Lower extremity peak force and gait kinematics in individuals with inclusion body myositis.

[inclusion body myositis]

Objective : To determine the relationship between peak isometric muscle force and temporal characteristics of gait in individuals with sporadic inclusion body myositis (s-IBM ). Patients and Methods : An observational study of 42 individuals with s-IBM (12 female ; age : 61 .6 ±7 .3 years [mean ±standard deviation ]; disease duration 8 .9 ±4 .3 years ) was conducted at a Federal hospital . Peak isometric force measurements for lower extremity (LE ) muscle groups were obtained using quantitative muscle testing . Temporal characteristics of gait during habitual and fast walking conditions were measured using a portable gait analysis system . Results : All observed muscle force values were significantly lower than predicted values (p <.001 ). During habitual walking , subjects ' gait speed and cadence were ≤ 83 % of normative literature values . During the fast walking , total gait cycle time was 133 % of normal , while gait speed and cadence were 58 % and 78 %, respectively , of normative literature values . Scaled LE peak muscle forces showed significant moderate correlations with the temporal gait variables . Weaker subjects demonstrated greater limitations in gait speed and cadence compared to stronger subjects (p <.05 ). Peak isometric force of the knee flexors and ankle plantar flexors , but not knee extensors , were significantly correlated with most temporal features of habitual gait . Conclusions : Muscle weakness associated with s-IBM disease activity may contribute to diminished gait kinematics . Temporal features of gait are not substantially influenced by knee extensor weakness alone , as the knee flexors and ankle plantar flexors play a compensatory role in maintaining the walking ability of individuals with s-IBM . © 2014 American College of Rheumatology .