title: Non-monotonicity on a spatio-temporally defined cyclic task: evidence of two movement types?
abstract: We tested 23 healthy participants who performed rhythmic horizontal movements of the elbow. The required amplitude and frequency ranges of the movements were specified to the participants using a closed shape on a phase-plane display, showing angular velocity versus angular position, such that participants had to continuously control both the speed and the displacement of their forearm. We found that the combined accuracy in velocity and position throughout the movement was not a monotonic function of movement speed. Our findings suggest that specific combinations of required movement frequency and amplitude give rise to two distinct types of movements: one of a more rhythmic nature, and the other of a more discrete nature.
authors.affiliation: Massachusetts Institute of Technology, 77 Massachusetts, Ave office 3-137, Cambridge, MA 02139, USA.
authors.forename: S
authors.initials: S
authors.lastname: Levy-Tzedek
authors.forename: Hermano Igo
authors.initials: HI
authors.lastname: Krebs
authors.forename: D
authors.initials: D
authors.lastname: Song
authors.forename: N
authors.initials: N
authors.lastname: Hogan
authors.forename: H
authors.initials: H
authors.lastname: Poizner
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D004550:Elbow / Q000502:physiology*; D005260:Female; D005542:Forearm / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009043:Motor Activity / Q000502:physiology*; D010507:Periodicity; D013997:Time Factors; D055815:Young Adult