A quantitative analysis of pendular motion of the lower leg in spastic human subjects

Gravity-induced oscillations of the lower leg in normal and spastic subjects were examined with a view towards evaluating a clinical test of spasticity called the pendulum test. For passive limb motion (in which no reflex excitation occurred), a second-order linear model did not provide an adequate description of the motion for either spastic or normal legs. System equations including nonlinear mechanical properties simulating asymmetries in the swing and amplitude dependent variations in stiffness and damping provided a more accurate description. For spastic limb motion (in which reflex excitation did occur) accurate simulation required components accounting for abnormal reflex activation, coinciding with the time course of EMG activation. These included increased stiffness and damping with their gains related to reflex EMG magnitude, and changes in the rest length of the stiffness. Comparison of numerical with experimental data showed that the nonlinear model simulated the motion accurately, with the variance accounted for usually exceeding 90%.<<ETX>>

[1]  R WARTENBERG,et al.  Pendulousness of the Legs as a Diagnostic Test , 1951, Neurology.

[2]  D Burke,et al.  The quadriceps stretch reflex in human spasticity. , 1970, Journal of neurology, neurosurgery, and psychiatry.

[3]  D. Burke,et al.  The reflex response to sinusoidal stretching in spastic man. , 1971, Brain : a journal of neurology.

[4]  T. Bajd,et al.  A dynamic model of the ankle joint under functional electrical stimulation in free movement and isometric conditions. , 1976, Journal of biomechanics.

[5]  Wrist compliance [proceedings]. , 1979, The Journal of physiology.

[6]  James W. Lance,et al.  The control of muscle tone, reflexes, and movement , 1980, Neurology.

[7]  J. van den Berg,et al.  EMG to force processing I: An electrical analogue of the Hill muscle model. , 1981, Journal of biomechanics.

[8]  T Bajd,et al.  Testing and modelling of spasticity. , 1982, Journal of biomedical engineering.

[9]  P. Rack,et al.  Response of the normal human ankle joint to imposed sinusoidal movements. , 1983, The Journal of physiology.

[10]  M. Lakie,et al.  Resonance at the wrist demonstrated by the use of a torque motor: an instrumental analysis of muscle tone in man. , 1984, The Journal of physiology.

[11]  T. Bajd,et al.  Pendulum testing of spasticity. , 1984, Journal of biomedical engineering.

[12]  K H Mauritz,et al.  Chronic transformation of muscle in spasticity: a peripheral contribution to increased tone. , 1985, Journal of neurology, neurosurgery, and psychiatry.

[13]  J. Mansour,et al.  The passive elastic moment at the knee and its influence on human gait. , 1986, Journal of biomechanics.

[14]  W Z Rymer,et al.  Quantitative relations between hypertonia and stretch reflex threshold in spastic hemiparesis , 1988, Annals of neurology.

[15]  I W Hunter,et al.  Human ankle joint stiffness over the full range of muscle activation levels. , 1988, Journal of biomechanics.

[16]  R A Brown,et al.  Observations on the applicability of the Wartenberg pendulum test to healthy, elderly subjects. , 1988, Journal of neurology, neurosurgery, and psychiatry.

[17]  M Lakie,et al.  Thixotropy: stiffness recovery rate in relaxed frog muscle. , 1988, Quarterly journal of experimental physiology.

[18]  William H. Press,et al.  Numerical recipes , 1990 .