Observations on the variability of the H reflex in human soleus

• Published in: Muscle & nerve 1999-03, Vol.22 (3), p.341-346
• Main Authors: Funase, Kozo, Miles, Timothy S.
• Format: Article
• Language: English
• Subjects: Adult; Ankle; Biological and medical sciences; Electric Stimulation; Electromyography; excitability; Fundamental and applied biological sciences. Psychology; H-Reflex - physiology; Humans; Isometric Contraction - physiology; Middle Aged; motoneurons; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Muscle, Skeletal - physiology; synaptic potential; Tibial Nerve - physiology; Torque; Vertebrates: nervous system and sense organs
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/(SICI)1097-4598(199903)22:3<341::AID-MUS6>3.0.CO;2-R

H reflexes were evoked in human soleus by stimulating the tibial nerve at a constant intensity. Each trial was then assigned to one of three groups on the basis of the amplitude of its H reflex; all trials in each group were then full‐wave rectified and reaveraged. There was a strong positive relationship between the amplitude of the H reflex and the level of electromyographic activity in the muscle at the time of onset of the H reflex, which reflects the activity of the motoneuronal pool when the afferent volley arrived. Thus, much of the variability of the H reflex is due to small changes in the level of activation of the motoneuronal pool during repeated trials. The steady torque preceding the H reflex was a poor predictor of the H‐reflex amplitude, presumably because of the delay between the changes in the electrical activity of motoneurons and the mechanical outcome thereof. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 341–346, 1999