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Physical activity and weight retention in postpartum black women.

Introduction

Obesity is a major worldwide public health problem (Khan & Bowman, 1999) with epidemic proportions reported in the United States (Pi-Sunyer, 2002) and still rising. Moreover, non-Hispanic black women demonstrate the highest prevalence of both overweight and obesity (49.7%) as compared to white women (30.1%) (Flegal et al, 2002) and retain twice as much weight during postpartum than white women (Parker & Abrams, 1993; Keppel & Taffel, 1993). Although pregnancy is a natural time for fat storage, the increased contribution of childbearing to weight gain and consequential obesity was found among black women (Rosenburg et al, 2003; Parker & Abrams, 1993; Keppel & Taffel, 1993; Lederman, Alfasi & Deckelbaum, 2002; Walker, Timmerman, Sterling, Kim & Dickson, 2004; Greene, Smiciklas-Wright, Scholl & Karp, 1988) is of increasing concern, primarily because African American women have greater difficulty in losing the retained weight postpartum, thus leading to the development of obesity and chronic disease (Walker et al, 2004; Parker & Abrams, 1993; Khan, Williams and Stevens, 1991). The apparent excess of weight among African American women, particularly during the postpartum period, poses an interesting question which provides the framework for the present study. Also of concern is the physically inactive lifestyle developed by the six weeks postpartum period (McCory, 2002). Hence, there is a pressing need to identify ways to address postpartum weight gain in African American women. According to McCrory (2000), many new mothers establish daily routines that fail to include regular physical activity and most are unacquainted with the importance of physical activity during the early postpartum period (Walker et al, 2004). Additionally, as part of the six weeks postpartum care plan, physicians usually give advice on proper diet; yet, overlook the opportunity to address recommendations for physical activity (Sampselle et al, 1999). Overall, researchers agree that little is known and limited information is available about the effects of physical activity on postpartum weight retention (Wolfe et al, 1997; Greene et al, 1988; Shauberger et al, 1992; Larson-Meyer, 2002; Sampselle et al, 1999; McCrory, 2000; Rossner, 1999). To date, the author found less than five published studies on physical activity in the early postpartum period. Only two included African-American women and both studies utilized qualitative research only. Therefore, further investigation of the influence of increased physical activity on postpartum weight gain in African-American women is warranted.

Purpose

This study determined the use of the pedometer to increase walking (physical activity) in African-American women who were between six weeks to six months postpartum. This study also investigated the influence of increased physical activity as measured and monitored by the pedometer on postpartum weight retention and body composition in this population. Measurable outcomes from the present study provide assistance in clinical decisions for health care professionals to manage weight in African American women during the early postpartum period.

Research Questions

The following research questions were answered in this study:

1. Did the use of the pedometer increase walking (physical activity) in African American women who were between six weeks and six months postpartum?

2. Was there a relationship between increased physical activity and body mass index of African American women who were between six weeks and six months postpartum?

3. Was there a relationship between increased physical activity and waist/hip ratio of African American women who were between six weeks and six months postpartum?

Operational Definitions

Gestational weight: the amount of weight gained from pre-pregnancy to childbirth.

Postpartum weight: the difference between pre-pregnancy weight and weight after childbirth.

Puerpurium: the period of 42 days (six weeks) following childbirth and expulsion of the placenta and membranes. The generative organs usually return to normal during this time.

Parity: the ability of a woman to carry a pregnancy to a point of viability (500g or 20 weeks) regardless of outcome.

Pedometer: a mechanical or digital device that measures vertical movement at the hip; a step counter.

Methods

This project was approved by the Institutional Review Boards (IRB) of Auburn University and Alabama State University.

Participants

Thirty-two postpartum African-American women between 18 and 40 years of age from the south central region of Alabama volunteered to be participants in this 12- week correlation study. New mothers meeting inclusion criteria were between six weeks and eight weeks postpartum, had a body mass index (BMI) of e" 1.0 above self-reported pre-pregnancy BMI of e" 24, had a normal vaginal delivery, had a single viable birth (no twins, triplets, etc.), were non-breast-feeding, non-smokers, free from major chronic disease, had at least a high school education, were sedentary (exercise less than 30 minutes a day, five to seven days per week) and had no contraindications for a low to moderate physical activity program.

Recruitment

All eligible women were recruited through flyers, area university/college campus e-mail, church announcements, newspapers, radio, television, postpartum support groups (i.e. Mocha Moms) and word-of-mouth. Flyers were distributed to the offices of area obstetricians/ gynecologists, pediatricians and Women Infants and Children (WIC) counselors. Flyers were also placed within neo-natal hospital wards, day-care centers, nurseries, child-birthing classes, merchant bulletin boards, area university/colleges and local military bases.

Procedure

The women who met the inclusion criteria were greeted and given an overview of the study. They were asked: 1) to read and sign an Alabama State University approved IRB informed consent form; 2) to read and sign a physical activity readiness questionnaire (PAR-Q), and 3) to complete an investigator administered form that included the following sociodemographic data: age, education, income, employment, marital status, number of children, pre-pregnancy weight, gestational weight, and infant feeding method as well as an exercise history.

Anthropometric Measures

Height was measured without shoes to the nearest % inch and weight to the nearest % pound using a Detecto[R] stadiometer/ balance scale (www.detecto.com). These measurements were converted into metric units of centimeters and kilograms, respectively. Body mass index (BMI: kg/m2 (weight/height2)) was then calculated. Waist and hip circumferences were measured to the nearest V2 cm with a standard flexible tape measure to assess body fat distribution. The mothers were instructed to stand with abdominal muscles relaxed. Waist circumference was measured at the narrowest part of the torso (above the umbilicus and below the xiphoid process); hip circumference at the maximal girth of the buttocks-hip area, above the gluteal fold.

Intervention

The general purpose of the study was explained to each subject. A Yamax Digiwalker SW-200 pedometer (step counter) (New-Lifestyles, Inc./ DIGIWALKER.com) was given to the mother. The women were shown how to set and reset the step counter to zero. The pedometer attachment was placed at the waist centered over the dominant foot. Women with greater abdominal girth were instructed to place the pedometer on their waist at the axillary line in order for the instrument to maintain an upright position. The mother was informed that if she wears clothing that does not have a waist site suitable for attachment, it is suggested by the investigators at the Cooper Institute of Aerobics Research in Dallas, Texas that the pedometer be placed on the waistband of the undergarment. Prior to monitoring, the subject evaluated the performance and accuracy of the pedometer during three brief walking trials as recommended by McClung et al. (2000). Each trial consisted of resetting the instrument to zero and walking while verbally counting a predetermined number of steps (50 steps). Pedometers were then checked for accuracy. The women were instructed to wear the pedometer daily for a total of 12 weeks excluding bedtime and bathing. The mothers received a structured physical activity pedometer program. All physical activities were performed at the convenience of the participant. Participants were instructed to wear the pedometer for three days; record the number of daily steps and calculate an average before changing their normal ambulatory routine. Participating individuals received a telephone call or e-mail on the third day of the study to obtain the average number of steps taken daily. This served as a pedometer baseline value.

The women were instructed to intentionally increase their average number of steps by at least 500 steps each week. Additionally, a target of 5000 steps per day (Hultquist, Albright & Thompson, 2005) at the American College of Sports Medicine (ACSM) recommended a frequency of three to five days per week to encourage an increase in ambulatory activity. Printed suggested methods to increase daily steps and prevent relapse were thoroughly explained/demonstrated and included the use of audio and video walking tapes, music, and other ambulatory activities. Additional instructions were given for maintaining an accurate activity log. As suggested by Tudor-Locke and Myers (2001) steps per day were recorded on an activity calendar (log). Activity calendars also served as an individual reminder of future scheduled follow-up dates. The women were encouraged to adhere to the advice of their physcian regarding dietary intake during the postpartum period and make no changes during the study. A printed "take home instruction" sheet, with contact information, was handed out to each participant as a reminder of what to do in the study. Incentive gifts were given to each of the mothers. These gifts included a less expensive pedometer so that the women could walk with a buddy (social support) and two AA batteries to be used with a new portable CD player with headphones to help them get started and stay motivated. Throughout the study, contact was made by phone/e-mail every two weeks. At week four, participants received a motivational letter by postal mail informing them of their individual expected four week goal and a CD with current upbeat music suitable for moderate walking. At week eight, a second motivational letter was sent informing each participant about eighth week goal and a "Walk Your Way Slim" video (Prevention Fitness Systems distributed by Anchor Bay Entertainment, Troy MI 48084). The week eight letter also included a reminder of when to schedule their follow-up session. All initial measurements were reassessed at the final session during week 12. All pedometers and activity calendars with self-reported data were collected at the end of the study.

Data Collection

Data were collected during two sessions: pre and post study (12 weeks). The pedometer was reset to zero at the beginning of each day. Participants recorded the pedometer readings (steps/day) on a calendar provided by the researcher. This allowed for daily and weekly totals to be attained and examined later for day to day variability. Primary data of height, weight, BMI, waist and hip girth as well as waist to hip ratio (WHR) were assessed at the initial session and at the end of the study (week 12).

Data Reduction

An average of the first three days of normal ambulation served as an individual baseline. Step counts based on a minimum of 36 out of 84 days (three days x week for 12 weeks) of wearing the pedometer served as the validation measure. Pre and post values of the dependent variables were averaged in order to determine the mean differences over time. These mean differences were correlated with the average change in steps taken per day to determine the existence of significant relationships. The magnitudes of effect were estimated by dividing the mean differences by the pre mean values.

Statistical Analysis

Change in Physical Activity

Data were analyzed using a paired-sample t-test. The principal data analysis assessed the difference between the average steps/day before the study and the average steps/day after the study (12 weeks). Data analysis was performed using Statistical Package for the Social Sciences (SPSS Version 14.0). An alpha level was established at p<0.05 for statistical significance.

Physical Activity: weight retention and body composition

Data were analyzed using Pearson Product Coefficient. The principal data analysis assessed the relationship between changes in physical activity (average steps/ day) and body mass index (BMI) as well as waist to hip ratio (WHR). The independent variable of changes in physical activity was quantified using self-reported steps per day determined from the pedometer values. A secondary analysis used a paired-samples t-test to assess; 1) pre and post differences in weight, BMI, waist girth, hip girth, WHR and 2) pre and post changes in physical activity (average steps/day) . Data analysis was performed using SPSS (Version 14.0). An alpha level was established at p<0.05 for statistical significance.

Results

A sample group of 32 apparently healthy postpartum African American females, 18-40 years of age (M = 29.58, SD = 5.188), met the inclusion criteria to participate in this study. One participant dropped out of the study due to relocation out of state. Therefore, the results reported are based on 31 participants that have completed the 12 week study. To avoid the possible confounds of daily biovariations pre and post study, participants were individually scheduled for lab assessments at the same time of day (morning: 9am-12 noon, afternoon: 12pm-5pm and evening: after 5:00).

Changes in Physical Activity

Results of a paired samples t-test revealed a significant difference in the average steps/day scores before and after the study (Mean difference = 3402, SD= 2309 t (30) = -8.204, p < .001). This indicates that the mean average steps/day after the study (M= 8749, SD = 2864) was statistically, significantly higher than the mean before the study (M = 5347, SD = 2380). An alpha level was established at the 0.05 level (Figure 1). The magnitude of the effect indicated a 63.6% increase in the average number of steps taken per day by postpartum African American women over the 12 week study period.

[FIGURE 1 OMITTED]

Physical Activity: postpartum weight and body mass index

Bivariate analysis revealed that a moderate correlation between the change in average steps taken per day and the change in BMI was statistically significant and in the expected inverse direction (r = -.543, p < .002) (Figure 2). This negative relationship failed to support the null hypothesis. A calculated coefficient of determination showed a shared variance between the change in average steps and change in BMI, [r.sup.2] = 0.295.

A paired samples t-test revealed a statistically significant difference in body mass index (BMI) before and after the 12 week pedometer based physical activity intervention, t (30) = 4.967, p < .001 (Figure 3). To investigate further, a second correlation was performed between the change in average steps/day and the change in weight (kg). Correlation results indicate a statistically significant inverse relationship between change in steps and change in weight (r = -.597, p < .001) (Figure 4) and an [r.sup.2] value of 0.356. Additionally, a paired samples t-test revealed a statistically significant difference in weight (kg) before and after the 12 week pedometer based physical activity intervention, t (30) = 3.970, p < .001(Figure 5). An estimate of the magnitude of the effect showed a 2.5 % decrease in postpartum weight (kg) as a result of increased physical activity. These analyses provide evidence that the pedometer driven intervention was effective in leading to a reduction in weight (kg) retained and BMI in this sample.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

Physical Activity: waist to hip ratio

Bivariate correlation revealed no statistically significant relationship between increased physical activity and waist/hip ratio (WHR) in this cohort. However, the secondary pre and post test analyses concluded that the pedometer driven intervention was seemingly effective in leading to a reduction in waist and hip circumference (cm) as well as the WHR (Figure 6) in African American women that are between six weeks to six months postpartum.

[FIGURE 6 OMITTED]

LIMITATIONS

1. This study was limited solely to apparently healthy African American women who were between six weeks and six months postpartum with no contraindications for minimal to moderate physical activity.

2. This study unexpectedly contained a homogenous group of women. Participants in this study were mostly college educated professionals and in the mid to upper socioecomonic status (SES) with an awareness of the importance of health and research. Findings of this study may not be generalized to postpartum women in a lower SES.

3. African American adolescents were not included. Participants under 18 years required parental consent for participation.

4. Weight loss was not analyzed for composition (fat mass (FM) or fat free mass (FFM) (muscle, bone, water, other). Further research would include the use of an instrument that would assess the composition of weight lost or gained.

5. Participants with a body mass index (BMI) below 24 were excluded because the primary focus of this study was to address excessive postpartum weight retained.

DISCUSSION

In a study of white women, Sampselle et al (1999) noted that the more physically active women retained the least amount of weight at six weeks postpartum. The authors also suggested that African American women may choose to rest rather than exercise in the early postpartum period. This was substantiated by self-reported data gleaned from this study. When asked "if you had an hour to yourself, what would you do with it?", the majority of the participants listed very sedentary, restful activities as their choices (i.e. sleep, read, or watch a movie). The cultural and generational advice "to rest" encourages new black mothers to be less active, thus promoting a sedentary lifestyle. On the other hand, black women have been found to have persistent weight in general, whether active or not. Researchers have reported that black women do not necessarily gain more weight than white women, but have greater difficulty in losing weight (Khan, 1991; Kumanyika, 1987; Walker, Timmerman, Sterling, Kim, & Dickson, 2004). This can be a potential problem since African American women appear to have a greater sensitivity to childbearing weight.

The results of this study support the findings of Khan (1991); Kumanyika (1988); and Walker et al (2004). Although, there was a collective weight loss found in this study, many of the women were frustrated with the minimal weight loss noted. A few participants began the study with ~10,000 steps at baseline and maintained this average or slightly better for 12 weeks. However, these participants stated that they just "couldn't seem to increase" beyond the upper limit, yet they were noted to "walk" five to seven days a week without much change in their weight. This seems to validate the previous studies on difficult weight loss in this population. Conversely, those who significantly increased steps showed larger amounts of weight loss and the three participants who were at the very upper end of the weight scale (approaching 300 lbs) lost the greatest amount of weight and increased their average daily steps. Perhaps these three were more determined or the weight that was lost was due to physiological changes that occur during the early postpartum period. As noted in the literature, physicians are failing to give adequate information regarding physical activity to early postpartum women. Thus, these women are unaware of its importance for overall health (Walker, 1996; McCrory et al, 2000).

The study was designed to increase ambulatory movement and positive lifestyle changes during the early postpartum period. The use of the pedometer did seem to have a positive effect, as evidenced by the increase in the number of daily steps measured at the end of the study as compared to baseline. Although the women were given a structured physical activity prescription for using the pedometer, many of the participants failed to follow with the progression of an average 500 steps/wk as prescribed. Some mothers would sleep/rest during the day and stay awake at night which prevented outdoor walking. The strategies to address this issue and to encourage an increase in the number of steps by an average of 500/week are described in the methods section. In general, there was a staggered increase in steps per day. The mothers made sincere attempts to reach their daily goal as time permitted over the 12 week period. The women were perfectly aware that they had not reached their personal goals as indicated by the logging in of data in the activity calendar. At the end of the study, several of the women wanted to continue walking and be reassessed within the following three to six months. A follow-up of these women is currently in progress. Some of the participants stated that they missed wearing their pedometer ("felt naked") and were seeking to purchase one for personal use.

The average expected weight loss during this time frame was reported to be ~0.5-1.0 kg/wk with diet and exercise programs (Lovelady et al, 2000; Leermakers et al, 1998; and O'Toole et al, 2003). However, these studies were mainly composed of white women. Also, the expected weight loss may be influenced by other factors such as breast feeding (Kac, 2004), smoking (Schauberger et al, 1992), and parity (Manson et al, 1994).

Although the magnitudes of change in weight and body composition found in the present study appear to be small, in reality, they are quite noteworthy when addressing the weight issues of this population. Additionally, the physical activity intervention was not equally effective in all participants so there is no assurance that increasing daily steps will influence retained weight and body composition in all postpartum African American females. Identifying other factors and individualizing interventions is of immediate concern. Nonetheless, the outcome of this study encourages lifestyle changes and provides assistance in clinical decision-making for health care providers to manage weight gain in African American women during the early postpartum period.

CONCLUSION/ CLINICAL IMPLICATIONS

Despite the limitations, this study is significant in that it is the first to objectively document the health benefits of increased physical activity during the early postpartum period, exclusively, in African American women. Moreover, it provides data specific evidence for physicians and healthcare providers to advise with confidence and subsequently complement a culturally appropriate postpartum care plan. Although this study is in the embryonic stage, the findings begin to fill a void that exists in the literature and provide the framework for future studies in this area.

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Valda Harris Montgomery, Ph.D., LAT

Assistant Professor

Department of Physcial Therapy

Alabama State University
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Date:Jan 1, 2009
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