european college of sport science

PP-PH17 Physiology 17
that one pathway able to modulate H-reflex could originate from group III and IV afferent fiber activation. For the first time, we have
identified directly the effect of metabosensitive group III-IV muscle afferent fibers on H-reflex changes in animal quadriceps and tibialis
anterior muscles.
Methods: After identification of KCl doses able to elicit a maximal activation of group III and IV afferent fibers, we evoked consecutive Hreflexes
on rat quadriceps or tibialis anterior muscles. Consecutive maximal H-reflexes (inter-stimulus: 10 s) and, then, consecutive
evoked Mmax were elicited before and after intra-arterial KCl injections (0.5 mL). A capsaicin-treated group (suppression of thin muscle
afferent) followed the same procedures. The Hmax/Mmax ratio and the corresponding MHmax/Mmax ratio were measured.
Results: A peak discharge was found after KCl injection at the dose of 10mM (+3.27±0.47 Hz, 108.9±1.2 % of the corresponding reference
discharge). The Hmax/Mmax ratio was significantly attenuated after the KCl injection (-23.9±4.6% of the corresponding reference ratio,
p