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Differences in H-reflex between athletes trained for explosive contractions and non-trained subjects
A Casabona1, M C Polizzi, V Perciavalle
1Institute of Human Physiology, University of Catania, Italy.
Summary
Athletes in explosive sports show a reduced Hmax: Mmax ratio, indicating fewer small alpha-motoneurons in their soleus and gastrocnemius muscles. This suggests training may alter motoneuron type for enhanced power output.
Area of Science:
- Neuroscience
- Exercise Physiology
- Motor Control
Background:
- The H-reflex technique assesses the excitability of alpha-motoneurons, particularly smaller ones.
- Explosive athletic training demands rapid, intense muscle contractions.
Purpose of the Study:
- To investigate the efficacy of type Ia synapse on alpha-motoneurons in sprinters and volleyball players compared to untrained individuals.
- To determine if explosive training influences motoneuron pool composition.
Main Methods:
- Utilized the H-reflex technique to measure maximal reflex response (Hmax) and maximal direct response (Mmax) via tibial nerve stimulation.
- Compared Hmax: Mmax ratios in soleus and lateral gastrocnemius muscles between trained athletes and untrained subjects.
Main Results:
- Athletes exhibited a significantly smaller Hmax: Mmax ratio, primarily due to reduced Hmax amplitude.
- No significant differences in Mmax amplitude were observed between groups.
- Soleus and lateral gastrocnemius muscles showed group differences in Hmax: Mmax ratio and Mmax, but not Hmax amplitude.
Conclusions:
- The reduced Hmax: Mmax ratio in athletes suggests a lower incidence of small alpha-motoneurons.
- This finding aligns with the mechanical demands of explosive power training.
- Explosive training may induce a transformation of slow, small motoneurons into fast, large ones, or be genetically influenced.