Surface and wire electromyographic. Recording during fatiguing exercise

Electromyographic (EMG) signals are routinely recorded during assessments of biomechanic activity for ergonomic and medical purposes. Surface and intramuscular electrodes (i.m.) are employed by different researchers and there is a continuing need to understand the indications for each. This research evaluated the reproducibility of the shift of the frequency content of the EMG signals during fatiguing exercise using simultaneous recording with these two electrode types. Using healthy adult volunteers, EMG recordings from the vastus lateralis (VL) and anterior tibial (AT) were made during repeated isokinetic exertions causing fatigue. The median power frequency (MPF) was calculated for a 0.5 sec sample of data taken during each concentric contraction. Test-retest, and multiple day repeat testing were performed to exclude the effects of training and fatigue upon the data. Surface electrode recordings demonstrated better reliability testing with values of 0.54 for VL and 0.68 for AT, while simultaneous i.m. recordings were -0.90 and 0.47, respectively. This finding of greater reliability, combined with the ease of use of surface electrodes suggest that they should be preferred for most studies of EMG analysis of muscle fatigue.