Article

In therapy after stroke, intensive and repetitive training is crucial for
relearning of motor abilities and functionalities. Besides conventional therapy,
rehabilitation robotic systems are used in the treatment, where a minimum jerk
model is used widely in the formation of the point-to-point movement trajectory,
which is not necessarily the appropriate choice for hemiparetic upper extremity
training. This paper examines and analyzes the influence of a selected form of a
flexor muscle tightness on trajectory formation and proposes a guidance scheme
that yields minimum effort in robot-assisted arm reaching movement. A dynamic
upper extremity model with the three clinically most relevant muscles that
develop tightness because of spasticity after stroke was used in the optimization
study that examined key features of trajectory formation. The results showed that
the trajectories and their velocity profiles become significantly different in
the presence of muscle tightness. On the basis of dynamic optimization results,
we experimentally examined selected trajectories in a selected individual with
chronic hemiparesis. The experimental results confirmed the importance of
appropriate selection of reaching trajectories' velocity profiles. The results of
optimization and experimentation showed the importance of the velocity profile of
the robot-based guidance scheme, which has an influence on the necessary invested
'effort' between starting/ending points to overcome muscle tightness. This study
showed that muscle tightness exerts a significant influence on trajectory
formation as well as on its velocity profile. The proposed innovative guidance
scheme might be useful for practical arm reaching robot-supported movement
training in the clinical environment. We suggested that for each hemiparetic
patient, the initial identification session before training should experimentally
determine the 'optimal' parameters for the rehabilitation guidance scheme that
would optimally match the particular muscle tightness constraints.

Langue : ANGLAIS