Influence of isometric voluntary contraction on time and frequency domain parameters of surface EMG

The main objective of this paper was to investigate the effect of increase of isometric voluntary contraction (IVC) on surface EMG recorded from the Biceps Brachii (BB) muscle. Five different force levels (FL) were used: 10, 30, 50, 70 and 100% of maximum voluntary contraction (MVC), with each recording lasting 5 seconds. The following sets of parameters were extracted: (i) in the time domain (turns (ts) and zero crossings per second (zc)), and (ii) in the frequency domain (median frequency (fp), frequency at maximum power (fx), maximum power (Px), and total power (Pt)). A total of 91 normal subjects aged between 5 and 69 years old were analyzed. The Wilcoxon paired two-tailed test (p<0.05), was used to classify changes in parameters examined as significant (S) or non-significant (NS) during transition from a force level to another. Results showed that: ts, zc, Px, and Pt increase with force whereas fp decreases with force. Moreover, these parameters showed significant difference between the different force levels examined.