Age differences and changes in midline-crossing inhibition in the lower extremities

The effects of crossing the body midline on the lower extremities of individuals 65 years of age and older was investigated. The subjects were 10 individuals 65-79 years of age, 10 individuals 80 years and older, and 10 individuals 20-35 years. The total testing phase consisted of 2 sets of 30 trials per leg on 2 days. The subjects performed trials that involved movements ipsilaterally, contralaterally, and directly in front of the anterior superior iliac crest of the leg being tested. Reaction time and movement time scores were recorded. Individuals 65 years of age and older were found to exhibit slower reaction times to movements in a contralateral direction when compared with movements made in the ipsilateral direction whereas individuals 80 years of age and older were also found to exhibit slower reaction times to movements in a contralateral direction when compared with movements made in the midline and ipsilateral direction. These findings indicate that the effects of midline-crossing inhibition on the lower extremities reemerge in individuals 65 years and older, whereas in early development this effect disappears by 8 or 9 years of age.