Temporal firing sequences of antagonistic muscles

The purpose of this study was to assess the relationship between paired agonist/antagonist muscle firing times and accompanying time to peak EMG amplitudes with a 75 degree ballistic right forearm flexion task during experimental conditions of A) no external limb resistance, B) 3.1 Kg., and C) 9.8 Kg. of premovement limb resistance. In addition, total reaction time and movement time values were compared relative to the experimental conditions. Twelve male subjects practiced the flexion task for three days until criterion measures stabilized. Following five control measures on each of the next two days, 10 trials each of conditions A, B, C appearing in random order were administered. Results indicated that as external limb resistance increased (from A to B to C), movement time decreased by 30 msec., total reaction time increased by 52 msec., while biceps latency remained unchanged. There were significant (p less than0.05) increases in triceps latency, biceps and triceps time to peak EMG amplitude only with respect to the greatest external resistance (condition C). It is speculated that coordination may be defined in terms of the temporal firing sequences within an agonist/antagonist muscle group.