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

Abstract

Objective: To determine the relationship between peak isometric muscle force and temporal characteristics of gait in individuals with sporadic inclusion body myositis (s-IBM).

Methods: An observational study of 42 individuals with s-IBM (12 women; mean ± SD age 61.8 ± 7.3 years and mean ± SD 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 ≤ 0.001). During habitual walking, the subjects' gait speed and cadence were ≤83% of normative literature values. During fast walking, total gait cycle time was 133% of normal, while gait speed and cadence were 58% and 78% of normative literature values, respectively. Scaled LE peak muscle forces showed significant moderate correlations with temporal gait variables. Weaker subjects had greater limitations in gait speed and cadence compared with stronger subjects (P < 0.05). Peak isometric force of the knee flexors and ankle plantar flexors was significantly correlated with most temporal features of habitual gait.

Conclusion: Muscle weakness associated with s-IBM disease activity may contribute to diminished gait kinematics. Temporal features of gait were not substantially influenced by knee extensor weakness alone, considering the knee flexors and ankle plantar flexors played a compensatory role in maintaining the walking ability of individuals with s-IBM.

Trial registration: ClinicalTrials.gov NCT00030212.

Copyright © 2015 by the American College of Rheumatology.

Figures

Figure 1

Peak isometric force for lower extremity muscle groups in our sample of individuals with inclusion body myositis (n = 42) expressed as a proportion of literature-based normative values (1.00). Error bars represent ±2 standard deviations. All differences between the cohort and normative values are statistically significant (p < .001; Mann–Whitney U test).

Figure 2

Temporal characteristics of gait in our sample of individuals with inclusion body myositis (n = 42) during gait at habitual walking speed and fast walking speed, expressed as a proportion of published literature values (1.00). Error bars represent ±2 standard deviations.