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1.
K. Funase K. Imanaka Y. Nishihira H. Araki 《European journal of applied physiology and occupational physiology》1994,69(1):21-25
In the present study, we investigated whether weak (10% of maximal voluntary contraction) tonic dorsiflexion (DF) and plantarflexion (PF) affects the two conventional parameters used for evaluating the excitability of the soleus motoneuron (MN) pool, i.e. the ratio of the threshold of H-reflex to that of M-response (Hth:Mth) and the ratio of the maximal amplitude of H-reflex to that of M-response (Hmax:Mmax) in human subjects. The results showed that the Hmax:Mmax decreased during DF and increased during PF compared with that during rest, whereas no clear alteration was observed in Hth:Mth. These results are consistent with the scheme proposed by earlier workers, who have argued that neither inhibitory nor facilitatory effects of the conditioning stimulus apply to specific spinal reflex circuits occurring around the threshold of the test H-reflex. It is suggested, therefore, that the conventional use of the Hth:Mth ratio as a parameter reflecting the excitability of the MN pool should be reconsidered. 相似文献
2.
Ronnie J.H. Wilmink Peter J. Slot Thomas Sinkjær 《Journal of computational neuroscience》1996,3(4):337-346
Healthy subjects were asked to make a voluntary ramp and hold contraction. The duration of the ramp stage was 500 ms, and the torque increment in this period was set to 15 Nm. The contraction was made from a relaxed and from a 5 Nm background torque situation. Hoffmann (H-) reflexes were elicited during the voluntary contraction, mostly with 100 ms intervals. These experiments showed an increase (facilitation) in the H-reflex before the torque or the EMG started to increase. This facilitation of the H-reflex remained during all the stages of the voluntary movement and declined to normal levels again only at the very end of the hold phase, which lasted for one second. This specific pattern of facilitation during a voluntary contraction was modeled using a modeling language, that is specifically designed to calculate neuronal systems with a high degree of reality (Ekeberg et al., 1991). Our model consisted of a motoneuron pool with 200 neurons connected to an EMG-model of the human soleus muscle and an extra group of higher-level neurons for controlling the amount of decrease of presynaptic inhibition. The model was used to simulate the observed modulation of the H-reflex with both a presynaptic and a postsynaptic mechanism. Simulations showed that a continuous change in the descending control signals is needed to make the model based on postsynaptic mechanism fit with the experimental data, whereas no extra control from the CNS over the excitatory drive to the motoneuron pool is needed when the decrease of presynaptic inhibition mechanism is applied. 相似文献
3.
David G. Behm Ashley Peach Meaghan Maddigan Saied Jalal Aboodarda Mario C. DiSanto Duane C. Button Nicola A. Maffiuletti 《Journal of electromyography and kinesiology》2013,23(5):1215-1221
Both stretching and massage can increase range of motion. Whereas the stretching-induced increases in ROM have been attributed to changes in neural and muscle responses, there is no literature investigating the ROM mechanisms underlying the interaction of stretch and massage. The objective of this paper was to evaluate changes in neural and evoked muscle responses with two types of massage and static stretching. With this repeated measures design, 30 s of plantar flexors musculotendinous junction (MTJ) and tapotement (TAP) massage were implemented either with or without 1 min of concurrent stretching as well as a control condition. Measures included the soleus maximum H-reflex/M-wave (H/M) ratio, as well as electromechanical delay (EMD), and evoked contractile properties of the triceps surae. With the exception of EMD, massage and stretch did not significantly alter triceps surae evoked contractile properties. Massage with and without stretching decreased the soleus H/M ratio. Both TAP conditions provided greater H/M ratio depression than MTJ massage while the addition of stretch provided the greatest inhibition. Both massage types when combined with stretching increased the duration of the EMD. In conclusion, MTJ and TAP massage as well as stretching decreased spinal reflex excitability, with TAP providing the strongest suppression. While static stretching prolongs EMD, massage did not affect contractile properties. 相似文献
4.
In this study we have investigated the effect of whole body vibration (WBV) on the tendon reflex (T-reflex) amplitude. Fifteen young adult healthy volunteer males were included in this study. Records of surface EMG of the right soleus muscle and accelerometer taped onto the right Achilles tendon were obtained while participant stood upright with the knees in extension, on the vibration platform. Tendon reflex was elicited before and during WBV. Subjects completed a set of WBV. Each WBV set consisted of six vibration sessions using different frequencies (25, 30, 35, 40, 45, 50 Hz) applied randomly. In each WBV session the Achilles tendon was tapped five times with a custom-made reflex hammer. The mean peak-to-peak (PP) amplitude of T-reflex was 1139.11 ± 498.99 µV before vibration. It decreased significantly during WBV (p < 0.0001). The maximum PP amplitude of T-reflex was 1333 ± 515 μV before vibration. It decreased significantly during WBV (p < 0.0001). No significant differences were obtained in the mean acceleration values of Achilles tendon with tapping between before and during vibration sessions. This study showed that T-reflex is suppressed during WBV. T-reflex suppression indicates that the spindle primary afferents must have been pre-synaptically inhibited during WBV similar to the findings in high frequency tendon vibration studies. 相似文献
5.
Michael Voigt Fabio Chelli Carlo Frigo 《European journal of applied physiology and occupational physiology》1998,78(6):522-532
Changes in the excitability of the human triceps surae muscle short latency stretch reflexes were investigated in six male
subjects before and after 4 weeks of progressive two-legged hopping training. During the measurements the subjects performed
2-Hz hopping with: preferred contact time (PCT) and short contact time. The following reflex parameters were examined before
and after the training period: the soleus muscle (SOL) Hoffmann-reflex (H-reflex) at rest and during hopping, the short latency
electromyogram (EMG) components of the movement induced stretch reflex (MSR) in SOL and medial gastrocnemius muscle (MG),
and the EMG amplitude of the SOL and MG tendon reflexes (T-reflexes) elicited at rest. The main results can be summarized
as follows: the SOL T-reflex had increased by about 28% (P < 0.05) after training while the MG T-reflex was unchanged; the SOL MSR (always evident) and the MG MSR (when observable)
did not change in amplitude with training, and before training the SOL H-reflex in both hopping situations was significantly
depressed to about 40% of the reference value at standing rest (P < 0.05). After training the H-reflex during PCT hopping was no longer depressed. As the value of the measured mechanical
parameters (the total work rate, joint angular velocity and the ankle joint work rate) was unchanged after training in both
hopping situations, the reflex changes observed could not be ascribed to changes in the movement pattern. To explain the observed
changes, hypotheses of changes in the excitability of the stretch reflex caused by the training were taken into consideration
and discussed.
Accepted: 22 May 1998 相似文献
6.
Mohammad Reza Emad Hadi Momeninejad Babak Pourabbas Tahvildari 《Somatosensory & motor research》2017,34(4):213-218
Despite differences in the anatomical and physiological characteristics of the medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (Sol) muscles, it is common practice to investigate them as single triceps surae H-reflex recordings. The aim of this study was to compare the latencies of H-reflex recordings from the Sol, MG, and LG in patients with explicit magnetic resonance imaging (MRI) evidence of unilateral S1 radiculopathy and also compare their diagnostic yield in varied clinical characteristics (i.e., symptom duration and severity of involvement). We found a significant difference between H-reflex latencies of Sol and the two others (p?0.05 for both comparisons). Although Sol had more sensitivity in patients with positive straight leg raising (SLR) of 30°–50° and also the sub-acute phase of the disease, and MG and LG had more sensitivity in the acute phase of the disease and patients with positive SLR of 50°–70°, there were no statistically significant differences between diagnostic ability of the three heads of the triceps surae in various clinical settings and they can be used interchangeably in patients with suspected S1 radiculopathies. 相似文献
7.
Soleus H-reflex reveals down modulation with increased postural difficulty. Role of this posture-related reflex modulation is thought to shift movement control toward higher motor centers in order to facilitate more precise postural control. Present study hypothesized that the ability to modulate H-reflex is related to one’s ability to dynamically balance while in an unstable posture. This study examined the relationship between dynamic balancing ability and soleus H-reflex posture-related modulation. Thirty healthy adults participated. The soleus maximal H-reflex (Hmax), motor response (Mmax), and background EMG activity (bEMG) were obtained during three postural conditions: prone, open-legged standing, and closed-legged standing. Hmax/Mmax ratios were normalized via the corresponding bEMG in order to remove the effects of background muscle activity from the obtained H-reflex. Reflex modulation was calculated as the ratio of the normalized Hmax/Mmax ratios in one postural condition to another posture in a more difficult condition. Dynamic balancing ability was assessed by testing stability while standing on a wobble board. A significant negative correlation was observed between balancing scores and reflex modulation from open-legged standing to closed-legged standing. This suggests that the ability to modulate monosynaptic stretch reflex excitability in response to a changing posture is a significant factor for dynamic balancing. 相似文献
8.
Yasuo Kawakami Digby G. Sale J. Duncan MacDougall John S. Moroz 《European journal of applied physiology and occupational physiology》1998,77(3):212-216
Six male subjects made maximal isometric plantar flexions unilaterally (UL) and bilaterally (BL), with the knee joint angle
positioned at 90° and 0° (full extension) and the ankle joint kept at 90°. Plantar flexion torque and electromyogram (EMG)
of the lateral gastrocnemius (LG) and the soleus (Sol) muscles were recorded. There was a deficit in torque in BL compared
to UL (P<0.05), and the deficit was greater when the knee was extended than when bent to 90° (13.9% vs 6.6%). The integrated EMG (iEMG)
of UL and BL did not differ when the knee was at 90°. On the other hand, when the knee was extended iEMG of LG was smaller
for BL than for UL, suggesting that the larger bilateral deficit when the knee was extended was due to a reduced activity
of the LG motor units. In addition, the H-reflex recorded from Sol when the contralateral leg was performing a maximal unilateral
plantarflexion was reduced. This would indicate that the force deficit was associated with a reduction of motoneuron excitability.
Accepted: 18 August 1997 相似文献
9.
A Web-based simulation system of the spinal cord circuitry responsible for muscle control is described. The simulator employs
two-compartment motoneuron models for S, FR and FF types, with synaptic inputs acting through conductance variations. Four
motoneuron pools with their associated interneurons are represented in the simulator, with the possibility of inclusion of
more than 2,000 neurons and 2,000,000 synapses. Each motoneuron action potential is followed, after a conduction delay, by
a motor unit potential and a motor unit twitch. The sums of all motor unit potentials and twitches result in the electromyogram
(EMG), and the muscle force, respectively. Inputs to the motoneuron pool come from populations of interneurons (Ia reciprocal
inhibitory interneurons, Ib interneurons, and Renshaw cells) and from stochastic point processes associated with descending
tracts. To simulate human electrophysiological experiments, the simulator incorporates external nerve stimulation with orthodromic
and antidromic propagation. This provides the mechanisms for reflex generation and activation of spinal neuronal circuits
that modulate the activity of another motoneuron pool (e.g., by reciprocal inhibition). The generation of the H-reflex by
the Ia-motoneuron pool system and its modulation by spinal cord interneurons is included in the simulation system. Studies
with the simulator may include the statistics of individual motoneuron or interneuron spike trains or the collective effect
of a motor nucleus on the dynamics of muscle force control. Properties associated with motor-unit recruitment, motor-unit
synchronization, recurrent inhibition and reciprocal inhibition may be investigated. 相似文献
10.
Arthrogenic muscle response induced by an experimental knee joint effusion is mediated by pre- and post-synaptic spinal mechanisms 总被引:1,自引:0,他引:1
Riann M. James A. Jeffery E. Arthur Ethan N. Danny J. Christopher D. 《Journal of electromyography and kinesiology》2004,14(6):631-640
Knee joint effusion results in quadriceps inhibition and is accompanied by increased excitability in the soleus musculature. The purpose of this study was to determine if soleus arthrogenic muscle response is regulated by pre- or post-synaptic spinal mechanisms. Ten healthy adults (two females and eight males) were measured on two occasions. At the first session, subjects had their knee injected with 60 ml of saline and in the other session they did not. Pre- and post-synaptic spinal mechanisms were measured at baseline, immediately following a needle stick, immediately following a Xylocaine injection, and 25 and 45 min post-saline injection. A mixed effects model for repeated measures was used to analyze each dependent variable. The a priori alpha level was set a P≤0.05. The percentage of the unconditioned reflex amplitude for recurrent inhibition (P<0.0001) and reflex activation history (P<0.0001) significantly increased from baseline at 25 and 45 min post-effusion. Soleus arthrogenic muscle response seen following knee joint effusion is mediated by both pre- and post-synaptic mechanisms. In conclusion, the arthrogenic muscle response seen in the soleus musculature following joint effusion is regulated by both pre- and post-synaptic control mechanisms. Our data are the first step in understanding the neural networks involved in the patterned muscle response that occurs following joint effusion. 相似文献