Robotic assessment of the influence of age on upper-limb sensorimotor function

PURPOSE This paper examines the influence of age on several attributes of sensorimotor performance while performing a reaching task. Our hypothesis, based on previous studies, is that aged persons will show differences in one or more of the attributes of sensorimotor performance. PATIENTS AND METHODS Fifty-one subjects (aged 20-80 years) with no known neuromotor disorders of the upper limbs participated in the study. Subjects were asked to grasp the end-effector of a pneumatic robotic device with two degrees of freedom in order to reach peripheral targets (1.0 cm radius), "quickly and accurately", from a centrally located target (1.0 cm radius). Subjects began each trial by holding the hand within the central target for 2000 milliseconds. Afterwards, a peripheral target was illuminated. Then participants were given 3000 milliseconds to complete the movement. When a target was reached, the participant had to return to the central target in order to start a new trial. A total of 64 trials were completed and each peripheral target was illuminated in a random block design. RESULTS SUBJECTS WERE DIVIDED INTO THREE GROUPS ACCORDING TO AGE: group 1 (age 20-40 years), group 2 (age 41-60 years), and group 3 (age 61-80 years). The Kruskal-Wallis test showed significant differences (P < 0.05) between groups, except for the variables postural speed in the dominant arm, and postural speed and initial deviation in the non-dominant arm (P > 0.05). These results suggest that age introduces significant differences in upper-limb motor function. CONCLUSION Our findings show that there are objective differences in sensorimotor function due to age, and that these differences are greater for the dominant arm. Therefore for the assessment of upper-limb function, we should take into account the influence of age. Moreover, these results suggest that robotic systems can provide a new and effective approach in the assessment of sensorimotor function.