Joint angle variability in the time course of reaching movements.

OBJECTIVE

Investigating motor control processes is of primary interest in a number of scientific and practical fields. Movement variability is of increasing interest in this context. However, until now little has been known about the time course of variability during movement execution. The objective of this study was to investigate the influence of visual information and task specification on the variability of joint angle motion in reaching movements.

METHODS

Subjects repetitively reached for a handle. Movement variability was quantified by the within-subjects standard deviation of mean joint angle. The analysis focused on the time course of variability during movement execution.

RESULTS

The availability of visual information did not influence the time course of joint angle variability whereas task specification on reaching accuracy did. Under high accuracy demand variability was reduced more strongly after reaching its maximum.

CONCLUSIONS

Results suggest that the availability of visual information plays a minor role in the control of well-trained reaching movements. This suggests that proprioceptive information is the main feedback source to control these movements.

SIGNIFICANCE

The analysis of the time course of movement variability might be a valuable method to investigate the central or peripheral causes of movement disorders for diagnostic and rehabilitation purposes.