More Complicated Than it Looks

Abstract

Activities thought to induce high intra-abdominal pressure (IAP), such as lifting weights, are restricted in women with pelvic floor disorders. Standardized procedures to assess IAP during activity are lacking and typically only focus on maximal IAP, variably defined. Our intent in this methods paper is to establish the best strategies for calculating maximal IAP and to add area under the curve and first moment of the area as potentially useful measures in understanding biologic effects of IAP. Thirteen women completed a range of activities while wearing an intra-vaginal pressure transducer. We first analyzed various strategies heuristically using data from 3 women. The measure that appeared to best represent maximal IAP was an average of the three, five or ten highest values, depending on activity, determined using a top down approach, with peaks at least 1 second apart using algorithms written for Matlab computer software, we then compared this strategy with others commonly reported in the literature quantitatively using data from 10 additional volunteers. Maximal IAP calculated using the top down approach differed for some, but not all, activities compared to the single highest peak or to averaging all peaks. We also calculated area under the curve, which allows for a time component, and first moment of the area, which maintains the time component while weighting pressure amplitude. We validated methods of assessing IAP using computer-generated sine waves. We offer standardized methods for assessing maximal, area under the curve and first moment of the area for IAP to improve future reporting and application of this clinically relevant measure in exercise science.

Effects of walking speeds and carrying techniques on intra-abdominal pressure in women

“…We approximated the power of a mixed model analysis of variance, with multiple comparisons of 5 lifting activities versus this reference activity, using formulae for Sidak corrected t-tests at the 1% significance level, adjusted for intra-woman clustering assuming an ICC = 0.45. Based on our preliminary data in which the net (that is, the difference between maximal and minimal IAP during a specific activity [12]) mean maximal IAP for lift-and-carry was (35.2 cm H 2 0, SD 9.3), this calculation indicated that a sample size of 46 women would provide approximately 80% power to detect a difference of 20 cm H 2 0 (ie, net mean IAP of 30 vs 50 cm H 2 0 or total mean IAP of 50 vs 70 cm H 2 0) in the comparison of one lifting activity versus the control. Therefore we planned to enroll up to 60 women to obtain a final complete dataset for 46.…”

Intra-abdominal pressures during activity in women using an intra-vaginal pressure transducer

“…Descriptions of how maximal intra-abdominal pressure is calculated vary or are absent from literature to date. We have described standardised methods for assessing maximal pressure during physical activity (Hamad et al, 2013). However, other qualities of intra-abdominal pressure besides maximal pressure may also be relevant to understanding the impact of strenuous activities on conditions such as pelvic floor disorders.…”

Intra-abdominal pressure during Pilates: unlikely to cause pelvic floor harm

“…As can be seen in Figure 4, this AUC is greater than that for the Mat and Reformer Pilates sessions combined. Area under the curve measurements describing IAP are used very little in the literature [23, 27]. However, AUC is commonly used in endocrinological and neuroscience research to reflect information that is contained in repeated measures over time, and in pharmacology to determine the effects of medication over a time period or to evaluate dose and response relationships [28].…”

“…A custom Matlab software (R2011A, MathWorks) program was used to evaluate the pressure data as previously described [23]. Maximal IAP was calculated by averaging the 10 maximal peaks in the waveform each separated by one second.…”

“…We standardized the repetitions of each exercise, not the duration of each exercise, as each woman completed it at her own rate. In previous work, we standardized the time component of AUC (cm H 2 O·s) in order to compare cumulative pressure between activities [23]. In the current study, we did not normalize AUC to time, as our goal was to measure the actual AUC of each prescribed activity.…”