MEASUREMENT OF ISOMETRIC FORCE IN CHILDREN WITH AND WITHOUT DUCHENNES MUSCULAR-DYSTROPHY

The purpose of this study was to examine the consistency of measurements of maximal isometric force production in children using an electronic strain gauge. A standardized protocol of force testing from the Tufts Quantitative Neuromuscular Examination was adapted to obtain isometric force measurements in seven muscle groups bilaterally. Ten children with Duchenne's muscular dystrophy (DMD) and 10 age-matched children without DMD were recruited for the study. A generalizability framework was used to examine variations in measurements attributable to group differences, test occasions within the same day, and extremity side. Intertester reliability estimates were also completed on a subsample of children with and without DMD. A three-way analysis of variance between groups, sides, and test occasions demonstrated a significant group main effect for all muscle groups. In general, significant main effects were not present for side or test occasion. Test-retest intraclass correlation coefficients (ICCs) for all muscle groups ranged from .88 to .99 for the children with DMD and from .85 to .98 for the children without DMD. Intertester ICCs were slightly lower, ranging from .74 to .97 for the children with DMD and from .71 to .98 for the children without DMD. The results indicate that the electronic strain-gauge protocol produces reproducible force measurements in seven selected muscle groups in children with and without DMD.