Project: Research project

Project Details


There are three distinct parts in the project. First, we are going to
test the experimental basis of the equilibrium-point hypothesis and to
compare some of the predictions of the hypothesis with experimental
observations. In particular, the reproducibility of performance of
subjects during different single-joint motor tasks requiring "not to
intervene voluntarily" will be studied, the performance under
instructions "not to intervene" and "to intervene" will be compared,
electromyograms during perturbed single-joint movements will be
theoretically predicted and compared with experimental observations.

The second part of the project will be based on a new method, recently
designed in our laboratory, which enables reconstruction of joint
compliant characteristics and central control variable changes ("virtual
trajectories") during single-joint movements. The method will be used
for analysis of discrete single-joint movements and oscillatory movements
against different loads. Reconstructed patterns of control variables
will be compared with those predicted from the equilibrium-point
hypothesis. Two hypotheses will be tested: 1). Joint stiffness changes
are directed towards minimizing the difference between movement frequency
and limb natural frequency; and 2) At the limb natural frequency, the
virtual trajectory will have minimal peak-to-peak changes while the
electromyograms of the major muscle groups will change monotonically with

During the third part of the project, we plan to study virtual
trajectories of multi-joint movements. In particular, we will be
interested in compliant properties of the working point and individual
joints and in compensation of errors created in one of the joints by
corrections in other joints. The major hypothesis to be, tested is: The
control variable for multi-joint movements is three-dimensional
compliance of the working point.

Experiments will be performed in which the subjects will learn a standard
movement against a constant external load. Then, they will be required
to reproduce the learned motor program while changes in the external load
will occur in some of the trials. The subjects will be instructed "to
reproduce the same time pattern of motor command while ignoring possible
external load changes". Kinematic and dynamic parameters of the
movements will be recorded. Electromyograms of major muscle groups will
be recorded as well.
Effective start/end date8/1/927/31/93


  • Eunice Kennedy Shriver National Institute of Child Health and Human Development

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