The effects of muscle fatigue on rapid finger oscillations.

Two types of model for the control of rapid finger oscillations can be contrasted. According to the first type, any change of muscle characteristics induced by sustained isometric contractions should result in kinematic changes. According to the second type, kinematic characteristics should remain invariant while the timing of bursts of muscle activity exhibits compensatory adjustments. Following sustained isometric contractions of finger flexors and extensors, we observed essentially unchanged durations of the flexion and extension components of rapid finger oscillations, while the pattern of inter-burst intervals was modified so as to compensate the changed phasing of electromyographic bursts. These findings strongly suggest that even in extremely simple rapid finger oscillations motor control is configured to result in invariant kinematics.