Neuromuscular adaptations induced by long-term motor skill training
von Robin Diedrichs
Datum der mündl. Prüfung:2018-10-11
Betreuer:Prof. Dr. Dario Farina
Gutachter:Prof. Dr. Ralf Heinrich
Gutachter:Prof. Dr. Dario Farina
EnglischThis thesis addresses the question of whether spinal cord’s monosynaptic circuitry can be altered due to long-term motor skill acquisition. We researched functional organization and skill-related adaptation in muscle spindle feedback distribution. In study 1 we examined reciprocal inhibition of lower limb’s extensor and flexor muscles and the underlying reflex arcs. After examining the interplay of lower limbs’ extensor and flexor muscles, we aimed to investigate the effects of long-term motor skill training in a group of martial artists (study 2) and Yoga practitioners (study 3), compared to moderately active control groups. We approach these effects by investigation of neural input of IA afferent fiber onto spinal cords motoneuron pool. Since several decades, resulting adaptations with regard to long-term motor skill acquisition are researched with intracellular recordings in model organisms and in humans. This brought up evidence to concept experiments with a non-invasive approach to analyze motor unit activity via H-reflex measurements. The technique of Hoffmann-reflex (H-reflex) allows standardized excitation of IA afferent fibers while analyzing large populations of motor units. The technique of high-density electromyography-recording and H-reflex gives opportunity to evaluate high counts of firing motoneurons. This gives us the opportunity to analyze their firing behavior. Within study 1 we found significant differences in lower limb’s extensor (M. soleus and M. gastrocnemius) and flexor (M. tibialis anterior) muscles’ reciprocal inhibitory reflex amplitudes. Our findings support the hypothesis that lower limb’s extensor and flexor muscle interplay is distributed asymmetrically; triceps surae muscles inhibit reflexes of M. tibialis anterior strongly. Furthermore we found significant differences in lower limb’s extensor muscles’ excitatory H-reflex amplitudes between groups of long-term trained martial artists and a moderately active control group (study 2). Our findings in a group of long-term trained yoga practitioners (study 3) were not significant, but indicate a trend with regard to neuromuscular and functional adaptations due to training experience.
Keywords: Neurorehabilitation; HDsEMG; Electromyography; H-reflex; Skill training