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ORIGINAL RESEARCH |
From the 1Department of Obstetrics and Gynecology, San Antonio Uniformed Services Health Education Consortium, San Antonio, Texas; 2Department of Obstetrics and Gynecology, University of Utah College of Medicine, Salt Lake City, Utah; 3Department of Physical Therapy and Rehabilitation Sciences University of Iowa; 4Department of Obstetrics and Gynecology, University of Iowa Carver College of Medicine; and 5Department of Health and Sports Studies University of Iowa, Iowa City, Iowa.
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ABSTRACT |
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METHODS: Thirty women of wide age and weight ranges who were not undergoing treatment for pelvic floor disorders performed 3 repetitions of various activities while intra-abdominal pressures (baseline and maximal) were approximated via microtip rectal catheters. We calculated median peak and net pressures (centimeters of H2O). We assessed correlations between abdominal pressures and body mass index, abdominal circumference, and grip strength (a proxy for overall strength). P < .025 was considered significant.
RESULTS: Median peak abdominal pressures ranged from 48 (lifting 8 lb from a counter) to 150 (lifting 35 lb from the floor), with much variation. Many activities did not raise the intra-abdominal pressure more than simply getting out of a chair, including lifting 8, 13, and 20 lb from a counter, lifting 8 or 13 lb from the floor, climbing stairs, walking briskly, or doing abdominal crunches. Body mass index and abdominal circumference each correlated positively with peak, but not net, pressures. Age and grip strength were not associated with abdominal pressure.
CONCLUSION: Some activities commonly restricted postoperatively have no greater effect on intra-abdominal pressures than unavoidable activities like rising from a chair. How lifting is done impacts intra-abdominal pressure. Many current postoperative guidelines are needlessly restrictive. Further research is needed to determine whether increased intra-abdominal pressure truly promotes pelvic floor disorders.
LEVEL OF EVIDENCE: III
There is a widespread but untested belief that increases in intra-abdominal pressure (that occur with activities like coughing, exercise, or lifting) contribute to the incidence, progression, or recurrence of pelvic floor disorders, perhaps by increasing stress on the pelvic floor muscles and ligaments. This belief causes some women to markedly alter physical activity, including exercise, housework, and job-related physical activity. Additionally, physicians often place activity and lifting restrictions on women with pelvic floor disorders before and after surgery.7 Some recommend life-long restrictions after surgery for pelvic floor disorders. Using a best-guess approach, physicians attempt to restrict activities that they believe raise the intra-abdominal pressure substantially. Thus, many patients are instructed to avoid lifting more than 5–10 pounds, to avoid exercise, and to avoid heavy labor after surgery.
Although there is some information in the spine literature about intra-abdominal pressure during lifting in populations of largely young healthy men under 40 years of age, we found little or no information about intra-abdominal pressures in older women (that is, those likely to undergo surgery for pelvic floor disorders) or during routine activities like walking, rising from a chair, or lying down (MEDLINE, English language, 1966 to June 2005; search terms: "abdominal pressure" or "intra-abdominal pressure" and "lifting" or "activity" or "physical activity" or "exercise" or "work"; also "activity restrictions" or "postoperative restrictions" or "postoperative activity"). We were curious about whether lifting actually increased intra-abdominal pressure more than these types of routine activities that patients are not prohibited from performing after surgery.
Because there is little evidence to guide the recommendations physicians make regarding activity restrictions, and because such restrictions can be life altering, we conducted this study to describe intra-abdominal pressures during a wide array of common physical activities. Additional aims were to compare intra-abdominal pressures between lifting tasks and other activities and to determine whether such pressures differed according to age, body mass index, and grip strength (as a proxy to overall strength). In doing so, we hoped to provide data to eventually develop more evidence-based activity guidelines for postoperative patients.
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MATERIALS AND METHODS |
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RESULTS |
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Each activity had a fairly consistent effect on abdominal pressure relative to the other activities (those which produced the lowest and highest pressures did so consistently between subjects). The median peak abdominal pressures in all activities ranged from 47.7 to 149.3 centimeters of H2O, and median net pressures ranged from 5.3 to 105.0 centimeters of H2O. Median and range values for peak pressures during activities are depicted in Table 1 in order of ascending median value. A similar trend is seen with net pressures (data not shown), with most median values falling 40–50 cm of H2O below the peak values.
Peak and net intra-abdominal pressures were highest while lifting 20 and 35 lb from the ground and coughing forcefully, and lowest while lifting 8 lb from counter height, low table height, and overhead. There was wide intersubject variability for both peak and net pressures for most activities. Activities that were most strenuous, lifting 20 and 35 lb off the floor and forceful coughing, produced the greatest intersubject variability.
Baseline pressure measurements remained relatively stable throughout the data collection (median baseline pressure 43.7 cm H2O, range 23.8–48.3 cm H2O), with lower baseline pressures observed with activities that began in the supine position. Most of the baseline measurements (16 of 25) were significantly higher (P < .025) in those subjects with a BMI of 30 or greater (median baseline pressure 50.0 cm H2O, range 27.3–58.0 cm H2O) than those with a BMI less than 30 (median baseline pressure 39.2 H2O, range 18.7–44.3 cm H2O).
We compared net abdominal pressure during activities with that produced by rising from a standard chair, a desk chair without arms. We chose this as our reference activity because it is a very common activity that is not routinely restricted, nor could it practically be. Surprisingly, performing abdominal crunches, climbing stairs, and walking on a treadmill at all 3 speeds did not increase the intra-abdominal pressure more than did rising from a chair. Many of the lifting activities increased intra-abdominal pressure significantly less than rising from the standard chair, including lifting 8 lb from the counter, low table, and overhead (P < .001 for all three), lifting 13 lb from the counter and the floor (P < .001 and .002, respectively), and lifting 20 lb from the counter (P = .003).
Lifting 20 and 35 lb from the floor, doing jumping jacks, and coughing forcefully did increase pressures significantly more than rising out of the chair (P < .001 for all three). Lying down supine on the floor and standing up from that supine position also increased pressure significantly more than rising from the standard chair (P = .005 and < .001, respectively).
Lifting 35 pounds is an activity generally restricted after surgery. Although lifting 35 pounds from the counter did not raise the intra-abdominal pressure any more than did brisk walking, lying down to and rising from a supine position, forceful coughing, or lifting 20 pounds from the floor, lifting 35 pounds from the floor did increase abdominal pressures more than these activities. In addition, lifting 35 pounds from the floor increased pressures more than all other activities tested with the exception of forceful coughing.
Body mass index impacted peak, but not net, intra-abdominal pressures for most activities. Although correlations between BMI and peak pressures were significant, the largest r value for the significant correlations was 0.65 (range 0.37–0.65), meaning that only 14–42% of the variability seen in peak abdominal pressures was accounted for by a difference in BMI. A similar trend was seen between increasing peak, but not net, abdominal pressure and increasing abdominal circumference. There was no significant correlation between either age or grip strength and either net or peak intra-abdominal pressures for any of the activities.
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DISCUSSION |
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Pressures recorded in our subjects during coughing are similar to those routinely obtained during urodynamic studies11 and are also generally similar to those recorded using different technologies in studies on lifting and spine dynamics. A study of 12 women undergoing laparoscopy revealed that measuring rectal pressure at a depth greater than 10 cm accurately reflected changes in intra-abdominal pressure.16 Of note, although each activity had a fairly consistent effect on intra-abdominal pressures and baseline measurements remained relatively stable during data collection, we observed high levels of intersubject variability.
Posture and performance technique should be considered when considering lifting limitations.12 Lifting from counter height raised the intra-abdominal pressure less than lifting from the floor. Modifying how activities are done may allow women to continue performing more strenuous tasks such as lifting children or lifting at work.
The association between higher intra-abdominal pressures and higher BMI is consistent with data from urodynamic studies.17 Higher BMI also correlates strongly with the prevalence of stress urinary incontinence18; less clear is whether obesity increases the risk of pelvic organ prolapse or of failure of urogynecologic surgeries. If decreasing abdominal pressure impacts surgical success, it might be beneficial to focus on preoperative weight loss and postoperative low-impact exercise.
Before beginning this study, we hypothesized that women with stronger arms would increase intra-abdominal pressure less during lifting tasks. However, using grip strength as a proxy for overall strength, strength had no effect on intra-abdominal pressures. Although it is plausible that no real relationship exists between strength and intra-abdominal pressure, grip strength may not adequately reflect overall strength and a different proxy might produce different results. We saw no effect of age on intra-abdominal pressures and see no reason to believe that activity restrictions should be based solely on patient age.
Although the activities performed in our study were designed to closely reflect those performed in daily life, it is impossible to simulate real life in a laboratory. Further, we examined peak pressures during many lifting activities but did not assess elements such as duration of lifting and fatigue. For example, although lifting 20 lb from counter height 3 times (as in our study) does not raise pressure more than rising from a chair, we do not know the cumulative effects of repeatedly lifting this amount.
Our study provides evidence to aid our understanding of intra-abdominal pressures during a range of activities, including common everyday tasks. However, long-term prospective studies are needed to understand the impact of physical activity on the incidence, progression, or recurrence of pelvic floor disorders. It is possible that physical activity may protect against certain pelvic floor disorders. For example, based on recent spine research, increased abdominal pressure may actually serve a protective role for the spine. Current thinking in that field holds that increased intra-abdominal pressure serves a protective role by increasing lumbar stability by forming a "rigid cylinder" of the abdominal musculature and stabilizing fascial connections to the vertebra.15
Similarly, current thinking about physical activity after hernia surgery is changing. Recent large-scale data from the Danish Hernia Database have not demonstrated more recurrences in people who quickly resumed activities after surgery compared with those with more traditional convalescence periods.19 These and other findings prompted a recent recommendation that "‘take it easy’ is the wrong advice" after hernia repairs.20 Whether the same is true for the pelvic floor remains to be determined.
In summary, current activity restrictions often placed on postoperative patients or patients with pelvic floor disorders are unsubstantiated and create unnecessary and life-altering limitations for women. This study helps lay the foundation for evidence-based activity restrictions as we await more long-term studies that will show us the true clinical impact of activity and intra-abdominal pressure on pelvic floor dysfunction.
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Footnotes |
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Corresponding author: Ingrid Nygaard, MD, 452 South Maryfield Drive, Salt Lake City, UT 84108; e-mail: Ingrid.nygaard{at}hsc.utah.edu.
doi:10.1097/01.AOG.0000197069.57873.d6
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REFERENCES |
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