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Table 4 Instruments used in the reviewed studies to measure pelvic floor muscle strength

From: Mechanisms of pelvic floor muscle training for managing urinary incontinence in women: a scoping review

 

Measures common name (review article)

What is assessed

Reliability

Validity

Subjective

Vaginal digital examination [23, 26]

Grading contraction, pressure around finger/s (4-point scale)

 

Modified Oxford scale [18]

Grading contraction, pressure around fingers, Poisson effect (as muscle is contracted, it expands a bulging up) (6-point scale)

r = 0.27–0.95 (inter-rater) [49,50,51,52,53]

r = 0.93 (test–retest) [50]

Correlation with perineometric pressure 0.79 [50]

Contaminated by IAP

 

A self-rated PFM strength question [20]

Self-reported improvement of PFM strength

Objective

Perineometer-like devices [16, 24]

Maximum voluntary vaginal closure pressure (mm Hg)

r = 0.79–0.80 (inter-rater) [54]

Good agreement with Brink digital exam score [55]

Contaminated by IAP

 

Intravaginal balloon-like device [15, 17, 21]

Maximum voluntary vaginal closure pressure (mm Hg)

r = 0.52–0.85 (test–retest) [56]

Contaminated by IAP [57]

 

Needle EMG: quantitative EMG [22]

Muscle electrical activity from individual motor units (in microvolt units)

r = 0.89 (range 0.78–0.95) [22]

hard to repeat

Not possible to measure contractile force using EMG [58]

Contaminated by IAP

 

Surface EMG (vaginally): quantitative EMG [25]

Muscle electrical activities from summated from many motor units (millivolt)

Between-visit ICC ranging 0.76–0.97 [59]

Measured PFM activity other than vaginal closure pressure

Contaminated by adjacent muscles [60, 61]

 

A handheld dynamometer (mTasMF-01, ANIMA, Japan) [19]

Hip adductor muscle strength

Not measure PFM strength

 

Sagittal dynamic (perineal) ultrasound [27]

Cephalic displacement (in mm) of the bladder neck in a sagittal view available as biofeedback (as opposed to caudal movement observable when she pushes down instead)

r = 0.52–0.96 (intra-rater) [62]

Visual “lift” of the bladder neck with a correct PFM contraction

  1. —, Information was not available; IAP, intraabdominal pressure; PFM, pelvic floor muscle; EMG, electromyography; ICC, intra-class correlation coefficients