What is the optimal repetition number in electromyographic reaction time studies?

Background. To find out how many trials of electromyographic reaction time measurements are needed for reliable interpretation. Methods. The electromyographic reaction time values were obtained by surface electromyography from the flexor digitorum superficialis muscle of the 20 healthy volunteers. After five practice trials, the measurements were repeated 20 times. The differences between the 20 reaction time measurements were analyzed to find out the optimal repetition number of reaction time trials. Findings. The electromyographic reaction time values decreased upon repetition. The first consecutive five records were significantly longer than the second, third and fourth consecutive five records. However no difference was found among second, third and fourth consecutive five records. Interpretation. The results of our study indicate that before 15 test trials, 10 practice trials are needed for learning in simple electromyographic reaction time studies that use similar testing conditions with our study. However this conclusion needs verification with a study using a larger group of subjects.