Reflex effects of induced muscle contraction in normal and spinal cord injured subjects

The modulation of the soleus H reflex in response to functional electrical stimulation (FES) of the rectus femoris (RF) muscle and its overlying skin was examined in 11 normal adults and 6 patients with a clinically defined complete spinal cord injury (SCI). Stimulation of RF at twice motor threshold (MT) resulted in a long-lasting (>1,000 ms) and significant reduction (50-70% of control) in the size of the soleus H reflex in all normal subjects tested. For five of the SCI subjects, 2MT stimulation of RF induced a 55-60% reduction in the soleus H reflex that was also long-lasting (>160 ms). In the remaining SCI subject, 2MT stimulation resulted in an initial period of significant H-reflex facilitation (0-14 ms) that was followed by a longer-lasting inhibition commencing 60 ms after the cessation of the conditioning stimulation. Decreasing the strength of stimulation to below that required to generate a clear contraction in RF resulted in mixed facilitatory and inhibitory actions that were subject dependent. The changes in H-reflex excitability resulting from FES highlight the potential use of FES in the management of hypertonicity in SCI but also suggest that the central actions of FES need to be considered when FES gait restoration programs are designed.     

Different excitability of type 1 and type 2 alpha-motoneurones: The recruitment curve of H- and M-responses in slow and fast muscles of rabbits

To evaluate the different excitability of Type 1 and Type 2 alpha-motoneurones, we analyzed comparatively the threshold and amplitude of the H-reflex and the $\text{H}{}_{\max }\text{M}{}_{\max }$ ratio in a slow muscle, soleus, and in a fast muscle, lateral gastrocnemius, of the rabbit.The H-reflex had almost always the same threshold in the muscles examined, but in soleus its amplitude increased much more than in lateral gastrocnemius when the stimulus intensity was increased. A clear difference in amplitude of the H-reflexes was already evident with stimuli subliminal for direct responses (M). The maximal H-reflex was always much higher in soleus than in lateral gastrocnemius. The calculation of the mean $\text{H}{}_{\max }\text{M}{}_{\max }$ ratio showed that it was 3 times higher in the slow than in the fast muscle.On the basis of these results, showing a clear-cut difference in the reflex excitability of slow and fast muscles and in the light of other experimental data available in the literature, we tend to conclude that Type 1 alpha-motoneurones are exclusively, or at least predominantly, depolarized by stimulation of afferent Ia fibres.     

Modulation of triceps surae H-reflexes as a function of the reflex activation history during standing and stepping

The facilitatory effectiveness of spindle afferent feedback is controlled by modulation of segmental reflex excitability such that the level of muscle activation is appropriate for the task. Phase-dependent modes of reflex modulation have been well-characterized. We hypothesized that segmental reflex excitability of the triceps surae was also modulated in a manner associated with the activation history of the spindle afferents and the segmental reflex pathway during isometric contractions, standing and stepping. In the first experiment. pairs of soleus (S) H-reflexes were evoked 80 ms apart with equal strength stimuli at rest and while subjects isometrically contracted their S against loads of 10%. 20%. and 50% of their maximum voluntary efforts. The percent depression of the second H-reflex relative to the first was used as a measure of the effect of reflex activation history. At rest, the second H-reflexes were depressed an average of 73% relative to the first. The degree of depression was progressively reduced as the plantarflexion torque increased. In the second experiment, paired H-reflexes were obtained from the S and medial (MG) and lateral gastrocnemii (LG) muscles while subjects were standing and during the stance phase of step initiation. The degree of depression of the second H-reflex during standing ( > 78%) was similar in magnitude to that produced at rest in Experiment I. At the end of the stance phase of stepping. depression of the second H-reflex of all three muscles was reduced to less than 25%. We conclude that the segmental reflex excitability is modulated as a function of the reflex activation history during these tasks.     

Limb segment vibration modulates spinal reflex excitability and muscle mRNA expression after spinal cord injury

ObjectiveWe investigated the effect of various doses of vertical oscillation (vibration) on soleus H-reflex amplitude and post-activation depression in individuals with and without SCI. We also explored the acute effect of short-term limb vibration on skeletal muscle mRNA expression of genes associated with spinal plasticity.MethodsSix healthy adults and five chronic complete SCI subjects received vibratory stimulation of their tibia over three different gravitational accelerations (0.3g, 0.6g, and 1.2g) at a fixed frequency (30 Hz). Soleus H-reflexes were measured before, during, and after vibration. Two additional chronic complete SCI subjects had soleus muscle biopsies 3 h following a single bout of vibration.ResultsH-reflex amplitude was depressed over 83% in both groups during vibration. This vibratory-induced inhibition lasted over 2 min in the control group, but not in the SCI group. Post-activation depression was modulated during the long-lasting vibratory inhibition. A single bout of mechanical oscillation altered mRNA expression from selected genes associated with synaptic plasticity.ConclusionsVibration of the lower leg inhibits the H-reflex amplitude, influences post-activation depression, and alters skeletal muscle mRNA expression of genes associated with synaptic plasticity.SignificanceLimb segment vibration may offer a long term method to reduce spinal reflex excitability after SCI.     

Latency of changes in spinal motoneuron excitability evoked by transcranial magnetic brain stimulation in spinal cord injured individuals

Objectives: To examine the basis for delay in the excitatory effects of transcranial magnetic stimulation (TMS) of motor cortex on motoneuron pools of muscles left partially-paralyzed by traumatic spinal cord injury (SCI).Methods: The effect of subthreshold transcranial magnetic stimulation (TMS) on just-suprathreshold H-reflex amplitude was examined in subjects (n=10) with incomplete cervical SCI, and in able-bodied (AB) subjects (n=20) for comparison. EMG activity was recorded from the soleus and the abductor hallucis muscles, and H-reflex was elicited by stimulation of the tibial nerve behind the knee. Comparison of the peak-to-peak amplitude of the TMS-conditioned H-reflex to that of the H-reflex alone (i.e. unconditioned H-reflex) was made for different conditioning-test intervals with multivariate analysis of variance and (when called for) t testing.Results: The absolute latencies of motor responses to suprathreshold TMS delivered during a weak voluntary contraction of the soleus and abductor hallucis were significantly prolonged in the SCI group relative to AB subjects. For the TMS-conditioned H-reflex, the time-course effect of TMS on the H-reflex amplitude in different AB subjects included an early effect (typically facilitation, but occasionally inhibition) seen between −5 and 0 ms, followed by a later period (i.e. >5 ms) of H-reflex facilitation. In contrast, the earliest indication of a TMS effect on H-reflex excitability in SCI subjects was between 5 and 10 ms after TMS. This difference between SCI and AB subjects of approximately 10 ms was similar to the prolongation of TMS-evoked response latencies in the soleus and the abductor hallucis muscles of the SCI subjects.Conclusions: The results suggest that motor conduction slowing after traumatic SCI most likely occurs across the population of the descending tract axons mediating the TMS-evoked motor responses.     

Redetermination of the optimal stimulation intensity modifies resting H‐reflex recovery after a sustained moderate‐intensity muscle contraction

This study aimed to determine whether the time‐course of maximal resting H‐reflex amplitude (H_max) recovery after a prolonged moderate‐intensity muscle contraction differs according to the optimal stimulation intensity used (predetermined vs. readjusted). Thirteen males performed a sustained isometric plantar flexion at 40% of their maximal voluntary contraction torque output until exhaustion. H_max of the soleus muscle was recorded before and 2, 6, 10, and 14 min after the end of the contraction, then normalized by the respective maximal M‐wave to form the H_max/M_max ratio. During recovery, pre‐ and redetermined optimal stimulation intensities (mini‐recruitment curve drawn before each recovery measurement) were applied randomly to measure H_max. When using redetermined stimulation intensities, normalized H‐reflex values were systematically greater (+11, +16, +15, and +15% after 2‐, 6‐, 10‐, and 14‐min recovery periods, respectively) than those obtained with the predetermined intensity. Keeping the stimulation intensity constant to evoke H_max after a sustained muscle contraction can underestimate the H‐reflex facilitation occurring after exhaustive exercise. It is therefore more appropriate to redefine the optimal stimulation intensity to evoke H_max (using mini‐recruitment curves) when the purpose is to analyze spinal modulation during the recovery phase. Muscle Nerve, 2010     

Caffeine increases spinal excitability in humans

The Hoffman reflex (H reflex) has long been established as a measure of spinal excitability. Caffeine is one of the most widely consumed drugs in the world. Because it is known to increase excitatory neurotransmission, we hypothesized that caffeine would increase spinal excitability and thus alter the H reflex by increasing its amplitude. Seven subjects each attended the laboratory on 2 days. Caffeine (6 mg/kg) was administered on one day and a placebo was administered on the other. The tibial nerve was stimulated at incremental intensities to create an H-reflex recruitment curve prior to capsule administration (pretest) and 1 h later (posttest) on each day. The slope of H-reflex recruitment curve normalized to that of the M wave (H(slp)/M(slp)) was compared (pretest to posttest). Caffeine increased spinal excitability 43 +/- 17% (P < 0.05). Thus, caffeine may be used to safely increase spinal excitability in electrophysiological studies of the human neuromuscular system. Our results also suggest that caffeine intake should be controlled when the H reflex is used in diagnostic and experimental situations.     

Comparison of soleus H-reflex gain from prone to standing in dancers and controls

To examine the differences in soleus H-reflex gain between trained dancers and control subjects, the soleus H-reflex amplitude and background muscle activity of 9 trained dancers (means of 20.3 ± 2.1 years of age, and 14.3 ± 3.8 years of training) and 9 control subjects (mean 23.3 ± 3.2 years of age) were compared at rest and at 10, 20, and 30% of a maximal voluntary soleus contraction during two conditions: prone and standing. The ratio of the maximal H-reflex (H-max) to the maximal motor response (M-max) was also measured during both conditions. Correlation was performed between background EMG and the resultant H-reflex to determine reflex gain. The results demonstrated that the control subjects and the dancers displayed a similar reflex gain during the prone condition (slope = 3.30 vs. 3.64, respectively). However, during the standing condition, dancers demonstrated a significantly lower reflex gain (slope = 1.78) than did control subjects (slope = 3.68). Furthermore, although both groups significantly decreased the H-max/M-max ratio from prone to standing, no differences were found between groups at either condition. This suggests that the differences in standing reflex gain between the dancers and control subjects were a product of differential control of reflex modulation involved in postural control. An initial hypothesis explaining the differences between the standing reflex gain of the groups relates to plasticity of central inhibitory control mechanisms, primarily presynaptic and/or reciprocal inhibition.     

Age comparison of H-reflex modulation with the Jendrássik maneuver and postural complexity.

OBJECTIVE: The purpose of this study was to examine modulation of the soleus Hoffmann (H)-reflex in response to the Jendrássik maneuver (JM) in standing positions in young and elderly subjects. METHODS: Seventeen elderly (mean age=72.0 years) and 23 young (mean age=23.2 years) apparently healthy subjects were examined in two separate experiments. The first experiment was conducted to compare the prone and standing position. The second experiment was conducted in the standing position with isotonic glideboard back support. The isotonic glideboard back support was inclined 30 degrees. In the standing position with back support, the knee and ankle joints were set at 0 degrees of flexion. All subjects were tested with two foot-positions: (1) with no soleus contraction on the platform (simple task) and (2) with an active calf muscle group contraction (complex task). To compare the amplitude of the H-reflex in each experiment between the control trials (relaxed) and JM trials (squeezing tennis balls), the stimulus intensity of 1.1 x motor threshold of the M-response was used for each subject in all body positions. RESULTS: To ensure experimental control, subjects did not show a difference in the amplitude of the trial M-response between the control and JM trials on any of the body positions. Also, no difference was found in the mean amplitude of the M-response between two different positions in either of the two experiments. Trial M-responses were all between 13 and 17% of M-max in the quiet standing position for the young subjects, and 17 and 21% for the elderly subjects. Results demonstrated that the JM facilitated the H-reflex in both young and elderly subjects. However, differential ability to modulate motoneuron excitability evoked by H-reflex pathways was found between the two groups. Young subjects demonstrated a significant difference in the amplitude of the H-reflex between control and JM trials in each standing position (P<0.05). The elderly subjects, in contrast, demonstrated no significant difference in the amplitude of the H-reflex between control and JM trials during normal standing. When examining standing with back support, the young subjects demonstrated a significant difference in the amplitude of the H-reflex between control and JM trials during both the simple and complex tasks (P<0.05). The elderly subjects, in contrast, demonstrated a significant difference only in the simple postural task (P<0.05). CONCLUSIONS: These results provide evidence of differential human spinal reflex modulation between young and elderly subjects. Further, these results may point towards the role of presynaptic inhibition in mediating these differences, and may lead to a more complete understanding of the different postural control strategies between young and elderly subjects.     

Changes in the recruitment curve of the soleus H-reflex associated with chronic low back pain.

OBJECTIVE: We investigated whether patients with chronic low back pain (CLBP) manifest changes in the excitability of the soleus H-reflex. METHODS: H-reflex stimulus-response curve was studied in 14 CLBP patients and 14 age-matched healthy subjects. H-threshold, H-maximum size, H-steepness and H-latency were determined for both legs. Homosynaptic depression (HD), following a train of H-reflexes, and presynaptic inhibition (PI) from flexor afferents onto soleus Ia afferents were also evaluated. RESULTS: H-threshold was significantly increased, H-size as a function of stimulus intensity was significantly different, and H-recruitment curve steepness was significantly lower in CLBP patients compared to healthy subjects. No significant difference in the amount of HD and PI of the H-reflex was found between the two groups. H-latency and Hmax/Mmax ratio was comparable between the subjects groups. CONCLUSIONS: In CLBP there is a reduced excitability of group Ia afferent fibres from the soleus muscle to which presynaptic factors do not seem to contribute and that presumably depend on changes in the peripheral sensory input. SIGNIFICANCE: Changes in H-reflex excitability may underlie a decrease in the gain of a peripheral sensor in CLBP. Estimation of soleus H-threshold and H-recruitment curve may contribute to the diagnostic evaluation of CLBP and may be used to monitor the efficacy of treatment.     

Altered Spinal Excitability in Patients with Primary Fibromyalgia: A Case-Control Study

Background and PurposeAbnormal excitability of the central nervous system, both spinal and supraspinal, has previously been described as a pathophysiological plastic mechanism for chronic pain syndromes. Primary fibromyalgia (FM) as one extreme of this spectrum of diseases. This case-control study aimed to determine the changes in the spinal excitability by investigating the Hoffman reflex (H-reflex) in patients with FM.MethodsThirty-eight patients with FM and 30 healthy controls participated in this case-control study. We measured the H-reflex bilaterally in the upper limbs (flexor carpi radialis) and the lower limbs (gastrocnemius and soleus). Moreover, pain-related variables were measured, including pain severity (using a visual analogue scale), pain duration, Widespread Pain Index, and the score on the Symptom Severity Scale. Various psychiatric comorbidities and quality-of-life parameters were measured for each patient, including scores on the Hamilton Depression Rating Scale, Taylor''s Manifest Anxiety Scale, and the Revised Fibromyalgia Impact Questionnaire.ResultsA significant increase in the ratio of the maximum baseline-to-peak amplitudes of H and M waves (H_max/M_max) but not in the H-wave minimum latency was found in patients with FM compared with healthy controls. There were no significant correlations between this ratio in both muscles and the various pain-related measures, psychiatric comorbidity, and quality of life in patients with FM. Patients with FM suffered more depression and anxiety than did the controls.ConclusionsWe found increased spinal excitability in patients with FM, which was not confined to the site of maximum pain. This information may help in the diagnosis of FM and supports the hypothesis of central sensitization.     

The excitability of a motoneuron pool assessed by the H-reflex method is correlated with the susceptibility of Ia terminals to repetitive discharges in humans

The correlation of the degree of the Hoffmann (H-) reflex depression induced by a passive stretch of the soleus muscle (Sol) and the excitability of the motoneuron (MN) pool was investigated in 24 healthy human subjects. The excitability of the Sol MN pool was determined by the ratio of the slope of the H-reflex (Hslp) and M-response recruitment curves (Mslp). The Hslp/Mslp ratio was decreased by a passive stretch of the Sol given 1 s before the H-reflex stimulus, and was significantly correlated with the amount of the H-reflex depression. These results suggest that the excitability of the MN pool assessed by the H-reflex method depends on the presynaptic mechanism involved in the efficiency of transmission across the synapses of Ia afferents in response to repetitive discharge.     

There is a close relationship between hand skill and the excitability of motor neurons innervating the postural soleus muscle in left-handed subjects

The claim that there is not a consistent inhibition of the H-reflex from the dominant leg was examined and rejected. It was re-established that there is an inverse relationship between hand skill and the excitability of motoneurons innervating the postural soleus muscle in left-handed subjects. In left-handers with significantly better left-hand skill, the height of the H-reflex recovery curve was significantly higher on the right leg (nondominant) than the left leg (dominant). There was a positive linear correlation between the asymmetries of hand skill greater than zero (better left-hand skill) and the H-reflex recovery curves from the right and left legs greater than zero (right dominance in reflex excitability). In left-handers with no significant difference between the right- and left-hand skills, there was no significant difference between the mean recovery curves from the right and left legs for the interstimulus intervals from 40 to 100 ms; the height of the left recovery curve was found to be significantly higher than the height of the right recovery curve for the interstimulus intervals from 150 to 1000 ms. It was concluded that there is close relationship between hand skill and motoneuronal excitability from right and left soleus muscle with regard to support and operative functions of legs in left-handers.     

Effects of changes in hip position on actions of spinal inhibitory interneurons in humans

The aim of the present study was to establish whether in healthy human subjects the actions of group I muscle afferents arising from the same spinal segments as the soleus innervation (e.g., common peroneal nerve; CPN) or from more proximal spinal segments (femoral nerve; FN) on the soleus H-reflex are modified by changes in hip position. Control and conditioned soleus H-reflexes were elicited and recorded via conventional methods. In seated subjects, CPN and FN stimulation resulted in similar effects to the soleus H-reflex to that previously reported in healthy subjects. However, during hip angle changes, CPN stimulation at the C-T interval of 2 ms resulted in soleus H-reflex depression only when the hip was flexed at 30 degrees , whereas with the hip flexed or extended at 10 degrees the H-reflex was facilitated. CPN stimulation delivered at 100 ms also induced soleus H-reflex facilitation regardless of the hip angle tested. The heteronymous reflex facilitation (conditioned H-reflex with FN stimulation) did not vary systematically with hip angle changes. These findings indicate that hip proprioceptors interact with spinal inhibitory interneurons to enhance spinal reflex excitability under static conditions. This neural switch might constitute an important feature of movement regulation in humans.     

Influence of flupirtine on human lower limb reflexes

The influence of a single oral dose (400 mg) of flupirtine on lower limb reflexes was investigated in normal human subjects using H-reflex testing, flexor reflex testing and dynamic posturography. Flupirtine did not significantly change the latency of the H-reflex or the H_max/M_max ratio. Both, the first (F1) and the second (F2) components of the flexor reflex were significantly depressed. Flupirtine significantly decreased the size of the ML response following fast transient platform movements rotating toe-up around the ankle joint. We conclude that flupirtine acts on polysynaptic spinal pathways. In addition to its well known analgesic effect flupirtine might have a muscle relaxant effect.     

Reassessment of H-reflex recovery curve using the double stimulation procedure

We conducted two types of experiments to assess the validity of the H-reflex recovery test, using double stimulation to test soleus motoneuron pool excitability in healthy and spastic subjects. One type dealt with the mechanical effect of the conditioning H reflex on the ankle joint; the other type with the effect of change in reflex size. The mechanical effect was tested both with the ankle joint fixed (FX) and free to move (FR). Differences between FX and FR conditions commenced with relaxation of soleus muscle contraction by the conditioning H reflex. In the FR condition, abrupt facilitation occurred, and changed to marked depression. We conclude that specific facilitation and inhibition in the FR condition were secondary effects of group Ia inflows caused by the ankle extensor muscle stretching on relaxation. In some spastic patients as well as in controls, facilitation due to the mechanical effect in the FR condition was observed despite the FX condition. The effects of systematic changes on soleus H-reflex size were investigated at conditioning–test intervals of 80 ms, so as to avoid mechanical effects. When conditioning and test reflexes were the same size, the amount of recovery increased as the H-reflex size increased. Comparison of the relation between amount of recovery and H-reflex size, expressed as a percentage of Mmax, showed no significant difference between the two groups. We speculate that the stronger recovery of spasticity mentioned in previous literature may have resulted from the fact that relatively greater H reflexes were tested in those studies. In conclusion, the present study indicates that double stimulation is not appropriate for assessing spinal motoneuron pool “excitability increase” in spasticity. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:352–360.     

Stimulus pulse-width influences H-reflex recruitment but not H(max)/M(max) ratio

It has been proposed that pulse-widths of 0.5-1.0 ms should be used to evoke H-reflexes in humans; however, the influence of pulse-width on H-reflex recruitment over a range of stimulus intensities has not been well characterized. We constructed soleus H-reflex vs. M-wave recruitment curves using 50, 200, 500, and 1000 micros pulses in 12 subjects. In contrast to previous findings, changing the pulse-width did not significantly alter maximal H-reflex (H(max)) or M-wave (M(max)) amplitudes or H(max)/M(max) ratios. In fact, the 1000 micros pulses resulted in larger H-reflexes when the M-wave was 5% M(max); smaller M-waves at H(max); and lower H-reflex thresholds compared with 50 micros pulses. These differences reflect a leftward shift in the H-reflex vs. M-wave recruitment curve when using wide vs. narrow pulses and, combined with no change in the H(max)/M(max) ratios, suggest that factors other than antidromic collision in motor axons limit H(max). These results support the idea that 1,000 micros pulses should be used to evoke H-reflexes and suggest that wider pulses may be beneficial to generate contractions with a greater reflex contribution when using neuromuscular stimulation for rehabilitation.     

Amplitude modulation of the soleus H-reflex in the human during walking and standing

Experiments were done to determine the amplitude of the monosynaptically mediated H-reflex of the soleus muscle at various phases of the step cycle, using a computer-based analysis procedure. In all subjects tested the amplitude of the H-reflex was strongly modulated in amplitude during the walking cycle and was highest during the stance phase. In many subjects the peak reflex amplitude occurred at about the same time as the peak soleus electromyographic (EMG) activity, but in others it occurred earlier. The form of the reflex variation (i.e., envelope of H-reflex amplitude versus phase in cycle) during the step cycle could also be quite different from that of the EMG produced during stepping. At an equal stimulus strength and EMG level, the H-reflex was always much larger, up to 3.5 X, during steadily maintained contractions while standing than during walking. The large reflexes when subjects were standing are consistent with the control of position required to maintain a stable posture in this task. Similarly, the reflexes during walking are greatest during the stance phase, when they will assist in maintaining the upright position of the body against gravity. The reflexes are smallest during the swing phase when they would oppose ankle flexion. However, since the reflex amplitude is task-dependent (i.e., greater during standing than during walking at the same EMG and stimulus levels) and is not always closely related to the EMG produced during a given task such as walking, the strong modulation of H-reflex during walking is not simply a passive consequence of the alpha-motoneuron excitation level.(ABSTRACT TRUNCATED AT 250 WORDS)     

Soleus muscle length, stretch reflex excitability, and the contractile properties of muscle in children and adults: a study of the functional joint angle

The influence of the joint angle on stretch reflex excitability of the soleus muscle at the ankle has been studied in 22 children aged 3.9 to 13.6 years and 9 adults aged 19 to 70 years. For all subjects, reflex EMG and mechanical twitch torque gain were trivial at resting plantar flexion. The reflex EMG gain reached a maximum between-15^o and-10^o of plantar flexion beyond the neutral angle, 0^o, denned as the foot at right angle to the tibia, diminishing steeply with further dorsiflexion. The reflex mechanical gain rose to a peak between 0^o and +10^o of dorsiflexion beyond neutral, declining steeply thereafter. By contrast, axonally stimulated muscle twitch torque increased serially up to +30^o dorsiflexion beyond neutral. For the soleus muscle, the optimal reflex neuromechanical angle lies approximately midway between the angle for optimal reflex EMG gain (in mild plantar flexion, at which the largest and strongest motor units can be activated) and the optimal muscle mechanical angle (at the extreme of soleus muscle dorsiflexion). These studies confirm that the excitability of the spinal alpha motor neuron pool in vivo is strongly influenced by muscle length and explain the variability in reflex excitability within and between subjects, if the joint angle is not controlled. They also indicate how posture influences movement, agreeing with the known function of the soleus muscle in the stance phase of gait and the modulation of motor unit recruitment during voluntary alternating movements at the ankle. Soleus muscle twitch characteristics show a fivefold to eightfold increase in peak force associated with a tenfold reduction in compliance in the first two decades of life and an apparent speeding up of twitch time in the first decade.     

After-effects of pedaling exercise on spinal excitability and spinal reciprocal inhibition in patients with chronic stroke

Purpose of the study: To evaluate the after-effects of pedaling on spinal excitability and spinal reciprocal inhibition in patients with post-stroke spastic hemiparesis. Materials and methods: Twenty stroke patients with severe hemiparesis participated in this study and were instructed to perform 7 min of active pedaling and 7 min of passive pedaling with a recumbent ergometer at a comfortable speed. H reflexes and M waves of paretic soleus muscles were recorded at rest before, immediately after and 30 min after active and passive pedaling. The Hmax/Mmax ratio and H recruitment curve were measured. Reciprocal inhibition was assessed using the soleus H reflex conditioning test paradigm. Results: The Hmax/Mmax ratio was significantly decreased after active and passive pedaling exercise. The decreased Hmax/Mmax ratio after active pedaling lasted at least for 30 min. The H recruitment curve and reciprocal inhibition did not change significantly after active or passive pedaling exercise. Conclusions: Pedaling exercise decreased spinal excitability in patients with severe hemiparesis. Pedaling may be effective in rehabilitation following stroke.