The International Classification of Impairments, Disabilities and Handicaps (ICIDH) (1997), lately changed to International Classification of Functioning, Disability, and Health (ICF) (2002), is a World Health Organization (WHO)-approved system for classification of health and health-related states in rehabilitation science. According to this system, the causes of a non-optimally functioning pelvic floor (e.g. muscle and nerve damage after vaginal birth) can be classified as the pathophysiological component. Nonfunctioning pelvic floor muscles (PFM) (reduced force generation, incorrect timing or coordination) are the impairment component, and the symptom of pelvic floor dysfunction (e.g. urinary leakage, fecal incontinence, or pelvic organ prolapse) is a disability. How the symptoms and conditions affect the women’s quality of life and participation in fitness activities is an activity or participation component.
Muscular endurance can be classified as:
2. ability to repeatedly develop near maximal or maximal force determined by assessing the maximum number of repetitions one can perform at a given percentage of 1RM. Muscle strength measurement may be considered an indirect measure of PFM function in real-life activities. Women with no leakage do not contract voluntarily before coughing or jumping. Their PFM contraction is considered to be an automatic co-contraction occurring as a quick and effective activation of an intact neural system. Other important factors for a quick and effective contraction are the location of the pelvic floor within the pelvis, the muscle bulk, stiffness/elasticity of the pelvic floor and intact connective tissue.
A stretched and weak pelvic floor may be positioned lower within the pelvis compared with a well-trained or non-injured pelvic floor. The time for stretched muscles to reach an optimal contraction may be too slow to be effective in preventing descent against increased abdominal pressure (e.g. sneeze), thereby allowing leakage to occur. In general, when measuring muscle strength it can be difficult to isolate the muscles to be tested, and many test subjects need adequate time and instruction in how to perform the test. In addition, the test situation may not reflect the whole function of the muscles, and the generalizability from the test situation to real-world activity (external validity) has to be established. Therefore, when reporting results from muscle testing, it is important to specify the equipment used, position during testing, testing procedure, instruction and motivation given, and what parameters are tested (e.g. ability to contract, maximum strength, endurance).
When testing the PFM, additional challenges are present because muscle action and location are not easily observable. Whether a measurement tool should be used in clinical practice or in research depends on its responsiveness, reliability and validity. These terms are used slightly different in different research areas and have somewhat different defi nitions in different textbooks of research methodology. The definitions given below are the ones we have chosen to use in this textbook.
• Reliability: consistency or repeatability of a measure. The most common way to establish stability of a test is to perform a test–retest. Intratest reliability is conducted by one researcher measuring the same procedure in the same subjects twice. Inter-test reliabilityis conducted when two or more clinicians or researchers are conducting measurement of the same subjects.
• Validity: degree to which a test or instrument measures what it is supposed to measure.
• Logical (face) validity: condition that is claimed when the measure obviously involves the performance being measured (e.g. squeeze and elevation of the PFM can be felt by vaginal palpation).
• Content validity: condition that is claimed when a test adequately samples what it should cover (few methods measure both squeeze pressure and elevation of the PFM).
• Criterion validity: the degree to which the scores on a test are related to some recognized standard, or criterion (e.g. clinical observation of inward movement of the perineum during attempts to contract the PFM compared with ultrasonography).
• Concurrent validity: involves a measuring instrument being correlated with some criterion administered at the same time or concurrently (e.g. simultaneous observation of inward movement during measurement of PFM strength with manometers and dynamometers).
• Predictive validity: degree to which scores of predictor variables can accurately predict criterion scores.
• Diagnostic validity: ability of a measure to detect differences between those having a diagnosis/problem/condition/symptom with those not.
• Sensitivity: the proportion of positives that are correctly identified by the test.
• Specificity: the proportion of negatives that are correctly identified by the test.
It is important for physiotherapists (PTs) who treat patients with pelvic floor dysfunction to understand the qualities and limitations of the measurement tools they use. This chapter will provide the information needed for PTs to understand the application of each tool to the measurement of the PFM. In many instances the PT may need thorough supervised instruction from other professionals before starting to use new equipment. In most cases, when available, receiving results from assessment of PFM activity from other professionals (e.g. radiologists) provides the best results.