Long latency reflex regulation in human ballistic movement

Step torque perturbations were applied to adduct the index during either a 25° ballistic or a 25° slow abduction movement. Subjects were instructed to react as quickly and as forcefully as possible in the opposite direction to the perturbation. The resulting long latency reflex (LLR) EMG activity was studied in the first dorsal interosseus. The LLR measured when the perturbation occurred in the first part of the movement was not different in a ballistic movement than a ramp movement. In our experiments, the LLR was the same in the first as well as in the second part of a ballistic movement. The LLR observed when the perturbation was applied at the onset of the agonist EMG burst (before the onset of a ballistic movement) was either similar or reduced when recorded during the ballistic movement.