Eccentric exercise inhibits the H reflex in the middle part of the trapezius muscle

Abstract

The objectives of this study were to (1) investigate the modulation of the H reflex immediately after and 24 h after eccentric exercise in the presence of delayed-onset muscle soreness (DOMS) and (2) test the reproducibility of the H reflex in trapezius across days. H reflexes were recorded from the dominant middle trapezius muscle by electrical stimulation of the C3/4 cervical nerve in ten healthy subjects. DOMS was induced by eccentric exercise of the dominant shoulder. H reflexes were obtained in four sessions: "24 h before", "Pre", "Post", and "24 h after" eccentric exercise. Ratios of maximal H reflex and M wave responses (H (max)/M (max)) were compared between sessions. In addition, a between session comparison was done for the ratios of H reflex amplitudes (H (i_75)/M (max), and H (i_50)/M (max)) obtained from the stimulus intensity needed to obtain 75 and 50 % of H (max) at "24 h before". No ratio changes were found when comparing "24 h before" and "Pre" recordings. A decrease in H (i_50)/M (max) was found at "Post" (P < 0.05) and decreases in both H (i_75)/M (max) and H (i_50)/M (max) were observed at "24 h after" (P < 0.05). This study presented evidence that an acceptable day-to-day reproducibility of the H reflex could be obtained with the applied experimental setup. Furthermore, immediately after and 24 h after exercise a stronger stimulus intensity was needed to reach the same magnitude of the H reflex reflecting that the recruitment curve was shifted to the right. This modulation of the stimulus-response relationship could be caused by presynaptic inhibition of Ia afferent fibres' input to the motoneuron by group III and IV afferents.

Eccentric exercise induces spatial changes in the mechanomyographic activity of the upper trapezius muscle

“…For instance, the pain intensity reported 24 hours after ECC has both been shown to increase and to remain constant. 18,24 In the present study, we found increased soreness intensity and soreness area at 24 hours after compared with before ECC in line with one of our previous studies. 8 Concerning the changes in maximal force, both decreased and unchanged maximal strengths during shoulder elevation have been reported.…”

“…Even for this muscle, the extent of changes in the assessed indirect biomarkers has been reported to fluctuate due to between‐subject variations in response to the same ECC protocol. For instance, the pain intensity reported 24 hours after ECC has both been shown to increase and to remain constant . In the present study, we found increased soreness intensity and soreness area at 24 hours after compared with before ECC in line with one of our previous studies .…”

Acute Strength Training Increases Responses to Stimulation of Corticospinal Axons

“…For the current findings, changes in excitability of spinal motoneurons cannot be ruled out. Previous studies, which have reported increases, decreases, or no change in H-reflexes after a single session of various types of training, have ascribed such findings to presynaptic mechanisms (i.e., altered presynaptic inhibition or homosynaptic postactivation depression of Ia afferents), rather than altered motoneuron excitability (17,22,34). Such processes, which change the level of facilitation from muscle spindle input to the motoneurons, are unlikely to influence the CMEP measured in a relaxed muscle, as in the current study.…”

Slope walking causes short-term changes in soleus H-reflex excitability

“…; Nottle and Nosaka ) that could have then affected walking and/or H‐reflexes on the other 2 days of testing (Vangsgaard et al. ). None of our participants had ever engaged in uninterrupted Ds treadmill walking as used in this study.…”

“…Upslope and Lv walking were randomized to days 1 and 2. Downslope walking was always reserved for day 3 because of the potential for delayed onset muscle soreness (Whitehead et al 2001;Farr et al 2002;Nottle and Nosaka 2005) that could have then affected walking and/ or H-reflexes on the other 2 days of testing (Vangsgaard et al 2013). None of our participants had ever engaged in uninterrupted Ds treadmill walking as used in this study.…”