Ulla Werlauff Methods to assess physical functioning - Danske ...

which alone or in combination provide a holistic picture of the patient and his performance”
[Sylvia Hyde, personal communication 2001].
In the clinical setting, as well as in research, it is important to decide the relevant outcome - what
should be measured? Is it capacity, capability or both? In rehabilitation research there are often
several outcomes of interest; the primary outcome is usually at the level of activities, and the
outcomes at impairment level act as a gold standard and help to interpret other findings.
Consequently, the applicability of the assessment methods depends on their ability to measure the
outcomes [Wade 2003].
Assessment at impairment level
Methods used to assess level of impairment are related to body function and physical capacity. One
of the primary characteristics in neuromuscular disorders is impaired muscle strength and it is
essential to be able to quantify muscle strength in order to diagnose the patient, to pick up changes
over time and to evaluate treatment. Muscle strength can be measured by manual or by quantitative
techniques and as dynamic or isometric muscle strength. The manual muscle test (MMT) was
developed by Lovett (1916) and has since become a widely used method. Is has been slightly
moderated over the years, and is typically scored using the 6-point Medical Research Council
(MRC) scale with 0 representing “ no muscle function” and 5 representing “normal” muscle
strength [Medical Research Council 1943]. Scores from the tested muscles are often summed into a
composite score to express overall muscle strength. The test is useful as a screening tool to evaluate
muscle strength and to plan for rehabilitation; it is easy to perform and does not require any form of
equipment. The scores from “0” – “3”, representing the most decreased muscle strength, are well
defined whereas scores above “3” are based on a subjective decision made by the evaluator. As a
consequence, inter and intra-rater agreement is better when testing weaker muscles compared to
stronger muscles [Florence 1992, Mahoney 2009]; agreement is further improved when the test is
performed by trained evaluators [Florence 1984, Escolar 2001]. In general, studies have provided
evidence for good reliability and validity in the use of MMT [Cutberth 2007], but the increasing
demands for objectivity based on interval scaling in measuring muscle strength have limited the use
of MMT in clinical trials in neuromuscular diseases.
Quantitative muscle strength is considered to be an “objective” measurement of
muscle strength. The method is highly correlated with MMT [Saraniti, 1980, Aitkens 1989,
Goonetilleke 1994] and is as such often considered as a gold standard in muscle strength
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