Post-activation depression of primary afferents reevaluated in humans

• Published in: Journal of electromyography and kinesiology Vol. 54; p. 102460
• Main Authors: Özyurt, Mustafa Görkem, Topkara, Betilay, Şenocak, Beatrice Selen, Budan, Abdullah Salih, Yüce, Murat Necdet, Türker, Kemal Sitki
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2020
• Subjects: Adult; Electrical stimulation; Electromyogram; H-Reflex; Humans; Motor control; Muscle Contraction; Muscle, Skeletal - physiology; Neural Inhibition; Neurons, Afferent - physiology; Soleus muscle; Tibial Nerve - physiology; Electrical stimulation; Electromyogram; Soleus muscle; H-reflex; Motor control
• ISSN: 1050-6411; 1873-5711
• DOI: 10.1016/j.jelekin.2020.102460

Amplitude variation of Hoffmann Reflex (H-reflex) was used as a tool to investigate many neuronal networks. However, H-reflex itself is a subject to intrinsic changes including post-activation depression (P-AD). We aimed to investigate P-AD and its implication on motor control in humans. Upon tibial nerve stimulation in 23 healthy participants, peak-to-peak amplitude change of H-reflex was investigated using surface electromyography (SEMG) of soleus muscle. Variety of stimulus intensities, interstimulus intervals (ISIs), voluntary contraction levels/types and force recording were used to investigate the nature of P-AD. We have shown that P-AD was significantly stronger in the shorter ISIs. The only exception was the ISI of 200 msecs which had a weaker P-AD than some of the longer ISIs. Sudden muscle relaxation, on the other hand, further increased the effectiveness of the ongoing P-AD. Moreover, P-AD displayed its full effect with the first stimulus when there was no muscle contraction and was efficient to reduce the muscle force output by about 30%. These findings provide insight about the variations and mechanism of P-AD and could lead to improvements in diagnostic tools in neurological diseases.