Abstract
The present study examined practice effects on the magnitude and structure of force variability using multiscale entropy analysis. Ten male participants (M age = 22.5 yr., SD = 1.7) produced unimanual isometric forces cycling between low levels of maximum voluntary contraction. The participants practiced the motor task over ten blocks: one block consisted of one self-paced recall trial immediately after nine audibly-synchronized practice trials with feedback of force output. Although the coefficient of variation of the force-time series in the recall trial had a greater magnitude than that in the practice, the recall trial had lower sample entropy values of force output (higher time structure of force variability). Multiscale entropy analysis did not find a practice effect on the time structure of force variability on a short time scale (10 msec.) but did on a long time scale (20–60 msec). Different tasks have different time scales of force output, and the task demands of the present experiment emphasized the long time scales.