Introduction

Participation in structured physical activity leads to many health benefits, including decreased risk of all-cause mortality, decreased disease-specific risk, and strengthening of the muscular system. Participation in physical activity is generally considered safe, yet strenuous and/or repetitive physical activity of long duration can increase the risk for muscular, tendon, and ligamentous damage. Whether strenuous physical activity increases risk for pelvic floor disorders is not known.

Up to 1 in 5 women in the United States will have surgery for pelvic organ prolapse (POP), which can negatively impact quality of life and may be a barrier to healthy physical activity. Vaginal delivery increases risk for POP, yet factors that impact pelvic floor support among young nulliparous women are not well characterized. Physical activity increases intraabdominal pressure, theoretically placing stress on the pelvic floor, and thus may be one behavior that affects pelvic support in nulliparous women.

Strenuous exercise programs such as CrossFit have become popular over the past decade, and concern regarding their safety is documented in the literature. CrossFit workouts are characterized by high intensity and variable activity. They include power-based exercises such as Olympic and other lifts using a barbell or other free-weight equipment, elements of gymnastics, basic calisthenics, and impact from running and jumping. Daily workouts are conducted in groups and individual performance results are posted publicly, which encourages competition. This training provides an ideal model for studying the impact of high-intensity, strenuous training on the pelvic floor. Therefore, we aimed to examine differences in measures of pelvic floor support and function between women who habitually participate in CrossFit (strenuous exercise) and women who do not strenuously exercise. Additionally, we sought to determine whether measures of pelvic floor support and function changed after an acute bout of typical exercise between strenuous and nonstrenuous groups.

Materials and Methods

We recruited participants through advertisements throughout the greater Salt Lake City, UT, area; at the University of Utah; throughout the local CrossFit community; and by word of mouth. The University of Utah Institutional Review Board approved recruitment and study procedures prior to data collection and eligible participants provided written consent. Inclusion criteria included: nulliparous women ages ≥18 and ≤35 years, “no” response to all questions on the commonly used preexercise screening tool, the Physical Activity Readiness Questionnaire (done to minimize chance of cardiac event during exercise), free of musculoskeletal injuries for the past 6 months, previously experienced at least 1 pelvic exam, relatively weight stable (no more than ∼10% body mass fluctuation) in the past 6 months, and willing to complete study measures. Women were excluded if they reported history of hysterectomy or pelvic surgery to correct prolapse or incontinence, or chronic cough.

Women were eligible for the nonstrenuous group if they reported no participation in any consistent form of heavy resistance, conditioning, or routine impact activity over the past 6 months. While being completely sedentary was not an exclusion criterion, based on the past-year Bone Loading History Questionnaire (BLHQ) (described below), all women in the nonstrenuous group were recreationally active. Specific inclusion criteria for those in the strenuous group included at least 6 months of consistent participation in CrossFit, completing at least 3 workouts per week, with no history or current use of performance-enhancing substance by self-report. All strenuous participants demonstrated the ability to execute the prescribed lifts in the exercise protocol.

Participants arrived to each of 2 testing sessions rested and well hydrated, reporting normal dietary patterns, no exercise, and no central nervous system stimulants (eg, caffeine supplements, energy drinks, or coffee, as these could in theory increase pelvic floor muscle activity) during the 24 hours prior to testing.

During the first session, participants completed the informed consent process, self-report questionnaires, anthropometric measures, and strength testing.

We used the validated Epidemiology of Prolapse and Incontinence Questionnaire to identify symptoms of pelvic floor disorders and the validated BLHQ to assess previous and current physical activity in the form of bone-loading exposure at the hip and spine from physical activity in specific age epochs. We chose this questionnaire to summarize past physical activity because the higher values indicate greater mechanical load and impact, potentially important for pelvic floor health as well as bone health.

We measured height without shoes using a stadiometer to the nearest 1.0 cm; weight to the nearest 1.0 kg on an electronic Tanita (Tanita Corporation of America, Inc., Arlington Heights, Illinois) scale, also without shoes; and waist and hip circumference using a tension-regulated tape measure. Body composition was analyzed using a Bod Pod (Cosmed Inc, Concord, CA), a valid and reliable measure of body composition when compared to hydrostatic weighing in healthy adults. The Bod Pod uses air displacement in a sealed chamber to analyze body composition, providing accurate representations of body fat percentage.

Handgrip strength is often used as a proxy for total body strength, since it tends to correlate with other measures of muscle strength and is more feasible to assess than other body segments. We assessed handgrip strength using a hydraulic handgrip dynamometer (5030J1; Jamar, Jackson, MI). Participants performed 3 maximal voluntary contraction (MVC) trials using their dominant hand while standing and positioned at 90 degrees of elbow flexion. The maximal value of the 3 trials, in kilograms of force, was used in analysis.

During the second study visit, participants completed a pelvic exam 2 separate times. The first was before the designated exercise session for the strenuous and nonstrenuous groups and the second was done within 15 minutes of exercise completion. After participants voided, a certified research nurse performed the POP Quantification (POP-Q) examination, a reproducible and reliable measurement of vaginal support. Maximal vaginal descent (MVD) was subsequently calculated as the greatest value for POP-Q points Ba (anterior vaginal wall), Bp (posterior vaginal wall), or C (cervix) during maximal strain. Pelvic floor muscle strength (PFMS) was assessed using Peritron 9300 V vaginal perineometer (Laborie, Mississauga, Ontario, Canada). Vaginal resting pressure (VRP), sometimes referred to as vaginal tone, is a measure in part of the activity of the pelvic floor muscles at rest. Unlike other skeletal muscle, the levator ani (pelvic floor) muscles are constantly active, even at rest, and their activity increases with volitional contraction of these muscles resulting in greater vaginal pressure. To measure VRP, we calibrated the probe to 0 before insertion, and recorded pressure after asking each participant to completely relax after the pressure sensor probe was inserted. Without removing the probe, PFMS was then assessed. Participants were asked to squeeze and lift strongly, for each of the 3 trials. On the fourth trial, participants were asked to squeeze and hold with verbal prompts for 10 seconds while pelvic floor muscle endurance was evaluated. We defined maximal contraction pressure as the greatest pressure obtained during the 3 MVC trials and mean contraction pressure as the mean of the 3 trials.

The strenuous and nonstrenuous group exercise protocols were designed to reflect typical physical effort for women in each group. Participants completed a 5-minute warm-up prior to the exercise protocol. The warm-up was activity-specific for each group, and engaged the muscular and circulatory systems at relatively low intensity to be consistent with the recommendations provided by the National Strength and Conditioning Association.

As outlined in Table 1 , following the 5-minute warm-up, the strenuous group completed the exercise selections with as many repetitions as possible in 20 minutes. Selected exercises are routinely performed in CrossFit and were not novel to the strenuous participants: 15 push-ups, 5 deadlifts at 80% of 3 repetition maximum, 5 push-presses at 80% of 3RM, 15 burpees, and 20 sit-ups. Following the warm-up, the nonstrenuous group completed a 20-minute walk at their self-selected exercise pace.

One research nurse conducted all pelvic exams for the study. She was masked to activity group and was not aware of the study aims. Efforts were taken to wipe body sweat from strenuous participants and to make both groups appear as similar as possible. Strenuous participants were asked to refrain from wearing clothing with CrossFit emblems, logos, or specific terminology. Both groups were asked to remove shoes prior to entering the examination room, as CrossFit footwear could have identified the specific group.

Data analysis

Data were analyzed using statistical software (Stata 13.1; StataCorp, College Station, TX). Means and SDs were used to provide descriptive statistics of the sample population ( Table 2 ). Two-tailed t tests were used to identify differences in groups’ means for descriptive data. Descriptive pelvic floor measures for MVD preexercise and postexercise were reported using the median with quartiles 1 and 3 ( Table 3 ). Only healthy, young women were included in this study, so the ordinal MVD data did not span their full range (–3 to +3) in the population and were not normally distributed. Therefore, the Wilcoxon rank sum test was used to analyze MVD between strenuous and nonstrenuous groups preexercise, and the Wilcoxon signed rank test was used to analyze MVD values preexercise-postexercise within each group.

Table 2

Participant characteristics

	Strenuous group, n = 35	Nonstrenuous group, n = 35	Total	P value
Age, y	26.8 ± 3.79	22.74 ± 3.89	24.77 ± 4.30	<.00 a
Height, cm	164.36 ± 7.91	163.52 ± 6.15	163.84 ± 7.0	.705
Weight, kg	64.70 ± 7.78	60.6 ± 8.99	62.11 ± 8.69	.027 a
Waist circumference, cm	74.0 ± 5.22	71.94 ± 6.54	72.91 ± 6.11	.186
Hip circumference, cm	98.69 ± 4.85	97.34 ± 6.35	97.89 ± 5.65	.416
Body composition, % fat mass	23.36 ± 5.88	27.55 ± 7.07	25.46 ± 6.10	.003 a
Handgrip strength, kg	20.78 ± 5.97	16.04 ± 11.04	18.41 ± 6.19	.001 a

Values expressed as mean ± SD.

Middlekauff et al. Acute and chronic strenuous exercise and pelvic floor muscle strength. Am J Obstet Gynecol 2016 .

a P < .05 between groups.

Table 3

Pelvic floor measures: preexercise and postexercise

	Strenuous group		P value	Nonstrenuous group		P value	Strenuous vs nonstrenuous preexercise P value
	Pre	Post	Strenuous group pre vs post	Pre	Post	Nonstrenuous group pre vs post
MVD [strenuous, n = 35; nonstrenuous, n = 35]	–2.0 (–3, –2)	–2.0 (–3, –2)	.008 a	–3.0 (–3, –2)	–2.0 (–3, –2)	.025 a	.494
VRP, cm H 2 O [strenuous, n = 22; nonstrenuous, n = 29]	36.0 (30.0, 42.6)	33.35 (28.4, 38.0)	.009 a	34.5 (25.4, 39.8)	30.8 (24.8, 36.5)	.038 a	.168
Maximum PFMS, cm H 2 O [strenuous, n = 22; nonstrenuous, n = 29]	49.65 (31.9, 62.1)	43.3 (32.0, 61.6)	.360	46.1 (31.2, 62.9)	44.1 (32.6, 64.5)	.931	.773
Mean PFMS, cm H 2 O [strenuous, n = 22; nonstrenuous, n = 29]	41.25 (28.3, 57.4)	40.42 (28.3, 56.5)	.695	40.8 (29.6, 59.6)	39.87 (29.0, 56.1)	.097	.896

Data represented as median (quartile 1, quartile 3).

MVD , maximal vaginal descent; PFMS , pelvic floor muscle strength; VRP , vaginal resting pressure.

Middlekauff et al. Acute and chronic strenuous exercise and pelvic floor muscle strength. Am J Obstet Gynecol 2016 .

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