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. 2019 Jan;59(1):70-75.
doi: 10.1002/mus.26307. Epub 2018 Dec 18.

Muscle endurance deficits in myositis patients despite normal manual muscle testing scores

David R Amici  1 , Iago Pinal-Fernandez  1 , Ruben Pagkatipunan  2 , Albert Mears  2 , Rebecca de Lorenzo  1 , Eleni Tiniakou  2 , Jemima Albayda  2 , Julie J Paik  2 , Thomas E Lloyd  2 , Lisa Christopher-Stine  2 , Andrew L Mammen  1   2 , Tae Chung  2
Affiliations

Muscle endurance deficits in myositis patients despite normal manual muscle testing scores

David R Amici et al. Muscle Nerve. 2019 Jan.

Abstract

Introduction: It is unclear whether quantitating muscle endurance adds nonredundant information useful for the care of patients with muscular disease.

Methods: Records were retrospectively reviewed for all Johns Hopkins Myositis Center patients with a muscle endurance assessment (n = 128, 226 patient-visits). Muscle endurance and strength were quantitated with the Myositis Functional Index-2 (FI2) and manual muscle testing (MMT), respectively.

Results: Composite FI2 muscle endurance scores were comparable in inclusion body myositis (n = 58), dermatomyositis (n = 31), and polymyositis (n = 39). Overall, muscle endurance correlated with and evolved similarly to strength, inversely to serum creatine kinase. However, in patients with normal or near-normal strength (mean MMT > 9.75/10), muscle endurance was typically abnormal and highly variable (mean FI2, 5.6/10; interquartile range, 3.3-7.8/10).

Discussion: Muscle endurance testing may identify muscle impairment inadequately described by MMT, particularly in patients with high MMT scores. Muscle Nerve 59:70-75, 2019.

Keywords: functional index; muscle strength; myositis; neuromuscular diseases; physical endurance.

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Conflict of interest statement

Disclosures of Conflicts of Interest: None of the authors has any conflict of interest to disclose.

Figures

Figure 1
Figure 1
Distribution of individual and composite Functional Index-2 (FI2) endurance scores in dermatomyositis (DM; =31), polymyositis (PM; n=39), and inclusion body myositis (IBM; n=58). Data represented as a box-and-whisker plot, with boxes, whiskers, and single points demonstrating quartiles, upper and lower bounds, and outliers, respectively.
Figure 2
Figure 2
Composite Functional Index-2 (FI2) endurance and manual muscle testing (MMT) strength scores in myositis patients, and the association between FI2 and MMT. FI2 performance was comparable between groups, although inclusion body myositis (IBM; n=58) patients had lower MMT scores than dermatomyositis (DM; n=31) and polymyositis (PM; n-39) patients (mean MMT± SEM , 8.4± 0.1 vs. 9.5± 0.1 and 9.4±0.1, P<0.01). Positive linear correlations were observed between FI2 and MMT (r=0.43), although the correlation was weaker in patients with MMT scores greater than 9 (r=0.25).
Figure 3
Figure 3
Manual muscle testing (MMT) and Functional Index-2 (FI2) scores evolved similarly over time, inversely to serum CK levels. Locally-weighted regression was performed on data from all myositis patients (n=128, 226 patient-visits).
Figure 4
Figure 4
The evolution of strength, serum creatine kinase (CK), and Functional Index-2 (FI2) scores in a dermatomyositis patient with high baseline muscle strength. CK levels and FI2 evolved in an inverse pattern, with manual muscle testing (MMT) remaining at a “ceiling” score of 10. This patient complained of worsened muscle weakness and rash at month 7.
Figure 5
Figure 5
The shoulder abduction-hip flexion subscore has a broad linear range and is strongly associated with the overall Functional Index-2 (FI2) score. Data are demonstrated as a scatterplot and a Bland-Altman plot demonstrating high correlation and agreement (respectively) between the subscore and overall FI2 score.
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References

    1. Dalakas MC. Inflammatory Muscle Diseases. N Engl J Med 2015;373:393–394. - PubMed
    1. Alexanderson H, Broman L, Tollback A, Josefson A, Lundberg IE, Stenstrom CH. Functional index-2: Validity and reliability of a disease-specific measure of impairment in patients with polymyositis and dermatomyositis. Arthritis Rheum 2006;55:114–122. - PubMed
    1. Alexanderson H, Regardt M, Ottosson C, Alemo Munters L, Dastmalchi M, Dani L, Lundberg IE. Muscle Strength and Muscle Endurance During the First Year of Treatment of Polymyositis and Dermatomyositis: A Prospective Study. J Rheumatol 2018;45:538–546 - PubMed
    1. Hanaoka BY, Cleary LC, Long DE, Srinivas A, Jenkins KA, Bush HM, Starnes CP, Rutledge M, Duan J, Fan Q, Fraser N, Crofford LJ. Physical impairment in patients with idiopathic inflammatory myopathies is associated with the American College of Rheumatology functional status measure. Clin Rheumatol 2015;34:1929–1937. - PMC - PubMed
    1. Alexanderson H, Dastmalchi M, Esbjornsson-Liljedahl M, Opava CH, Lundberg IE. Benefits of intensive resistance training in patients with chronic polymyositis or dermatomyositis. Arthritis Rheum 2007;57:768–777. - PubMed

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