Corticomuscular coherence after muscle fatigue

Functional correlation between two separated neural systems can be studied using coherence function. Coherence function is a frequency domain measurement of similarity and phase lock between two different signals. The aim of this study is to determine the changes in corticomuscular coherence after muscle fatigue during maximum voluntary contraction (MVC) and 50% of MVC of the tested muscle (right Adductor Pollicis muscles "APM"). Nine right- handed normal volunteers, four women and five men, whose age was 3512 years (SD) were studied. Maximum coherence values of (0.041) at 38 Hz. (in gamma band) were seen in non-fatigued MVC; and values of (0.042) at 32 Hz and 34 Hz. (in gamma band) for fatigued MVC of right APM were demonstrated. During 50% of MVC of right APM (in non-fatigued contraction), maximum coherence value of (0.044) at 26 Hz (beta band) is noted. In fatigued 50%MVC, maximum coherence value is seen at beta frequency band (0.048 at 14 Hz). These results have demonstrated the functional coupling between the motor cortex and the contracting muscle during fatigued muscular contraction. The pattern of maximum coherence values, which is related to EEG frequency bands, seen in non-fatigued muscular contraction is also demonstrated in fatigued muscular contraction.