• Brian Korsholm Flaskager
  • Lars Tønners Nørgaard
  • Steffen Vangsgaard
The aim of this study was 1) to test the reproducibility of the H reflex across consecutive days and 2) to investigate the effect on the H reflex immediately after eccentric exercise and during delayed-onset muscle soreness (DOMS) (24h after eccentric exercise).
H reflexes were recorded from subjects' (n=10) dominant middle trapezius muscle by electrical stimulation of the C3/4 cervical nerve. DOMS was induced by eccentric exercise of the shoulder joint in an experimental setting. H reflexes were obtained in four sessions: ``24h before'', ``Pre'', ``Post'', and ``24h after'' eccentric exercise. Ratios of maximal H reflex and M wave responses (Hmax/Mmax) were compared between sessions. Additionally, ratios of H reflex amplitudes obtained from 75% and 50% of stimulus intensity needed to obtain Hmax in the session 24h before eccentric exercise (H75/Mmax, and H50/Mmax) were also compared between sessions.
Results obtained from sessions before eccentric exercise showed no change in ratios. A decrease in H50/Mmax ratios was found immediately after eccentric exercise (P<0.05). The presence of DOMS 24h after eccentric exercise resulted in a decrease in H75/Mmax and H50/Mmax ratios (P<0.05).

This study presents evidence that comparison of baseline measures showed acceptable reproducibility of the H reflex with the study's experimental design. Furthermore, stronger stimulus intensity was needed immediately after and 24h after exercise to reach the same magnitude of the H reflex. This modulation of the stimulus-response relationship may be caused by presynaptic inhibition of Ia afferent fibres' input to the motoneuron by group III and IV afferent fibres.
Publication date1 Jun 2011
Number of pages128


ID: 52690389