Hoffmann Reflex Research Articles

“EPIDEMIOLOGY AND PREVENTION OF ACCIDENTS IN ROLLER SPORTS (RS). FOUR YEARS OF STUDIES AND OBSERVATIONS ON ACCIDENTS OF ITALIAN FEDERATION (FIHP) SKATERS. PROBABLE CAUSES AND PREVENTION”

BackgroundRoller sports (RS) have continuous spreading, not only a recreational activity. There are different sports modalities, ruled by national/international organizations. We investigated at the FIHP, being the world leader for...

Contributions of neural excitability and voluntary activation to quadriceps muscle strength following anterior cruciate ligament reconstruction

BackgroundPersistent quadriceps weakness is common following anterior cruciate ligament reconstruction (ACLr). Alterations in spinal-reflexive excitability, corticospinal excitability and voluntary activation have been hypothesized as underlying mechanisms contributing to quadriceps weakness. The aim of this study was to evaluate the predictive capabilities of spinal-reflexive excitability, corticospinal excitability and voluntary activation on quadriceps strength in healthy and ACLr participants. MethodsQuadriceps strength was measured using maximal voluntary isometric contractions (MVIC). Voluntary activation was quantified via the central activation ratio (CAR). Corticospinal and spinal-reflexive excitability were measured using active motor thresholds (AMT) and Hoffmann reflexes normalized to maximal muscle responses (H:M), respectively. ACLr individuals were also split into high and low strength subsets based on MVIC. ResultsCAR was the only significant predictor in the healthy group. In the ACLr group, CAR and H:M significantly predicted 47% of the variance in MVIC. ACLr individuals in the high strength subset demonstrated significantly higher CAR and H:M than those in the low strength subset. ConclusionIncreased quadriceps voluntary activation, spinal-reflexive excitability and corticospinal excitability relates to increased quadriceps strength in participants following ACLr. Clinical relevanceRehabilitation strategies used to target neural alterations may be beneficial for the restoration of muscle strength following ACLr.

Input–output characteristics of soleus homonymous Ia afferents and corticospinal pathways during upright standing differ between young and elderly adults

This study investigated the effects of ageing on the excitability of soleus homonymous Ia afferents and corticospinal pathways during bipedal upright standing. The input-output relations for the Hoffmann (H) reflex and motor-evoked potential (MEP) were computed for the soleus in response to electrical nerve stimulation and transcranial magnetic stimulation, respectively, in young (n = 16) and elderly (n = 16) adults. In subsets of subjects, the input-output relations were compared between normal and supported upright standing, and corticomotoneuronal excitability was assessed during upright standing with an H-reflex conditioning method. For the H-reflex and MEP threshold, maximal amplitude (Hmax , MEPmax ) and the slope of the input-output relation (Hslope , MEPslope ) were measured and normalized to the corresponding M-wave value. In normal standing, the Hmax /Mmax [mean (SD); young: 48.3 (14.2)%; elderly: 17.3 (6.4)%] and Hslope /Mslope were significantly (P < 0.05) lower in elderly than in young adults, whereas the MEPmax /Mmax [young: 13.6 (7.5)%; elderly: 24.5 (12.8)%] and MEPslope /Mslope were greater in elderly adults (P < 0.05). The Hslope /Mslope and MEPslope /Mslope decreased and increased, respectively, from supported to normal standing for both age groups but more so in elderly adults. Furthermore, the conditioned H reflex was greater (P < 0.05) in elderly [175.1 (34.3)%] than in young adults [141.8 (29.8)%] during normal standing. This is the first study that clearly indicates lower efficacy of Ia afferents to discharge spinal motor neurones accompanied by greater corticospinal excitability in elderly adults, suggesting an increased contribution of the descending drive in controlling soleus activity during upright standing with ageing.

Weakened rate-dependent depression of Hoffmann’s reflex and increased motoneuron hyperactivity after motor cortical infarction in mice

Abnormal reflexes associated with spasticity are considered a major determinant of motor impairments occurring after stroke; however, the mechanisms underlying post-stroke spasticity remain unclear. This may be because of the lack of suitable rodent models for studying spasticity after cortical injuries. Thus, the purpose of the present study was to establish an appropriate post-stroke spasticity mouse model. We induced photothrombotic injury in the rostral and caudal forelimb motor areas of mice and used the rate-dependent depression (RDD) of Hoffmann's reflex (H-reflex) as an indicator of spastic symptoms. To detect motoneuron excitability, we examined c-fos mRNA levels and c-Fos immunoreactivity in affected motoneurons using quantitative real-time reverse transcription PCR and immunohistochemical analysis, respectively. To confirm the validity of our model, we confirmed the effect of the anti-spasticity drug baclofen on H-reflex RDDs 1 week post stroke. We found that 3 days after stroke, the RDD was significantly weakened in the affected muscles of stroke mice compared with sham-operated mice, and this was observed for 8 weeks. The c-fos mRNA levels in affected motoneurons were significantly increased in stroke mice compared with sham-operated mice. Immunohistochemical analysis revealed a significant increase in the number of c-Fos-positive motoneurons in stroke mice compared with sham-operated mice at 1, 2, 4, and 8 weeks after stroke; however, the number of c-Fos-positive motoneurons on both sides of the brain gradually decreased over time. Baclofen treatment resulted in recovery of the weakened RDD at 1 week post stroke. Our findings suggest that this is a viable animal model of post-stroke spasticity.

Effect of Joint Traction and Approximation on H- Reflex in Normal Subjects

Introduction : Proprioceptive sensation (kinaesthesia and/or joint position sense), one of the most important somatosensory modalities, is known to play an important role in body balance and motor control. Joint traction and approximation are two proprioceptive stimuli applied at the joint. Studies reveal that an unidentified set of muscle afferent fibres and cutaneous receptors both contribute to the sense of movement and position. The Hoffmann reflex (H- reflex), an electrically evoked monosynaptic reflex, is a measure of the final common pathway, or the motor output. Objective : To find out the effect of traction and approximation on H-reflex. Method : Study performed on 20 normal subjects both males and females taken from the city Anand under the age group of 19-26 years. This is an experimental study, which is performed in the clinic of physiotherapy. The subject was made to lie prone comfortably on a plinth. The tibial nerve was stimulated at the popliteal fossa using 1 ms pulse and then finds H- latency and amplitude of Hwave. The subject was made to stand on the wooden board with same electrode arrangement to approximate the articular surfaces of the knee joint. The procedure was repeated to find H- latency, and amplitude of H- wave. The subject was made to sit on the stool with same electrode arrangement and right leg hanging freely off the stool. A 2 kg weight was tied at the ankle to distract the knee joint. The procedure was repeated to find H- latency, and amplitude of H- wave. Results : There is significant difference in H-reflex latency and amplitude in prone, joint traction and approximation. Conclusion : There is significant change in latency with proprioceptive input.

Carbon dioxide alters the Hoffmann reflex independent of hydrogen ions

The purpose of this study was to examine the effect of changes in capillary blood pH on the resting soleus Hoffmann (H) reflex in the intact human. H-max size, H-wave at 20% of H-max, M-max and H-reflex latency were recorded in 10 subjects (apparently healthy, ages 19–36) before and after exposure to 3 hours of NaHCO3, CaCO3, NH4Cl (all at 0.3 g/kg) or 10 minutes 7% Carbon dioxide (CO2) administration. NaHCO3 increased capillary blood pH, CaCO3 did not change capillary blood pH, and NH4Cl and 7% CO2 decreased capillary blood pH. H-max and H-wave at 20% of M-max size were significantly decreased with no change in M-max, and H-reflex latency significantly increased during 7% CO2 administration only. No other changes in H-maximum size or H-reflex latency in response to dry chemical administration were observed. Seven percent CO2 administration reduces the size and increases the latency of the H-maximum size as previously found, but other chemicals which alter capillary blood pH do not. CO2 modulates afferent nerve function, and does so, it appears, independent of changes in capillary blood pH.

Cognitive demand does not influence the responsiveness of homonymous Ia afferents pathway during postural dual task in young and elderly adults

This study was designed to investigate the influence of a cognitive task on the responsiveness of the homonymous Ia afferents pathway during upright standing in young and elderly adults. Twelve young and twelve elderly adults stood upright on a foam surface positioned over a force platform, and performed a colour-naming test (cognitive task) with two cognitive loads: congruent and incongruent colour conditions. The rate of correct response in naming colour (accuracy) and associated reaction time (RT) were recorded for the cognitive task. The excursion of the centre of pressure and surface electromyogramme (EMG) of leg muscles were measured. Modulation in the efficacy of homonymous Ia afferents to discharge spinal motor neurones was assessed by means of the Hoffmann (H) reflex method. The accuracy and RT were similar in the congruent condition between young and elderly adults (p > 0.05), and increased for both age groups in the incongruent condition, but more so for elderly adults (p = 0.014). In contrast, the H reflex amplitude did not change with the cognitive load. The excursions of the centre of pressure in the sagittal plane and muscle EMG did not vary with colour conditions in both groups (p > 0.05). This study indicates a lack of modulation in the efficacy of group Ia afferent to activate soleus motor neurones with the cognitive demand of a concurrent task during upright standing in young and elderly adults.

Cortical inhibition is reduced following short-term training in young and older adults

The purpose of this study was to investigate age-related differences in short-term training adaptations in cortical excitability and inhibition. Thirty young (21.9 ± 3.1years) and 30 older (72.9 ± 4.6years) individuals participated in the study. Each participant was randomly assigned to a control (n = 30) or a resistance training (n = 30) group, with equal numbers of young and older subjects in each group. Participants completed 2days of testing, separated by 2weeks during which time the training group participated in resistance training of the ankle dorsiflexor muscles three times per week. During each testing session, transcranial magnetic stimulation was used to generate motor evoked potentials (MEPs) and silent periods in the tibialis anterior. Hoffmann reflexes (H-reflexes) and compound muscle action potentials (M-waves) were also evoked via electrical stimulation of the peroneal nerve. At baseline, young subjects had higher maximum voluntary contraction (MVC) force (p = 0.002), larger M-wave amplitude (p < 0.001), and longer duration silent periods (p = 0.01) than older individuals, with no differences in the maximal amplitude of the MEP (p = 0.23) or H-reflex (p = 0.57). In the trained group, MVC increased in both young (17.4%) and older (19.8%) participants (p < 0.001), and the duration of the silent period decreased by ~15 and 12ms, respectively (p < 0.001). Training did not significantly impact MEP (p = 0.69) or H-reflex amplitudes (p = 0.38). There were no significant changes in any measures in the control group (p ≥ 0.19) across the two testing sessions. These results indicate that a reduction in cortical inhibition may be an important neural adaptation in response to training in both young and older adults.

Diagnostic advantage of S1 foramen-evoked H-reflex for S1 radiculopathy in patients with diabetes mellitus

Hoffmann reflex to tibial nerve stimulation at the popliteal fossa (tibial H-reflex) is routinely used to evaluate S1 radiculopathy. However, it lacks sensitivity because other lesions along this reflex circuit affect the H-reflex bilaterally. This study was undertaken to determine whether the H-reflex evoked by stimulating proximally at the S1 foramen (S1 foramen H-reflex) could improve S1 root lesion evaluation sensitivity in patients with diabetes mellitus. A randomized paired study was designed to evaluate tibial and S1 foramen H-reflexes; bilateral H-M interval (HMI) and H-reflex latency were compared in 22 diabetic patients with unilateral S1 radiculopathy. Other electrophysiological evaluations included standard tibial conduction studies, sural conduction studies and needle electromyography (EMG). The S1 foramen H-reflex had a significantly higher sensitivity (91.0%, 20 of 22) in evaluating S1 radiculopathy than the conventional tibial H-reflex (63.6%, 14 of 22, p < 0.05). Bilateral tibial compound muscle action potential amplitudes were reduced in 3 patients, and sural sensory nerve action potential amplitudes decreased in 7 patients. Needle EMG revealed denervation restricted to the paraspinal muscle and myotomes supplied by the S1 nerve root on the ipsilateral side in 18 patients, and multiple lumbosacral nerve roots were involved bilaterally in the other 4 patients. Our results demonstrate that the S1 foramen H-reflex is a more sensitive assessment of S1 compressive radiculopathy in patients with diabetes mellitus.

Long-term neuromechanical results of selective tibial neurotomy in patients with spastic equinus foot

The neuromechanical consequences of tibial neurotomy have not been extensively studied. Fifteen patients were evaluated before and after selective tibial neurotomy (after 2 months and after 15 months) by means of clinical, neurophysiological [tendon (T) reflexes, Hoffmann (H) reflexes and maximum motor response, Mmax] and mechanical parameters (passive stiffness of plantar flexors at the ankle). The neurotomy concerned the soleus (100 % of cases), gastrocnemius (20 % of cases), posterior tibial (60 % of cases) and flexor digitorum longus (47 % of cases) nerves. Neurotomy provided more than 90 % improvement of clinical spasticity scores, 20 % improvement of walking scores and the angle of passive dorsiflexion (APDF) of the ankle (mean angle: 7°), temporary reduction of the soleus Mmax (18 % at 2 months with return to the preoperative value at 15 months), and lasting reduction of the soleus Hmax/Mmax (68 % at 2 months, 78 % at 15 months) and T/Mmax (84 % at 2 months, 80 % at 15 months). M and H responses of the gastrocnemius (whether or not they were included in the neurotomy) were not modified, while T/Mmax decreased to the same degree as for soleus. Passive stiffness was lastingly decreased from 64.0 Nm/rad to 49.0 Nm/rad (2 months) and 49.5 Nm/rad (15 months). Selective tibial neurotomy of the soleus nerve induces long-term reduction of reflex hyperexcitability and passive stiffness of plantar flexors in spastic patients, with no lasting impairment of motor efferents. In parallel, it modifies the tendon reflexes of synergistic muscles (gastrocnemius) not concerned by the neurotomy.

Effects of postural threat on spinal stretch reflexes: evidence for increased muscle spindle sensitivity?

Standing balance is often threatened in everyday life. These threats typically involve scenarios in which either the likelihood or the consequence of falling is higher than normal. When cats are placed in these scenarios they respond by increasing the sensitivity of muscle spindles imbedded in the leg muscles, presumably to increase balance-relevant afferent information available to the nervous system. At present, it is unknown whether humans also respond to such postural threats by altering muscle spindle sensitivity. Here we present two studies that probed the effects of postural threat on spinal stretch reflexes. In study 1 we manipulated the threat associated with an increased consequence of a fall by having subjects stand at the edge of an elevated surface (3.2 m). In study 2 we manipulated the threat by increasing the likelihood of a fall by occasionally tilting the support surface on which subjects stood. In both scenarios we used Hoffmann (H) and tendon stretch (T) reflexes to probe the spinal stretch reflex circuit of the soleus muscle. We observed increased T-reflex amplitudes and unchanged H-reflex amplitudes in both threat scenarios. These results suggest that the synaptic state of the spinal stretch reflex is unaffected by postural threat and that therefore the muscle spindles activated in the T-reflexes must be more sensitive in the threatening conditions. We propose that this increase in sensitivity may function to satisfy the conflicting needs to restrict movement with threat, while maintaining a certain amount of sensory information related to postural control.

Corticospinal responses of resistance-trained and un-trained males during dynamic muscle contractions

Little is known regarding the modulation and the plasticity of the neural pathway interconnecting elements of the central nervous system and skeletal muscle in resistant-trained individuals. The aim of the study was to compare corticospinal and spinal responses measured during dynamic muscle contractions of the tibialis anterior in resistance trained (RT) and un-trained (UT) males. Nine UT and 10 RT male volunteers reported to the laboratory 24h following a familiarisation session. Motor evoked potentials (MEPs) and the cortical silent period were evoked using transcranial magnetic stimulation at a range of contraction intensities and was delivered as the ankle passed 90° during shortening and lengthening contractions. The Hoffmann reflex (H-reflex) and V-waves were evoked with peripheral nerve stimulation. Despite the RT group being significantly stronger during shortening (28%; P=0.023: CI=1.27–15.1Nm), lengthening (25%; P=0.041: CI=0.27–17.0Nm) and isometric muscle actions (20%; P=0.041; CI=0.77–14.9Nm), no differences between the groups existed for corticospinal or spinal variables. Lack of detectable differences between RT and UT individuals may be linked to minimal exposure to task specific, isolated high intensity resistance training of the TA muscle.

Neuromechanical assessment of lidocaine test block in spastic lower limbs

The objective of this study was to quantify in spastic lower limbs the changes in reflex EMGs and in ankle stiffness after a lidocaine block of the soleus nerve to better understand physiological effects of lidocaine. Twenty patients were prospectively included and assessed before and after lidocaine block of the soleus nerve. We studied clinical and neuromechanical parameters of the triceps surae, including quantification of the maximum Hoffmann's reflex (Hmax) and tendinous reflex (T) normalized to the maximum direct motor response (Mmax), and passive ankle stiffness assessed by sinusoidal length perturbations. All patients whatever the aetiology of spasticity were improved in clinical parameters of spasticity after the block (62% reduction of the Ashworth score, 85% reduction of stretch reflex scores, increased score on the Physicians' Rating Scale). All patients presented a reduction of the Hmax-Mmax ratio (mean reduction of 67%) and the T-Mmax ratio (82%). Ankle stiffness was decreased by an average of 23%. Measured stiffness was correlated with the Ashworth score and the T-Mmax ratio. Relatively greater change in the T reflex than in the H reflex suggests that lidocaine block reduces hyperreflexia not only by interfering with generation of afferent volleys in the injected nerve, but also probably by altering generation of the volleys at the level of muscle spindles in the affected spastic muscles, presumably by blocking the transmission along gamma-efferent fibers.

Time Course of the Soleus M Response and H Reflex after Lidocaine Tibial Nerve Block in the Rat

Aims. In spastic subjects, lidocaine is often used to induce a block predictive of the result provided by subsequent surgery. Lidocaine has been demonstrated to inhibit the Hoffmann (H) reflex to a greater extent than the direct motor (M) response induced by electrical stimulation, but the timecourse of these responses has not been investigated. Methods. An animal (rat) model of the effects of lidocaine on M and H responses was therefore developed to assess this time course. M and H responses were recorded in 18 adult rats before and after application of lidocaine to the sciatic nerve. Results. Two to five minutes after lidocaine injection, M responses were markedly reduced (mean reduction of 44%) and H reflexes were completely abolished. Changes were observed more rapidly for the H reflex. The effects of lidocaine then persisted for 100 minutes. The effect of lidocaine was therefore more prolonged on the H reflex than on the M response. Conclusion. This study confirms that lidocaine blocks not only alpha motoneurons but also Ia afferent fibres responsible for the H reflex. The authors describe, for the first time, the detailed time course of the effect of lidocaine on direct or reflex activation of motoneurons in the rat.

Induced Anterior Knee Pain Immediately Reduces Involuntary and Voluntary Quadriceps Activation

To examine the immediate effects of experimentally induced anterior knee pain (AKP) on involuntary and voluntary quadriceps strength and activation. Crossover 3 × 3 randomized controlled laboratory study with repeated measures. Human Performance Research Center, Brigham Young University. Thirteen neurologically sound volunteers (age, 21.9 ± 3.2 years). Subjects underwent 3 different conditions (pain, sham, and control). To induce AKP and sham condition, 5% sodium chloride and 0.9% sodium chloride (total volume of 1.0 mL for each condition), respectively, were injected into the infrapatellar fat pad on the dominant leg. No injection was performed for the control condition. The vastus medialis peak Hoffmann reflex normalized by the peak motor response (H:M ratio) was used to measure involuntary quadriceps activation. Quadriceps central activation ratio (CAR) using maximal isometric knee extension torque (N·m) was calculated to assess voluntary quadriceps activation. The visual analog scale was used to measure pain perception. Our pain model increased perceived pain immediately after the 5% hypertonic saline injection and pain lasted for 12 minutes on average (F40,743 = 16.85, P < 0.001). During the pain condition, subjects showed a 12% decrease in H:M ratio (F2,59 = 8.64, P < 0.001), a 34% decrease in maximal isometric knee extension torque (F2,59 = 5.89, P < 0.01), and a 5% decrease in CAR (F2,59 = 3.83, P = 0.03). Our data showed that joint pain may be an independent factor to alter function of the muscles surrounding the painful joint. Both involuntary and voluntary inhibitory pathways may play a role in an immediate reduction of muscle activation.

Theta burst repetitive transcranial magnetic stimulation attenuates somatosensory evoked potentials from the lower limb

BackgroundContinuous theta burst stimulation (cTBS) is a form of repetitive transcranial magnetic stimulation which has been shown to alter cortical excitability in the upper limb representation of primary somatosensory cortex (SI). However, it is unknown whether cTBS modulates cortical excitability within the lower limb representation in SI. The present study investigates the effects of cTBS over the SI lower limb representation on cortical somatosensory evoked potentials (SEPs) and Hoffmann reflex (H-reflex) following tibial nerve stimulation at the knee. SEPs and H-reflex were recorded before and in four time blocks up to 30 minutes following cTBS targeting the lower limb representation within SI.ResultsFollowing cTBS, the P1-N1 first cortical potential was significantly decreased at 12–16 minutes. CTBS also suppressed the P2-N2 second cortical potential for up to 30 minutes following stimulation. The H-reflex remained statistically unchanged following cTBS although there was a modest suppression observed.ConclusionWe conclude that cTBS decreases cortical excitability of the lower limb representation of SI as evidenced by suppressed SEP amplitude. The duration and magnitude of the cTBS after effects are similar to those observed in upper limb studies.

Age‐related influence of vision and proprioception on Ia presynaptic inhibition in soleus muscle during upright stance

This study investigated the modulation of Ia afferent input in young and elderly adults during quiet upright stance in normal and modified visual and proprioceptive conditions. The surface EMG of leg muscles, recruitment curve of the soleus (SOL) Hoffmann (H) reflex and presynaptic inhibition of Ia afferents from SOL, assessed with the D1 inhibition and single motor unit methods, were recorded when young and elderly adults stood with eyes open or closed on two surfaces (rigid vs. foam) placed over a force platform. The results showed that elderly adults had a longer path length for the centre of pressure and larger antero-posterior body sway across balance conditions (P < 0.05). Muscle EMG activities were greater in elderly compared with young adults (P < 0.05), whereas the H(max) expressed as a percentage of the H(max) was lower (P = 0.048) in elderly (38 ± 16%) than young adults (58 ± 16%). The conditioned H reflex/test H reflex ratio (D1 inhibition method) increased with eye closure and when standing on foam (P < 0.05), with greater increases for elderly adults (P = 0.019). These changes were accompanied by a reduced peak motor unit discharge probability when standing on rigid and foam surfaces (P 0.001), with a greater effect for elderly adults (P = 0.026). Based on these latter results, the increased conditioned H reflex/test H reflex ratio in similar sensory conditions is likely to reflect occlusion at the level of presynaptic inhibitory interneurones. Together, these findings indicate that elderly adults exhibit greater modulation of Ia presynaptic inhibition than young adults with variation in the sensory conditions during upright standing.

Immediate Effects of Acupuncture and Cryotherapy on Quadriceps Motoneuron Pool Excitability: Randomised Trial Using Anterior Knee Infusion Model

The authors asked the following research questions: will an anterior knee infusion model induce constant pain? will perceived pain alter motoneuron pool (MNP) excitability? and will treatments alter perceived pain and/or MNP excitability? Thirty-six neurologically healthy volunteers participated in this randomised controlled laboratory study. To induce anterior knee pain (AKP), 5% hypertonic saline (0.12 ml/min with a total volume of 8.5 ml over 70 min) was injected into the infrapatellar fat pad of the dominant leg. One of four 30-min treatments was randomly assigned to each subject after pain was induced (acupuncture, cryotherapy, sham cryotherapy and no treatment). Five acupuncture needles (SP9, SP10, ST36, GB34 and an ah shi point) were inserted to a depth of 1 cm. Vastus medialis (VM) maximum Hoffmann reflexes normalised by maximum motor response were recorded from each subject at baseline, 20 min post-injection, 50 min post-injection and 70 min post-injection. To record pain perception, a visual analogue scale was used every 5 min after injection. An anterior knee infusion pain model increased perceived pain (p<0.0001). No change was found in VM MNP excitability among the four treatments (p<0.19) or at any of the time intervals (p<0.52). Cryotherapy reduced perceived pain compared with acupuncture (p=0.0003) and sham treatment (p=0.0002). A pain model may be used in other neurophysiological intervention studies related to AKP. AKP alone may not directly alter quadriceps activation. None of the treatments altered VM MNP excitability. Cryotherapy reduced pain while a single session of acupuncture and sham treatments did not.

Are H-reflex and M-wave recruitment curve parameters related to aerobic capacity?

Soleus Hoffmann reflex (H-reflex) amplitude is affected by a training period and type and level of training are also well known to modify aerobic capacities. Previously, paired changes in H-reflex and aerobic capacity have been evidenced after endurance training. The aim of this study was to investigate possible links between H- and M-recruitment curve parameters and aerobic capacity collected on a cohort of subjects (56 young men) that were not involved in regular physical training. Maximal H-reflex normalized with respect to maximal M-wave (H(max)/M(max)) was measured as well as other parameters of the H- or M-recruitment curves that provide information about the reflex or direct excitability of the motoneuron pool, such as thresholds of stimulus intensity to obtain H or M response (H(th) and M(th)), the ascending slope of H-reflex, or M-wave recruitment curves (H(slp) and M(slp)) and their ratio (H(slp)/M(slp)). Aerobic capacity, i.e., maximal oxygen consumption and maximal aerobic power (MAP) were, respectively, estimated from a running field test and from an incremental test on a cycle ergometer. Maximal oxygen consumption was only correlated with M(slp), an indicator of muscle fiber heterogeneity (p< 0.05), whereas MAP was not correlated with any of the tested parameters (p> 0.05). Although higher H-reflex are often described for subjects with a high aerobic capacity because of endurance training, at a basic level (i.e., without training period context) no correlation was observed between maximal H-reflex and aerobic capacity. Thus, none of the H-reflex or M-wave recruitment curve parameters, except M(slp), was related to the aerobic capacity of young, untrained male subjects.

Usefulness of the Tendon Reflex for Assessing Spasticity After Botulinum Toxin-A Injection in Children With Cerebral Palsy

This study sought to investigate the relationships between clinical and neurophysiologic assessments of spasticity after injection of botulinum toxin-A in children with cerebral palsy. A total of 40 children were recruited. Clinical assessments included the modified Ashworth scale and modified Tardieu scale parameters R1, R2, and D. Neurophysiologic assessment included compound motor action potential, Hoffmann, and tendon reflex. Children showed significant decreases in modified Ashworth scale, R1, and R2 at 2, 4, and 12 weeks and in D at 2 and 4 weeks. Amplitude of compound motor action potential decreased at 2 weeks, Hoffmann reflex amplitude decreased at 4 weeks, and tendon reflex amplitude decreased at 2 and 4 weeks. At 12 weeks, none of the neurophysiologic parameters differed from baseline. The correlations among R2, D, and the amplitude of tendon reflex were significant. Neurophysiologic tests could be used to evaluate reduced spasticity after botulinum toxin-A injection. The amplitude of tendon reflex showed the highest correlation with severity of spasticity.