THE RELIABILITY OF MUSCLE FUNCTION-ANALYSIS USING DIFFERENT METHODS OF STIMULATION

Background: The purpose of our study was to determine the reliability of nonvolitional muscle function analysis (MFA) by determining the day -to-day and within-day reliability of conventional electrical stimulat ion and a newer, magneto-electrical stimulation method, using standard laboratory methodology. Methods: Ten healthy, human immunodeficiency virus-negative adult men volunteered as subjects. MFA consisted of mea suring the maximal relaxation rate, for magneto-electrical stimulation at 1 Hz and conventional electrical stimulation at 20 Hz, and force-f requency ratios using conventional electrical stimulation at 10 Hz:20 Hz and 10 Hz:50 Hz. Within-day and day-to-day reliability were determi ned by calculating the coefficient of variation (CV) for all subjects. Results: Maximal relaxation rate using magnetoelectrical stimulation had a significantly lower CV compared with the other nonvolitional MFA methods (P = .002). Conclusions: Maximal relaxation rate using magnet o-electrical stimulation was more reliable and technically easier than the other muscle function parameters examined. However, the day-to-da y CV of muscle function parameters is larger than traditional nutritio n assessment techniques. Development within the field should strive to improve testing techniques so that the reliability of MFA will allow definition of a range of normal values against which an individual's v alue can be compared. Until this is available, the precision and relia bility of MFA restrict its use to research and population studies.