Mmax Ratio Research Articles

Dry Needling for Arthrogenic Muscle Inhibition of Quadriceps Femoris in Patients after Reconstruction of Anterior Cruciate Ligament: a Protocol for a Randomized Controlled Trial.

: Dry needling (DN) is recommended as a therapeutic modality for various neuromusculoskeletal disorders. No study has been performed on the impact of DN on arthrogenic muscle inhibition (AMI) after anterior cruciate ligament reconstruction (ACLR). This study protocol is aimed to investigate the impacts of DN on AMI of quadriceps femoris, corticomotor, and spinal reflex excitability in patients with ACLR. : A double-blind, between-subject, randomized, controlled trial will be conducted to measure changes in AMI after DN. Twenty-four subjects with ACLR will be recruited to receive a DN or a sham DN, providing that they met the inclusion criteria. Three sessions of DN on the quadriceps femoris will be applied during a one-week period. The primary outcome measures are the active motor threshold, motor evoked potential, and Hmax - Mmax ratio. The secondary outcomes are the International Knee Documentation Committee subjective knee form questionnaire score and maximum quadriceps isometric torque. Data will be collected at baseline, immediately after the first session, after the third session, and at the one-month follow-up visit. : The results of this study will provide preliminary evidence regarding the effects of DN on AMI of quadriceps femoris in patients with ACLR.

The effects of 72 h of dynamic ankle immobilization on neural excitability and lower extremity kinematics

BackgroundAnkle injuries can foster maladaptive changes in nervous system function that predisposes patients to subsequent injury. Patients are often placed in a dynamic boot immobilizer (BI) following injury; however, little is known about the effects of this treatment on neuromechanical function. Research questionWe aimed to determine the effect of 72 h of BI-use on neural excitability and lower extremity joint motion in a healthy cohort. MethodsTwelve uninjured individuals (20.8 ± 1.4 yrs, 1.7 ± 0.1 m, 75.2 ± 9.9 kg) participated in this crossover study. Neural excitability and lower extremity kinematics were assessed before and after 72 h of BI or compression sock (CS) use. Neural excitability was assessed via the Hoffmann (H) reflex and transcranial magnetic stimulation of the motor cortex by measuring muscle activation at the tibialis anterior, peroneus longus, and soleus of the immobilized extremity. Three-dimensional lower extremity joint angles were assessed while participants walked on a treadmill. Repeated-measures analyses of variance detected changes in neural excitability and peak joint angles across time-points and testing conditions, while statistical parametric mapping (SPM) was implemented to determine continuous joint angle changes (α = 0.05). ResultsPre-BI to post-BI, HMax:MMax ratio (F = 6.496; p = 0.031) significantly decreased. The BI did not alter resting motor threshold (F = 0.601; p = 0.468), or motor evoked potential amplitudes (F > 2.82; p > 0.608). Significant changes in peak knee and hip angles in the frontal and transverse planes were observed (p < 0.05), with no changes at the ankle. SPM analyses revealed significant hip and knee changes in range of motion (p < 0.05). SignificanceDecreased measures of reflex but not corticospinal excitability suggest that BI-use for 72 h unloaded the joint enough to generate peripheral changes, but not the CNS, as has been described in casting models. Further, kinematic changes were observed in proximal lower extremity joints, likely due to swing-phase adaptations while wearing the BI.

Dose-response relationship of transcutaneous spinal direct current stimulation in healthy humans: A proof of concept study.

Non-invasive transcranial direct current stimulation has been shown to modulate cortical excitability in various studies. Similarly, recent preliminary studies suggest that transcutaneous spinal direct current stimulation (tsDCS) may engender a modulation effect on spinal and cortical neurons. The purpose of this study was to evaluate the dose-response effects of tsDCS in healthy subjects and thereby lay groundwork for expanding treatment options for patients with spinal cord injury (SCI). Nine healthy subjects received each of the following 2 tsDCS conditions: Anodal and cathodal, in random order with at least 1 week washout period between each session. In order to test safety and dose response, various current intensities were used (2, 2.5 and 3 mA) for 20 minutes. The active electrode was placed vertically over T10-T11, and the reference electrode was placed over the left shoulder. To evaluate corticospinal excitability, motor evoked potentials over soleus muscle elicited by transcranial magnetic stimulation were measured. To assess spinal cord excitability, H- and M- wave over soleus muscle to calculate Hmax/ Mmax ratio were measured. Linear regression showed a dose response with cathodal tsDCS on motor evoked potentials measured from the left leg as well as with anodal tsDCS on Hmax/ Mmax ratio measured from the left leg. These findings indicate tsDCS effects are dose-dependent. These effects should be investigated in a larger sample.

Relationships Between Hoffman Reflex Parameters, Trait Stress, and Athletic Performance.

This study evaluated the relationships between trait stress, Hoffman reflex, and performance among 36 healthy amateur male athletes. We first obtained a trait stress questionnaire from participants and then assigned them to high- and low-stress groups. We next recorded Hoffman reflex data from the soleus and lateral gastrocnemius muscles and then examined their athletic performance on testing protocols separated by a 72-hour washout period. Performance testing utilized vertical jump height, 20 -m sprint time, and standing stork tests. There were significant correlations between (a) the standing stork test, vertical jump height, and trait stress and (b) Hmax/ Mmax ratios, threshold intensity ( Hth), the intensity of the Hmax, and the intensity of the Hlast. Hth, the intensity of Hmax, and the intensity of Hlast were significantly higher among the low-stress compared with the high-stress participant groups ( p < .05), despite participants' similar training history. We suggest that self-perceived psychological stress affects performance through neural adaptation.

Muscle-specific Cortical Adaptations To Balance Training With Electromyographic Biofeedback In Able-bodied Individuals

The use of electromyography biofeedback (EMG-BF) is frequently incorporated among patients with neurological and musculoskeletal injury to restore neuromuscular function and improve real-time awareness of muscle function. Its effects on central nervous system function are not well documented in lower leg models, leaving its efficacy in certain populations unclear. PURPOSE: This study aimed to measure reflexive and cortical excitability before and after a balance training intervention with and without EMG-BF. METHODS: Nineteen healthy participants volunteered for this study (183.0±20.1cm; 69.0±13.1kg; 21.1±2.3yrs). Reflexive excitability was assessed using the Hoffmann reflex from the tibialis anterior (TA), peroneus longus (PL), and soleus (SOL) through peripheral stimulation of the sciatic nerve in the popliteal fossa to obtain Hmax:Mmax ratios. Cortical excitability was assessed via transcranial magnetic stimulation to quantify motor evoked potential (MEP) size at 110 percent of TA resting motor threshold. Neural excitability was measured before and after two 30-minute balance training sessions. The control group (n=9) performed only balance training while the experimental group (n=10) received balance training with EMG-BF to maintain 30 percent of maximal PL contraction. Differences before and after training across groups were assessed using factorial analysis of variance (α=0.05). RESULTS: No differences between groups were observed for reflexive excitability (F=0.00, p=0.96). No MEP size differences were observed for TA (F=0.63, p=0.45) or PL (F=0.53, p=0.48); but a significant time by group interaction was observed for SOL (F=4.315, p=0.044). EMG-BF decreased SOL MEP size after training (0.083%Mmax to 0.048%Mmax). CONCLUSIONS: EMG-BF with short-term balance training decreased cortical excitability to SOL compared to balance training alone, perhaps representing reciprocal inhibitory mechanisms to the postural plantarflexors. These findings may have implications when considering interventions for dystonic or spastic populations.

Nervous system excitability and joint stiffness following short-term dynamic ankle immobilization

Joint immobilization has been demonstrated to modify neural excitability in subsets of healthy populations, leading to disinhibition of cortical and reflexive pathways. However, these findings may have limited clinical application as most models have investigated casting and rigid immobilization, while many musculoskeletal injuries often utilize dynamic immobilization devices such as boot immobilizers and pneumatic splints that allow for modified ambulation. We therefore aimed to determine the short-term effects of ambulation in ankle immobilization devices on nervous system excitability and stiffness in able-bodied individuals. A repeated-measures design was implemented where 12 healthy individuals were tested for cortical excitability to the ankle musculature using transcranial magnetic stimulation, reflexive excitability using the Hoffmann reflex, and ankle joint stiffness using arthrometry before and after 30min of ambulation with a boot immobilizer, pneumatic leg splint, or barefoot. Motor evoked potential (MEP), cortical silent period (CSP), Hmax to Mmax ratio, and ankle joint displacement were extracted as dependent variables. Results indicated that despite the novel motor demands of walking in immobilization devices, no significant changes in cortical excitability (F≥0.335, P≥0.169), reflexive excitability (F≥0.027, P≥0.083), or joint stiffness (F≥0.558, P≥0.169) occurred. These findings indicate that short-term ambulation in dynamic immobilization devices does not modify neural excitability despite forced constraints on the sensorimotor system. We may therefore conclude that modifications to neural excitability in previous immobilization models are mediated by long-term nervous system plasticity rather than acute mechanisms, and there appear to be no robust changes in corticomotor or spinal excitability acutely posed by ambulation with immobilization devices.

Modulation of the Fibularis Longus Hoffmann Reflex and Postural Instability Associated With Chronic Ankle Instability.

Individuals with chronic ankle instability (CAI) present with decreased modulation of the Hoffmann reflex (H-reflex) from a simple to a more challenging task. The neural alteration is associated with impaired postural control, but the relationship has not been investigated in individuals with CAI. To determine differences in H-reflex modulation and postural control between individuals with or without CAI and to identify if they are correlated in individuals with CAI. Descriptive laboratory study. Laboratory. A total of 15 volunteers with CAI (9 males, 6 females; age = 22.6 ± 5.8 years, height = 174.7 ± 8.1 cm, mass = 74.9 ± 12.8 kg) and 15 healthy sex-matched volunteers serving as controls (9 males, 6 females; age = 23.8 ± 5.8 years, height = 171.9 ± 9.9 cm, mass = 68.9 ± 15.5 kg) participated. Maximum H-reflex (Hmax) and motor wave (Mmax) from the soleus and fibularis longus were recorded while participants lay prone and then stood in unipedal stance. We assessed postural tasks of unipedal stance with participants' eyes closed for 10 seconds using a forceplate. We normalized Hmax to Mmax to obtain Hmax : Mmax ratios for the 2 positions. For each muscle, H-reflex modulation was quantified using the percentage change scores in Hmax : Mmax ratios calculated from prone position to unipedal stance. Center-of-pressure data were used to compute 4 time-to-boundary variables. Separate independent-samples t tests were performed to determine group differences. Pearson product moment correlation coefficients were calculated between the modulation and balance measures in the CAI group. The CAI group presented less H-reflex modulation in the soleus (t26 = -3.77, P = .001) and fibularis longus (t25 = -2.59, P = .02). The mean of the time-to-boundary minima in the anteroposterior direction was lower in the CAI group (t28 = -2.06, P = .048). We observed a correlation (r = 0.578, P = .049) between the fibular longus modulation and mean of time-to-boundary minima in the anteroposterior direction. The strong relationship indicated that, as H-reflex amplitude in unipedal stance was less down modulated, unipedal postural control was more impaired. Given the deficits in H-reflex modulation and postural control in the CAI group, the relationship may provide insights into the neurophysiologic mechanism of postural instability.

Assessment of the H‐reflex at two contraction levels before and after fatigue

The aim of the present study was to compare the H-reflex evoked at rest and at 20% maximal voluntary contraction (MVC) prior to and after fatiguing the lateral gastrocnemius (LG). The maximal H-reflex and M-wave were recorded in the LG, and soleus (SOL). Electrical evoked potentials were delivered to the posterior tibial nerve when muscles were inactivated and at 20% MVC. After fatigue, the Hmax /Mmax ratio of the fatigued LG was increased for both contraction levels (rest and 20% MVC) and remained unaltered for non-fatigued SOL. Before fatigue, the Hmax /Mmax ratio of SOL was enhanced at rest compared with the Hmax /Mmax ratio at 20% MVC. No differences were observed for LG. Fatigue of a single muscle leads to increased spinal reflex activity of the homonymous muscle. Contrary to previous recommendations in the literature, there appears to be no benefit withregard to the H-reflex amplitude in evoking electricalpotentials during constant voluntary contractions at 20% MVC compared with inactivated muscles. The observed difference in SOL prior to fatigue was most likelydue to hyperpolarization of the muscle fiber membrane.

Relationships between self-reported ankle function and modulation of Hoffmann reflex in patients with chronic ankle instability

ObjectiveTo examine relationships between self-reported ankle function and Hoffmann (H) reflex modulation during changes in body positions in patients with chronic ankle instability (CAI). DesignObservational. SettingLaboratory. ParticipantsThirty-one young adults with CAI (19 males, 12 females) participated. Main outcome measuresThere were two subscales of Foot and Ankle Ability Measure (FAAM) to quantify self-reported ankle function during activities of daily living (ADL) and sports activities. Maximum H-reflexes (H-max) and motor waves (M-max) from soleus and fibularis longus were recorded while participants lied prone and stood in bipedal and unipedal stances. For each muscle, percent change scores in Hmax:Mmax ratios were calculated between each pair of positions: prone-to-bipedal, bipedal-to-unipedal, and prone-to-unipedal, and used as a measure of H-reflex modulation. Pearson correlation coefficients were calculated between FAAM and H-reflex modulation measures. ResultsThere were significant correlations between: (1) FAAM-ADL and soleus prone-to-unipedal modulation (r = 0.384, p = 0.04), (2) FAAM-Sport and soleus prone-to-unipedal modulation (r = 0.505, p = 0.005), (3) FAAM-Sport and fibular bipedal-to-unipedal modulation (r = 0.377, p = 0.05), and (4) FAAM-Sport and fibular prone-to-unipedal modulation (r = 0.396, p = 0.04). ConclusionsCAI patients presented moderate, positive relationships between self-reported ankle function and H-reflex modulation during changes in body positions.

Facilitation of Hoffmann Reflexes of Ankle Muscles in Prone but Not Standing Positions by Focal Ankle-Joint Cooling

Focal ankle-joint cooling (FAJC) has been shown to increase Hoffmann (H) reflex amplitudes of select leg muscles while subjects lie prone, but it is unknown whether the neurophysiological cooling effects persist in standing. To assess the effects of FAJC on H-reflexes of the soleus and fibularis longus during 3 body positions (prone, bipedal, and unipedal stances) in individuals with and without chronic ankle instability (CAI). Crossover. Laboratory. 15 young adults with CAI (9 male, 6 female) and 15 healthy controls. All subjects received both FAJC and sham treatments on separate days in a randomized order. FAJC was accomplished by applying a 1.5-L plastic bag filled with crushed ice to the ankle for 20 min. Sham treatment involved room-temperature candy corn. Maximum amplitudes of H-reflexes and motor (M) waves were recorded while subjects lay prone and then stood in quiet bipedal and unipedal stances before and immediately after each treatment. Primary outcome measures were H(max):M(max) ratios for the soleus and fibularis longus. Three-factor (group × treatment condition × time) repeated-measures ANOVAs and Fisher LSD tests were performed for statistical analyses. Significant interactions of treatment condition by time for prone H(max):M(max) ratios were found in the soleus (P = .001) and fibularis longus (P = .003). In both muscles, prone H(max):M(max) ratios moderately increased after FAJC but not after sham treatment. The CAI and healthy groups responded similarly to FAJC. In contrast, there were no significant interactions or main effects in the bipedal and unipedal stances in either muscle (P > .05). FAJC moderately increased H-reflex amplitudes of the soleus and fibularis longus while subjects were prone but not during bipedal or unipedal standing. These results were not different between groups with and without CAI.

Muscle hypertonia after permanent focal cerebral ischemia in rats: a qualitative and quantitative behavioral and electrophysiological study

Objectives: To examine the level of peripheral muscle resistance after cerebral ischemia. Methods: A total of 326 healthy male Sprague-Dawley rats were used in the present experiments. We used a modified method to establish peripheral muscle resistance in rat model of stroke, and qualified the recovery of motor functional deficits by behavioral measures and quantified the level of peripheral muscle resistance by electrophysiological test. Results: Neurological score started to go up from day 0, achieved its peak on day 3 (1.49 ± 0.56) and kept at a high level within 10 days after surgery. Compared with 1 day before surgery, both the turn score in corner test and asymmetry score in cylinder test were increased significantly on day 3, day 6 and day 9 after surgery (p < 0.01). On day 6 and day 9 after surgery, the Hmax:Mmax ratio of hemiplegic side of middle cerebral artery occlusion (MCAO) rats was obviously higher than the same side in healthy rat (p < 0.01) and the ratio on the contralateral side of MCAO rats (p < 0.05). Conclusions: There is a progressive increase in peripheral muscle resistance on day 6 to day 9 after surgery in a rat model of postischemic stroke.

Altered postural modulation of Hoffmann reflex in the soleus and fibularis longus associated with chronic ankle instability

Our purpose was to assess Hoffmann (H) reflex modulations of the soleus and fibularis longus in three body positions (prone, bipedal and unipedal stances) in subjects with and without chronic ankle instability (CAI). Sixteen subjects with unilateral CAI and 15 healthy controls participated. Maximum H-reflexes and motor (M) waves were recorded bilaterally from the soleus and fibularis longus while subjects lied prone and then stood in quiet bipedal and unipedal stances. Maximum H-reflexes were normalized to maximum M waves to obtain Hmax:Mmax ratios for the three positions. H-reflex modulations, for each muscle, were quantified as the percent change scores in Hmax:Mmax ratios between each pair of positions: prone to bipedal, bipedal to unipedal, and prone to unipedal. There were significant group by limb interactions found for all three modulations (P<0.05) for the soleus. In the CAI group, soleus modulations in involved limbs were significantly lower than in uninvolved limbs and both limbs in the controls. For the fibularis longus, similar results were found for the bipedal to unipedal and prone to unipedal modulations. Constrained ability of the sensorimotor system to down regulate H-reflex in more demanding postures may represent a potential mechanism of postural control deficits associated with CAI.

Hand Splinting for Poststroke Spasticity: A Randomized Controlled Trial

Purpose: To determine the effect of volar and dorsal splinting on the spasticity of the wrist flexor muscles in patients who had stroke. Method: Thirty-nine subjects were prospectively randomized to use a dorsal or volar splint or no splint (control group). All the patients underwent home-based exercise program, and the experimental groups used either dorsal or volar hand splints according to their distribution. The primary outcome measure was spasticity assessed clinically by the Modified Ashworth Scale (MAS) and electrophysiologically by H latency and Hmax:Mmax ratio of flexor carpi radialis. Secondary outcome measure was passive range of motion (PROM) of wrist extension. Results: Spasticity parameters (MAS, H latency, Hmax:Mmax ratio) and wrist PROM were not significantly different among the groups. Conclusions: This study failed to demonstrate any statistically significant difference in spasticity or in wrist PROM of both the volar and dorsal splint groups. These splints could be recommended as part of an integrative approach without expecting a major clinical effect rather than as an alternative to other treatment.

The effect of operant-conditioning balance training on the down-regulation of spinal H-reflexes in a spastic patient

Spasticity in chronic hemiparetic stroke patients has primarily been treated pharmacologically. However, there is increasing evidence that physical rehabilitation can help manage hyper-excitability of reflexes (hyperreflexia), which is a primary contributor to spasticity. In the present study, one chronic hemiparetic stroke patient operantly conditioned the soleus H-reflex while training on a balance board for two weeks. The results showed a minimal decrease in the Hmax–Mmax ratio for both the affected and unaffected limb, indicating that the H-reflex was not significantly altered with training. Alternatively, paired-reflex depression (PRD), a measure of history-dependent changes in reflex excitability, could be conditioned. This was evident by the rightward shift and decreased slope of reflex excitability in the affected limb. The non-affected limb decreased as well, although the non-affected limb was very sensitive to PRD initially, whereas the affected limb was not. Based on these results, it was concluded that PRD is a better index of hyperreflexia, and this measurement could be more informative of synapse function than simple H-reflexes. This study presents a novel and non-pharmacological means of managing spasticity that warrants further investigation with the potential of being translated to the clinic.

Motor-Neuron Pool Excitability of the Lower Leg Muscles After Acute Lateral Ankle Sprain

Neuromuscular deficits in leg muscles that are associated with arthrogenic muscle inhibition have been reported in people with chronic ankle instability, yet whether these neuromuscular alterations are present in individuals with acute sprains is unknown. To compare the effect of acute lateral ankle sprain on the motor-neuron pool excitability (MNPE) of injured leg muscles with that of uninjured contralateral leg muscles and the leg muscles of healthy controls. Case-control study. Laboratory. Ten individuals with acute ankle sprains (6 females, 4 males; age= 19.2 ± 3.8 years, height= 169.4 ± 8.5 cm, mass= 66.3 ± 11.6 kg) and 10 healthy individuals(6 females,4 males; age= 20.6 ± 4.0 years, height = 169.9 ± 10.6 cm, mass= 66.3 ± 10.2 kg) participated. The independent variables were group (acute ankle sprain, healthy) and limb (injured, uninjured). Separate dependent t tests were used to determine differences in MNPE between legs. The MNPE of the soleus, fibularis longus, and tibialis anterior was measured by the maximal Hoffmann reflex (H(max)) and maximal muscle response (M(max)) and was then normalized using the H(max):M(max) ratio. The soleus MNPE in the ankle-sprain group was higher in the injured limb (H(max):M(max) = 0.63; 95% confidence interval [Cl],0.46, 0.80) than the uninjured limb (H(max):M(max) = 0.47; 95%Cl, 0.08, 0.93)(t(6) = 3.62,P =.01).In the acute ankle-sprain group, tibialis anterior MNPE tended to be lower in the injured ankle (H(max):M(max) =0.06; 95% Cl, 0.01, 0.10) than in the uninjured ankle (H(max):M(max) =0.22; 95%Cl, 0.09, 0.35),but this finding was not different (t(9) =-2.01, P =.07). No differences were detected between injured (0.22; 95% Cl, 0.14, 0.29) and uninjured (0.25; 95%Cl, 0.12, 0.38) ankles for the fibularis longus in the ankle-sprain group (t(9) =-0.739, P =.48). We found no side-to-side differences in any muscle among the healthy group. Facilitated MNPE was present in the involved soleus muscle of patients with acute ankle sprains, but no differences were found in the fibularis longus or tibialis anterior muscles.

Spinal Reflex Adaptation in Dancers

Dancers undergo specific activity-dependent neuromuscular adaptations following long-term training that allow them to develop the refined motor skills required for success in dance. The spinal stretch reflex circuit has demonstrated specific adaptations following prolonged dance training. Adaptations in the spinal stretch reflex can be studied using H-reflex methodology, first described by Paul Hoffmann in 1910. This article discusses H-reflex methodology and presents data that examine the neural mechanisms that contribute to adaptations in the spinal stretch reflex with dance training. Two groups of subjects, modern dancers (N = 5) and untrained controls (N = 5), were tested. On one-half of the trials common peronal nerve (CPN) conditioning of the soleus H-reflex was used to assess one spinal mechanism, pre-synaptic inhibition; the other half tested the soleus H-reflex only (unconditioned). The dependent variables were the Hmax/Mmax ratios, unconditioned and with CPN conditioning, expressed as percent values. The results revealed three main findings: 1. Modern dancers had smaller Hmax/Mmax ratios than control subjects; 2. The Hmax/ Mmax ratio was smaller in standing posture than in prone among both dancers and controls; and 3. Pre-synaptic inhibition was not different between dancers and controls in standing. In conclusion, modern dancers have smaller H-reflexes than untrained controls, but pre-synaptic inhibition does not appear to explain this difference.

Effect of breathing 7% carbon dioxide on the human soleus Hoffmann-reflex recruitment curve

Objective To examine the effect of inhaling 7% carbon dioxide on the recruitment curve of the soleus H-reflex. Methods Five males and five females (apparently healthy; 21–40 yr) with surface EMG electrodes over the soleus muscle randomly breathed room air or a 7% CO 2, 21% O 2, balance N 2 mix for 10 min. The tibial nerve was stimulated to elicit the H-reflex recruitment curve. H-reflex threshold, motor threshold, slope of ascending H-reflex curve, Hmax:Mmax ratio, and latency of Hmax were compared. Results Breathing 7% carbon dioxide increased the H-reflex threshold (as a percent of motor threshold) from 73% (SD 0.09) to 84% (SD 0.12; p < 0.05), decreased the Hmax:Mmax ratio from 0.504 (SD 0.290) to 0.403 (SD 0.253; p < 0.05), and increased the H wave latency (in msec) from 32.8 (SD 1.6) to 34.6 (SD 2.6; p < 0.05). Slope of ascending H-reflex curve (room air: 125 (SD 89); CO 2: 135 (SD 92); p > 0.05), Mmax (room air: 3.70 mV (SD 1.57); CO 2: 3.69 mV (SD 1.53); p > 0.05), and motor threshold ( p > 0.05) remained unchanged. Conclusions Breathing 7% carbon dioxide reduces afferent synaptic transmission in the soleus muscle by slowing transmission, increasing threshold stimulus, and reducing H wave size. Significance Clinicians and scientists should consider the possibility that carbon dioxide can reduce afferent synaptic transmission.

An Investigation of the Neurophysiologic Effect of Tone-Reducing AFOs on Reflex Excitability in Subjects with Spasticity Following Stroke while Standing

Tone-reducing ankle-foot orthoses (TRAFOs) are said to improve the control and functioning of spastic lower limbs by their biomechanic and neurophysiologic effects. Unfortunately, there is limited evidence in literature to support the theory that TRAFOs can effectively decrease spasticity in the foot and ankle neurophysiologically. The primary purpose of this investigation was to determine the neurophysiologic effect of TRAFOs on soleus muscle reflex excitability in subjects with spasticity following stroke while standing. A repeated-measures intervention study was conducted on 15 adult subjects with stroke who were recruited from the community. Custom-made articulated ankle-foot orthoses (AFOs) and TRAFOs with orthokinetic compression garments (OCGs) were fabricated for each subject. Five conditions were tested: (1) Shoes only, (2) AFO, (3) TRAFO, (4) TRAFO with OCG, (5) shoes only, to determine if the TRAFOs were most effective in decreasing spasticity as assessed by the ratio of maximum Hoffmann reflex amplitude to maximum muscle response amplitude (Hmax:Mmax ratio) of the soleus. The results found that there were no significant treatment effects for the interventions (F = 0.992, df = 2.167, p = 0.388), however, when analysed subject-by-subject, four subjects displayed significant increases in their Hmax:Mmax ratios to at least one treatment condition. Overall, the results demonstrated that the tone-reducing devices had no significant neurophysiologic effect on soleus reflex excitability in subjects with spasticity, however individual responses showed that the TRAFOs increased spasticity in some individuals.

Effects of Menthol-Based Counterirritant on Quadriceps Motoneuron-Pool Excitability

Motoneuron-pool facilitation after cryotherapy may be mediated by stimulation of thermoreceptors surrounding a joint. It is unknown whether menthol counterirritants, which also stimulate thermoreceptors, have the same effect on motoneuron-pool excitability (MNPE). To compare quadriceps MNPE after a menthol-counterirritant application to the anterior knee, a sham counterirritant application, and a control treatment in healthy subjects. A blinded, randomized controlled laboratory study. Laboratory. Thirty healthy subjects (16 m, 14 f; 24.1 +/- 3.9 y, 170.6 +/- 11.4 cm, 72.1 +/- 15.6 kg) with no history of lower extremity surgery volunteered for this study. Two milliliters of menthol or sham counterirritant was applied to the anterior knee; control subjects received no intervention. The average vastus medialis normalized Hoffmann reflex (Hmax:Mmax ratio) was used to measure MNPE. Measurements were recorded at 5, 15, 25, and 35 minutes postintervention and compared with baseline measures. Hmax:Mmax ratios for all groups significantly decreased over time (F(4,108) = 10.52, P < .001; menthol: baseline = .32 +/- .20, 5 min = .29 +/- .18, 15 min = .27 +/- .18, 25 min = .28 +/- .19, 35 min = .27 +/- .18; sham: baseline = .46 +/- .26, 5 min = .36 +/- .20, 15 min = .35 +/- .19, 25 min = .35 +/- .20, 35 min = .34 +/- .18; control: baseline = .48 +/- .32, 5 min = .37 +/- .27, 15 min = .37 +/- .27, 25 min = .37 +/- .29, 35 min = .35 +/- .28). No significant Group x Time interaction or group differences in Hmax:Mmax were found. Menthol did not affect quadriceps MNPE in healthy subjects.

Long term course of the H reflex after selective tibial neurotomy

Objectives: This study was conducted to evaluate the long term clinical and electrophysiological outcome by recording the H reflex in a consecutive series of six patients treated by selective tibial...