Search results for "H-reflex"
showing 10 items of 51 documents
Central Contribution to Electrically Induced Fatigue depends on Stimulation Frequency
2017
International audience; PURPOSE: This study analyzed the impact of several protocols of neuromuscular electrical stimulation (NMES), matched with a similar total torque-time integral, on muscle activation pathways and neuromuscular fatigue.METHODS: Ten young healthy participants (age: 24.6 +/- 4.2) performed 3 randomized NMES sessions on the triceps surae muscles with 20 Hz, 60 Hz or 100 Hz stimulation frequencies (pulse duration: 1 ms), with pulse amplitude (IES) set at 20 % of isometric maximal voluntary contraction (MVC). Muscle activity during NMES was assessed by means of the twitch, the soleus H-reflex and M wave responses evoked by single muscle stimulation at IES. Neuromuscular fati…
Effects of 10 weeks of military training on neuromuscular function in non-overreached and overreached conscripts
2018
The purpose of the study was to examine how military training influences neuromuscular function in non-overreached and overreached conscripts. A total of 24 male conscripts participated in the study (8 weeks basic training + 2 weeks specialized training). All measurements were conducted during weeks 1, 5, 8 and 10. After the training period, non-overreached (NOR, n = 16) and overreached (OR, n = 8) groups were compared. Isometric maximal forces (bench press, elbow flexion and knee extension), single twitch (plantar flexors), H-reflex, M-wave (Hmax/Mmax) and V-wave (V/Mmax) (soleus) were measured. In knee extension, force production increased in NOR by 22.5 ± 20.5% (p 0.01) between weeks 1 …
Corticospinal Modulations during Motor Imagery of Concentric, Eccentric, and Isometric Actions
2019
PURPOSE It is not known yet whether the neurophysiological specificity of eccentric, concentric, and isometric contractions can also be observed when these are mentally simulated. Therefore, our aim was to assess corticospinal excitability during motor imagery (MI) of different contraction types and to test whether a passive movement during MI could have additional effects. METHODS Twelve young participants imagined contractions of the wrist flexors, firstly with the arm motionless (static mode) and second, with a congruent passive movement (wrist extension during eccentric MI and wrist flexion during concentric MI). Motor-evoked potentials (MEP) and H-reflexes were elicited in flexor carpi…
Effect of angular velocity on soleus and medial gastrocnemius H-reflex during maximal concentric and eccentric muscle contraction.
2009
At rest, the H-reflex is lower during lengthening than shortening actions. During passive lengthening, both soleus (SOL) and medial gastrocnemius (MG) H-reflex amplitudes decrease with increasing angular velocity. This study was designed to investigate whether H-reflex amplitude is affected by angular velocity during concentric and eccentric maximal voluntary contraction (MVC). Experiments were performed on nine healthy men. At a constant angular velocity of 60 degrees /s and 20 degrees /s, maximal H-reflex and M-wave potentials were evoked at rest (i.e., H(max) and M(max), respectively) and during concentric and eccentric MVC (i.e., H(sup) and M(sup), respectively). Regardless of the muscl…
The Hoffmann reflex of human plantar foot muscles
1998
Electrical stimulation of the tibial nerve in the popliteal fossa evoked an M wave (10.9 ms) and a late reflex response (38.1 ms) in the plantar foot muscles of all 10 volunteers. The late response had a somewhat lower electrical threshold than the corresponding M wave (8.5 versus 9 mA), and reached a maximum of amplitude when the stimulus intensity was increased, but was strongly suppressed by further increased intensity. A more distal stimulation of the tibial nerve at the ankle shortened the onset latency of the M wave and lengthened that of the late response. The reflex was facilitated by activation of synergists and inhibited by activation of antagonists. We showed that the late respon…
Age dependency of neuromuscular function and dynamic balance control
2010
Abstract The purpose of the present study was to examine whether static and dynamic balance control are related to neuromuscular function and ageing. For this purpose, we constructed a new dynamic balance measurement system that simulates natural falling. Ten young (age 21–31 years) and 20 elderly (age 60–70 years) men participated in the experiment. Maximal isometric torque (MVC) and activation level were measured from the quadriceps and plantar flexor muscles. The H-reflex, V-wave, and maximal M-wave were measured from the soleus muscle. In dynamic balance control, anterior-posterior centre-of-pressure swaying was 74±8.1 mm in the young men and 91.5±19.4 mm in the elderly men (P<0.05), wh…
Modulation of H-reflex and V-wave responses during dynamic balance perturbations
2023
AbstractMotoneuron excitability is possible to measure using H-reflex and V-wave responses. However, it is not known how the motor control is organized, how the H-reflex and V-wave responses modulate and how repeatable these are during dynamic balance perturbations. To assess the repeatability, 16 participants (8 men, 8 women) went through two, identical measurement sessions with ~ 48 h intervals, where maximal isometric plantar flexion (IMVC) and dynamic balance perturbations in horizontal, anterior–posterior direction were performed. Soleus muscle (SOL) neural modulation during balance perturbations were measured at 40, 70, 100 and 130 ms after ankle movement by using both H-reflex and V-…
Soleus and lateral gastrocnemius H-reflexes during standing with unstable footwear
2015
Introduction: Unstable footwear has been shown to increase lower extremity muscle activity, but the reflex response to perturbations induced by this intervention is unknown. Methods: Twenty healthy subjects stood in stable and unstable footwear conditions (presented randomly) while H-reflex amplitude and background muscle activity were measured in the soleus and lateral gastrocnemius (LG) muscles. Results: Wearing unstable footwear resulted in larger H-reflexes (normalized to the maximal M-wave) for the LG (+12%; P = 0.025), but not for the soleus (+4%; P > 0.05). Background activity of both muscles was significantly higher in the unstable condition. Conclusions: The H-reflex facilitation o…
Spinal and supraspinal mechanisms affecting torque development at different joint angles
2015
INTRODUCTION We examined the neural mechanisms responsible for plantar flexion torque changes at different joint positions. METHODS Nine subjects performed maximal voluntary contractions (MVC) at 6 ankle-knee angle combinations [3 ankle angles (dorsiflexion, anatomic position, plantar flexion) and 2 knee angles (flexion, full extension)]. Neural mechanisms were determined by V-wave, H-reflex (at rest and during MVC), and electromyography during MVC (RMS), normalized to the muscle compound action potential (V/Msup, Hmax/Mmax, Hsup Msup and RMS/Msup) and voluntary activation (VA), while muscle function was assessed by doublet amplitude. RESULTS MVC and doublet amplitude were significantly low…
Neurophysiological Changes After Paired Brain and Spinal Cord Stimulation Coupled With Locomotor Training in Human Spinal Cord Injury
2021
Neurophysiological changes that involve activity-dependent neuroplasticity mechanisms via repeated stimulation and locomotor training are not commonly employed in research even though combination of interventions is a common clinical practice. In this randomized clinical trial, we established neurophysiological changes when transcranial magnetic stimulation (TMS) of the motor cortex was paired with transcutaneous thoracolumbar spinal (transspinal) stimulation in human spinal cord injury (SCI) delivered during locomotor training. We hypothesized that TMS delivered before transspinal (TMS-transspinal) stimulation promotes functional reorganization of spinal networks during stepping. In this p…