Fractionated reaction times and performance times as a function of practice

The purpose of this study was to assess the effects of practice and its influence upon the onset of EMG firing for agonist and antagonist muscles associated with a 75 degree ballistic right forearm flexion task. In addition, the performance measures of reaction time and movement time were measured. Twelve females performed 2 bouts of 15 trials each on 3 practice days. Analysis of the data indicated that subjects improved their response performance as a function of reduced reaction time (in particular, biceps motor time values). Practice had no effect upon the onset of biceps, brachialis, or triceps EMG firing. The greatest intraindividual variability was found with the EMG latency associated with the antagonist muscle. Between individual variability was greatest with triceps latency and actual limb displacement (movement time). These results are discussed in terms of stored neuromotor memory programs and coordinated movement.