Evidence for increased tone or overactivity of pelvic floor muscles in pelvic health conditions: a systematic review.

OBJECTIVE: Pelvic floor muscle tone, which includes active and passive components, is argued to be increased in many pelvic health conditions, including those involving pain. This study systematically reviewed evidence for increased pelvic floor muscle tone in pelvic health conditions. DATA SOURCES: Electronic databases (PubMed, CINAHL, and Embase) were searched up to May 31, 2021. The search strategy included variants of pelvic and/or floor, muscle, and tone using keywords and Medical Subject Headings (MeSH) terms. STUDY ELIGIBILITY CRITERIA: Studies were included if they investigated increased tone of the pelvic floor muscle and reported measures of active or mechanical properties of the pelvic floor muscle in humans with any pelvic health condition, including pain, bowel, urogenital, or sexual dysfunctions. Studies of any design were included, except systematic and narrative reviews. Reference lists of studies, reviews, and book chapters were searched for additional studies. METHODS: Data were extracted using a standardized form, including measurement tool and outcome measure. Risk of bias was analyzed using a modified ROBINS-I (Risk of Bias In Non-randomized Studies - of Interventions) tool, and a score was allocated to determine whether the study provided "convincing" interpretation (comparison with condition-free control group, valid measure, no application issues). RESULTS: In total, 151 studies were included, reporting 8 different tools (electromyography, dynamometry, manometry, digital palpation, defecography, ultrasound, magnetic resonance imaging, other). The most common pelvic health condition was pelvic pain (n=16 conditions), followed by bowel and urogenital conditions. Most studies (57%) were cross-sectional. A healthy control group was infrequently included for comparison (27%). Unvalidated methods or methods applied in a manner that precluded convincing interpretation were common (94%). Of the 15 measurement tools that provided convincing evidence, 10 demonstrated greater tone in a pelvic health condition (all pain) compared with controls, and 5 showed no difference. CONCLUSION: Despite the large literature, few studies provide convincing evidence for increased tone/overactivity of pelvic floor muscles in pelvic health conditions. Interpretation is hampered by design and measurement issues. Terminology was often inaccurate. Few studies investigate male, transgender, and pediatric groups.

Pelvic floor muscle length changes with breathing in males: A preliminary report.

The study aimed to identify whether pelvic floor muscles modulate length with breathing, and if any length changes induced by breathing relate to abdominal cavity displacement and intra-abdominal pressure. To investigate these relationships, displacement of pelvic landmarks that related to pelvic floor muscle length using transperineal ultrasound imaging, breath volume, intra-abdominal pressure, abdominal and ribcage displacement, and abdominal and anal sphincter muscle electromyography were measured during quiet breathing and breathing with increased dead-space in ten healthy men. Pelvic floor muscle landmark displacement modulated with ribcage motion during breathing. This relationship was stronger for: i) motion of the urethrovesical junction (puborectalis muscle length change) than the mid-urethra landmark (striated urethral sphincter muscle length change), and ii) dead-space breathing in standing than dead-space breathing in supine or quiet breathing in standing. In most (but not all) participants, the urethrovesical junction descended during inspiration and elevated during expiration. Striated urethral sphincter length changes during the respiratory cycle was independent of intra-abdominal pressure. In summary, breathing involves pelvic floor muscle length changes and is consistent with the role of these muscles during respiration to aid maintenance of continence, lung ventilation and/or provision of support to the abdominal cavity. Clinicians who train pelvic floor muscles need to be aware that length change of pelvic floor muscles is expected with breathing.