Reaction time can be measured during voluntary contractions with electrode array.

Reaction time (RT) is classically divided into premotor time (PMT) and electromechanical delay (EMD). However, the determination of the onset of electromyographic activity (EMG) during voluntary contraction remains questionable. In addition, the reliability of RT, PMT and EMD needs to be determined. Twelve participants performed two sessions of RT trials, separated by 5 min. RT was evaluated during voluntary isometric contractions of the elbow flexors, i.e., time between a light signal (stimulus) and the onset of the mechanical response. To assess EMD, an electrode array (64 channels) was used to accurately detect the onset of EMG activity. PMT represented the major part of the RT (~88%). Coefficients of variation were reasonably satisfactory for all parameters (range: 11·9-13·4%). The use of electrode array appears to be a relevant method to measure EMD. Moreover, sessions based on two trials are reliable enough to detect changes in RT components.