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Table 1 Characteristics of 10 studies of the intraexaminer and interexaminer reliability of manual muscle testing (RCTs indicated by **)

From: On the reliability and validity of manual muscle testing: a literature review

Authors, date Subjects Examiners Design Findings and statistics
Pollard et al55 (2005) ** 106 volunteers Novice examiner (5th year) chiropractic student; experienced examiner (15 years MMT experience) Interexaminer reliability of 2 common muscle tests Deltoid muscle showed Cohen kappa value (k 0.62) and psoas muscle showed (k 0.67). Good interexaminer reliability shown between experienced and novice examiners.
Perry et al43 (2004) ** 16 patients with post-polio syndrome; 18 patients without pathology; 26 patients with signs of hip extensor weakness and post-polio syndrome Several examiners Supine MMT of hip extensor strength compared to strength values obtained by traditional prone test of hip extensor muscles in patients with post-polio syndrome Reliability testing showed excellent agreement (82%). Subjects with pathology had significant differences in mean muscle torque (P < .01) strength. Predictive validity of MMT in patients with symptomatic post-polio syndrome affecting hip extensor muscles was excellent.
Escolar et al56 (2001) 12 children with muscular dystrophy 12 novice and experienced examiners To determine reliability of quantitative muscle testing (QMT, an instrument for measuring strength) compared to MMT MMT was not as reliable among novice examiners as QMT. With adequate training of examiners an interclass correlation coefficient > 0.75 was achieved for MMT.
Caruso and Leisman 36 (2000) 27 volunteers who knew nothing about MMT or AK 2 examiners To show the difference between "weak" and "strong" muscles, using MMT and dynamometer testing Study showed that examiners with over 5 years experience using AK had reliability and reproducibility (98.2%) when their outcomes were compared. Perception of "inhibition" or weakness made by examiner was corroborated by test pressure analysis using the dynamometer.
Florence et al 47 (1992) ** 102 boys aged 5 to 15 years. Physical therapists A double-blind, multicenter trial to document the effects of prednisone on muscle strength in patients with Duchenne's muscular dystrophy (DMD). Reliability of muscle strength grades obtained for individual muscle groups and of individual muscle strength grades was analyzed using Cohen's weighted Kappa. The reliability of grades for individual muscle groups ranged from .65 to .93, with the proximal muscles having the higher reliability values. The reliability of individual muscle strength grades ranged from .80 to .99, with those in the gravity-eliminated range scoring the highest. Concluded that the MMT was reliable for assessing muscle strength in boys with DMD when consecutive evaluations are performed by the same physical therapist.
Barr et al 42 (1991) 36 boys (11.7 +/- 3.9 years) with Duchenne or Becker muscular dystrophy.   Upper and lower extremities were evaluated by MMT for function, range of motion, and strength. The data were analyzed using intraclass correlation coefficients (ICCs). For the interevaluator phase, ICCs for MMT was .90; For the intraevaluator phase, corresponding ICC was .80 to .96. Results confirm and extend observations by others that these assessment measures are sufficiently reliable for use in multiinstitutional collaborative efforts. These results can be used to design clinical trials that have sufficient statistical power to detect changes in the rate of disease progression.
Hsieh and Phillips 46 (1990) 15 asymptomatic subjects 3 chiropractors To determine the reliability of manual dynamometry using AK style of MMT, comparing doctor-initiated and patient-initiated MMT Intratester reliability and correlation coefficients for testers 1, 2, and 3 were 0.55, 0.75, and 0.76 with doctor-initiated method; 0.96, 0.99, and 0.97 when patient-initiated MMT method. The intertester reliability coefficients were 0.77 and 0.59 on day 1 and 2 respectively for doctor-initiated method; and 0.95 and 0.96 for the patient-initiated method.
Wadsworth et al 45 (1987) 5 muscle groups on 11 patients physical therapists To compare the intrarater reliability of MMT and hand-held dynamometer tests The correlation coefficients were high and significantly different from zero for four muscle groups tested dynametrically and for two muscle groups tested manually. The test-retest reliability coefficients for two muscle groups tested manually could not be calculated because the values between subjects were identical. Concluded that both MMT and dynamometry are reliable testing methods, given the conditions described in this study.
Florence et al 34 (1984) Patients with Duchenne Muscular Dystrophy physical therapists To evaluate the (intraobserver) and (interobserver) reliability of MMT evaluation procedures to assess the efficacy of treatment of Duchenne muscular dystrophy. Showed there was significant improvement in the degree of consistency of a given examiner's MMT scores when the examiner had more clinical experience and training in MMT. Author's concluded that MMT demonstrated reliability for an evaluation method that provided an objective foundation on which to claim if a drug or therapeutic procedure does or does not have an effect in treating Duchenne muscular dystrophy.
Jacobs 44(1981) 65 patients with suspected thyroid dysfunction 2 chiropractors To compare AK diagnostic findings with laboratory findings This double-blind study demonstrated an 81.9% agreement between two testers, indicating good inter-examiner reliability.