health (2016) 12:255–260 123 Intervention The 12-week exercise program consisted of 50-min ses- sions, three-times a week. Both programs were divided into four different phases, including the same activities, inten- sity, frequency and duration. Phase I: heating—the WG participants walked in water, with the water level at the xiphoid process, and the LG walked for 10 min outside the pool. Phase II: lower limb stretching—both groups performed lower limbs muscle stretching (10 min). Phase III: lower limb isotonic move- ments based on the deep water running technique [18]. The dry land exercise was performed on stationary bikes Caloi� (São Paulo, Brazil). Heart rate was verified every 5 min by pulse palpation of the radial artery. In the dry land exercise program, heart rate was maintained at around 50–60 % of the heart rate reserve [19], deducting 17 heart beats for aquatic exercise [20]. This phase lasted for 20 min for both Recruitment and Screening n = 78 WG n = 20 Excluded n = 18 LG n = 20 CG n = 20 Loss n = 3 Loss n = 6 Loss n = 11 Analyzed n = 17 Analyzed n = 14 Analyzed n = 9 Randomized n = 60 Fig. 1 Design of randomization and follow-up of participants Table 1 Baseline characteristics of the study population Characteristics WG (n = 17) LG (n = 14) CG (n = 9) Age (years) 65 ± 7.8 62 ± 7.3 64 ± 4.9 Body weight (kg) 69.6 ± 12.7 68.9 ± 12.4 76.2 ± 9.1 Height (cm) 1.57 ± 0.05 1.55 ± 0.06 1.55 ± 0.05 BMI (Kg/cm2) 28.1 ± 4.9 28.4 ± 4.2 31.6 ± 3.55 AC (cm) 106.3 ± 7.9 105.6 ± 8.1 105.5 ± 10.7 SBP (mm Hg) 131 ± 17.7 134 ± 19.5 130 ± 19.22 DBP (mm Hg) 78 ± 10.6 77 ± 8.3 81 ± 14.8 HR (beats/min) 79 ± 16 75 ± 13 74 ± 14.3 HDL (mg/dL) 48.9 ± 11.6 44.5 ± 7.2 55.4 ± 11.9 LDL (mg/dL) 124.1 ± 35.8 120.5 ± 44.4 147.7 ± 33.9 VLDL (mg/dL) 33.8 ± 57.2 33.5 ± 15.5 26.8 ± 10.7 Cholesterol (mg/dL) 194 ± 41.3 199 ± 46.4 230 ± 40.1 Triglicerides (mg/dL) 133.8 ± 57.2 164.4 ± 77.4 134 ± 53.9 Urea (mg/dL) 38.4 ± 8.3 34.9 ± 8.8 50.8 ± 12.9 Creatinine (mg/dL) 0.7 ± 0.2 0.8 ± 0.3 0.8 ± 0.1 Urinary sodium (mEq/24 h) 150.2 ± 58 170.7 ± 78.4 161.2 ± 56 Values are mean ± SD. p[ 0.05 for all comparisons WG water group, LG land group, CG control group, BMI body mass index, AC abdominal circumference, SBP systolic blood pressure, DBP diastolic blood pressure, HR heart rate, HDL high-density lipoprotein, LDL low-density lipoprotein, VLDL very low-density lipoprotein Sport Sci Health (2016) 12:255–260 257 123 programs. Phase IV: relaxation—in the WG, the partici- pants remained afloat, relaxing for 10 min, in the LG, the patients remained lying on mats, softly breathing (10 min). The aquatic exercises were performed in a heated pool with the water temperature maintained at between 33 and 33.5 �C and the exercises on dry land were performed at ambient temperatures of between 25 and 27 �C. Statistical analysis We used G*Power 3.1 software (Düsseldorf, Germany) to determine that a sample size of thirteen subjects was the minimum needed to provide a statistical power of 85 % with an alpha of 5 % for the analysis. The Shapiro–Wilk test was used to confirm the data normality. The data were expressed as mean ± standard deviation. The ANOVA statistical test was used to compare the differences between groups and moments pre and post intervention. The significance level was considered when p was lower than 5 %. Results Figure 2 presents BNP values before and after treatment. There was a significant reduction in BNP in the WG (from 37 ± 11.1 to 22 ± 9.4 ng/L) when compared the pre and post-intervention. Figure 3 shows PRA values before and after treatment. No changes were found between the moments and the groups. Discussion According to the present study, the WG presented a sig- nificant reduction in BNP levels compared the pre and post-intervention. In part, these results could be explained by warm water immersion having a diuretic like antihypertensive drug effect, which may reduce the over- load volume and enhance water and salt excretion. This is in accordance with the experiment of Melo et al. [21] who studied antihypertensive treatment using two types of drugs (losartan/hydrochlorothiazide) with different mechanisms yielded powerful antihypertensive efficacy with safety and decreased plasma levels of BNP. In relation acute physiological responses, it is known that immersion change the hydrostatic gradient promoting thoracic hypervolemia [22], a fact that causes an increase in plasma concentrations of atrial natriuretic peptide (ANP) [23]. The ANP and BNP are produced in the atria and ven- tricles of the heart and secreted by distension of these heart chambers and the elevated blood pressure [24]. Their acute effects are increased regulation of glomerular filtration and renal sodium and water excretion as well as suppression of secretion of renin and aldosterone [25]. However, there were differences in the responses of BNP levels, when individuals were subjected to acute immersion. In the study by Navasiolava et al. [26] eight healthy young volunteers were evaluated before, during and after 7 days of immersion. The levels of NT-proBNP increased significantly during recovery (10 ± 3 ng/L before dry immersion vs 26 ± 5 ng/L on the fourth recovery day). It was not found in the literature any study that exam- ined the chronic effects of aquatic exercise using the deep water running technique in BNP levels in hypertensive postmenopausal women. However, it is believed that the reduction in plasma BNP levels in the WG was due to association of the physiological effects of immersion and chronic exercise. These factors contributed to a decrease in peripheral vascular resistance, sympathetic activity, blood pressure, increased urine output and suppression of renin– angiotensin–aldosterone system (RAAS) [15, 27, 28]. The PRA data in Fig. 3 remained at the same level between groups in pre and post moments showing that PRA values were not influenced by the interventions. Despite 0 20 40 60 WG LG CG * Pre Post B N P (n g/ L) Fig. 2 Values of BNP in different groups pre and post treatment. *p\ 0.05 in WG post vs pre 0 2 4 6 8 WG LG CG Pre Post PR A (n g/ m l/h ) Fig. 3 Values of PRA in different groups pre and post treatment 258 Sport Sci Health (2016) 12:255–260 123 showing great numerical difference, there was no statisti- cally significant difference, probably due to the large standard deviation. The limitations of the study were firstly in the training protocol, the control of aerobic exercise intensity was evaluated through manual pulse checking, which is an intermittent method. Secondly, due to the difficulty of finding male volunteers, only postmenopausal females participated in the study. On the other hand, it is important to note that there are more hypertensive women than men in the age range studied. Despite the difference between the temperatures of the two environments in which programs have been conducted, it is quite complicated to equalize temperatures for carrying out exercises on dry land and water. However, previous studies of the authors [13, 15] showed that exercise per- formed with low and moderate-intensity at warm temper- atures are recommended to decreased blood pressure in hypertensive women. Finally, all patients were users of anti-hypertensive drugs, which were not withdrawn for ethical reasons. However, none of the patients changed the medication or its dose during the research protocol, mitigating this issue. The clinical relevance of these observations is that the reduction in BNP levels in hypertensive postmenopausal women may indicate a decrease in cardiac work, which could contribute to the control of hypertension and car- diovascular diseases. In addition, the immersion decreases the joint overload, making possible to perform exercises in older people with chronic degenerative joint diseases [29, 30]. Conclusion The present study showed the effectiveness of aquatic exercise in reducing BNP values in postmenopausal hypertensive women. PRA values were not influenced by either of the interventions. Acknowledgments This source was supported by Fundação de Amparo a Pesquisa do Estado de São Paulo—FAPESP—process: 2006/06134-5. Compliance with ethical standards Conflict of interest The authors declare that they have no conflict of interest. Ethical approval This study was performed according to the National Health Council resolution 196/96 and was approved by the local Research Ethics Committee (protocol: 041/05) and have been performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. 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