Johan Van Doornik⁽¹⁾, Dimitris Patikas⁽²⁾, Daniel Olivier⁽³⁾, Gabriella Cerri⁽⁴⁾, Michel Ladouceur⁽⁵⁾, Jens Bo Nielsen⁽⁶⁾, Thomas Sinkjaer^(7)
(1)Centre for Sensory-Motor Interaction - Aalborg. Denmark
⁽²⁾Aristotle University of Thessaloniki - Thessaloniki. Greece
⁽⁵⁾Dept. of Medical Informatics and Image Analysis. Center for Sensory-Motor Interaction (SMI). Institute of Electronic Systems, Aalborg University - Aalborg O. Denmark
⁽⁷⁾Center for Sensory Motor Interaction. Aalborg University - Aalborg. Denmark

	[Neuroscience]	[Physiology]	[Neurology]	[Physical Therapeutics & Rehabilitation]

METHODS

Stretch reflex

The participants were seated in an adjustable chair. The right foot was strapped to a foot plate attached to a DC motor. A DC amplifier (Bruel and Kjær, Model 2708) powered the DC motor. The axis of rotation of the ankle joint and the foot plate were the same. The rotational velocity was controlled by a personal computer. The ankle torque was measured using strain gauges mounted on the connecting beam between the foot plate and the motor. The ankle angle was measured with a potentiometer.

A preliminary experiment consisting of establishing the optimal rotational velocity to measure the M3 component was effectuated. The effect of the stretch velocity on the amplitude of the stretch reflex components was investigated on four different participants. The subjects were asked to maintain a constant level of precontraction in the ankle dorsiflexors (5-10 Nm). The stretch reflex was recorded with 6 different velocities (12, 16, 25, 50, 85, 140 deg/s) and averaged over 40 times (after filtering as described above). The processed TA EMGs were then manually examined for the M1, M2 and M3 peaks. The amplitude was measured in relation to the background EMG level (50 ms average before stretch onset). In the balance training experiments the rotational velocity was set to 50 deg/s.

Transcranial magnetic stimulation

The transcranial magnetic stimulation was done with a Dantec Lite R-25 stimulator. The stimulus strength was manually adjustable on a scale from 0 to 100. A circular coil (Dantec NMC 140; Æ 70 mm) was used in order to elicit MEPs in both the TA and Soleus muscle. The peak-to-peak value of the short latency MEP as a function of the stimulus intensity was established for stimuli intensity ranging from 20% to 100% of maximal stimulator output. The data points were fitted with a Boltzmann sigmoidal curve. This was done by an iterative process, which minimised the sum of the squared errors (Prism, GraphPad Software Inc.).

Data acquisition

The TA and SOL electromyograms (EMG) were recorded with bipolar surface electrodes at a sample frequency of 2 kHz, after they were band pass filtered between 20 Hz and 1 kHz. The raw data was then rectified and low pass filtered with a 2nd order Butterworth filter at 20 Hz. The ankle torque and ankle angle were recorded with a sample frequency of 1 kHz.

Protocol

The effect of balance training on the stretch reflex and MEP was investigated in six different participants. They where asked to perform two sessions of 15 minutes balance training on a balance board used for rehabilitation, consisting of a bottom half sphere under a circular wooden plate. During the sessions the participants were encouraged to keep standing, but no clues where given regarding the technique. The number of errors where counted to monitor the learning process. The TA stretch reflex and MEP input-output curve were recorded before and immediately after balance training.

Discussion Board

Any Comment to this presentation?

[ABSTRACT] [INTRODUCTION] [METHODS] [RESULTS] [FIGURES] [CONCLUSION & DISCUSSION] [REFERENCES] [Discussion Board]

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	[Neuroscience]	[Physiology]	[Neurology]	[Physical Therapeutics & Rehabilitation]

Johan Van Doornik, Dimitris Patikas, Daniel Olivier, Gabriella Cerri, Michel Ladouceur, Jens Bo Nielsen, Thomas Sinkjaer
Copyright © 1999-2000. All rights reserved.

Last update: 11/02/00