Effects of leg muscle tendon vibration on group Ia and group II reflex responses to stance perturbation in humans

Impact of Focal Muscle Vibration on Flaccid Upper Limb Motor Paralysis following Acute Brain Disease: A Case Study

Focal muscle vibration (FMV) is increasingly being recognized as a rehabilitative therapy for enhancing motor function in central nervous system (CNS) diseases, particularly in patients with fine motor control deficits stemming from CNS damage. Brain lesions from these diseases disrupt the motor networks, necessitating novel rehabilitation strategies. By applying vibrations to muscles, FMV stimulates sensory fibers to induce cortical activity and kinesthetic illusions. While initial studies have highlighted FMV's role in reducing spasticity, recent evidence points to its potential in treating motor paralysis. However, prior research has been limited by the lack of acute-phase studies and a focus on patients with minimal muscle contraction capability. This report aimed to explore FMV's efficacy on upper limb motor function in patients with flaccid motor paralysis immediately after acute CNS diseases. We report the case of a septuagenarian male with a brain abscess in the right parietal lobe, leading to flaccid motor paralysis. Rehabilitation included 28 sessions of occupational and physical therapy that incorporated FMV. Significant improvements were observed in upper extremity function, with moderate to very large effect sizes, while lower limb function showed lesser improvement without adverse effects. This case suggests the utility of FMV in enhancing upper-limb motor function after acute CNS injuries, potentially serving as a supplementary therapy for spontaneous recovery. This report contributes to emerging evidence on FMV's benefits in acute flaccid motor paralysis, expanding the documented therapeutic scope.

Inhibitory Effects of Prolonged Focal Muscle Vibration on Maximal Grip Strength and Muscle Activity of Wrist and Extrinsic Finger Flexor Muscles

Objective

The objective of this study was to identify effective stimulus time by quantifying the inhibitory effects of focal muscle vibration (FMV) on maximal grip strength and muscle activities of the wrist and extrinsic finger flexors.

Methods

A randomized repeated-measures design was used in this study. A total of 22 healthy volunteers (mean age, 20.9 years) participated. An FMV of 86 Hz was applied to the anterior surface of the distal forearm under the following 3 conditions: no FMV (control), 5-minute FMV, and 10-minute FMV. Maximal grip strength was measured before and after FMV. The muscle activities of the flexor digitorum superficialis, flexor digitorum profundus (FDP), and flexor carpi ulnaris were simultaneously recorded using surface electromyography. Discomfort and complications following FMV were also assessed.

Results

Compared with the control group, a significant decrease in muscle activity was observed in both the flexor digitorum superficialis and flexor carpi ulnaris after 5 and 10 minutes of FMV. In contrast, there was no significant decrease in the maximal grip strength or FDP muscle activity after either FMV condition. The discomfort was significantly higher immediately after both FMV conditions than in the control group, but it decreased 15 minutes after FMV, indicating no significant difference among the 3 conditions. Redness and/or swelling were observed in 13.6% and 36.3% of the participants after 5 and 10 minutes of FMV, respectively.

Conclusion

Five-minute FMV to the distal forearm could be a useful therapeutic method with few complications. However, the FMV in this area alone was not sufficient to suppress the muscle activity of the FDP located in the deep layer.

Effects of Whole-Body Vibration and Manually Assisted Locomotor Therapy on Neurotrophin-3 Expression and Microglia/Macrophage Mobilization Following Thoracic Spinal Cord Injury in Rats

Microglial cells play an important role in neuroinflammation and secondary damages after spinal cord injury (SCI). Progressive microglia/macrophage inflammation along the entire spinal axis follows SCI, and various factors may determine the microglial activation profile. Neurotrophin-3 (NT-3) is known to control the survival of neurons, the function of synapses, and the release of neurotransmitters, while also stimulating axon plasticity and growth. We examined the effects of whole-body vibration (WBV) and forms of assisted locomotor therapy, such as passive flexion-extension (PFE) therapy, at the neuronal level after SCI, with a focus on changes in NT-3 expression and on microglia/macrophage reaction, as they play a major role in the reconstitution of CNS integrity after injury and they may critically account for the observed structural and functional benefits of physical therapy. More specifically, the WBV therapy resulted in the best overall functional recovery when initiated at day 14, while inducing a decrease in Iba1 and the highest increase in NT-3. Therefore, the WBV therapy at the 14th day appeared to be superior to the PFE therapy in terms of recovery. Functional deficits and subsequent rehabilitation depend heavily upon the inflammatory processes occurring caudally to the injury site; thus, we propose that increased expression of NT-3, especially in the dorsal horn, could potentially be the mediator of this favorable outcome.

The acute effects of periodic and noisy tendon vibration on wrist muscle stretch responses

Mechanical muscle tendon vibration activates multiple sensory receptors in the muscle and tendon. In particular, tendon vibration tends to activate the Ia afferents the strongest, but also will activate group II and Ib afferents. This activation can cause three main effects in the central nervous system: proprioceptive illusions, tonic vibration reflexes, and suppression of the stretch response. Noisy tendon vibration has been used to assess the frequency characteristics of proprioceptive reflexes and, interestingly there appeared to be no evidence for proprioceptive illusions or tonic vibration reflexes during standing [9]. However, it remains unknown if noisy vibration induces a suppression of the muscle stretch response. Therefore, the purpose of this study was to investigate the effects of noisy and periodic tendon vibration on the stretch response in the flexor carpi radialis muscle (FCR). We examined FCR stretch responses with and without periodic (20 and 100 Hz) and noisy (∼10-100 Hz) tendon vibration. We additionally had participants perform the task under the instruction set to either not respond to the perturbation or to respond as fast as possible. The key finding from this study was that both periodic and noisy vibration resulted in a reduced stretch response amplitude. Additionally, it was found that a participant's intent to respond did not modulate the amount of suppression observed. The findings from this study provide a more detailed understanding of the effects of tendon vibration on the muscle stretch response.

Enhanced Effect of Botulinum Toxin A Injections into the Extensor Digitorum Brevis Muscle after Local Mechanical Leg Vibration: A Case Report

Background: The aim of this study was to demonstrate an increase in muscle action potentials and an enhancement of the efficacy of botulinum toxin (BoNT) after mechanical leg vibration. Methods: A 53-year-old healthy male volunteer underwent vibration ergometry training (VET) every morning and every evening for 10 min for 14 days. Compound muscle action potential (CMAP) of the right (R) and left (L) extensor digitorum brevis (EDB) muscle was analyzed by supramaximal peroneal nerve stimulation before and after VET 12 times during the 14 days. Thereafter, VET was stopped and 20 U incobotulinumtoxin (incoBoNT/A) were injected into the right EDB. During the following 10 days, CMAP of both EDBs was tested 12 times. Results: Under VET, the CMAP of both EDBs significantly increased (L: p < 0.01; R: p < 0.01). During the first 14 days, CMAP of the left EDB before VET was significantly (<0.008) lower than 20 min later after VET. This was not the case for the better trained right EDB. After day 14, CMAP of the untreated left EDB further increased for 6 days and then decreased again. In the right EDB, BoNT-treated EDB CMAP rapidly and highly significantly (p < 0.0001) decreased during the first 48 h by about 90%, from a level of about 14 mV down to a plateau of around 1.5 mV. Conclusion: Local mechanical leg vibration has a short- and long-term training effect. Compared to other studies analyzing the reduction in EDB CMAPs after BoNT injections, the reduction of EDB CMAPs in the present study observed after combined application of BoNT and VET was much faster and more pronounced.

Influence of wide-pulse neuromuscular electrical stimulation frequency and superimposed tendon vibration on occurrence and magnitude of extra torque

Low-frequency and high-frequency wide-pulse neuromuscular electrical stimulation (NMES) can generate extra torque (ET) via afferent pathways. Superimposing tendon vibration (TV) to NMES can increase the activation of these afferent pathways and favor ET generation. Knowledge of the characteristics of ET is essential to implement these stimulation paradigms in clinical practice. Thus, we aimed to investigate the effects of frequency and TV superimposition on the occurrence and magnitude of ET in response to wide-pulse NMES. NMES-induced isometric plantar flexion torque was recorded in 30 healthy individuals who performed five NMES protocols: wide-pulse low-frequency (1 ms; 20 Hz; WPLF) and wide-pulse high-frequency (1 ms; 100 Hz; WPHF) without and with superimposed TV (1 mm; 100 Hz) and conventional NMES (50 µs; 20 Hz; reference protocol). Each NMES protocol consisted of three 20-s trains interspersed by 90 s of rest, with NMES intensity being adjusted to reach 10% of maximal voluntary contraction. The ET occurrence was similar for WPLF and WPHF (P = 0.822). In the responders, the ET magnitude was greater for WPHF than WPLF (P < 0.001). There was no effect of superimposed TV on ET characteristics. This study reported an effect of NMES frequency on ET magnitude, whereas TV superimposition did not affect this parameter. In the context of our experimental design decisions, the present findings question the clinical use of wide-pulse NMES and its combination with superimposed TV. Yet, further research is needed to maximize force production through the occurrence and magnitude of ET.NEW & NOTEWORTHY This study is the first to assess the effect of stimulation frequency and superimposed tendon vibration on extra torque characteristics generated by wide-pulse neuromuscular electrical stimulation. The percentage of subjects showing extra torque (i.e., considered as responders) was similar for low-frequency and high-frequency wide-pulse neuromuscular electrical stimulation. In the responders, the extra torque was greater for high-frequency than for low-frequency wide-pulse neuromuscular electrical stimulation. The superimposition of tendon vibration had no effect on extra torque occurrence or magnitude.

Alteration of H-reflex amplitude modulation is a marker of impaired postural responses in individuals with incomplete spinal cord injury

Individuals with incomplete spinal cord injury (iSCI) show altered postural reactions leading to increased risk of falls. To investigate neural correlates underlying this deficit, we assessed the modulation pattern of the Soleus H-reflex in iSCI individuals following unexpected perturbations of a base of support. Ten men with iSCI (AIS D) and 8 age-matched controls (CTRL) stood on a force-platform randomly tilted forward or backward. The center of pressure (CoP) excursion, 95% confidence ellipse area and electromyographic (EMG) activity of the Soleus (SOL) and Tibialis Anterior (TA) muscles were analyzed. SOL H-reflex amplitude was assessed by stimulating the tibial nerve prior to and at 100, 150 and 200 ms following perturbation onset. Although SOL and TA short-latency EMG responses were comparable in both groups, long-latency EMG responses occurred later in the iSCI group for both directions: during backward tilt, a decrease in H-reflex amplitude was observed at all stimulus timings post-tilt in CTRL, but only at 200 ms in iSCI. The decrease in H-reflex amplitude was smaller in iSCI participants. During forward tilt, an increase in H-reflex amplitude was observed at 150 and 200 ms in the CTRL group, but no increase was observed in the iSCI group. Decreased and delayed SOL H-reflex amplitude modulation in the iSCI group accompanied impaired balance control as assessed clinically with the Berg Balance Scale and biomechanically through CoP displacement. Overall, delayed and reduced spinal reflex processing may contribute to impaired balance control in people with iSCI.

Localized muscle vibration in the treatment of motor impairment and spasticity in post-stroke patients: a systematic review

INTRODUCTION

During the last decades, many studies have been carried out to understand the possible positive effects of vibration therapy in post-stroke rehabilitation. In particular, the use of localized muscle vibration (LMV) seems to have promising results. The aim of this systematic review was to describe the use of LMV in post-stroke patients to improve motor recovery, reducing spasticity and disability in both upper and lower limb.

EVIDENCE ACQUISITION

A search was conducted on PubMed, Scopus, Pedro and REHABDATA electronic database. Only randomized controlled trials have been included, excluding no-localized vibratory treatments and other pathological conditions. Fourteen studies met the inclusion criteria and were included in this review.

EVIDENCE SYNTHESIS

Collectively, the studies involved 425 stroke patients. Most studies included chronic stroke patients (ten) and treated only the upper limb (eleven). There is evidence that LMV therapy is effective in reducing spasticity and improving motor recovery, especially when associated with conventional physical therapy.

CONCLUSIONS

LMV may be a feasible and safe tool to be integrated into traditional and conventional neurorehabilitation programs for post-stroke patients to reduce spasticity. Analysis of the available clinical trials do not allow us to indicate vibration therapy as effective in functional motor recovery, despite some studies showed encouraging results. Further studies, with larger size of homogeneous patients and with a shared methodology are needed to produce more reliable data, especially on the lower limb.

Immediate effects of plantar vibration stimuli during static upright posture following total hip arthroplasty in females

PURPOSE

Proprioceptive function of the lower limbs deteriorates in patients following total hip arthroplasty. Patients show poor balance and rely more on visual information than proprioceptive information. Plantar vibration stimuli can mechanically enhance somatosensory input from the plantar cutaneous mechanoreceptors, thereby improving static balance. Plantar vibration stimuli may improve static balance in patients after total hip arthroplasty. This is the first study to investigate whether plantar vibration stimuli affects static balance during the early phase following total hip arthroplasty.

MATERIALS AND METHODS

In this cross-over design study, 16 female patients (aged 65.1 ± 11.0 years) received plantar vibration stimuli for 2 minutes or the sham interventions after total hip arthroplasty in a randomized order on different days. The foot centre of pressure was measured for the total path length, mediolateral path length, and anteroposterior path length directions before and immediately after the interventions in the static standing position both with eyes open and closed. Patients were instructed to minimize body sway when standing.

RESULTS

A significant increase was observed in the centre of pressure parameters in the eyes closed condition than in the eyes open condition. The centre of pressure parameters for the eyes closed condition was significantly decreased after vibration interventions than that before intervention.

CONCLUSIONS

This study supports the view that plantar vibration stimuli can change static balance in patients in the early phase after total hip arthroplasty temporarily by up-weighting sensory information. These stimuli may serve as a treatment option for influencing balance following total hip arthroplasty.

Vibration attenuates spasm-like activity in humans with spinal cord injury

KEY POINTS

Cutaneous reflexes were tested to examine the neuronal mechanisms contributing to muscle spasms in humans with chronic spinal cord injury (SCI). Specifically, we tested the effect of Achilles and tibialis anterior tendon vibration on the early and late components of the cutaneous reflex and reciprocal Ia inhibition in the soleus and tibialis anterior muscles in humans with chronic SCI. We found that tendon vibration reduced the amplitude of later but not earlier cutaneous reflex in the antagonist but not in the agonist muscle relative to the location of the vibration. In addition, reciprocal Ia inhibition between antagonist ankle muscles increased with tendon vibration and participants with a larger suppression of the later component of the cutaneous reflex had stronger reciprocal Ia inhibition from the antagonistic muscle. Our study is the first to provide evidence that tendon vibration attenuates late cutaneous spasm-like reflex activity, likely via reciprocal inhibitory mechanisms, and may represent a method, when properly targeted, for controlling spasms in humans with SCI.

ABSTRACT

The neuronal mechanisms contributing to the generation of involuntary muscle contractions (spasms) in humans with spinal cord injury (SCI) remain poorly understood. To address this question, we examined the effect of Achilles and tibialis anterior tendon vibration at 20, 40, 80 and 120 Hz on the amplitude of the long-polysynaptic (LPR, from reflex onset to 500 ms) and long-lasting (LLR, from 500 ms to reflex offset) cutaneous reflex evoked by medial plantar nerve stimulation in the soleus and tibialis anterior, and reciprocal Ia inhibition between these muscles, in 25 individuals with chronic SCI. We found that Achilles tendon vibration at 40 and 80 Hz, but not other frequencies, reduced the amplitude of the LLR in the tibialis anterior, but not the soleus muscle, without affecting the amplitude of the LPR. Vibratory effects were stronger at 80 than 40 Hz. Similar results were found in the soleus muscle when the tibialis anterior tendon was vibrated. Notably, tendon vibration at 80 Hz increased reciprocal Ia inhibition between antagonistic ankle muscles and vibratory-induced increases in reciprocal Ia inhibition were correlated with decreases in the LLR, suggesting that participants with a larger suppression of later cutaneous reflex activity had stronger reciprocal Ia inhibition from the antagonistic muscle. Our study is the first to provide evidence that tendon vibration suppresses late spasm-like activity in antagonist but not agonist muscles, likely via reciprocal inhibitory mechanisms, in humans with chronic SCI. We argue that targeted vibration of antagonistic tendons might help to control spasms after SCI.

Corticospinal responses during passive shortening and lengthening of tibialis anterior and soleus in older compared to younger adults

NEW FINDINGS

What is the central question of this study? Are there age-related differences in corticospinal responses whilst passively changing muscle length? What is the main finding and its importance? In contrast to young, older adults exhibited no modulation of corticospinal excitability in tibialis anterior during passive ankle movement. These data show impaired sensorimotor response in older adults during length changes of tibialis anterior, thus contributing to our understanding of age-related changes in sensorimotor control.

ABSTRACT

Corticospinal responses have been shown to increase and decrease with passive muscle shortening and lengthening, respectively, as a result of changes in muscle spindle afferent feedback. The ageing sensory system is accompanied by a number of alterations that might influence the processing and integration of sensory information. Consequently, corticospinal excitability might be modulated differently whilst changing muscle length. In 10 older adults (66 ± 4 years), corticospinal responses (MEP/M_max ) were evoked in a static position, and during passive shortening and lengthening of soleus (SOL) and tibialis anterior (TA), and these data were compared to the re-analysed data pool of 18 younger adults (25 ± 4 years) published previously. Resting motor threshold was greater in SOL compared to TA (P < 0.001), but did not differ between young and older (P = 0.405). No differences were observed in MEP/M_max between the static position, passive shortening or lengthening in SOL (young: all 0.02 ± 0.01; older: 0.05 ± 0.04, 0.03 ± 0.02 and 0.04 ± 0.01, respectively; P = 0.298), and responses were not dependent on age (P = 0.090). Conversely, corticospinal responses in TA were modulated differently between the age groups (P = 0.002), with greater MEP/M_max during passive shortening (0.22 ± 0.12) compared to passive lengthening (0.13 ± 0.10) and static position (0.10 ± 0.05) in young (P < 0.001), but unchanged in older adults (0.19 ± 0.11, 0.22 ± 0.11 and 0.18 ± 0.07, respectively; P ≥ 0.867). The present experiment shows that length-dependent changes in corticospinal excitability in TA of the young are not evident in older adults. This suggests impaired sensorimotor response during muscle length changes in older age that might only be present in ankle flexors, but not extensors.

Human Balance in Response to Continuous, Predictable Translations of the Support Base: Integration of Sensory Information, Adaptation to Perturbations, and the Effect of Age, Neuropathy and Parkinson’s Disease

This short narrative review article moves from early papers that described the behaviour of healthy subjects balancing on a motorized platform continuously translating in the antero-posterior direction. Research from the laboratories of two of the authors and related investigations on dynamic balancing behaviour are briefly summarized. More recent findings challenging time-honoured views are considered, such as the statement that vision plays a head-in-space stabilizing role. The time interval to integrate vision or its withdrawal in the balancing pattern is mentioned as well. Similarities and differences between ageing subjects and patients with peripheral or central disorders are concisely reported. The muscle activities recorded during the translation cycles suggest that vision and amplitude changes of the anticipatory postural activities play a predominant role in controlling dynamic balance during prolonged administration of the predictable perturbation. The potential of this paradigm for rehabilitation of balance problems is discussed.

Focal Vibration Stretches Muscle Fibers by Producing Muscle Waves

Focal vibration is an effective intervention for the management of spasticity. However, its neuromechanical effects, particularly how tonic vibration reflex is induced explicitly, remain implicit. In this paper, we utilize a high-speed camera and a method of image processing to quantify the muscle vibration rigorously and disclose the neuromechanical mechanism of focal vibration. The vibration of 75 Hz is applied on the muscle belly of the biceps brachii and muscle responses are captured by a high-speed camera in profile. The muscle silhouettes are identified by the Canny edge detector to represent the stretch of muscle fibers, and the consistency between the muscle stretch and profile deformation has been confirmed by the magnetic resonance imaging in advance. Oscillations of muscle points discretized by pixels are identified by the fast Fourier transformation, respectively, and results demonstrate that focal vibration stretches muscle by producing muscle waves. Specifically, each point vibrates harmonically, and, given the linear phase modulation with transverse position, the muscle vibration propagates as traveling waves. The propagation of muscle waves is associated with muscle stretch, whose frequency is the same with the vibrator due to the curved baseline, and thus induces the tonic vibration reflex via spinal circuits.

Repeatability of spinal reflexes of lower limb muscles evoked by transcutaneous spinal cord stimulation

Transcutaneous electrical stimulation is a relatively new technique to evoke spinal reflexes in lower limb muscles. The advantage of this technique is that the spinal reflex responses can be obtained from multiple lower limb muscles simultaneously. However, repeatability of spinal reflexes evoked by transcutaneous spinal cord stimulation between days has not been evaluated. We aimed to examine repeatability of recruitment properties of the spinal reflexes evoked by transcutaneous spinal cord stimulation. Recruitment curves of the spinal reflexes evoked by transcutaneous spinal cord stimulation of 8 lower limb muscles (i.e., foot, lower leg, and thigh muscles) of 20 males were measured on two consecutive days. To confirm that responses were caused by activation of the sensory fiber, a double-pulse stimulation with 50 ms inter-pulse interval was delivered. Peak-to-peak amplitude of the first response was calculated for each muscle when no response was observed in the second response owing to post-activation depression. For comparison with the spinal reflexes evoked by transcutaneous spinal cord stimulation, the recruitment curves of the H-reflex amplitude of the soleus of 9 males were measured. Threshold intensity and maximal slope of the recruitment curves were calculated, and inter-day repeatability of the properties was quantified using intraclass correlation coefficients. For the spinal reflexes evoked by transcutaneous spinal cord stimulation, the intraclass correlation coefficient values of threshold intensity and maximal slope for each muscle ranged from 0.487 to 0.874 and from 0.471 to 0.964, respectively. Regarding the soleus H-reflex, the intraclass correlation coefficients of threshold intensity and maximal slope were 0.936 and 0.751, respectively. The present data showed that repeatability of the recruitment properties of the spinal reflexes evoked by transcutaneous spinal cord stimulation in the lower limb was moderate to high. Measurement of the spinal reflexes evoked by transcutaneous spinal cord stimulation would be useful for longitudinal neurophysiological studies.

H-reflex modulation preceding changes in soleus EMG activity during balance perturbation

When balance is compromised, postural strategies are induced to quickly recover from the perturbation. However, neuronal mechanisms underlying these strategies are not fully understood. Here, we assessed the amplitude of the soleus (SOL) H-reflex during forward and backward tilts of the support surface during standing (n = 15 healthy participants). Electrical stimulation of the tibial nerve was applied randomly before platform tilt (control) and 0, 25, 50, 75, 100 or 200 ms after tilt onset. During backward tilt, a significant decrease in H-reflex amplitude was observed at 75, 100 and 200 ms. The onset of the decreased H-reflex amplitude significantly preceded the onset of the SOL EMG decrease (latency: 144 ± 16 ms). During forward tilt, the amplitude of the H-reflex increased at 100 and 200 ms after tilt onset. The onset of H-reflex increase did not occur significantly earlier than the onset of the SOL EMG increase (127 ± 5 ms). An important inter-subject variability was observed for the onset of H-reflex modulation with respect to EMG response for each direction of tilt, but this variability could not be explained by the subject's height. Taken together, the results establish the time course of change in SOL H-reflex excitability and its relation to the increase and decrease in SOL EMG activity during forward and backward tilts. The data presented here also suggest that balance mechanisms may differ between forward and backward tilts.

Intermediate Muscle Length and Tendon Vibration Optimize Corticospinal Excitability During Knee Extensors Local Vibration

While local vibration (LV) has been recently proposed as a potential modality for neuromuscular conditioning, no practical recommendations to optimize its effects have been published. Because changes in corticospinal excitability may reflect at which degree the neuromuscular function is modulated during LV exposure, this study investigated the effects of muscle length and vibration site on LV-induced on motor evoked potentials (MEPs) changes. Twenty-one subjects participated in a single session in which MEPs were evoked on the relaxed knee extensors (KE) during three conditions, i.e., no vibration (CON), muscle (VIBMU), and tendon vibration (VIBTD). Three muscle lengths were tested for each condition, i.e., short/intermediate/long KE muscle length. Both VIBMU and VIBTD significantly increase MEPs compared to CON. Higher increases (P < 0.001) were found for VIBTD compared to VIBMU for vastus lateralis (mean increases of the three angles: +241% vs.+ 148%), vastus medialis (+273% vs. + 180%) and rectus femoris muscles (+191% vs. +141%). The increase in MEPs amplitude was higher (p < 0.001) at an intermediate (mean pooled increase for VIBTD and VIBMU: +265%, +290%, and +212% for VL, VM, and RF, respectively) compared to short (+136%, + 144%, and + 127%) or long (+ 184%, + 246% and + 160%) muscle lengths. These results suggest that LV should be applied to the tendon at an intermediate muscle length to optimize the acute effects of LV on the KE neuromuscular function.

A clinical single blind study to investigate the immediate effects of plantar vibration on balance in patients after stroke

Balance disorder is a very common cause of disability in patients after a stroke. Vibration therapy is one of the physiotherapeutic modalities used to improve balance.

OBJECTIVE

To investigate the immediate effects of plantar vibration on balance in patients with stroke.

METHODS

In this single blind comparative study, 22 patients with stroke (8 females, 14 males; age 55.82 ± 11.87 years old) participated. Patients underwent treatment, first with the placebo vibration and 1 week later with active vibration (frequency 100 HZ, 5 min). Mini-BESTest score, Modified Modified Ashworth Scale for plantar flexor spasticity, and ankle dorsiflexion passive range of motion (PROM) were evaluated before and immediately after the placebo or active vibration.

RESULTS

A significant clinical improvement in balance, ankle plantar flexor spasticity, and the ankle dorsiflexion PROM was observed following either placebo or active vibration. The improvements after active vibration were significantly greater for all outcome measures compared with placebo vibration. There was a large effect size (Cohen's d = 0.85) for balance after active vibration.

CONCLUSION

The vibration applied to the sole of the affected foot of patients after stroke was effective for improving balance, reducing ankle plantar flexor spasticity, and increasing ankle dorsiflexion PROM.

Variable impact of tizanidine on the medium latency reflex of upper and lower limbs

Sudden limb displacement evokes a complex sequence of compensatory muscle activity. Following the short-latency reflex and preceding voluntary reactions is an epoch termed the medium-latency reflex (MLR) that could reflect spinal processing of group II muscle afferents. One way to test this possibility is oral ingestion of tizanidine, an alpha-2 adrenergic agonist that inhibits the interneurons transmitting group II signals onto spinal motor neurons. We examined whether group II afferents contribute to MLR activity throughout the major muscles that span the elbow and shoulder. MLRs of ankle muscles were also tested during walking on the same day, in the same participants as well as during sitting in a different group of subjects. In contrast to previous reports, the ingestion of tizanidine had minimal impact on MLRs of arm or leg muscles during motor actions. A significant decrease in magnitude was observed for 2/16 contrasts in arm muscles and 0/4 contrasts in leg muscles. This discrepancy with previous studies could indicate that tizanidine's efficacy is altered by subtle changes in protocol or that group II afferents do not substantially contribute to MLRs.

The association between brain activity and motor imagery during motor illusion induction by vibratory stimulation

Background:

The association between motor imagery ability and brain neural activity that leads to the manifestation of a motor illusion remains unclear.

Objective:

In this study, we examined the association between the ability to generate motor imagery and brain neural activity leading to the induction of a motor illusion by vibratory stimulation.

Methods:

The sample consisted of 20 healthy individuals who did not have movement or sensory disorders. We measured the time between the starting and ending points of a motor illusion (the time to illusion induction, TII) and performed electroencephalography (EEG). We conducted a temporo-spatial analysis on brain activity leading to the induction of motor illusions using the EEG microstate segmentation method. Additionally, we assessed the ability to generate motor imagery using the Japanese version of the Movement Imagery Questionnaire-Revised (JMIQ-R) prior to performing the task and examined the associations among brain neural activity levels as identified by microstate segmentation method, TII, and the JMIQ-R scores.

Results:

The results showed four typical microstates during TII and significantly higher neural activity in the ventrolateral prefrontal cortex, primary sensorimotor area, supplementary motor area (SMA), and inferior parietal lobule (IPL). Moreover, there were significant negative correlations between the neural activity of the primary motor cortex (MI), SMA, IPL, and TII, and a significant positive correlation between the neural activity of the SMA and the JMIQ-R scores.

Conclusion:

These findings suggest the possibility that a neural network primarily comprised of the neural activity of SMA and M1, which are involved in generating motor imagery, may be the neural basis for inducing motor illusions. This may aid in creating a new approach to neurorehabilitation that enables a more robust reorganization of the neural base for patients with brain dysfunction with a motor function disorder.

Low back cutaneous vibration and its effect on trunk postural control

The current study investigated the effects of a low back pain (LBP) vibration modality on trunk motor control. Trunk repositioning error and responses to a sudden loading trunk perturbation were evaluated pre- and post-vibration (15min vibration exposure while sitting on a standard chair) as well as when concurrent cutaneous low back vibration was applied. Only minor effects were observed post-vibration when compared to pre-vibration. However, when vibration was applied at the same time as the sudden trunk perturbations, lumbar erector spinae and external oblique muscles were significantly more delayed in activating following the perturbation. In addition, the resting muscle activation prior to the trunk perturbation was higher in both the back extensor and abdominal muscles when concurrent vibration was applied. These findings suggest that cutaneous low back vibration significantly alters motor control responses and this should be considered before implementing cutaneous vibration as a low back pain management strategy.

Neuroimaging of Human Balance Control: A Systematic Review

This review examined 83 articles using neuroimaging modalities to investigate the neural correlates underlying static and dynamic human balance control, with aims to support future mobile neuroimaging research in the balance control domain. Furthermore, this review analyzed the mobility of the neuroimaging hardware and research paradigms as well as the analytical methodology to identify and remove movement artifact in the acquired brain signal. We found that the majority of static balance control tasks utilized mechanical perturbations to invoke feet-in-place responses (27 out of 38 studies), while cognitive dual-task conditions were commonly used to challenge balance in dynamic balance control tasks (20 out of 32 studies). While frequency analysis and event related potential characteristics supported enhanced brain activation during static balance control, that in dynamic balance control studies was supported by spatial and frequency analysis. Twenty-three of the 50 studies utilizing EEG utilized independent component analysis to remove movement artifacts from the acquired brain signals. Lastly, only eight studies used truly mobile neuroimaging hardware systems. This review provides evidence to support an increase in brain activation in balance control tasks, regardless of mechanical, cognitive, or sensory challenges. Furthermore, the current body of literature demonstrates the use of advanced signal processing methodologies to analyze brain activity during movement. However, the static nature of neuroimaging hardware and conventional balance control paradigms prevent full mobility and limit our knowledge of neural mechanisms underlying balance control.

Change in the natural head-neck orientation momentarily altered sensorimotor control during sensory transition

Achilles tendon vibration generates proprioceptive information that is incongruent with the actual body position; it alters the perception of body orientation leading to a vibration-induced postural response. When a person is standing freely, vibration of the Achilles tendon shifts the internal representation of the verticality backward thus the vibration-induced postural response realigned the whole body orientation with the shifted subjective vertical. Because utricular otoliths information participates in the creation of the internal representation of the verticality, changing the natural orientation of the head-neck system during Achilles tendon vibration could alter the internal representation of the earth vertical to a greater extent. Consequently, it was hypothesized that compared to neutral head-neck orientation, alteration in the head-neck orientation should impair balance control immediately after Achilles tendon vibration onset or offset (i.e., sensory transition) as accurate perception of the earth vertical is required. Results revealed that balance control impairment was observed only immediately following Achilles tendon vibration offset; both groups with the head-neck either extended or flexed showed larger body sway (i.e., larger root mean square scalar distance between the center of pressure and center of gravity) compared to the group with the neutral head-neck orientation. The fact that balance control was uninfluenced by head-neck orientation immediately following vibration onset suggests the error signal needs to accumulate to a certain threshold before the internal representation of the earth vertical becomes incorrect.

Acute effects of high-frequency microfocal vibratory stimulation on the H reflex of the soleus muscle. A double-blind study in healthy subjects

This study in healthy subjects examined the effects of a system delivering focal microvibrations at high frequency (Equistasi®) on tonic vibration stimulus (TVS)-induced inhibition of the soleus muscle H reflex. Highfrequency microvibrations significantly increased the inhibitory effect of TVS on the H reflex for up to three minutes. Moreover, Equistasi® also significantly reduced alpha-motoneuron excitability, as indicated by the changes in the ratio between the maximumamplitude H reflex (Hmax reflex) and the maximumamplitude muscle response (Mmax response); this effect was due to reduction of the amplitude of the H reflex because the amplitude of muscle response remained unchanged. The present findings indicate that Equistasi® has a modulatory effect on proprioceptive reflex circuits. Therefore, Equistasi® might interfere with some mechanisms involved in both physiological and pathophysiological control of movement and of posture.

Effects of whole-body vibration on neuromuscular performance in individuals with spinal cord injury: a systematic review

OBJECTIVE

To examine the effects of whole-body vibration on neuromuscular performance in people with spinal cord injury and evaluate the safe and effective vibration protocols.

METHODS

PubMed, EMBASE, CINAHL and PEDro were mainly searched for English literatures. Other data sources were ClinicalTrials.gov , Current Controlled Trials and reference lists of all relevant articles. The PEDro scale was used to evaluate the methodological quality, and the Oxford Centre for Evidence-based Medicine level of evidence was used to assess the level of evidence. Basic information and whole-body vibration protocols were extracted by two independent researchers. Any disagreements were resolved by the third researcher.

RESULTS

Of the eight included studies involving 94 individuals with spinal cord injury and 24 able-bodied participants, six of them reported beneficial effects of whole-body vibration on muscle activation and the other two on muscle spasticity. Based on the reviewed studies, an intermittent mode of whole-body vibration (frequency: 10-50 Hz; amplitude: 0.6-4 mm) is less likely to cause adverse events when applying to spinal cord injury subjects standing on platform (knees flexed at 10°-40°).

CONCLUSIONS

The strength of evidence is insufficient in supporting the benefits of whole-body vibration on neuromuscular performance in individuals with spinal cord injury. The intermittent vibration (frequency: 10-50 Hz; amplitude: 0.6-4 mm; knee flexion: 10°-40°) may be the possible effective range and have good compliance.

Effects of vibratory training on plantar impression in patients affected by stroke

Aim:

The aim of this study was to investigate the effect of vibration training on plantar impression and motor function in patients affected by stroke.

Methods:

The sample consisted of 28 individuals with hemiparesis after stroke who were randomly assigned to the intervention group (n=18) and the control group (n=10). The instruments used for evaluation were the mini-mental state examination, photopodoscopy and the 6-minute walk test. For treatment, whole body vibration training was used three times a week for 8 weeks. The treatment was carried out in two phases. The first phase, which lasted for 4 weeks, consisted of four sets of exercises with 60 seconds of vibration. In the first exercise, the participants were in a static standing position, feet apart with knees flexed at 30°. In the second exercise, the same position was implemented, with knees flexed at 90°. In the third exercise, a standing position with one-leg support on the affected limb with flexed knee at 30°. The fourth exercise was a repetition of the first exercise. The second phase also lasted for 4 weeks. It consisted of the same exercises but the amount of sets of exercises was doubled.

Results:

Data were analysed by independent t-test and repeated measures ANOVA with two factors. There was no intergroup nor intragroup statistical difference (P=0.05) in the plantar impression area on the affected and unaffected side; there was only intragroup statistical differences in the 6-minute walk test (P=0.03).

Conclusions:

Whole-body vibration training did not influence the increase of the plantar impression area and motor function in stroke patients.

Techniques and Methods for Testing the Postural Function in Healthy and Pathological Subjects

The different techniques and methods employed as well as the different quantitative and qualitative variables measured in order to objectify postural control are often chosen without taking into account the population studied, the objective of the postural test, and the environmental conditions. For these reasons, the aim of this review was to present and justify the different testing techniques and methods with their different quantitative and qualitative variables to make it possible to precisely evaluate each sensory, central, and motor component of the postural function according to the experiment protocol under consideration. The main practical and technological methods and techniques used in evaluating postural control were explained and justified according to the experimental protocol defined. The main postural conditions (postural stance, visual condition, balance condition, and test duration) were also analyzed. Moreover, the mechanistic exploration of the postural function often requires implementing disturbing postural conditions by using motor disturbance (mechanical disturbance), sensory stimulation (sensory manipulation), and/or cognitive disturbance (cognitive task associated with maintaining postural balance) protocols. Each type of disturbance was tackled in order to facilitate understanding of subtle postural control mechanisms and the means to explore them.

Optic flow improves adaptability of spatiotemporal characteristics during split-belt locomotor adaptation with tactile stimulation

Human locomotor adaptation requires feedback and feed-forward control processes to maintain an appropriate walking pattern. Adaptation may require the use of visual and proprioceptive input to decode altered movement dynamics and generate an appropriate response. After a person transfers from an extreme sensory environment and back, as astronauts do when they return from spaceflight, the prolonged period required for re-adaptation can pose a significant burden. In our previous paper, we showed that plantar tactile vibration during a split-belt adaptation task did not interfere with the treadmill adaptation however, larger overground transfer effects with a slower decay resulted. Such effects, in the absence of visual feedback (of motion) and perturbation of tactile feedback, are believed to be due to a higher proprioceptive gain because, in the absence of relevant external dynamic cues such as optic flow, reliance on body-based cues is enhanced during gait tasks through multisensory integration. In this study, we therefore investigated the effect of optic flow on tactile-stimulated split-belt adaptation as a paradigm to facilitate the sensorimotor adaptation process. Twenty healthy young adults, separated into two matched groups, participated in the study. All participants performed an overground walking trial followed by a split-belt treadmill adaptation protocol. The tactile group (TC) received vibratory plantar tactile stimulation only, whereas the virtual reality and tactile group (VRT) received an additional concurrent visual stimulation: a moving virtual corridor, inducing perceived self-motion. A post-treadmill overground trial was performed to determine adaptation transfer. Interlimb coordination of spatiotemporal and kinetic variables was quantified using symmetry indices and analyzed using repeated-measures ANOVA. Marked changes of step length characteristics were observed in both groups during split-belt adaptation. Stance and swing time symmetries were similar in the two groups, suggesting that temporal parameters are not modified by optic flow. However, whereas the TC group displayed significant stance time asymmetries during the post-treadmill session, such aftereffects were absent in the VRT group. The results indicated that the enhanced transfer resulting from exposure to plantar cutaneous vibration during adaptation was alleviated by optic flow information. The presence of visual self-motion information may have reduced proprioceptive gain during learning. Thus, during overground walking, the learned proprioceptive split-belt pattern is more rapidly overridden by visual input due to its increased relative gain. The results suggest that when visual stimulation is provided during adaptive training, the system acquires the novel movement dynamics while maintaining the ability to flexibly adapt to different environments.

The Impact of a Vestibular-Stimulating Exercise Regime on Postural Stability in People with Visual Impairment

The aim of the study was to assess the impact of a vestibular-stimulating exercise regime on postural stability in individuals with visual impairment. The study group consisted of 70 people, including 28 persons (15 female and 13 male) with visual impairment and 42 (21 female and 21 male) without visual impairment. Each individual in the group with visual impairment was medically qualified for a 3-month training program. The research methodology included medical examination, anthropometric tests, and stabilometry tests on a Biodex Balance System SD (BBS). The tests were conducted twice: once before the start of training and again after 3 months of rehabilitation. The group with visual impairment showed significantly worse postural stability results than the control group for most of the stability parameters evaluated (OSI, APSI, and MLSI). Differences were noted between the groups with and without visual impairment for dynamic tests in women and for static tests in men. After training, the two groups showed roughly similar results for the stabilometry test with eyes closed. We conclude that exercises stimulating the vestibular system with head and body movements should be recommended for individuals with visual impairments to achieve better balance retention.

Effect of experimentally reduced distal sensation on postural response to hip abductor/ankle evertor muscle vibration

This study assessed whether postural responses induced by vibratory perturbations of the hip abductors and ankle evertors, were modified when distal tactile sensation was experimentally reduced through cooling. Sixteen healthy subjects were investigated pre and post cooling. Subjects stood with their eyes closed with a stance width of 4 cm. A 2s vibratory stimulus was applied to the left or right hip abductor or ankle evertor muscle. The order of the site and side of the stimulation was randomised. The postural response to hip abductor and ankle evertor vibration was recorded using 3D motion analysis (Codamotion, Leicestershire). Medio-lateral centre of pressure motion was simultaneously recorded during quiet standing via a force plate (Kistler, UK). Pre-cooling people responded to unilateral ankle vibration with an ipsilateral translation and tilt of the pelvis, and an ipsilateral tilt of the trunk. People responded to unilateral hip vibration with a contralateral translation and tilt of the pelvis, and an ipsilateral tilt of the trunk. Following an experimental reduction in distal tactile sensation there was a significant reduction in the amplitude of pelvic tilt in response to ankle vibration (F(6.2)=P<0.05) and a significant increase in amplitude of pelvic tilt in response to hip vibration (F(5.2)=P<0.05). This suggests that the sensitivity to artificial stimulation of hip proprioception increases with distal cooling, possibly indicating a change in the gain/weighting placed upon sensory information from the hips.

A wearable proprioceptive stabilizer (Equistasi®) for rehabilitation of postural instability in Parkinson's disease: a phase II randomized double-blind, double-dummy, controlled study

Background

Muscle spindles endings are extremely sensitive to externally applied vibrations, and under such circumstances they convey proprioceptive inflows to the central nervous system that modulate the spinal reflexes excitability or the muscle responses elicited by postural perturbations. The aim of this pilot study is to test the feasibility and effectiveness of a balance training program in association with a wearable proprioceptive stabilizer (Equistasi) that emits focal mechanical vibrations in patients with PD.

Methods

Forty patients with PD were randomly divided in two groups wearing an active or inactive device. All the patients received a 2-month intensive program of balance training. Assessments were performed at baseline, after the rehabilitation period (T1), and two more months after (T2). Posturographic measures were used as primary endpoint; secondary measures of outcome included the number of falls and several clinical scales for balance and quality of life.

Results

Both groups improved at the end of the rehabilitation period and we did not find significant between-group differences in any of the principal posturographic measures with the exception of higher sway area and limit of stability on the instrumental functional reach test during visual deprivation at T1 in the Equistasi group. As for the secondary outcome, we found an overall better outcome in patients enrolled in the Equistasi group: 1) significant improvement at T1 on Berg Balance Scale (+45.0%, p = .026), Activities-specific Balance Confidence (+83.7, p = .004), Falls Efficacy Scale (−33.3%, p = .026) and PDQ-39 (−48.8%, p = .004); 2) sustained improvement at T2 in terms of UPDRS-III, Berg Balance Scales, Time Up and Go and PDQ-39; 3) significant and sustained reduction of the falls rate.

Conclusions

This pilot trial shows that a physiotherapy program for training balance in association with focal mechanical vibration exerted by a wearable proprioceptive stabilizer might be superior than rehabilitation alone in improving patients’ balance.

Trial Registration

EudraCT 2013-003020-36 and ClinicalTrials.gov (number not assigned)

Neck proprioception shapes body orientation and perception of motion

This review article deals with some effects of neck muscle proprioception on human balance, gait trajectory, subjective straight-ahead (SSA), and self-motion perception. These effects are easily observed during neck muscle vibration, a strong stimulus for the spindle primary afferent fibers. We first remind the early findings on human balance, gait trajectory, SSA, induced by limb, and neck muscle vibration. Then, more recent findings on self-motion perception of vestibular origin are described. The use of a vestibular asymmetric yaw-rotation stimulus for emphasizing the proprioceptive modulation of motion perception from the neck is mentioned. In addition, an attempt has been made to conjointly discuss the effects of unilateral neck proprioception on motion perception, SSA, and walking trajectory. Neck vibration also induces persistent aftereffects on the SSA and on self-motion perception of vestibular origin. These perceptive effects depend on intensity, duration, side of the conditioning vibratory stimulation, and on muscle status. These effects can be maintained for hours when prolonged high-frequency vibration is superimposed on muscle contraction. Overall, this brief outline emphasizes the contribution of neck muscle inflow to the construction and fine-tuning of perception of body orientation and motion. Furthermore, it indicates that tonic neck-proprioceptive input may induce persistent influences on the subject's mental representation of space. These plastic changes might adapt motion sensitiveness to lasting or permanent head positional or motor changes.

Whole body vibration exercises and the improvement of the flexibility in patient with metabolic syndrome

Vibrations produced in oscillating/vibratory platform generate whole body vibration (WBV) exercises, which are important in sports, as well as in treating diseases, promoting rehabilitation, and improving the quality of life. WBV exercises relevantly increase the muscle strength, muscle power, and the bone mineral density, as well as improving the postural control, the balance, and the gait. An important number of publications are found in the PubMed database with the keyword “flexibility” and eight of the analyzed papers involving WBV and flexibility reached a level of evidence II. The biggest distance between the third finger of the hand to the floor (DBTFF) of a patient with metabolic syndrome (MS) was found before the first session and was considered to be 100%. The percentages to the other measurements in the different sessions were determined to be related to the 100%. It is possible to see an immediate improvement after each session with a decrease of the %DBTFF. As the presence of MS is associated with poorer physical performance, a simple and safe protocol using WBV exercises promoted an improvement of the flexibility in a patient with MS.

Postural stabilization during bilateral and unilateral vibration of ankle muscles in the sagittal and frontal planes

BACKGROUND

The purpose was to investigate the postural consequences of proprioceptive perturbation of the Triceps Surae and Peroneus Longus muscles. These muscles are known to control posture respectively in the sagittal and frontal planes during standing.

METHODS

Standard parameters and the time course of center of pressure (CoP) displacements were recorded in 21 young adults, instructed to maintain their balance during tendon vibration. Following 4 s of baseline recording, three types of vibration (80 Hz) were applied for 20 s each on the Peroneus or Achilles tendons, either unilaterally or bilaterally (with eyes shut). The recording continued for a further 24 s after the end of the vibration during the re-stabilization phase. To evaluate the time course of the CoP displacement, each phase of the trial was divided into periods of 4 seconds. Differences between the type of tendon vibration, phases and periods were analyzed using ANOVA.

RESULTS

During all tendon vibrations, the speed of the CoP increased and a posterior displacement occurred. These changes were greater during Achilles than during Peroneus vibration for each type of vibration and also during bilateral compared with unilateral vibration. All maximal posterior positions occurred at a similar instant (between 12.7 and 14 s of vibration). Only unilateral Achilles vibration led to a significant medio-lateral displacement compared to the initial state.

CONCLUSIONS

The effect of the proprioceptive perturbation seems to be influenced by the position of the vibrated muscle according to the planes of the musculoskeletal postural organization. The amplitude of the destabilization may be related to the importance of the muscle for postural control. The medial CoP displacement which occurred during unilateral Achilles vibration is not a general reaction to a single-limb perturbation. Proprioceptive input from the non-perturbed leg was not sufficient for the antero-posterior displacement to be avoided; however, it helped to gain stability over time. The non-perturbed limb clearly plays an important role in the restoration of the postural referential, both during and immediately following the end of the vibration. The results demonstrated that at least 16 s of vibration are necessary to induce most postural effects in young adults.

A computational model for epidural electrical stimulation of spinal sensorimotor circuits

Epidural electrical stimulation (EES) of lumbosacral segments can restore a range of movements after spinal cord injury. However, the mechanisms and neural structures through which EES facilitates movement execution remain unclear. Here, we designed a computational model and performed in vivo experiments to investigate the type of fibers, neurons, and circuits recruited in response to EES. We first developed a realistic finite element computer model of rat lumbosacral segments to identify the currents generated by EES. To evaluate the impact of these currents on sensorimotor circuits, we coupled this model with an anatomically realistic axon-cable model of motoneurons, interneurons, and myelinated afferent fibers for antagonistic ankle muscles. Comparisons between computer simulations and experiments revealed the ability of the model to predict EES-evoked motor responses over multiple intensities and locations. Analysis of the recruited neural structures revealed the lack of direct influence of EES on motoneurons and interneurons. Simulations and pharmacological experiments demonstrated that EES engages spinal circuits trans-synaptically through the recruitment of myelinated afferent fibers. The model also predicted the capacity of spatially distinct EES to modulate side-specific limb movements and, to a lesser extent, extension versus flexion. These predictions were confirmed during standing and walking enabled by EES in spinal rats. These combined results provide a mechanistic framework for the design of spinal neuroprosthetic systems to improve standing and walking after neurological disorders.

Effect of a local vibration stimulus training programme on postural sway and gait in chronic stroke patients: a randomized controlled trial

Objective:

To investigate the effect of a local vibration stimulus training programme on postural sway and gait in stroke patients.

Design:

A randomized controlled trial with two groups: a local vibration stimulus training programme group and a sham group.

Setting:

Inpatient rehabilitation centre.

Subjects:

Thirty-one chronic stroke patients.

Interventions:

Both groups underwent a standard rehabilitation programme. The local vibration stimulus training programme group ( n = 16) participated in the local vibration stimulus training programme for 30 minutes a day, five times a week, for six weeks. The sham group ( n = 15) participated in a sham local vibration stimulus training programme for 30 minutes a day, five times a week, for six weeks.

Main measures:

A forceplate was used to measure postural sway under two conditions: standing with eyes open and eyes closed. Gait ability was measured using the GAITRite system.

Results:

In postural sway, greater improvements in the postural sway distance with eyes-open (–11.91 vs. 0.80) and eyes-closed (–20.67 vs. –0.34) conditions and postural sway velocity with eyes-open (–0.40 vs. 0.03) and eyes-closed (–0.69 vs. –0.01) conditions were observed in the local vibration stimulus training programme group, compared with the sham group ( P < 0.05). In gait ability, greater improvement in gait speed (15.06 vs. 2.85), cadence (8.46 vs. 1.55), step length (7.90 vs. 3.64), and single limb support time (0.12 vs. 0.01) were observed in the local vibration stimulus training programme group, compared with the sham group ( P < 0.05).

Conclusions:

These findings suggest that local vibration stimulus training programme is an effective method for improvement of the postural sway and gait ability of chronic stroke patients.

Independent control of presynaptic inhibition by reticulospinal and sensory inputs at rest and during rhythmic activities in the cat

To be functionally relevant during movement, the transmission from primary afferents must be efficiently controlled by presynaptic inhibition. Sensory feedback, central pattern generators, and supraspinal structures can all evoke presynaptic inhibition, but we do not understand how these inputs interact during movement. Here, we investigated the convergence of inputs from the reticular formation and sensory afferents on presynaptic inhibitory pathways and their modulation at rest and during two fictive motor tasks (locomotion and scratch) in decerebrate cats. The amplitude of primary afferent depolarization (PAD), an estimate of presynaptic inhibition, was recorded in individual afferents with intra-axonal recordings and in a mix of afferents in lumbar dorsal rootlets (dorsal root potential [DRP]) with bipolar electrodes. There was no spatial facilitation between inputs from reticulospinal and sensory afferents with DRPs or PADs, indicating an absence of convergence. However, spatial facilitation could be observed by combining two sensory inputs, indicating that convergence was possible. Task-dependent changes in the amplitude of responses were similar for reticulospinal and sensory inputs, increasing during fictive locomotion and decreasing during fictive scratch. During fictive locomotion, DRP and PAD amplitudes evoked by reticulospinal inputs were increased during the flexion phase, whereas sensory-evoked DRPs and PADs showed maximal amplitude in either flexion or extension phases. During fictive scratch, the amplitudes of DRPs and PADs evoked by both sources were maximal in flexion. The absence of spatial facilitation and different phase-dependent modulation patterns during fictive locomotion are consistent with independent presynaptic inhibitory pathways for reticulospinal and sensory inputs.