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Effect of a physical activity programme in the aquatic environment on haemodynamic constants in pregnant women
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Enferm Clin. 2017;xxx(xx):xxx---xxx
www.elsevier.es/enfermeriaclinica
ORIGINAL ARTICLE
Effect of a physical activity programme in the aquatic environment on haemodynamic constants in pregnant women夽 Juana María Vázquez-Laraa,∗ , Carlos Ruiz-Frutosb,c , Luciano Rodríguez-Díaza , Jesús Ramírez-Rodrigod , Carmen Villaverde-Gutiérreze , Gema Torres-Luquef a
Hospital Universitario de Ceuta, Ceuta, Spain Departamento de Sociología, Trabajo Social y Salud Pública, Universidad de Huelva, Huelva, Spain c Universidad Espíritu Santo, Guayaquil, Ecuador d Facultad de Ciencias de la Salud, Campus Universitario de Ceuta, Ceuta, Spain e Facultad de Ciencias de la Salud de Granada, Granada, Spain f Facultad de Humanidades y Ciencias de la Educación, Universidad de Jaén, Jaén, Spain b
Received 13 June 2017; accepted 29 July 2017
KEYWORDS Exercise; Pregnancy; Immersion; Haemodynamics
Abstract Objective: To evaluate the effect of a physical activity programme in the aquatic environment with immersion up to the neck, of six weeks duration, on haemodynamic constants in pregnant women. Methods: A six-week physical activity programme in the aquatic environment was carried out with a total of 46 pregnant women, who were distributed into an experimental group (n = 18), which participated in the programme, and a control group (n = 28), which followed routine care. In both groups different haemodynamic measurements were evaluated before and after the programme. Results: At the beginning of the programme the mean systolic blood pressure was similar between groups, but diastolic blood pressure was slightly higher in the experimental group. When the measurements at the last session were compared, arterial pressures (systolic, diastolic and mean) were significantly higher in the control group (p < .050). Similarly, the initial plasma volume values did not differ between groups, but after the intervention, the control group women showed a higher mean (p < .010). The fraction of sodium excretion (FENa) increased significantly in the experimental group, after the programme, with a mean three times higher (p < .050). Aldosterone plasma levels did not show significant differences between the groups in the different measurements.
DOI of original article: http://dx.doi.org/10.1016/j.enfcli.2017.07.009 Please cite this article as: Vázquez-Lara JM, Ruiz-Frutos C, Rodríguez-Díaz L, Ramírez-Rodrigo J, Villaverde-Gutiérrez C, Torres-Luque G. Efecto de un programa de actividad física en el medio acuático sobre las constantes hemodinámicas en mujeres embarazadas. Enferm Clin. 2017. https://doi.org/10.1016/j.enfcli.2017.07.009 ∗ Corresponding author. E-mail address: [email protected] (J.M. Vázquez-Lara). 夽
2445-1479/© 2017 Elsevier Espa˜ na, S.L.U. All rights reserved.
ENFCLE-702; No. of Pages 9
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J.M. Vázquez-Lara et al. Conclusion: A programme of swimming and immersion exercises in pregnant women contributes to hydrosaline balance, preventing an excessive increase in usual plasma volume during pregnancy and in the activity of the renin-aldosterone axis. © 2017 Elsevier Espa˜ na, S.L.U. All rights reserved.
PALABRAS CLAVE Ejercicio; Embarazo; Inmersión; Hemodinámica
Efecto de un programa de actividad física en el medio acuático sobre las constantes hemodinámicas en mujeres embarazadas Resumen Objetivo: Evaluar el efecto de un programa de actividad física en el medio acuático con inmersión hasta el cuello, de seis semanas de duración, sobre las constantes hemodinámicas en mujeres gestantes. Método: Se llevó a cabo un programa de actividad física en el medio acuático, de seis semanas de duración a un total de 46 mujeres embarazadas, que fueron distribuidas en grupo experimental que participó en el programa (n = 18) y grupo control (n = 28) que desarrolló los cuidados habituales. En los dos grupos se valoraron diferentes medidas hemodinámicas antes y después del programa. Resultados: Al inicio del programa el promedio de presión arterial sistólica era similar en ambos grupos pero la presión arterial diastólica era ligeramente mayor en el grupo experimental. Cuando se contrastan las medidas en la última sesión, resultan significativamente mayores las presiones arteriales (sistólica, diastólica y media), en el grupo control (p < 0,050). De forma similar, los valores iniciales de volumen plasmático no diferían en ambos grupos, pero tras la intervención las mujeres del grupo control evidencian un mayor promedio (p < 0,010). La fracción de excreción de sodio (FENa) aumenta significativamente en el grupo experimental, tras la realización del programa, cuyo promedio se triplica (p < 0,050). Los niveles plasmáticos de aldosterona no muestran diferencias significativas entre ambos grupos en las distintas mediciones. Conclusión: Un programa de ejercicios de natación e inmersión, en mujeres gestantes, contribuye al equilibrio hidrosalino, previniendo el aumento excesivo de volumen plasmático habitual en el embarazo, y en la actividad del eje renina-aldosterona. © 2017 Elsevier Espa˜ na, S.L.U. Todos los derechos reservados.
What is known? The effect of immersion in water on hydrosaline balance is well known, however more specific studies are necessary in pregnant women to help elucidate the precise circulatory and neuroendocrine mechanisms involved.
What do we contribute? The positive outcomes on various haemodynamic variables of a physical activity programme immersed to the neck in an aquatic environment specifically designed for pregnant women.
Introduction There is sufficient scientific evidence to show that regular, moderate, physical exercise in healthy pregnant women, with normal pregnancies not only holds no risk to the health
of mother or foetus, but is beneficial throughout pregnancy, during labour and the postpartum period.1,2 Sport and physical exercise in general benefits the cardiovascular system, blood circulation and tones the musculoskeletal system.3 Studies show that moderate sport suitable to the specific pregnancy can be undertaken without risk to maternal or foetal health. Furthermore, other recent studies indicate the effect of regular physical exercise in preventing excessive weight gain during pregnancy, helping to control blood pressure and preventing hypertension and gestational diabetes. Therefore, exercise is beneficial for both mother and foetus, and prevents the risk of excess weight and, as a consequence, helps to prevent complications in labour.4---6 The profound changes in the body during pregnancy include cardiovascular changes with increased cardiovascular system capacity, as a result of vasodilatation of the peripheral vascular system and increased venous circulation and increased circulating volume, which at the end of pregnancy is elevated around 30---60%. Similarly, water and salt retention occurs due to the intensive activity of the renin-angiotensin-aldosterone system.7---10 Several vasodilatory factors have been identified such as progesterone, increased glomerular filtration rate and natriuretic agents such as atrial natriuretic peptide (ANP).11,12
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Effect of a physical activity programme in the aquatic environment Water provides an excellent medium for pregnant women to exercise, especially because of the buoyancy it provides. Swimming has been recommended as one of the most suitable activities for pregnant women. Activities in water offer many areas to work on and are fun and therefore are often included in physical exercise programmes during pregnancy.13---15 The buoyancy and weightlessness provided by water helps pregnant women to move freely and adopt positions that would be uncomfortable or impossible on terra firma. Water pressure reduces the risk of injury to both mother and baby through trauma or sudden movement, since it prevents any limits being exceeded. These physical benefits also favour a more positive psychological attitude, since moving freely, relaxing with other women in the same condition, and enjoying the activity all encourage relaxation.1,16---18 On a physiological level, the main effect of immersion has been highlighted as the redistribution of extravascular fluid in the vascular space and increased diuresis. This effect occurs very rapidly and is proportional to the depth of immersion and causes reflex cardiovascular adjustments that elicit an increase in central blood volume, reduced heart rate, increased systolic volume, increased cardiac output and increased diuresis and natriuresis.19---21 This eventually leads to a reduction in peripheral vascular resistance, reduced systemic blood pressure (both systolic and diastolic) and activation of the above-mentioned renin-antiotensinaldosterone system. With these effects, it has also been suggested that immersion might even prevent the oedema that can occur during pregnancy.22---26 In humans, exposure to hyperbaric environments and by extension any model that subjects the body to a pressure gradient, results in several changes: (a) general effects of pressure on the body, from a physiochemical and physiological perspective (b) the buoyancy effect and (c) altered diuresis and ion excretion.27,28 Therefore, immersion encourages significantly higher diuresis compared to the preimmersion levels, and reduced maternal blood pressure and heart rate29 ; prenatal exercise appears to cause haemodynamic improvement in pregnant women.19,23---26,29,30 Depth affects the level of physiological changes caused by immersion and when up to the neck, or complete, these changes are much more drastic, with increased diuresis and natriuresis and redistribution of fluids by hydrostatic pressure proportional to the pregnant woman’s level of oedema.19,25 Moderate aquatic exercise during pregnancy is a safe and effective alternative for mother and foetus. However, due to the scarcity and heterogeneity of data in the specific literature, additional research studies are needed.30,31 Therefore the objective of this research study was to evaluate the effect on haemodynamic constants of a physical activity programme in the aquatic environment with immersion up to the neck, of 6 weeks’ duration, in healthy pregnant women.
Method A randomised clinical trial was designed for this study, with measurements before and after the intervention. The experimental group (EG) underwent an aquatic exercise programme for pregnant women (AEPPW), immersed up to the
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neck, specifically designed for these women, and the control group (CG) followed their usual routines. The study was performed from May to July 2016 in the Body-Factory sports centre.
Sample The reference population were pregnant women included in the Public Health System of the Ceuta Health Area. To establish the appropriate sample size, the minimum number of subjects needed to enable a test of the mean plasma volume differences to detect a difference of 5 units as significant, with an alpha error = .050 and beta error = .020 was considered. This required at least two groups of 19 women. In anticipation of dropouts, an initial total of 48 pregnant women was chosen and distributed using an allocation model of 20 blocks of 5 randomised numbers distributed between the CG and the EG. Twenty-eight women were assigned to the CG who followed no exercise programme but underwent routine monitoring of their pregnancy with checks at the start and end of the time period, and 20 women were assigned to the EG (n = 20), who followed the AEPPW outlined in the intervention. Once the intervention had started, two women from the experimental group left due to an obstetric disorder that involved a threatened preterm delivery, which left a final group of 18 participants (Fig. 1). Despite this, retrospective analysis of the test with these 46 women confirmed the ability of the model to detect a significant difference of 5.2 units in contrasting plasma volume.
Inclusion criteria The requirements to participate in the sample were, for the CG to be: (1) of legal age, (2) in the second stage of pregnancy onwards, not a multiple pregnancy, (3) healthy with no disease, (4) not taking part in other exercise programmes, (5) not taking any medication that might interfere in the results and (6) not having any physical or medical reason for not exercising; and for the EG, in addition to the former, the participants had to start in weeks 24---28 and finish in weeks 32---36 and to attend at least 90% of the sessions.
Intervention The AEPPW took place over 6 weeks, with two 45 min sessions per week (12 sessions in total). Proposed models were looked at and then used to design aquatic exercise activities as well as hyperbaric stimuli with immersion up to the neck and short periods of full immersion.32---34 Each session was structured into warm-up and exercises to adjust to the water (5 min) followed by a group of moderate level aerobic exercises (20 min), working the muscle groups (upper limb, lower limb, respiratory, dorsal and abdominal work), then working the pelvis (10 min), ending with a relaxation phase and some fun exercises (10 min). The exercise sessions took place in a swimming pool; the women were within their depth, in a temperature
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J.M. Vázquez-Lara et al.
Pregnant women recruited at the start of the programme
60
-12
48
Randomised
Withdrew due to threatened premature labour -2
Excluded because they did not fulfil the criteria
Experimental 20
Control 28
18
28 Women analysed
Figure 1
Flow diagram of the randomised clinical trial.
of 28◦ ---30◦ , and in safe conditions. The programme was delivered in groups of 8---10 pregnant women to ensure an appropriate working climate.12 The participants received instructions before the sessions, which included having breakfast before going to the sports centre for the activity. The CG also received appropriate instructions, in particular to have their usual breakfast on the day of the check-up, and continue with their routine clinical practice, which did not include any formal physical activity. They underwent the initial assessment and at the end of the 6 weeks, with an identical protocol.
Constants and data collection The participants were interviewed to gather their sociodemographic data, such as age and weeks of gestation. The assessments outlined below were undertaken at the beginning and after 6 weeks of the AEPPW. These assessments were made at the initial consultation of the GC and at the beginning of the EG training. The EG underwent a further assessment immediately after completing the training session on the last day of the programme. This enabled us to see the direct effect of exercising in water and of immersion (measured before and after), on the last day, when we expected to see a degree of adjustment. (1) Assessment of haemodynamic parameters: (a) arterial blood pressure (BP) at rest and comfortably seated, a manual BP monitor (RIESTER) was used and the BP was taken manually. (b) Heart rate, the heart rate was measured at least 5 min after taking the BP measurement using the Polar F4 heart rate monitor (Polar, Finland). (2) Analytical measurements, (a) blood: haemoglobin, haematocrit, creatinine, calcium, phosphorus, sodium, potassium, chlorine, total proteins, osmolarity and aldosterone. (b) Urine: creatinine, calcium, phosphorus, sodium, potassium, chlorine and osmolarity. Blood and urine samples were collected from the women in the CG in their second and third trimester
visits to the health area during their routine pregnancy checks. This took place at practically the same time as for the EG. These samples were taken from the EG in the sports centre, at the start and at the end of the programme, where appropriate, before starting training, and thus equivalent conditions to those of the CG were maintained. All the samples were processed in the laboratory allocated for this purpose and followed identical protocols. (3) Estimated variation in plasma volume Using Dill and Costill’s method,35 which calculates plasma volume (PV) percentages in a subsequent situation, according to an initial baseline obtained at a previous time. Variation observed can relate to the procedure or intervention between the previous and subsequent situation. The initial volume baseline is obtained according to the haematocrit count (Hcr) considering 100% blood volume (VS1 ): 100 = Hcr + VP1, therefore VP1 = 100 − Htc1 . For example, a woman with an Hcr of 41 would have an initial plasma volume of 59. The VP2 is obtained over this value, bearing in mind the quotient between the initial (Hg1) and final (Hg2) haemoglobin. The variation at time 2 depends on the quotient between haemoglobins calculated as: VS2 = 100 * Hb1 /Hb2 . Finally, to calculate the VP2, the cell volume is considered according to the following formula: VC2 = VS2 − Htc2 , therefore VP2 = VS2 − VC2 .
Statistical analysis We used SPSS 20.0 © for Windows for the statistical analysis. Once the parametric character had been confirmed of the measurements using the Kolmogorov---Smirnov test, the student’s t-test for paired samples was used for contrasting the intragroup means, and for the differences between groups, the student’s t-test for independent samples. The homoscedasticity of the samples was checked using Levene’s test.
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Effect of a physical activity programme in the aquatic environment Table 1
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Characteristics of the sample. Levels measured at the start of the programme. May to July 2016.
Groups
Experimental (No. = 18)
Control (No. = 28)
Initial values
Mean (DT)
95% CI
Mean (DT)
95% CI
Age (years) Weeks gestation Systolic BP (mmHg) Diastolic BP (mmHg) Mean BP (mmHg) HR (beat/min) Plasma volume (%) Plasma Na+ (mEq/l) Urine Na+ (mEq/l) NaFE Aldosterone (ng/l)
31.0 27.3 110.6 68.5 78.0 85.3 65.7 135.7 147.5 .6 690.4
29.0---32.9 26.1---28.5 106.0---115.2 65.2---71.8 74.6---81.4 82.2---88.4 64.6---66.8 135.1---136.4 120.0---175.0 .5---.7 605.7---775.1
29.5 (6.1) 26.9 (2.9) 109.0 (11) 64.1 (9.6) 79.0 (8.7) 81.9(11.5) 66.4 (2.4) 136.3 (3.9) 113.7 (46.9) .5 (.2) 528.3 (318.9)
27.4---31.6 25.8---27.8 104.9---113.1 60.5---67.7 75.8---82.2 77.6---86.2 65.5---67.3 134.8---137.7 96.3---131.1 .4---.6 410.2---646.4
BMI < 25 25 to <30 ≥30
(4.6) (2.6) (10) (7.2) (7.4) (6.8) (2.4) (1.4) (59.6) (.3) (183.3) n=4 n=7 n=7
n = 10 n = 10 n=8
p
.236 .234 .697 .032 .069 .062 .401 .523 .059 .360 .132 .532
SD: standard deviation; HR: heart rate; NaFE: sodium excretion fraction; 95%CI: 95% confidence interval; BMI: body mass index; BP: blood pressure.
We also used the ANCOVA test for cases where the participation of fixed and variable effects had to be tested, and for covariables which might intervene in the behaviour of the dependent variable. Similarly the ANCOVA test was used to evaluate the effect on final plasma volume, with the groups (experimental or control group) as the fixed effect factor using the baseline plasma volume as the covariable. In all cases, a probability value of p ≤ .050 was considered statistically significant.
Ethical aspects All the women took part voluntarily in the study from their prenatal consultation, were informed about the procedures, risks and benefits of the study by specialist personnel and signed their informed consent at the beginning of the study in line with the Declaration of Helsinki. This research paper received the consent of the Research Ethics Committee of the University Hospital of Ceuta.
Results The characteristics are shown in Table 1. The mean age in the CG was 31 and the mean gestation weeks at the start of the study were 27.3, and the EG had an average age of 29.5 years and the mean gestation weeks at the start of the study were 24.1, most of the women were between gestation weeks 24 and 27 (76%) and there were no statistically significant differences in these constants.
Blood pressure and heart rate All the measurements obtained were moderate to low BP levels. In the intragroup comparison, the EG group had no significant changes in their BP throughout the programme, except when the initial measurement was compared with
the measurement at the last session after exercise (Table 2), where systolic blood pressure was significantly lower than the initial measurement (p < .050). In the GC, the BP levels at the last measurement were significantly higher than the initial measurements. Comparison between the groups showed a statistically significant difference in diastolic BP at the initial measurement (p = .032), higher in the EG than the CG. Subsequent covariance analysis highlighted that this difference did not intervene in the variation produced at the end of the programme (p < .001; power = .951). Moreover, when the measurements at the last session were contrasted the BP measurements (systolic, diastolic and mean) were significantly higher in the CG compared to the EG (p < .050) (Table 2).
Variation of plasma volume In the intragroup comparison, the PV levels obtaining using Dill and Costill’s method (Table 3), at the final measurement, before the training session, showed no significant variation, although there was a tendency to a decrease of around 3% (65.7 vs 63.3) compared to the level calculated at the start of the programme. After the training session, there was an average decrease of 7.2% (65 vs 60.3) compared to the volume before exercise, which in this case did achieve statistical consistency (p < .001). The control group, by contrast, showed an average increase in PV levels of 5.6% (66.4 vs 70.1), although with no statistical consistency. In the comparison between groups, the initial values did not differ, but at the final measurement, the women in the CG showed a higher average PV than those who followed the programme (p < .010). The group effect was statistically significant (p < .001, power .990 and corrected model: p < .001, power .984) in the ANCOVA test of PV at the end of the programme.
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J.M. Vázquez-Lara et al. Table 2 Comparison of blood pressure and heart rate in the different measurements and between the experimental group and the control group. May to July 2016. SBP mmHg Experimental group
Initial (a)
Final (b) (before the training session) Final (c) (after the training session)
Initial (d)
Final (e)
dif d---e
HR lpm
68.5 7.2 1.8 66.1 8.8 2.1 65.8 8.1 1.9 .406 .265 .856
78.0 20.8 4.9 68.0 29.6 6.5 67.5 29.1 6.4 .80 .332 .214
85.3 6.8 1.6 82.4 4.8 1.1 80.7 18.0 4.3
Mean SD S.E.M. Mean SD S.E.M. .006
109.0 10.8 1.8 117.0 13.0 2.6 .004
64.1 9.6 1.6 72.2 9.7 1.9 .002
79.0 8.7 1.5 77.8 29.1 5.5 .475
81.9 11.5 2.0 82.8 11.0 2.2
Differences between groups (experimental --- control) .697 .031 .070 .014 .050 .016
dif a---d dif b---e
MBP mmHg
110.6 10.0 2.4 105.8 12.0 2.8 104.4 9.4 2.2 .150 .043 .472
dif a---b dif a---c dif b---c Control group
DBP mmHg
Mean SD S.E.M. Mean SD S.E.M. Mean SD S.E.M.
.065 .337
S.E.M: Standard error of mean. HR: heart rate (measured in beats per minute); DBP: diastolic blood pressure; MBP: mean blood pressure; SBP: systolic blood pressure (measured in mmHg); The significant differences are shown.
Table 3 Variation in plasma volume (PV) (Dill and Costill’s method) in the different measurements and between the experimental group and the control group. May to July 2016. Group
Measurement
Measurement on last day of training (only EG)
Initial
Final
Before
After
GE Mean SD S.E.M.
65.7 2.4 .6
63.6 6.3 1.5
64.0 3.3 .80
58.6*** 3.2 .8
CG Mean SD S.E.M.
66.4 2.4 .5
70.1 6.1 1.4
Total Mean SD S.E.M. p≤
66.1 2.4 .4 .401
65.7 7.7 1.2 .001
Initial measurement baseline PV in initial situation. Final measurement: estimated variation from the initial PV. Before: baseline PV in the last session in the EG, before the training. After: estimated variation from PV in the last session in the EG after the training. Level of significance in the intragroup differences. *** p < .001. In the intergroup comparison, the p value is indicated in the lower row.
Sodium homeostasis (plasmatic, urinary, excretion fraction [Na+ ] and aldosterone) In both the intragroup comparison and the comparison between groups, the plasmatic [Na+ ] (Table 4) remained constant, within normal levels, in all cases, even after the training session at the last measurement in the EG. With regard to the urinary values at the final measurement, the CG displayed significantly lower average values to those measured at the start (p < .050) and also lower than that of the EG (p < .010). The average sodium excretion fractions (NaEF) obtained were also constant, there were no differences in any case between the groups (Table 5). However the important significant increase in the parameter is notable in the EG, after exercising in water, when the averages tripled (p < .050). There were no significant differences in plasma levels of aldosterone between the groups at either the initial or the final measurement, prior to the training (Table 5). In the intragroup comparison, there was a significant increase in these levels in the CG (p < .050), while those of the EG were maintained in the last measurement prior to the training. Furthermore, at the final measurement after the training the average aldosterone levels dropped significantly (p < .050) in that group.
Discussion We know that during pregnancy there is arterial vasodilation, with increased arterial compliance and reduced BP
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Table 4 Plasma and urine sodium levels (mEq/l) in the different measurements and between the experimental and the control group. May to July 2016. Group
Plasmatic sodium (mEq/l) Na S-1
Urinary sodium (mEq/l)
Na S-2A
Na S-2D
Na O-1
Na O-2A
Na O-2D
Experimental n = 18 Mean 135.7 SD 1.4 S.E.M. .3
136.4 2.3 .5
136.4 1.5 .3
147.5 59.6 13.7
154.4 54.5 12.8
152.7 108.4 25.5
Control n = 28 Mean SD S.E.M.
136.3 3.9 .7
135.8 1.3 .3
113.7 46.9 9.6
98.2* 35.8 8.0
Total n = 46 Mean SD S.E.M. p≤
136.0 3.1 .5 .523
136.1 1.8 .3 .285
128.7 54.9 8.4 .064
124.8 53.2 8.6 .001
S.E.M.: standard error of the mean. The significant intragroup differences are indicated. * p < .050. The p value for the statistically significant intergroup differences is shown on the lower line. Plasmatic sodium (Na S) measured in milliequivalent per litre. Na S-1: first session; Na S-2A: final session before training; Na S-2D: final session after training. Urinary sodium (Na O) milliequivalent per litre. Na O-1: first session; Na O-2A: final session before the training; Na O-2D: final session after the training.
Table 5 Sodium excretion fraction and plasma levels of aldosterone in the different measurements and between the experimental and the control group. May to July 2016. Group
NaEF (1)
NaEF (2A)
NaEF (2D)
ALD (1) ng/l
ALD (2A) ng/l
ALD (2D) ng/l
Experimental n = 18 Mean .6 SD .3 S.E.M. .1
.5 .6 .2
1.5* 1.5 .3
690.4 183.3 42.1
731.3 284.5 67.1
466.1** 212.3 50.0
Control n = 28 Mean SD S.E.M.
.5 .2 .0
.5 .3 .1
528.3 318.9 60.3
679.9* 296.1 69.8
Total n = 46 Mean SD S.E.M.
.5 .3 .0
.5 .5 .1
593.8 281.6 41.1
705.6 287.3 47.9
Both measured in nanograms per litre at the start of the programme (1) and in the last week: before the session (2A) and after the session (2D). The significant intragroup differences are highlighted. * p < .050. ** p < .010. No intergroup differences were found. ALD: aldosterone; NaEF: sodium excretion fraction.
with increased sodium excretion as a consequence of factors such as increased glomerular filtration, the effect of progesterone and the participation of other mediators such as atrial natriuretic peptide, and increased levels of aldosterone levels have been highlighted as an essential mechanism for maintaining the homeostasis of this ion, contributing to increased volaemia.11,12 Our data, in the CG, appeared to adapt to this model, as shown by the maintenance of the Na plasma levels at the final measurement,
together with a reduction in urinary sodium, parallel with an increase in aldosterone. However, although the levels of the ion remained stable in the EG, urinary levels did not alter in this group, and neither did the average aldosterone levels increase significantly. There were no significant changes in the mean values of NaEF in the initial and final measurements in either of the groups, which is logical as the result of normal tubular function in healthy women, which keeps the excreted sodium
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8 fraction constant. The fact that in the EG, at the end of the programme, it reduced slightly, although with no statistical evidence, might indicate a tendency towards improved sodium reabsorption in this group. After the training session, the significant increase in NaEF was striking in the mothers who took part in the programme, which indicates a clear natriuretic effect as a consequence of the activity under the water. The variation in the aldosterone levels is consistent with the above. Thus, in the CG, the maintenance of NaEF would be associated with an increase in aldosterone, which would mitigate the natriuretic effects observed during pregnancy, so that in the women who followed the programme, the additional increase of the hormone did not seem necessary. We can deduce from this that the activities in the water and the effect of immersion contributed towards Na homeostasis, without the effect of fluid retention resulting from it. In addition, the variations observed in plasma volume levels support this effect of the programme. As our results indicate, training in immersion appears to moderate an increase in volaemia, with a lower average PV level, in the end, compared to the women in the CG. In line with the above, this reduction in PV might be a consequence of adjusting to the repeated stimulus of diuresis and natriuresis during the sessions in the water. Likewise, this effect would explain the fact that the blood pressures did not increase, which would be expected, as the pregnancies advanced, as happened in the CG, according to the results observed, where the systolic, diastolic and mean blood pressures were significantly higher. These results were in line with those obtained by Torres-Luque et al.14 on monitoring the blood pressure of a group of pregnant women who followed a physical activity programme over several weeks. At this point, we need to refer to the initial difference in diastolic BP between the groups, higher in the experimental group, which might be put down to a response to the novelty of starting the programme, as a possible confusion factor in the behaviour of the variable in the subsequent measurements. An analysis of covariance enabled us to rule out the influence of this initial variable on the subsequent measurements, which did respond, however, to the effect of the intervention. To explain the vascular and endocrine changes during pregnancy, it has been posited that as pregnancy advances there is continual adjustment of the hydrosaline balance to the new conditions, with stimulation of the activity of the renin-angiotensin-aldosterone system and expansion of PV, which implies that the haemostatic control systems must adapt, and assume the new situation as normal.12 Furthermore, the role of the volume receptors (carotid and lung) has been highlighted, whose tolerance to raised PV increases, as an adaptation mechanism to elevate volaemia in trained athletes.36 This phenomenon might also occur during pregnancy. In terms of immersion, the effect of the pressure gradients created has been widely demonstrated; these result in increased thoracic circulation, responsible for a characteristic haemostatic response, with reduced sympathetic tone, acute renin inhibition, increased Na excretion and subsequent increased dieresis.19---21 This repeated acute
J.M. Vázquez-Lara et al. effect, throughout the programme, might have acted as a drainage system and helped to prevent growing adaptation in the participants’ volume receptors,36 as well as stimulating the mechanisms responsible for Na reabsorption and counteracting the effect of other factors such as that of natriuretic peptide, which, as a consequence, would result in better control of volaemia and of the activity of the reninaldosterone axis, as our data appear to show. As a whole, our results support the fact that a programme of physical exercise submerged in water, due to exposure to pressure gradients, induces circulatory and endocrine adjustments which contribute to sodium homeostasis and volaemia, moderating the mineralocorticoid response. The explanation for this might be because, unlike the progressive adaptation that takes place in pregnancy, submersion involves an acute response that triggers diuresis and natriuresis, which might interfere in accommodating the mechanisms responsible for hydrosaline homeostasis, and therefore chronic increases in volume. In this regard, some published results indicate its positive effect on oedema and in pregnant women,29,37 and it has been suggested that immersion in water is an effective means of reducing peripheral oedema during pregnancy.25 It is worth mentioning that we found few studies that had undertaken a physical programme with these characteristics, on submersion in water in a population of pregnant women and with a haemodynamic and hydrosaline focus, and therefore we consider that our data might contribute towards understanding the fluid changes that occur during pregnancy and the effect of certain physical activities. However, this study has some limitations, principally the reduced sample size and that the EG group was smaller than the CG and was not as had been initially calculated to calculate the statistical significance, since, as we specify on the flow diagram, two women withdrew from the EG in the second week of the programme. Because this was such a short period of time, it was not considered appropriate to make any analysis of the number of sessions that they attended. Furthermore, due to the characteristics of the test, a masking process was not feasible, which might have contributed to a potential bias. Nonetheless, in all the tests undertaken the parametricity and homogeneity of variances between the groups contrasted was confirmed. Finally, the effects of the programme were only established in the last session before and just after the training; it would be interesting to know whether they were maintained subsequently medium or long term. All these elements mean that these results should be interpreted with care and further studies are necessary to consolidate them. Despite all of the above and in conclusion, our evidence shows that an exercise programme of swimming and immersion for pregnant women, contributes to hydrosaline balance, prevents the excessive increases in plasma volume that are common in pregnancy, and acts on the activity of the renin-angiotensin-aldosterone axis.
Conflicts of interest The authors have no conflicts of interest to declare.
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References 1. Miranda MD, Navío C, Rodríguez V. Beneficios de la natación en el embarazo. La educación maternal en el agua. Trances. 2013;5:373---8. 2. Artal R, O’Toole M. Guidelines of the American college of obstetricians and Gynaecologists for exercise during pregnancy and postpartum period. Br J Sports Med. 2003;37: 6---12. 3. Gaston A, Prapavessis H. Tired, moody and pregnant? Exercise may be the answer. Psychol Health. 2013;28:1353---69. 4. Leppänen M, Aittasalo M, Raitanen J, Kinnunen TI, Kujala UM, Luoto R. Physical activity during pregnancy: predictors of change perceived support and barriers among women at increased risk of gestational diabetes. Matern Child Health J. 2014;18:2158---66. 5. Barakat R. El ejercicio aeróbico moderado durante el embarazo su relación con el comportamiento de la tensión arterial materna. Eur J Hum Mov. 2005;13:119---31. 6. Carpenter RE, Emery SJ, Uzun O, D’Silva LA, Lewis MJ. Influence of antenatal physical exercise on haemodynamics in pregnant women: a flexible randomisation approach. BMC Pregnancy Childbirth. 2015;15:186. 7. Amezcua C [tesis doctoral] Patrón de actividad física en el embarazo: Factores asociados con la realización de actividad física en el tiempo libre. Granada: Universidad de Granada; 2010. 8. Perales M, Luaces M, Barriopedro MI, Montejo R, Barakat R. Efectos de un programa de ejercicio físico supervisado sobre la estructura cardiaca durante la gestación. Ensayo clínico aleatorizado. Progr Obstet Ginecol. 2012;55:209---15. 9. Bajo Arenas JM, Melchor Marcos JC, Mercé LT. Fundamentos de nola de Ginecología y Obsteobstetricia. Madrid: Sociedad Espa˜ tricia(SEGO); 2007. 10. Kim EH, Lim JH, Kim YH, Park YW. The relationship between aldosterone to renin ratio and RI value of the uterine artery in the preeclamptic patient vs normal pregnancy. Yonsei Med J. 2008;49:138---43. 11. Luft FC, Gallery EDM, Lindheimer MD. Normal and abnormal volume homeostasis. San Diego: Elsevier; 2009. p. 269---85. 12. Lindheimer MD, August PH. Aldosterone, maternal volumen status and healty pregnancies: a cycle of differing views. Nephrol Dial Transplant. 2009;24:1712---4. 13. Sans Otero R, Santandreu Ojeda MA. Preparación maternal en el agua. Matronas Profesión. 2002;7:33---6. 14. Torres-Luque G, Torres-Luque L, García Chacón S, Villaverde Gutiérrez C. Seguimiento de un programa de actividad física en el medio acuático para mujeres embarazadas, vol. XI. Kronos: Actividad Física y Salud; 2012. p. 84---92. II. 15. Lynch AM, McDonald S, Magann EF, Evans SF, Choy PL, Dawson B, et al. Effectiveness and safety of a structured swimming program in previously sedentary women during pregnancy. J Matern Fetal Neonatal Med. 2003;14:163---9. 16. Smith SA, Michel Y. A pilot study on the effects of aquatic exercises on discomforts of pregnancy. J Obstet Gynecol Neonatal Nurs. 2006;35:315---23.
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17. Bgeginski R, Finkelstein I, Alberton CL, Tartaruga MP, Kruel LFM. Effects of water-gymnastics training on hemodynamic variables in pregnant women at rest. IJARE. 2009;3:6. 18. Cuesta-Vargas AI, González-Sánchez M. Calidad de vida relacionada con la salud tras un programa comunitario de hidrocinesiterapia para embarazadas. Rev Iberoam Fisioter Kinesiol. 2010;13:22---8. 19. Soultanakis H. Aquatic exercise and thermoregulation in pregnancy. Clin Obstet Gynecol. 2016;59:576---90. 20. Goodlin RC, Hoffmann KL, Williams NE, Buchan P. Shoulder-out immersion in pregnant women. J Perinat Med. 1984;12:173---8. 21. Baciuk EP, Pereira RI, Cecatti JG, Braga AF, Cavalcante SR. Water aerobics in pregnancy: cardiovascular response, labor and neonatal outcomes. Reprod Health. 2008;5:10. 22. Torres G, Torres L, Villaverde C. Directrices en programas de actividad física durante el período de gestación. Rev Educ Fís DEFDER. 2011;1:39---50. 23. Aristizabal JAC. Enfermedad cardiaca y embarazo. Mem Curso Actual Ginecol Obstet. 2013;19:21. 24. Kent T, Gregor J, Deardorff L, Katz V. Edema of pregnancy: a comparison of water aerobics and static immersion. Obstetr Gynecol. 1999;94:726---9. Part1. 25. Irion JM, Irion GL. Water immersion to reduce peripheral edema in pregnancy. J Womens Health Phys Therapy. 2011;35:46---9. 26. Katz VL. Water exercise in pregnancy. Semin Perinatol. 1996;20:285---91. 27. Sánchez García J, Villaverde Gutiérrez C, Ramírez Rodrigo J, Ruiz Villaverde G, Arroyo Morales M, Ruiz Villaverde R. ACTH, beta-endorphin, and levels of anxiety in middle-age athletes. Int J Sport Psychol. 2004;35:149---56. 28. Heenan AP, Wolfe LA, Davies GA, McGrath MJ. Effects of human pregnancy on fluid regulation responses to short-term exercise. J Appl Physiol. 2003;95:2321---7. 29. Katz VL, Rozas L, Ryder R, Cefalo RC. Effect of daily immersion on the edema of pregnancy. Am J Perinatol. 1992;9:225---7. 30. Iglesias Constante SM. Revisión de la efectividad del ejercicio acuático durante el embarazo. Metas Enferm. 2014;17:13. 31. Hartmann S, Bung P. Physical exercise during pregnancyphysiological considerations and recommendations. J Perinat Med. 1999;27:204---15. 32. Dill DB, Costill DL. Calculation of percentage changes in volumes of blood, plasma, and red cells in dehydration. J Appl Physiol (1985). 1974;37:247---8. 33. Jiménez Jaén F. Efecto de aplicación del programa de ® preparación al parto AIPAP (acondicionamiento integral y pélvico en el agua), en la finalización del parto. In: Libro de ponencias y comunicaciones del congreso nacional de matronas del XI congreso de la FAME. 2012. p. 107---8. 34. Del Castillo Obeso M. Disfruta de tu embarazo en el agua: actividades acuáticas para la mujer gestante. Barcelona: INDE; 2002. p. 139. 35. Almagro ALC, Rojas PPS. Educación maternal en el agua: una alternativa en la Región de Murcia. Enferm Clin. 2003;13:321---3. 36. Convertino VA. Blood volume response to physical activity and inactivity. Am J Med Sci. 2007;334:72. 37. Smyth RM, Aflaifel N, Bamigboye AA. Interventions for varicose veins and leg oedema in pregnancy. Cochrane Libr. 2015;19.
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Enferm Clin. 2017;xxx(xx):xxx---xxx
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ORIGINAL ARTICLE
Effect of a physical activity programme in the aquatic environment on haemodynamic constants in pregnant women夽 Juana María Vázquez-Laraa,∗ , Carlos Ruiz-Frutosb,c , Luciano Rodríguez-Díaza , Jesús Ramírez-Rodrigod , Carmen Villaverde-Gutiérreze , Gema Torres-Luquef a
Hospital Universitario de Ceuta, Ceuta, Spain Departamento de Sociología, Trabajo Social y Salud Pública, Universidad de Huelva, Huelva, Spain c Universidad Espíritu Santo, Guayaquil, Ecuador d Facultad de Ciencias de la Salud, Campus Universitario de Ceuta, Ceuta, Spain e Facultad de Ciencias de la Salud de Granada, Granada, Spain f Facultad de Humanidades y Ciencias de la Educación, Universidad de Jaén, Jaén, Spain b
Received 13 June 2017; accepted 29 July 2017
KEYWORDS Exercise; Pregnancy; Immersion; Haemodynamics
Abstract Objective: To evaluate the effect of a physical activity programme in the aquatic environment with immersion up to the neck, of six weeks duration, on haemodynamic constants in pregnant women. Methods: A six-week physical activity programme in the aquatic environment was carried out with a total of 46 pregnant women, who were distributed into an experimental group (n = 18), which participated in the programme, and a control group (n = 28), which followed routine care. In both groups different haemodynamic measurements were evaluated before and after the programme. Results: At the beginning of the programme the mean systolic blood pressure was similar between groups, but diastolic blood pressure was slightly higher in the experimental group. When the measurements at the last session were compared, arterial pressures (systolic, diastolic and mean) were significantly higher in the control group (p < .050). Similarly, the initial plasma volume values did not differ between groups, but after the intervention, the control group women showed a higher mean (p < .010). The fraction of sodium excretion (FENa) increased significantly in the experimental group, after the programme, with a mean three times higher (p < .050). Aldosterone plasma levels did not show significant differences between the groups in the different measurements.
DOI of original article: http://dx.doi.org/10.1016/j.enfcli.2017.07.009 Please cite this article as: Vázquez-Lara JM, Ruiz-Frutos C, Rodríguez-Díaz L, Ramírez-Rodrigo J, Villaverde-Gutiérrez C, Torres-Luque G. Efecto de un programa de actividad física en el medio acuático sobre las constantes hemodinámicas en mujeres embarazadas. Enferm Clin. 2017. https://doi.org/10.1016/j.enfcli.2017.07.009 ∗ Corresponding author. E-mail address: [email protected] (J.M. Vázquez-Lara). 夽
2445-1479/© 2017 Elsevier Espa˜ na, S.L.U. All rights reserved.
ENFCLE-702; No. of Pages 9
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J.M. Vázquez-Lara et al. Conclusion: A programme of swimming and immersion exercises in pregnant women contributes to hydrosaline balance, preventing an excessive increase in usual plasma volume during pregnancy and in the activity of the renin-aldosterone axis. © 2017 Elsevier Espa˜ na, S.L.U. All rights reserved.
PALABRAS CLAVE Ejercicio; Embarazo; Inmersión; Hemodinámica
Efecto de un programa de actividad física en el medio acuático sobre las constantes hemodinámicas en mujeres embarazadas Resumen Objetivo: Evaluar el efecto de un programa de actividad física en el medio acuático con inmersión hasta el cuello, de seis semanas de duración, sobre las constantes hemodinámicas en mujeres gestantes. Método: Se llevó a cabo un programa de actividad física en el medio acuático, de seis semanas de duración a un total de 46 mujeres embarazadas, que fueron distribuidas en grupo experimental que participó en el programa (n = 18) y grupo control (n = 28) que desarrolló los cuidados habituales. En los dos grupos se valoraron diferentes medidas hemodinámicas antes y después del programa. Resultados: Al inicio del programa el promedio de presión arterial sistólica era similar en ambos grupos pero la presión arterial diastólica era ligeramente mayor en el grupo experimental. Cuando se contrastan las medidas en la última sesión, resultan significativamente mayores las presiones arteriales (sistólica, diastólica y media), en el grupo control (p < 0,050). De forma similar, los valores iniciales de volumen plasmático no diferían en ambos grupos, pero tras la intervención las mujeres del grupo control evidencian un mayor promedio (p < 0,010). La fracción de excreción de sodio (FENa) aumenta significativamente en el grupo experimental, tras la realización del programa, cuyo promedio se triplica (p < 0,050). Los niveles plasmáticos de aldosterona no muestran diferencias significativas entre ambos grupos en las distintas mediciones. Conclusión: Un programa de ejercicios de natación e inmersión, en mujeres gestantes, contribuye al equilibrio hidrosalino, previniendo el aumento excesivo de volumen plasmático habitual en el embarazo, y en la actividad del eje renina-aldosterona. © 2017 Elsevier Espa˜ na, S.L.U. Todos los derechos reservados.
What is known? The effect of immersion in water on hydrosaline balance is well known, however more specific studies are necessary in pregnant women to help elucidate the precise circulatory and neuroendocrine mechanisms involved.
What do we contribute? The positive outcomes on various haemodynamic variables of a physical activity programme immersed to the neck in an aquatic environment specifically designed for pregnant women.
Introduction There is sufficient scientific evidence to show that regular, moderate, physical exercise in healthy pregnant women, with normal pregnancies not only holds no risk to the health
of mother or foetus, but is beneficial throughout pregnancy, during labour and the postpartum period.1,2 Sport and physical exercise in general benefits the cardiovascular system, blood circulation and tones the musculoskeletal system.3 Studies show that moderate sport suitable to the specific pregnancy can be undertaken without risk to maternal or foetal health. Furthermore, other recent studies indicate the effect of regular physical exercise in preventing excessive weight gain during pregnancy, helping to control blood pressure and preventing hypertension and gestational diabetes. Therefore, exercise is beneficial for both mother and foetus, and prevents the risk of excess weight and, as a consequence, helps to prevent complications in labour.4---6 The profound changes in the body during pregnancy include cardiovascular changes with increased cardiovascular system capacity, as a result of vasodilatation of the peripheral vascular system and increased venous circulation and increased circulating volume, which at the end of pregnancy is elevated around 30---60%. Similarly, water and salt retention occurs due to the intensive activity of the renin-angiotensin-aldosterone system.7---10 Several vasodilatory factors have been identified such as progesterone, increased glomerular filtration rate and natriuretic agents such as atrial natriuretic peptide (ANP).11,12
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Effect of a physical activity programme in the aquatic environment Water provides an excellent medium for pregnant women to exercise, especially because of the buoyancy it provides. Swimming has been recommended as one of the most suitable activities for pregnant women. Activities in water offer many areas to work on and are fun and therefore are often included in physical exercise programmes during pregnancy.13---15 The buoyancy and weightlessness provided by water helps pregnant women to move freely and adopt positions that would be uncomfortable or impossible on terra firma. Water pressure reduces the risk of injury to both mother and baby through trauma or sudden movement, since it prevents any limits being exceeded. These physical benefits also favour a more positive psychological attitude, since moving freely, relaxing with other women in the same condition, and enjoying the activity all encourage relaxation.1,16---18 On a physiological level, the main effect of immersion has been highlighted as the redistribution of extravascular fluid in the vascular space and increased diuresis. This effect occurs very rapidly and is proportional to the depth of immersion and causes reflex cardiovascular adjustments that elicit an increase in central blood volume, reduced heart rate, increased systolic volume, increased cardiac output and increased diuresis and natriuresis.19---21 This eventually leads to a reduction in peripheral vascular resistance, reduced systemic blood pressure (both systolic and diastolic) and activation of the above-mentioned renin-antiotensinaldosterone system. With these effects, it has also been suggested that immersion might even prevent the oedema that can occur during pregnancy.22---26 In humans, exposure to hyperbaric environments and by extension any model that subjects the body to a pressure gradient, results in several changes: (a) general effects of pressure on the body, from a physiochemical and physiological perspective (b) the buoyancy effect and (c) altered diuresis and ion excretion.27,28 Therefore, immersion encourages significantly higher diuresis compared to the preimmersion levels, and reduced maternal blood pressure and heart rate29 ; prenatal exercise appears to cause haemodynamic improvement in pregnant women.19,23---26,29,30 Depth affects the level of physiological changes caused by immersion and when up to the neck, or complete, these changes are much more drastic, with increased diuresis and natriuresis and redistribution of fluids by hydrostatic pressure proportional to the pregnant woman’s level of oedema.19,25 Moderate aquatic exercise during pregnancy is a safe and effective alternative for mother and foetus. However, due to the scarcity and heterogeneity of data in the specific literature, additional research studies are needed.30,31 Therefore the objective of this research study was to evaluate the effect on haemodynamic constants of a physical activity programme in the aquatic environment with immersion up to the neck, of 6 weeks’ duration, in healthy pregnant women.
Method A randomised clinical trial was designed for this study, with measurements before and after the intervention. The experimental group (EG) underwent an aquatic exercise programme for pregnant women (AEPPW), immersed up to the
3
neck, specifically designed for these women, and the control group (CG) followed their usual routines. The study was performed from May to July 2016 in the Body-Factory sports centre.
Sample The reference population were pregnant women included in the Public Health System of the Ceuta Health Area. To establish the appropriate sample size, the minimum number of subjects needed to enable a test of the mean plasma volume differences to detect a difference of 5 units as significant, with an alpha error = .050 and beta error = .020 was considered. This required at least two groups of 19 women. In anticipation of dropouts, an initial total of 48 pregnant women was chosen and distributed using an allocation model of 20 blocks of 5 randomised numbers distributed between the CG and the EG. Twenty-eight women were assigned to the CG who followed no exercise programme but underwent routine monitoring of their pregnancy with checks at the start and end of the time period, and 20 women were assigned to the EG (n = 20), who followed the AEPPW outlined in the intervention. Once the intervention had started, two women from the experimental group left due to an obstetric disorder that involved a threatened preterm delivery, which left a final group of 18 participants (Fig. 1). Despite this, retrospective analysis of the test with these 46 women confirmed the ability of the model to detect a significant difference of 5.2 units in contrasting plasma volume.
Inclusion criteria The requirements to participate in the sample were, for the CG to be: (1) of legal age, (2) in the second stage of pregnancy onwards, not a multiple pregnancy, (3) healthy with no disease, (4) not taking part in other exercise programmes, (5) not taking any medication that might interfere in the results and (6) not having any physical or medical reason for not exercising; and for the EG, in addition to the former, the participants had to start in weeks 24---28 and finish in weeks 32---36 and to attend at least 90% of the sessions.
Intervention The AEPPW took place over 6 weeks, with two 45 min sessions per week (12 sessions in total). Proposed models were looked at and then used to design aquatic exercise activities as well as hyperbaric stimuli with immersion up to the neck and short periods of full immersion.32---34 Each session was structured into warm-up and exercises to adjust to the water (5 min) followed by a group of moderate level aerobic exercises (20 min), working the muscle groups (upper limb, lower limb, respiratory, dorsal and abdominal work), then working the pelvis (10 min), ending with a relaxation phase and some fun exercises (10 min). The exercise sessions took place in a swimming pool; the women were within their depth, in a temperature
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Pregnant women recruited at the start of the programme
60
-12
48
Randomised
Withdrew due to threatened premature labour -2
Excluded because they did not fulfil the criteria
Experimental 20
Control 28
18
28 Women analysed
Figure 1
Flow diagram of the randomised clinical trial.
of 28◦ ---30◦ , and in safe conditions. The programme was delivered in groups of 8---10 pregnant women to ensure an appropriate working climate.12 The participants received instructions before the sessions, which included having breakfast before going to the sports centre for the activity. The CG also received appropriate instructions, in particular to have their usual breakfast on the day of the check-up, and continue with their routine clinical practice, which did not include any formal physical activity. They underwent the initial assessment and at the end of the 6 weeks, with an identical protocol.
Constants and data collection The participants were interviewed to gather their sociodemographic data, such as age and weeks of gestation. The assessments outlined below were undertaken at the beginning and after 6 weeks of the AEPPW. These assessments were made at the initial consultation of the GC and at the beginning of the EG training. The EG underwent a further assessment immediately after completing the training session on the last day of the programme. This enabled us to see the direct effect of exercising in water and of immersion (measured before and after), on the last day, when we expected to see a degree of adjustment. (1) Assessment of haemodynamic parameters: (a) arterial blood pressure (BP) at rest and comfortably seated, a manual BP monitor (RIESTER) was used and the BP was taken manually. (b) Heart rate, the heart rate was measured at least 5 min after taking the BP measurement using the Polar F4 heart rate monitor (Polar, Finland). (2) Analytical measurements, (a) blood: haemoglobin, haematocrit, creatinine, calcium, phosphorus, sodium, potassium, chlorine, total proteins, osmolarity and aldosterone. (b) Urine: creatinine, calcium, phosphorus, sodium, potassium, chlorine and osmolarity. Blood and urine samples were collected from the women in the CG in their second and third trimester
visits to the health area during their routine pregnancy checks. This took place at practically the same time as for the EG. These samples were taken from the EG in the sports centre, at the start and at the end of the programme, where appropriate, before starting training, and thus equivalent conditions to those of the CG were maintained. All the samples were processed in the laboratory allocated for this purpose and followed identical protocols. (3) Estimated variation in plasma volume Using Dill and Costill’s method,35 which calculates plasma volume (PV) percentages in a subsequent situation, according to an initial baseline obtained at a previous time. Variation observed can relate to the procedure or intervention between the previous and subsequent situation. The initial volume baseline is obtained according to the haematocrit count (Hcr) considering 100% blood volume (VS1 ): 100 = Hcr + VP1, therefore VP1 = 100 − Htc1 . For example, a woman with an Hcr of 41 would have an initial plasma volume of 59. The VP2 is obtained over this value, bearing in mind the quotient between the initial (Hg1) and final (Hg2) haemoglobin. The variation at time 2 depends on the quotient between haemoglobins calculated as: VS2 = 100 * Hb1 /Hb2 . Finally, to calculate the VP2, the cell volume is considered according to the following formula: VC2 = VS2 − Htc2 , therefore VP2 = VS2 − VC2 .
Statistical analysis We used SPSS 20.0 © for Windows for the statistical analysis. Once the parametric character had been confirmed of the measurements using the Kolmogorov---Smirnov test, the student’s t-test for paired samples was used for contrasting the intragroup means, and for the differences between groups, the student’s t-test for independent samples. The homoscedasticity of the samples was checked using Levene’s test.
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Effect of a physical activity programme in the aquatic environment Table 1
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Characteristics of the sample. Levels measured at the start of the programme. May to July 2016.
Groups
Experimental (No. = 18)
Control (No. = 28)
Initial values
Mean (DT)
95% CI
Mean (DT)
95% CI
Age (years) Weeks gestation Systolic BP (mmHg) Diastolic BP (mmHg) Mean BP (mmHg) HR (beat/min) Plasma volume (%) Plasma Na+ (mEq/l) Urine Na+ (mEq/l) NaFE Aldosterone (ng/l)
31.0 27.3 110.6 68.5 78.0 85.3 65.7 135.7 147.5 .6 690.4
29.0---32.9 26.1---28.5 106.0---115.2 65.2---71.8 74.6---81.4 82.2---88.4 64.6---66.8 135.1---136.4 120.0---175.0 .5---.7 605.7---775.1
29.5 (6.1) 26.9 (2.9) 109.0 (11) 64.1 (9.6) 79.0 (8.7) 81.9(11.5) 66.4 (2.4) 136.3 (3.9) 113.7 (46.9) .5 (.2) 528.3 (318.9)
27.4---31.6 25.8---27.8 104.9---113.1 60.5---67.7 75.8---82.2 77.6---86.2 65.5---67.3 134.8---137.7 96.3---131.1 .4---.6 410.2---646.4
BMI < 25 25 to <30 ≥30
(4.6) (2.6) (10) (7.2) (7.4) (6.8) (2.4) (1.4) (59.6) (.3) (183.3) n=4 n=7 n=7
n = 10 n = 10 n=8
p
.236 .234 .697 .032 .069 .062 .401 .523 .059 .360 .132 .532
SD: standard deviation; HR: heart rate; NaFE: sodium excretion fraction; 95%CI: 95% confidence interval; BMI: body mass index; BP: blood pressure.
We also used the ANCOVA test for cases where the participation of fixed and variable effects had to be tested, and for covariables which might intervene in the behaviour of the dependent variable. Similarly the ANCOVA test was used to evaluate the effect on final plasma volume, with the groups (experimental or control group) as the fixed effect factor using the baseline plasma volume as the covariable. In all cases, a probability value of p ≤ .050 was considered statistically significant.
Ethical aspects All the women took part voluntarily in the study from their prenatal consultation, were informed about the procedures, risks and benefits of the study by specialist personnel and signed their informed consent at the beginning of the study in line with the Declaration of Helsinki. This research paper received the consent of the Research Ethics Committee of the University Hospital of Ceuta.
Results The characteristics are shown in Table 1. The mean age in the CG was 31 and the mean gestation weeks at the start of the study were 27.3, and the EG had an average age of 29.5 years and the mean gestation weeks at the start of the study were 24.1, most of the women were between gestation weeks 24 and 27 (76%) and there were no statistically significant differences in these constants.
Blood pressure and heart rate All the measurements obtained were moderate to low BP levels. In the intragroup comparison, the EG group had no significant changes in their BP throughout the programme, except when the initial measurement was compared with
the measurement at the last session after exercise (Table 2), where systolic blood pressure was significantly lower than the initial measurement (p < .050). In the GC, the BP levels at the last measurement were significantly higher than the initial measurements. Comparison between the groups showed a statistically significant difference in diastolic BP at the initial measurement (p = .032), higher in the EG than the CG. Subsequent covariance analysis highlighted that this difference did not intervene in the variation produced at the end of the programme (p < .001; power = .951). Moreover, when the measurements at the last session were contrasted the BP measurements (systolic, diastolic and mean) were significantly higher in the CG compared to the EG (p < .050) (Table 2).
Variation of plasma volume In the intragroup comparison, the PV levels obtaining using Dill and Costill’s method (Table 3), at the final measurement, before the training session, showed no significant variation, although there was a tendency to a decrease of around 3% (65.7 vs 63.3) compared to the level calculated at the start of the programme. After the training session, there was an average decrease of 7.2% (65 vs 60.3) compared to the volume before exercise, which in this case did achieve statistical consistency (p < .001). The control group, by contrast, showed an average increase in PV levels of 5.6% (66.4 vs 70.1), although with no statistical consistency. In the comparison between groups, the initial values did not differ, but at the final measurement, the women in the CG showed a higher average PV than those who followed the programme (p < .010). The group effect was statistically significant (p < .001, power .990 and corrected model: p < .001, power .984) in the ANCOVA test of PV at the end of the programme.
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J.M. Vázquez-Lara et al. Table 2 Comparison of blood pressure and heart rate in the different measurements and between the experimental group and the control group. May to July 2016. SBP mmHg Experimental group
Initial (a)
Final (b) (before the training session) Final (c) (after the training session)
Initial (d)
Final (e)
dif d---e
HR lpm
68.5 7.2 1.8 66.1 8.8 2.1 65.8 8.1 1.9 .406 .265 .856
78.0 20.8 4.9 68.0 29.6 6.5 67.5 29.1 6.4 .80 .332 .214
85.3 6.8 1.6 82.4 4.8 1.1 80.7 18.0 4.3
Mean SD S.E.M. Mean SD S.E.M. .006
109.0 10.8 1.8 117.0 13.0 2.6 .004
64.1 9.6 1.6 72.2 9.7 1.9 .002
79.0 8.7 1.5 77.8 29.1 5.5 .475
81.9 11.5 2.0 82.8 11.0 2.2
Differences between groups (experimental --- control) .697 .031 .070 .014 .050 .016
dif a---d dif b---e
MBP mmHg
110.6 10.0 2.4 105.8 12.0 2.8 104.4 9.4 2.2 .150 .043 .472
dif a---b dif a---c dif b---c Control group
DBP mmHg
Mean SD S.E.M. Mean SD S.E.M. Mean SD S.E.M.
.065 .337
S.E.M: Standard error of mean. HR: heart rate (measured in beats per minute); DBP: diastolic blood pressure; MBP: mean blood pressure; SBP: systolic blood pressure (measured in mmHg); The significant differences are shown.
Table 3 Variation in plasma volume (PV) (Dill and Costill’s method) in the different measurements and between the experimental group and the control group. May to July 2016. Group
Measurement
Measurement on last day of training (only EG)
Initial
Final
Before
After
GE Mean SD S.E.M.
65.7 2.4 .6
63.6 6.3 1.5
64.0 3.3 .80
58.6*** 3.2 .8
CG Mean SD S.E.M.
66.4 2.4 .5
70.1 6.1 1.4
Total Mean SD S.E.M. p≤
66.1 2.4 .4 .401
65.7 7.7 1.2 .001
Initial measurement baseline PV in initial situation. Final measurement: estimated variation from the initial PV. Before: baseline PV in the last session in the EG, before the training. After: estimated variation from PV in the last session in the EG after the training. Level of significance in the intragroup differences. *** p < .001. In the intergroup comparison, the p value is indicated in the lower row.
Sodium homeostasis (plasmatic, urinary, excretion fraction [Na+ ] and aldosterone) In both the intragroup comparison and the comparison between groups, the plasmatic [Na+ ] (Table 4) remained constant, within normal levels, in all cases, even after the training session at the last measurement in the EG. With regard to the urinary values at the final measurement, the CG displayed significantly lower average values to those measured at the start (p < .050) and also lower than that of the EG (p < .010). The average sodium excretion fractions (NaEF) obtained were also constant, there were no differences in any case between the groups (Table 5). However the important significant increase in the parameter is notable in the EG, after exercising in water, when the averages tripled (p < .050). There were no significant differences in plasma levels of aldosterone between the groups at either the initial or the final measurement, prior to the training (Table 5). In the intragroup comparison, there was a significant increase in these levels in the CG (p < .050), while those of the EG were maintained in the last measurement prior to the training. Furthermore, at the final measurement after the training the average aldosterone levels dropped significantly (p < .050) in that group.
Discussion We know that during pregnancy there is arterial vasodilation, with increased arterial compliance and reduced BP
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Table 4 Plasma and urine sodium levels (mEq/l) in the different measurements and between the experimental and the control group. May to July 2016. Group
Plasmatic sodium (mEq/l) Na S-1
Urinary sodium (mEq/l)
Na S-2A
Na S-2D
Na O-1
Na O-2A
Na O-2D
Experimental n = 18 Mean 135.7 SD 1.4 S.E.M. .3
136.4 2.3 .5
136.4 1.5 .3
147.5 59.6 13.7
154.4 54.5 12.8
152.7 108.4 25.5
Control n = 28 Mean SD S.E.M.
136.3 3.9 .7
135.8 1.3 .3
113.7 46.9 9.6
98.2* 35.8 8.0
Total n = 46 Mean SD S.E.M. p≤
136.0 3.1 .5 .523
136.1 1.8 .3 .285
128.7 54.9 8.4 .064
124.8 53.2 8.6 .001
S.E.M.: standard error of the mean. The significant intragroup differences are indicated. * p < .050. The p value for the statistically significant intergroup differences is shown on the lower line. Plasmatic sodium (Na S) measured in milliequivalent per litre. Na S-1: first session; Na S-2A: final session before training; Na S-2D: final session after training. Urinary sodium (Na O) milliequivalent per litre. Na O-1: first session; Na O-2A: final session before the training; Na O-2D: final session after the training.
Table 5 Sodium excretion fraction and plasma levels of aldosterone in the different measurements and between the experimental and the control group. May to July 2016. Group
NaEF (1)
NaEF (2A)
NaEF (2D)
ALD (1) ng/l
ALD (2A) ng/l
ALD (2D) ng/l
Experimental n = 18 Mean .6 SD .3 S.E.M. .1
.5 .6 .2
1.5* 1.5 .3
690.4 183.3 42.1
731.3 284.5 67.1
466.1** 212.3 50.0
Control n = 28 Mean SD S.E.M.
.5 .2 .0
.5 .3 .1
528.3 318.9 60.3
679.9* 296.1 69.8
Total n = 46 Mean SD S.E.M.
.5 .3 .0
.5 .5 .1
593.8 281.6 41.1
705.6 287.3 47.9
Both measured in nanograms per litre at the start of the programme (1) and in the last week: before the session (2A) and after the session (2D). The significant intragroup differences are highlighted. * p < .050. ** p < .010. No intergroup differences were found. ALD: aldosterone; NaEF: sodium excretion fraction.
with increased sodium excretion as a consequence of factors such as increased glomerular filtration, the effect of progesterone and the participation of other mediators such as atrial natriuretic peptide, and increased levels of aldosterone levels have been highlighted as an essential mechanism for maintaining the homeostasis of this ion, contributing to increased volaemia.11,12 Our data, in the CG, appeared to adapt to this model, as shown by the maintenance of the Na plasma levels at the final measurement,
together with a reduction in urinary sodium, parallel with an increase in aldosterone. However, although the levels of the ion remained stable in the EG, urinary levels did not alter in this group, and neither did the average aldosterone levels increase significantly. There were no significant changes in the mean values of NaEF in the initial and final measurements in either of the groups, which is logical as the result of normal tubular function in healthy women, which keeps the excreted sodium
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8 fraction constant. The fact that in the EG, at the end of the programme, it reduced slightly, although with no statistical evidence, might indicate a tendency towards improved sodium reabsorption in this group. After the training session, the significant increase in NaEF was striking in the mothers who took part in the programme, which indicates a clear natriuretic effect as a consequence of the activity under the water. The variation in the aldosterone levels is consistent with the above. Thus, in the CG, the maintenance of NaEF would be associated with an increase in aldosterone, which would mitigate the natriuretic effects observed during pregnancy, so that in the women who followed the programme, the additional increase of the hormone did not seem necessary. We can deduce from this that the activities in the water and the effect of immersion contributed towards Na homeostasis, without the effect of fluid retention resulting from it. In addition, the variations observed in plasma volume levels support this effect of the programme. As our results indicate, training in immersion appears to moderate an increase in volaemia, with a lower average PV level, in the end, compared to the women in the CG. In line with the above, this reduction in PV might be a consequence of adjusting to the repeated stimulus of diuresis and natriuresis during the sessions in the water. Likewise, this effect would explain the fact that the blood pressures did not increase, which would be expected, as the pregnancies advanced, as happened in the CG, according to the results observed, where the systolic, diastolic and mean blood pressures were significantly higher. These results were in line with those obtained by Torres-Luque et al.14 on monitoring the blood pressure of a group of pregnant women who followed a physical activity programme over several weeks. At this point, we need to refer to the initial difference in diastolic BP between the groups, higher in the experimental group, which might be put down to a response to the novelty of starting the programme, as a possible confusion factor in the behaviour of the variable in the subsequent measurements. An analysis of covariance enabled us to rule out the influence of this initial variable on the subsequent measurements, which did respond, however, to the effect of the intervention. To explain the vascular and endocrine changes during pregnancy, it has been posited that as pregnancy advances there is continual adjustment of the hydrosaline balance to the new conditions, with stimulation of the activity of the renin-angiotensin-aldosterone system and expansion of PV, which implies that the haemostatic control systems must adapt, and assume the new situation as normal.12 Furthermore, the role of the volume receptors (carotid and lung) has been highlighted, whose tolerance to raised PV increases, as an adaptation mechanism to elevate volaemia in trained athletes.36 This phenomenon might also occur during pregnancy. In terms of immersion, the effect of the pressure gradients created has been widely demonstrated; these result in increased thoracic circulation, responsible for a characteristic haemostatic response, with reduced sympathetic tone, acute renin inhibition, increased Na excretion and subsequent increased dieresis.19---21 This repeated acute
J.M. Vázquez-Lara et al. effect, throughout the programme, might have acted as a drainage system and helped to prevent growing adaptation in the participants’ volume receptors,36 as well as stimulating the mechanisms responsible for Na reabsorption and counteracting the effect of other factors such as that of natriuretic peptide, which, as a consequence, would result in better control of volaemia and of the activity of the reninaldosterone axis, as our data appear to show. As a whole, our results support the fact that a programme of physical exercise submerged in water, due to exposure to pressure gradients, induces circulatory and endocrine adjustments which contribute to sodium homeostasis and volaemia, moderating the mineralocorticoid response. The explanation for this might be because, unlike the progressive adaptation that takes place in pregnancy, submersion involves an acute response that triggers diuresis and natriuresis, which might interfere in accommodating the mechanisms responsible for hydrosaline homeostasis, and therefore chronic increases in volume. In this regard, some published results indicate its positive effect on oedema and in pregnant women,29,37 and it has been suggested that immersion in water is an effective means of reducing peripheral oedema during pregnancy.25 It is worth mentioning that we found few studies that had undertaken a physical programme with these characteristics, on submersion in water in a population of pregnant women and with a haemodynamic and hydrosaline focus, and therefore we consider that our data might contribute towards understanding the fluid changes that occur during pregnancy and the effect of certain physical activities. However, this study has some limitations, principally the reduced sample size and that the EG group was smaller than the CG and was not as had been initially calculated to calculate the statistical significance, since, as we specify on the flow diagram, two women withdrew from the EG in the second week of the programme. Because this was such a short period of time, it was not considered appropriate to make any analysis of the number of sessions that they attended. Furthermore, due to the characteristics of the test, a masking process was not feasible, which might have contributed to a potential bias. Nonetheless, in all the tests undertaken the parametricity and homogeneity of variances between the groups contrasted was confirmed. Finally, the effects of the programme were only established in the last session before and just after the training; it would be interesting to know whether they were maintained subsequently medium or long term. All these elements mean that these results should be interpreted with care and further studies are necessary to consolidate them. Despite all of the above and in conclusion, our evidence shows that an exercise programme of swimming and immersion for pregnant women, contributes to hydrosaline balance, prevents the excessive increases in plasma volume that are common in pregnancy, and acts on the activity of the renin-angiotensin-aldosterone axis.
Conflicts of interest The authors have no conflicts of interest to declare.
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References 1. Miranda MD, Navío C, Rodríguez V. Beneficios de la natación en el embarazo. La educación maternal en el agua. Trances. 2013;5:373---8. 2. Artal R, O’Toole M. Guidelines of the American college of obstetricians and Gynaecologists for exercise during pregnancy and postpartum period. Br J Sports Med. 2003;37: 6---12. 3. Gaston A, Prapavessis H. Tired, moody and pregnant? Exercise may be the answer. Psychol Health. 2013;28:1353---69. 4. Leppänen M, Aittasalo M, Raitanen J, Kinnunen TI, Kujala UM, Luoto R. Physical activity during pregnancy: predictors of change perceived support and barriers among women at increased risk of gestational diabetes. Matern Child Health J. 2014;18:2158---66. 5. Barakat R. El ejercicio aeróbico moderado durante el embarazo su relación con el comportamiento de la tensión arterial materna. Eur J Hum Mov. 2005;13:119---31. 6. Carpenter RE, Emery SJ, Uzun O, D’Silva LA, Lewis MJ. Influence of antenatal physical exercise on haemodynamics in pregnant women: a flexible randomisation approach. BMC Pregnancy Childbirth. 2015;15:186. 7. Amezcua C [tesis doctoral] Patrón de actividad física en el embarazo: Factores asociados con la realización de actividad física en el tiempo libre. Granada: Universidad de Granada; 2010. 8. Perales M, Luaces M, Barriopedro MI, Montejo R, Barakat R. Efectos de un programa de ejercicio físico supervisado sobre la estructura cardiaca durante la gestación. Ensayo clínico aleatorizado. Progr Obstet Ginecol. 2012;55:209---15. 9. Bajo Arenas JM, Melchor Marcos JC, Mercé LT. Fundamentos de nola de Ginecología y Obsteobstetricia. Madrid: Sociedad Espa˜ tricia(SEGO); 2007. 10. Kim EH, Lim JH, Kim YH, Park YW. The relationship between aldosterone to renin ratio and RI value of the uterine artery in the preeclamptic patient vs normal pregnancy. Yonsei Med J. 2008;49:138---43. 11. Luft FC, Gallery EDM, Lindheimer MD. Normal and abnormal volume homeostasis. San Diego: Elsevier; 2009. p. 269---85. 12. Lindheimer MD, August PH. Aldosterone, maternal volumen status and healty pregnancies: a cycle of differing views. Nephrol Dial Transplant. 2009;24:1712---4. 13. Sans Otero R, Santandreu Ojeda MA. Preparación maternal en el agua. Matronas Profesión. 2002;7:33---6. 14. Torres-Luque G, Torres-Luque L, García Chacón S, Villaverde Gutiérrez C. Seguimiento de un programa de actividad física en el medio acuático para mujeres embarazadas, vol. XI. Kronos: Actividad Física y Salud; 2012. p. 84---92. II. 15. Lynch AM, McDonald S, Magann EF, Evans SF, Choy PL, Dawson B, et al. Effectiveness and safety of a structured swimming program in previously sedentary women during pregnancy. J Matern Fetal Neonatal Med. 2003;14:163---9. 16. Smith SA, Michel Y. A pilot study on the effects of aquatic exercises on discomforts of pregnancy. J Obstet Gynecol Neonatal Nurs. 2006;35:315---23.
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17. Bgeginski R, Finkelstein I, Alberton CL, Tartaruga MP, Kruel LFM. Effects of water-gymnastics training on hemodynamic variables in pregnant women at rest. IJARE. 2009;3:6. 18. Cuesta-Vargas AI, González-Sánchez M. Calidad de vida relacionada con la salud tras un programa comunitario de hidrocinesiterapia para embarazadas. Rev Iberoam Fisioter Kinesiol. 2010;13:22---8. 19. Soultanakis H. Aquatic exercise and thermoregulation in pregnancy. Clin Obstet Gynecol. 2016;59:576---90. 20. Goodlin RC, Hoffmann KL, Williams NE, Buchan P. Shoulder-out immersion in pregnant women. J Perinat Med. 1984;12:173---8. 21. Baciuk EP, Pereira RI, Cecatti JG, Braga AF, Cavalcante SR. Water aerobics in pregnancy: cardiovascular response, labor and neonatal outcomes. Reprod Health. 2008;5:10. 22. Torres G, Torres L, Villaverde C. Directrices en programas de actividad física durante el período de gestación. Rev Educ Fís DEFDER. 2011;1:39---50. 23. Aristizabal JAC. Enfermedad cardiaca y embarazo. Mem Curso Actual Ginecol Obstet. 2013;19:21. 24. Kent T, Gregor J, Deardorff L, Katz V. Edema of pregnancy: a comparison of water aerobics and static immersion. Obstetr Gynecol. 1999;94:726---9. Part1. 25. Irion JM, Irion GL. Water immersion to reduce peripheral edema in pregnancy. J Womens Health Phys Therapy. 2011;35:46---9. 26. Katz VL. Water exercise in pregnancy. Semin Perinatol. 1996;20:285---91. 27. Sánchez García J, Villaverde Gutiérrez C, Ramírez Rodrigo J, Ruiz Villaverde G, Arroyo Morales M, Ruiz Villaverde R. ACTH, beta-endorphin, and levels of anxiety in middle-age athletes. Int J Sport Psychol. 2004;35:149---56. 28. Heenan AP, Wolfe LA, Davies GA, McGrath MJ. Effects of human pregnancy on fluid regulation responses to short-term exercise. J Appl Physiol. 2003;95:2321---7. 29. Katz VL, Rozas L, Ryder R, Cefalo RC. Effect of daily immersion on the edema of pregnancy. Am J Perinatol. 1992;9:225---7. 30. Iglesias Constante SM. Revisión de la efectividad del ejercicio acuático durante el embarazo. Metas Enferm. 2014;17:13. 31. Hartmann S, Bung P. Physical exercise during pregnancyphysiological considerations and recommendations. J Perinat Med. 1999;27:204---15. 32. Dill DB, Costill DL. Calculation of percentage changes in volumes of blood, plasma, and red cells in dehydration. J Appl Physiol (1985). 1974;37:247---8. 33. Jiménez Jaén F. Efecto de aplicación del programa de ® preparación al parto AIPAP (acondicionamiento integral y pélvico en el agua), en la finalización del parto. In: Libro de ponencias y comunicaciones del congreso nacional de matronas del XI congreso de la FAME. 2012. p. 107---8. 34. Del Castillo Obeso M. Disfruta de tu embarazo en el agua: actividades acuáticas para la mujer gestante. Barcelona: INDE; 2002. p. 139. 35. Almagro ALC, Rojas PPS. Educación maternal en el agua: una alternativa en la Región de Murcia. Enferm Clin. 2003;13:321---3. 36. Convertino VA. Blood volume response to physical activity and inactivity. Am J Med Sci. 2007;334:72. 37. Smyth RM, Aflaifel N, Bamigboye AA. Interventions for varicose veins and leg oedema in pregnancy. Cochrane Libr. 2015;19.