Control strategies for the transition from multijoint to single-joint arm movements studied using a simple mechanical constraint. J Neurophysiol 2000 Jan;83(1):1-12
Date
01/15/2000Pubmed ID
10634848DOI
10.1152/jn.2000.83.1.1aScopus ID
2-s2.0-0033988781 (requires institutional sign-in at Scopus site) 21 CitationsAbstract
Changes were studied in neuromotor control that were evoked by constraining the motion of the elbow joint during planar, supported movements of the dominant arm in eight normal human subjects. Electromyograph (EMG) recordings from shoulder and arm muscles were used to determine whether the normal multijoint muscle activity patterns associated with reaching to a visual target were modified when the movement was reduced to a single-joint task, by pinning the elbow to a particular location in the planar work space. Three blocks of 150 movements each were used in the experiments. Subjects were presented with the unconstrained task in the first and third blocks with an intervening block of constrained trials. Kinematic, dynamic, and EMG measures of performance were compared across blocks. The imposition of the pin constraint caused predictable changes in kinematic performance, in that near-linear motions of the hand became curved. This was followed by changes in limb dynamic performance at the elbow. However, changes in EMG activity at the shoulder lagged the kinematic changes substantially (by about 15 trials). The gradual character of the changes in EMG timing does not support a primary role for segmental reflex action in mediating the transition between multijoint and single-joint control strategies. Furthermore, the scope and magnitude of these changes argues against the notion that human motor performance is driven by the optimization of muscle- or joint-related criteria alone. The findings are best described as reflecting the actions of a feedforward adaptive controller that has properties that are modified progressively according to the environmental state.
Author List
Scheidt RA, Rymer WZAuthor
Robert Scheidt BS,MS,PhD Associate Professor in the Biomedical Engineering department at Marquette UniversityMESH terms used to index this publication - Major topics in bold
AdultArm
Biomechanical Phenomena
Electromyography
Female
Humans
Joints
Male
Motor Activity
Movement
Muscle, Skeletal
Psychomotor Performance
Restraint, Physical