CONSISTENCY OF SURFACE EMG PATTERNS OBTAINED DURING GAIT FROM 3 LABORATORIES USING STANDARDIZED MEASUREMENT TECHNIQUE

The paper investigates the consistency of EMG recordings of gait obtai ned in three different laboratories using a standardised measurement t echnique. Ensemble averaged surface EMG profiles were recorded in rect us femoris, semitendinosus, tibialis anterior, and gastrocnemius media lis muscles in a group of 20 normal subjects who walked at comfortable walking speed. Each subject was studied in three separate laboratorie s and the data were compared. Experimental protocols and electromyogra phic instrumentation were standardised, and functionally equivalent fo otswitch systems were used. Consistency of the shape of the subjects' profiles across laboratories was described using correlation coefficie nts. The signal magnitudes were compared using the coefficient of vari ation and mean value of profiles. The across-laboratory inter-subject variability was determined for peak, onset and cessation times of EMG activity, A marked similarity in the shape of profiles across laborato ries was found. Times of peak, onset and cessation of EMG activity wer e repeatable within few percent of the gait cycle. The absolute magnit ude of the profiles was less consistent. The results of this study sug gest that meaningful exchange of EMG data amongst laboratories for mul ti-centre trials and teleconsultation purposes is possible. The study underlines the value of EMG recording as a tool in gait analysis, It i s concluded that standardisation of instrumentation, experimental prot ocols and data processing techniques is strongly needed. (C) 1997 Else vier Science Ireland B.V.