Surfaceelectromyography: Skin And Subcutaneous Fat Tissue Attenuate Amplitude And Frequency Parameters

The purpose of this study was to identify the attenuating influence on surface-EMG amplitude (IEMG) and mean power frequency (MPF) by skin and subcutaneous fat tissue. The electrode-muscle-distance (∆EM) of the left m. biceps brachii is determined by tissue thickness. This was established by ultrasound in 12 females and 15 males six times each during a 43-week period (n=162). IEMG and MPF were measured during isometric maximum voluntary contractions (MVC). ∆EM explained up to 31 % of the variance of EMG-amplitude during MVC, which corresponds to previous studies on submaximum and maximum contractions. MPF variation was explained by ∆EM with up to 16 % and requires further validation. These results are important for the assessment of long-term training studies and neuromuscular fatigue measurements. KEY WORDS: MVC, subcutaneous fat, surface EMG, ultrasound. INTRODUCTION: Amplitude and power spectrum of surface-EMG (sEMG) are commonly used to quantify neuromuscular activity and fatigue. Despite standardisation in measuring procedures and data analysis, inter-individual variations, in particular of amplitude, may be observed (Day, 2003). Petrofsky and Lind (1975) and Gandevia (2001) stated that sEM