ANALYSIS DURING FATIGUE - SURFACE AND FINE WIRE ELECTRODE COMPARISON

Fine wire (FW) intramuscular electrodes and spectral analysis have not previously been used to quantify metabolic muscle fatigue in deep mus cles not accessible with surface electrodes. This study compares initi al median frequency (IMF) and decline in median frequency with fatigue (SLOPE) using surface and FW electrodes. Eighteen men performed isome tric biceps contractions for 100 s. Electromyographic signals were col lected using FW and surface electrodes. The recordings of SLOPE was gr eater with FW (-0.44 v -0.23 %IMF/s) and IMF was higher (195 v 69 Hz). Intrasession reliability for slope was better with FW electrode (intr aclass correlation coefficient (ICC) = 0.74; P < 0.0001) than with the surface electrode (ICC = 0.43; P = 0.006), but intersession reliabili ty was best with the surface electrode (ICC 0.50; P = 0.03). Spectral analysis using FW electrodes provides earlier detection of muscle fati gue and can be used in deep muscles, but the reliability must be impro ved before clinical application.