Health-Related Quality of Life in Postpartum Recovery of Women who Practice Hypopressive Physical Activity. Randomized Clinical Trial

way and it has demonstrated it and We found statistically signicant differences (p<0.05) in general health components, vitality, emotional role, and mental health in the sample group of under the Low-Pressure who obtained a higher We found statistically signicant differences in all aspects between the postpartum weeks 16 and 28. The interaction between time and group affect in general health components, vitality, emotional role and the score of mental component. In all of them the score is higher at week 28 and in the Low-Pressure Fitness group. Group affects physical component punctuation (PCS) in women with obesity, in this case LPF shows a higher punctuation. Punctuation for mental components (MCS) is affected by group in the category for overweight women, having an average punctuation higher tan LPF. In both cases the effect of can be a sample and the treatment group carried out a structured training programme centered on trunk tness. They measured HRQoL using questionnaire SF-36v2 on pregnancy week 24 and 2 months after labour. They found that all the SF-36v2 domains were more favourable in the training group two months after labour than in the sedentary group. Their results are similar to the ones we obtained in our study using the SF-36v2 questionnaire at six months after labour.


Background
Health-Related Quality of Life (HRQoL) is de ned by Urzúa 1 as "the well-being level obtained from the selfassessment that is made from diverse domains of someone's life, considering the impact that these domains have in his/her own health state". The use of this concept is especially important when describing the impact of a disease in the life of patients and in the assessment of the e cacy of treatments.
The American College of Sports Medicine (ACSM) 2 , in its last edition about physical exercise prescription, recommends practicing 150 minutes of weekly exercise in adults, spreading the physical activity among most days of the week, in order to improve the cardiovascular and central nervous systems. Currently, the American College of Obstetricians and Gynecologists (ACOG) 3 recommends regular exercise during pregnancy and after labour, in the absence of medical and obstetric complications, at least three times a week for 30-40 minutes, being a continuous Page 3/14 activity preferred over an intermittent one 2 . After labour, physical exercise not only help women recuperate their pregestational weight, but also improves mental health, generates positive feelings, and reduces depression [4][5][6][7] .
For all these reasons, we suggest the hypothesis that moderated physical exercise, following the guidelines of the Low-Pressure Fitness (LPF) method, developed from week 16 until week 28 after labour, will be associated to a better score in the SF-36v2 Health Questionnaire.
The LPF methodology consists of a series of hypopressive exercises aimed at improving the muscle tone of the pelvic area and abdomen. The basis of these exercises is the reduction of intrabdominal pressure in a combination of physical and respiratory exercise with speci c techniques 8 . The SF-36v2 is a questionnaire of 36 questions where positive and negative aspects of health are valued, this is used globally to assess the relationship between quality of life and health 9 .

Aim
To determine the impact of a physical exercise programme, under the LPF methodology, on the HRQoL of women after labour.

Methodology Design
We designed an open-label randomized clinical trial in which both subjects and researchers knew about the treatments. We followed the CONSORT rules published in 2010 8 . The trial is registered in the USA National Institutes of Health (ClinicalTrials.gov) and titled "Physical Activity in Pregnancy and Postpartum Period, Effects on Women". Number NCT02761967. This project was approved by the Ethical Committee for Research in Granada, with the license number 2601.20.15.
All participant women signed an informed consent form before the study, following the rules stablished at the Helsinki Declaration and reviewed by the World Medical Association regarding Informed Consent, on May 5th, 2015 9 .

Subjects
The subjects were women whose babies were 14 weeks old, meaning their labour took place on the rst fortnight of September 2016. The recruitment took place on the rst fortnight of October 2016 at the Healthcare Centers of the Granada-Metropolitan Healthcare District (SAS). We selected women that ful lled the inclusion criterion of labour date, and they were later contacted by phone. The recruitment responsible researcher phoned the eligible subjects and provided them with verbal information. Those subjects that showed interest in participating in the project were sent an email that included an attached le with further information about the study.

Inclusion criteria
The inclusion criteria were to have a healthy pregnancy and an eutocic delivery.

Exclusion criterion
All women that did not sign the informed consent form.
Once the study ended, we excluded all subjects that attended less than 80% of the planned sessions.

Study
Between the postpartum weeks 14 to 16 during the second fortnight of December 2016, we met the subjects to obtain a written informed consent. In the next individual meeting, during the same two weeks, we collected their anthropometric data and HRQoL questionnaire.
The study covered a 12-week period, from January to the end of March of 2017. We carried out three weekly sessions of 60 minutes each on Mondays, Wednesdays, and Fridays. Each session consisted on three phases. The rst one was a warming up session for the muscles involved in the workout. In the second or main phase, the subjects followed each of the postures of the hypopressive method described by Rial & Pinsach 10 . The nal phase consisted on stretching exercises and relaxation.
After 12 weeks, we collected the post-study data which consisted again on anthropometric data and a HRQoL questionnaire.
The subjects in the Sedentary group, attended the regular appointments of postpartum control, just as the subjects in the LPF group.

Social-demographic and Anthropometric Variables
The following variables were collected in the personalized meeting with the researcher in charge: subject age, marital status, height, weight at 16 weeks after labour (Weight1), weight at 28 weeks after labour (Weight2), parity, gestation time, education level, social class, and previous physical activity.
The weight (Kg) was assessed with a calibrated scale. The height (m) was measured with a calibrated metal stadiometer. To calculate the body-mass index (BMI) we used the formula BMI = weight (in Kg)/height 2 (in m 2 ) 11-14 .
We classi ed the subjects following the World Health Organization (WHO) classi cation regarding nutritional states, in accordance with the BMI, in the following categories: Low weight < 18.50 Kg/m 2 , Normoweight 18.50-24.99 Kg/m 2 , Overweight 25-29.99 Kg/m 2 , and Obesity ≥ 30.00 Kg/m 2 .
The subjects' Social Class was ranked using a questionnaire of social class assessment in health sciences by Álvarez-Dardet et al., 1995 20 , which ranks subjects in ve social groups according to their working abilities.
The previous physical activity was assessed in postpartum week 16 according to the subjects' personal report to the question "a typical day of a typical week" using the tool Global Physical Activity Questionnaire (GPAQ, from WHO "Global recommendations on physical activity for health") 21 .

Level of Effort and Workout Intensity
We used the classical Borg Scale of Perceived Exertion, or Rating of Perceived Exertion (RPE) 22 , in which scores between 12 and 14 "somewhat hard" mean moderate level.
Heart rate was measured at the end of each workout using the pulse oxymeter Quirumed OXYM2000 in all women that had an RPE higher than 14.

Sample size
This study is a component of a main project registered at Clinical Trials, hence the sample size was calculated for the main project according to previous studies by Barakat et al. (2011) 24 . In their study, Barakat et al. followed a programme of physical exercises with pregnant women form gestation weeks (GW) 6-9 until GW 38-39. They found that the percentage of women with a perception of good/very good health reached 96.9% in the treatment group, compared to 81.8% in the Sedentary group. In order to achieve an 80% power when detecting differences in a null hypothesis test H0:p1 = p2 using a bilateral chi-square test for two independent samples and considering a signi cance level of 5%, our sample should be of 56 subjects per group, or 112 in total. In this study, the sample size for the Sedentary group was 65 women, and the sample size for the LPF workout was 64 women, a total of 129 subjects.
The programme started 16 weeks after labour, in January 2017, and ended 12 weeks later, at the end of March 2017.

Randomization
The sample allocation was randomized, following an open-label technique of simple and without replacement randomized sampling, where both subjects and researchers knew about the treatments. Once the participants were met at the Healthcare Center and after verifying that they met the inclusion criterion, we introduced copies of the numbers assigned to the subjects in a vase and the main researcher of the randomized clinical trial (RCT) extracted the numbers and assigned rstly the Sedentary group members (n = 65) and then the LPF workout group member (n = 64). The women randomly assigned to the LPF workout group had an interview with the main researcher, who informed them of the bene ts of attending the sessions and provided them with the documents explaining the treatment.

Statistical Analysis
We ran a descriptive analysis of the main studied variables per group.
We have made the comparison between groups using Student's t-distribution proof for continuous variables and the Chi-Squared Test for qualitative variables.
We obtained the commercial license #QM035814 from the company Quality Metric Incorporated to analyze the SF-36v2 Health Questionnaire, and we studied the questionnaire variables in independent groups.

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We used SPSS statistical package for Social Sciences Software (version 19 for Windows, SPSS Inc., Chicago, IL, USA) to run the statistical analysis with a statistically signi cant level de ned at < 0.05.

Results
During the study we lost subjects in each group, mostly due to subjects returning to their working schedules, being the nal sample size 119 subjects. The nal sample size for the LPF group was 56 women, and for the Sedentary group was 63 women. Table 1 shows the basal characteristics of the sample. We did not nd statistically signi cant differences in the basal characteristics of the sample.
With the purpose of knowing if group, data recopilation week and the interaction between week and group affect each of the measured parameters of the survey, a factorial design with two factors with xed effect has been used. Table 2 shows the average and typical deviation for each aspect per group, week and interaction between week and group, p-value for each comparison and factor effect in the value of each aspect.
Just as can be seen on Table 2 Table 2 shows the median for each according to group and week, being in all cases higher on week 28, particularly for LPF group. The effect of interaction is small for general health (GH) and emotional role (RE), while medium for vitality (VT) and sum of mental component punctuation (MCS). Figure 2 shows the estimated population marginal means for each group and week, with a distinct line for each group.
The effect of time and group, and their interaction with each category according to Body Mass Index (BMI) has been studied for physical components punctuation (PCS) and mental component punctuation (MCS). The results of this analysis, with means and standard deviations for each group can be found on Table 3. The effect of this interaction on each Body Mass Index (BMI) category is showed in Fig. 3.

Discussion
The high number of participants in this study, including the high follow-up rate, gives strength to this study. Our results can be extrapolated to help other women with healthy pregnancies and eutocic deliveries.
Although using a self-administered questionnaire could be considered a limitation, Ware el al. (1993) 25 claimed that there were no differences in the internal consistency between the SF-36v2 questionnaire and intervieweradministered questionnaires. Attracting pregnant women to participate in the study was also a limitation, which we attribute to the lack of existing information in the Healthcare Services about the importance of physical activity for pregnant women. The need to reduce the environmental barriers was an additional limitation we had to resolve, which we did by offering a daycare service to the women participating in the study. Singh et al., 2015 26 tried to determine the impact of parity in women's HRQoL. They studied 60 women that met the inclusion criterion and found that women with a higher level of parity tend to have worse HRQoL. In our study we did not nd statistically signi cant differences between groups regarding parity. However, we did nd that HRQoL is inversely associated with sedentariness during the studied period, meaning that HRQoL is reduced as sedentariness increases.
Haas et al., 2005 27 , already con rmed that the lack of physical exercise, before, during, and after pregnancy, is associated to a worse state in all health indicators. Doya et al., 2013 28 , examined the effect of speci c workouts of physical training during pregnancy, and particularly the ones centered in core, on QoL at the end of pregnancy and during the 2 months after labour. They studied a sample size of 49 nulliparous women between pregnancy weeks 24 and 36 and the treatment group carried out a structured training programme centered on trunk tness. They measured HRQoL using questionnaire SF-36v2 on pregnancy week 24 and 2 months after labour. They found that all the SF-36v2 domains were more favourable in the training group two months after labour than in the sedentary group. Their results are similar to the ones we obtained in our study using the SF-36v2 questionnaire at six months after labour.
Haruna et al., 2.013 29 , carried out a clinical trial studying a workout programme at three months after labour, consisting on a 4-weeks programme of 90 minutes of exercise per week. They found that the workout programme for healthy women during the postpartum period improved their HRQoL and self-esteem. However, in that study they only found a statistically signi cant difference between the domains PF and VT, but not between PCS and MCS.
Their results are in contrast with the results of our study, in which from the fourth to the sixth postpartum month we found statistically signi cant differences in the SF-36v2 domains GH, VT, SF, ER and MH. We reach the same conclusion as Haruna et al., con rming that physical exercise contributes to improving HRQoL.
In a systematic revision of the scienti c literature published by our research group (Sánchez-García, 2016), we concluded that supervised workouts of moderate intensity and with a longer duration than six weeks yields statistically signi cant results in HRQoL, which we also con rm in our clinical study. Additionally, in our study we found the exception that categorizing women on both groups by BMI creates a statistically signi cant increment of the recorded scores in the SF-36v2 questionnaire of the PCS and MCS in both groups.
Similarly, Yan and Chen 31 , carried out a pilot simple randomized blind study with the objective of exploring whether aerobic workouts improve postpartum stress, sleep quality, fatigue, and depression. To measure their data, they used the perceived stress scale, postpartum fatigue scale, postpartum sleep quality scale, and the Edinburgh postnatal depression scale. They found results similar to ours, which can motivate women that gave birth to practice postpartum physical exercise to improve the studied parameters. In this same line of research, an additional study 32 was made where the improvement of the sleep quality associated to postpartum physical exercise was studied.

Conclusions
In this study we found that offering a physical exercise programme following the Low Pressure Fitness method to postpartum women signi cantly improves the HRQoL of these women. Sedentary women improve their SF-36v2 questionnaire score. However, that improvement is normal just as postpartum period advances, having scores clearly lower than women that get exercise during the postpartum period.
Based on the above described study concludes that it is bene cial to recommend physical exercise following the Low Pressure Fitness methodology in postpartum to any woman who has no contraindication to be able to perform physical exercise.
Declarations -The has the ethics approval and consent to participate.