Pelvic floor muscle training is recommended as first line treatment for urinary incontinence in women based on three proposed theorized mechanisms: \'Enhanced Pelvic Floor Muscle Strength,\' \'Maximized Awareness of Timing,\' and \'Strengthened Core Muscles\'. The purpose of this scoping review was to systematically map evidence for and against theorized mechanisms through which pelvic floor muscle training interventions work to reduce urinary incontinence in women.
The scoping review is based upon a comprehensive search of relevant literature published from 1990 to 2020 in PubMed, CINAHL, PsycINFO, ClinialTrials.gov, reference lists from review articles, and hand searches of articles by known researchers in the field. We included English-language, peer-reviewed articles on pelvic floor muscle training as an intervention for adult women if they provided empirical evidence to testing the theorized intervention mechanisms. Two independent reviewers screened articles for inclusion and extracted data to describe details of each study (author, year, country, design, sampling), measures of pelvic floor muscle strength and urinary incontinence, statistical analysis of linkage between changes in the measures, and pelvic floor muscle training regimens. Data were summarized to facilitate the integration of diverse evidence to draw conclusions on supporting or refuting the three proposed theorized mechanisms for managing urinary incontinence in women.
Of the 278 articles identified with the search, 13 (4.7%) met inclusion criteria. There was weak to no evidence for the mechanism of enhanced pelvic floor muscle strength, equivocal support for maximized awareness of timing, and no evidence for strengthened core muscles.
This review revealed extremely limited data supporting the proposed theorized mechanisms underlying pelvic floor muscle training programs to manage urinary incontinence in women. Such evidence is needed to help women and clinicians understand how, why and when a woman benefits from pelvic floor muscle training. Future studies should specifically state and report statistical analysis that relates the theorized mechanisms to the training outcomes observed.

Low back pain is one of most common musculoskeletal disorders around the world. One major problem clinicians face is the lack of objective assessment modalities. Computed tomography and magnetic resonance imaging are commonly utilized but are unable to clearly distinguish patients with low back pain from healthy patients with respect to abnormalities. The reason may be the anisotropic nature of muscles, which is altered in function, and the scans provide only structural assessment. In view of this, ultrasound may be helpful in understanding the disease as it is performed in real-time and comprises different modes that measure thickness, blood flow and stiffness. By the use of ultrasound, patients with low back pain have been found to differ from healthy patients with respect to the thickness and stiffness of the transversus abdominis, thoracolumbar fascia and multifidus. The study results are currently still not conclusive, and further study is necessary to validate. Future work should focus on quantitative assessment of these tissues to provide textural, structural, hemodynamic and mechanical studies of low back pain. This review highlights the current understanding of how medical ultrasound has been used for diagnosis and study of low back pain and discusses potential new applications.

BACKGROUND: Therapeutic exercises are frequently prescribed to patients with low back pain. Numerous exercise programs for patients with low back pain have been described. Many of these treatment programs are based on 1 of 2 popular rehabilitation strategies: a motor control exercise approach or a general exercise approach.
METHODS: PubMed clinical queries from 1966 to March 2013 for keyword combinations including motor control exercise, core stability exercise, therapeutic exercise, general exercise, global exercise, local exercise, transversus abdominis, segmental stabilization, and low back pain.
METHODS: Randomized controlled trials that assessed the effects of a motor control exercise approach, a general exercise approach, or both for patients with low back pain that were published in scientific peer-reviewed journals.
METHODS: Included studies underwent appraisal for exercise intervention and outcomes.
RESULTS: Fifteen studies were identified (8, motor control exercise approach without general exercise comparison; 7, general exercise approach with or without motor control exercise approach comparison). Current evidence suggests that exercise interventions may be effective at reducing pain or disability in patients with low back pain.
CONCLUSIONS: Stabilization exercises for patients with low back pain may help to decrease pain and disability. It may not be necessary to prescribe exercises purported to restore motor control of specific muscles.

Previous research describes an inconsistent relation between temporal changes in transversus abdominis or lumbar multifidus and temporal changes in clinical outcomes. Unfortunately, a relevant systematic review is unavailable. As a result, this systematic review was designed to summarize evidence regarding the association between temporal changes in muscle morphometry and activity in response to treatment, and temporal changes in clinical outcomes. Candidate publications were identified from 6 electronic databases. Fifteen articles were included after scrutinization by 2 reviewers using predetermined selection criteria. The methodological quality of these articles was appraised using a standard tool. These methods revealed strong evidence that temporal alterations in transversus abdominis thickness change during contraction (as measured by B-mode or M-mode ultrasound) or feedforward activation of transversus abdominis (assessed via electromyography, tissue Doppler imaging, or M-mode ultrasound) were unrelated to temporal changes in low back pain (LBP)/LBP-related disability. There was limited evidence that temporal changes in transversus abdominis lateral sliding or lumbar multifidus endurance were unrelated to temporal changes in LBP intensity. Conflicting evidence was found for the relation between temporal changes in lumbar multifidus morphometry and temporal changes in LBP/LBP-related disability. This review highlights that temporal changes in transversus abdominis features tend to be unrelated to the corresponding LBP/LBP-related disability improvements, whereas the relation between multifidus changes and clinical improvements remains uncertain.
CONCLUSIONS: This systematic review highlighted that changes in morphometry or activation of transversus abdominis following conservative treatments tend not to be associated with the corresponding changes in clinical outcomes. The relation between posttreatment changes in characteristics of lumbar multifidus and clinical improvements remains uncertain.

Although individual reports suggest that baseline morphometry or activity of transversus abdominis or lumbar multifidus predict clinical outcome of low back pain (LBP), a related systematic review is unavailable. Therefore, this review summarized evidence regarding the predictive value of these muscular characteristics. Candidate publications were identified from 6 electronic medical databases. After review, 5 cohort studies were included. Although this review intended to encompass studies using different muscle assessment methods, all included studies coincidentally used ultrasound imaging. No research investigated the relation between static morphometry and clinical outcomes. Evidence synthesis showed limited evidence supporting poor baseline transversus abdominis contraction thickness ratio as a treatment effect modifier favoring motor control exercise. Limited evidence supported that high baseline transversus abdominis lateral slide was associated with higher pain intensity after various exercise interventions at 1-year follow-up. However, there was limited evidence for the absence of relation between the contraction thickness ratio of transversus abdominis or anticipatory onset of lateral abdominal muscles at baseline and the short- or long-term LBP intensity after exercise interventions. There was conflicting evidence for a relation between baseline percent thickness change of lumbar multifidus during contraction and the clinical outcomes of patients after various conservative treatments. Given study heterogeneity, the small number of included studies and the inability of conventional greyscale B-mode ultrasound imaging to measure muscle activity, our findings should be interpreted with caution. Further large-scale prospective studies that use appropriate technology (ie, electromyography to assess muscle activity) should be conducted to investigate the predictive value of morphometry or activity of these muscles with respect to LBP-related outcomes measures.