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]

INTRODUCTION

The stretch reflex is one of the tools used in assessing neurophysiological changes over time. After a stretch of the ankle dorsiflexors, three distinct peaks (M1, M2, and M3) can be recognised in the EMG recorded from the Tibialis Anterior (TA) muscle. The first peak M1 reflects most probably the monosynaptic spinal reflex originating in the Ia afferents (Toft et al. 1989). The medium-latency response (M2) is mediated by afferent fibers with a slower conduction velocity; most likely spindle group II afferents (Schiepatti et al. 1997). The long-latency response (M3) is supposed to be - at least partly - mediated by a transcortical reflex. One of the evidences for this statement is shown by the facilitation that takes place in the PSTH of single TA motor units when the peaks evoked by transcranial magnetic stimulation (TMS) come at the same time as the M3 response (Petersen et al. 1998). TMS is a tool to study motor output in human subjects. The Motor Evoked Potentials (MEPs) are influenced by the excitablility of the motor cortex and the -motoneuronal pool (Rothwell 1997; Taylor et al. 1996).

In this study both changes in the size of each of the components of the stretch reflex and changes in the MEPs in participants performing a specific type of physical exercise (2 x 15 minutes balance training) are examined with the aim of finding a relation between this type of exercise and the occurring changes in the transmission that underlies the different pathways. Some evidence of a relationship between physical activity and the size of the monosynaptic H-reflex and the M1 component of the stretch reflex has already been presented (Casabona et al. 1990; Nielsen et al. 1993; Trimble and Koceja 1994), whereas it was also found that the M3 component was specifically increased in weightlifters (Mortimer and Webster (1983). Plastic changes in the motor systems of the spinal cord and cortex are also well documented from animal experiments (Wolpaw 1997; Nudo et al. 1997). Changes in the effect of TMS have also been demonstrated in relation to motor learning in human subjects (Cohen et al. 1998). For this study it was hypothesised that the required continuing attention of the participant to his or her balance would be reflected by a differential change in the size of the TA M3 component directly after the training session. In addition, it is expected that a differential change in M3 will be concomitant with a similar change in MEP.

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
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Last update: 11/02/00