Changes in corticospinal excitability during motor imagery by physical practice of a force production task: Effect of the rate of force development during practice.

Transcranial magnetic stimulation studies have indicated that the physical practice of a force production task increases corticospinal excitability during motor imagery (MI) of that task. However, it is unclear whether this practice-induced facilitation of corticospinal excitability during MI depends on a repeatedly practiced rate of force development (RFD). We aimed to investigate whether corticospinal excitability during MI of an isometric force production task is facilitated only when imagining the motor task with the same RFD as the physically practiced RFD. Furthermore, we aimed to examine whether corticospinal excitability during MI only occurs immediately after physical practice or is maintained. Twenty-eight right-handed young adults practiced isometric ramp force production using right index finger abduction. Half of the participants (high group) practiced the force production with high RFD, and the other half (low group) practiced the force production with low RFD. Questionnaire scores indicating MI ability were similar in the two groups. We examined the force error relative to the target force during the force production task without visual feedback, and motor evoked potential (MEP) amplitudes of the first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles during the MI of the force production task under practiced and unpracticed RFD conditions before, immediately after, and 20 min after physical practice. Our results demonstrated that the force error in both RFD conditions significantly decreased immediately after physical practice, irrespective of the RFD condition practiced. In the high group, the MEP amplitude of the FDI muscle during MI in the high RFD condition significantly increased immediately after practice compared to that before, whereas the MEP amplitude 20 min after practice was not significantly different from that before practice. Conversely, the MEP amplitude during MI in the high RFD condition did not change significantly in the low group, and neither group had significant changes in MEP amplitude during MI in the low RFD condition. The facilitatory effect of corticospinal excitability during MI with high RFD observed only immediately after physical practice in the high RFD condition may reflect short-term functional changes in the primary motor cortex induced by physical practice.

Relationship between individual hip extensor muscle size and sprint running performance: sprint phase dependence.

The muscle size of the hip extensors has been suggested to be important in sprint running performance; however, reported findings are partly inconsistent. Here, we hypothesised that the association between hip extensor size and sprint performance may vary by sprint phase (early-acceleration, maximal-velocity and deceleration phases). To test this hypothesis, we measured the volumes of individual hip extensors of 26 male sprinters via magnetic resonance imaging and their sprint velocities for each 10-m interval during a maximal-effort 100-m sprint. Based on the sprint velocities, the maximal-velocity phase was determined for each sprinter. At the individual muscle level, the semimembranosus volume relative to body mass was positively correlated with sprint velocity only in the early-acceleration phase (0-10 m, r = 0.592, corrected p = 0.003). On the other hand, the semitendinosus volume relative to body mass was positively correlated with sprint velocities in the maximal-velocity (r = 0.483, corrected p = 0.020) and deceleration (90-100 m, r = 0.605, corrected p = 0.003) phases. These results show that the association between hip extensor size and sprint performance is not constant but changes through the sprint phases.

Alterations in step frequency and muscle activities using body weight support influence the ventilatory response to sinusoidal walking in humans.

The use of body weight support (BWS) can reveal important insights into the relationship between lower-limb muscle activities and the ventilatory response during sinusoidal walking. Here, healthy participants (n = 15) walked on a treadmill while 0%, 30%, and 50% of their body weight was supported with BWS. The walking speed was varied sinusoidally between 3 and 6 km h-1, and three different frequencies, and periods ranging from 2 to 10 min were used. Breath-by-breath ventilation ([Formula: see text]) and CO2 output ([Formula: see text]) were measured. The tibialis anterior (TA) muscle activity was measured by electromyography throughout the walking. The amplitude (Amp), normalized Amp [Amp ratio (%)], and phase shift (PS) of the sinusoidal variations in measurement variables were calculated using a Fourier analysis. The results revealed that the Amp ratio in [Formula: see text] increased with the increase in BWS. A steeper slope of the [Formula: see text]-[Formula: see text] relationship and greater [Formula: see text]/[Formula: see text] values were observed under reduced body weight conditions. The Amp ratio in TA muscle was significantly positively associated with the Amp ratio in the [Formula: see text] (p < 0.001). These findings indicate that the greater amplitude in the TA muscle under BWS may have been a potent stimulus for the greater response of ventilation during sinusoidal walking.

Corticospinal excitability during observation of basketball free-throw movement: Effects of video playback speed and stimulus timing.

Transcranial magnetic stimulation studies have indicated that action observation (AO) modulates corticospinal excitability. Although a few previous studies have shown that the AO of simple motor movements at a slow playback speed facilitates corticospinal excitability more than that at normal playback speed, it is unclear if this effect occurs during the AO of sport-related complex movements. Therefore, we investigated the changes in the motor evoked potential (MEP) amplitudes of the flexor carpi radialis (FCR) and abductor digiti minimi (ADM) muscles during the AO of a basketball free-throw movement at three different playback speeds (100%, 75%, and 50% speeds). Additionally, we evaluated the effects of stimulus timing (holding the ball vs. releasing the ball for shooting) and motor expertise (expert basketball players vs. novices) on the MEP amplitude during the AO. Our results demonstrated that regardless of motor expertise, the MEP amplitude of the FCR muscle was significantly smaller in the 50% speed condition than in the 100% condition. In the ADM muscle, the MEP amplitude was significantly larger when the ball was held after dribbling than when the ball was released. Therefore, it is suggested that corticospinal excitability in specific muscles during the observation of complex whole-body movements is influenced by video playback speed and stimulus timing.

Modulation of Muscle Synergies in Lower-Limb Muscles Associated With Split-Belt Locomotor Adaptation.

Humans have great locomotor adaptability to environmental demands, which has been investigated using a split-belt treadmill with belts on both the left and right sides. Thus far, neuromuscular control in split-belt locomotor adaptation has been evaluated by analyzing muscle activities at the individual muscle level. Meanwhile, in the motor control field, the muscle synergy concept has been proposed. Muscle synergies are considered the fundamental building blocks of movement and are groups of coactive muscles and time-varying activation patterns, thereby, reflecting the neurophysiological characteristics of movement. To date, it remains unclear how such muscle synergies change during the adaptation and de-adaptation processes on the split-belt treadmill. Hence, we chronologically extracted muscle synergies while walking on the split-belt treadmill and examined changes in the number, muscle weightings, and temporal activation patterns of muscle synergies. Twelve healthy young males participated, and surface electromyography (EMG) signals were recorded bilaterally from 13 lower-limb muscles. Muscle synergies were extracted by applying non-negative matrix factorization to the EMG data of each leg. We found that during split-belt walking, the number of synergies in the slow leg increased while an extra synergy appeared and disappeared in the fast leg. Additionally, the areas under the temporal activation patterns in several synergies in both legs decreased. When both belts returned to the same speed, a decrease in the number of synergies and an increase in the areas under the temporal activation patterns of several synergies were temporally shown in each leg. Subsequently, the number of synergies and the areas under the temporal activation patterns returned to those of normal walking before split-belt walking. Thus, changes in the number, muscle weightings, and temporal activation patterns of synergies were noted in the split-belt locomotor adaptation, suggesting that the adaptation and de-adaptation occurred at the muscle synergy level.

Influence of Step Frequency on the Dynamic Characteristics of Ventilation and Gas Exchange During Sinusoidal Walking in humans.

We tested the hypothesis that restricting either step frequency (SF) or stride length (SL) causes a decrease in ventilatory response with limited breath frequency during sinusoidal walking. In this study, 13 healthy male and female volunteers (mean ± SD; age: 21.5 ± 1.8 years, height: 168 ± 7 cm, weight: 61.5 ± 8.3 kg) participated. The walking speed was sinusoidally changed between 50 and 100 m⋅min-1 with periods from 10 to 1 min. Using a customized sound system, we fixed the SF at 120 steps⋅min-1 with SL variation (0.83-0.41 m) (SF fix ) or fixed the SL at 0.7 m with SF variation (143-71 steps⋅min-1) (SL fix ) during the subjects' sinusoidal walking. Both the subjects' preferred locomotion pattern without a sound system (Free) and the unprompted spontaneous locomotor pattern for each subject (Free) served as the control condition. We measured breath-by-breath ventilation [tidal volume (VT) and breathing frequency (Bf)] and gas exchange [CO2 output ( V . CO2), O2 uptake ( V . O2)]. The amplitude (Amp) and the phase shift (PS) of the fundamental component of the ventilatory and gas exchange variables were calculated. The results revealed that the SF fix condition decreased the Amp of the Bf response compared with SL fix and Free conditions. Notably, the Amp of the Bf response under SF fix was reduced by less than one breath at the periods of 5 and 10 min. In contrast, the SL fix condition resulted in larger Amps of Bf and V . E responses as well as Free. We thus speculate that the steeper slope of the V . E - V . CO2 relationship observed under the SL fix might be attributable to the central feed-forward command or upward information from afferent neural activity by sinusoidal locomotive cadence. The PSs of the V . E , V . O2, and V . CO2 responses were unaffected by any locomotion patterns. Such a sinusoidal wave manipulation of locomotion variables may offer new insights into the dynamics of exercise hyperpnea.

Gluteus and posterior thigh muscle sizes in sprinters: Their distributions along muscle length.

Muscle hypertrophy can occur non-uniformly in athletes who repetitively perform particular movements, presumably leading to a unique muscle size distribution along the length. The present study aimed to examine if sprinters have unique size distributions within the gluteus and posterior thigh muscles. Nineteen male sprinters and 20 untrained males participated in the present study. T1-weighted magnetic resonance images of the hips and right thigh were obtained in order to determine whole and regional (proximal, middle, and distal) volumes of the gluteus maximus and individual posterior thigh muscles. The results showed that the volumes of all the examined muscles relative to body mass were significantly larger in sprinters than in untrained males (all P < 0.001, d = 1.40-3.29). Moreover, the magnitude of the difference in relative volume between sprinters and untrained males was different between the regions within the gluteus maximus (P = 0.048, partial η2 = 0.187), semitendinosus (P = 0.004, partial η2 = 0.331), and adductor magnus (P = 0.007, partial η2 = 0.322), but not within the other posterior thigh muscles (P = 0.091-0.555, partial η2 = 0.025-0.176). The magnitude of the difference in relative volume between the sprinters and untrained males was greatest in the distal regions within the gluteus maximus and semitendinosus, while the proximal region within the adductor magnus. These findings indicate that sprinters have unique size distributions within the gluteus maximus, semitendinosus, and adductor magnus, which may be attributed to their competitive and training activities. HighlightsSprinters showed larger gluteus maximus and individual posterior thigh muscles than untrained males.The magnitude of difference varied within the gluteus maximus, semitendinosus, and adductor magnus.The greatest difference was found in distal regions within the gluteus maximus and semitendinosus, while proximal region within the adductor magnus.

Time-series changes in intramuscular coherence associated with split-belt treadmill adaptation in humans.

Humans can flexibly modify their walking patterns. A split-belt treadmill has been widely used to study locomotor adaptation. Although previous studies have examined in detail the time-series changes in the spatiotemporal characteristics of walking during and after split-belt walking, it is not clear how intramuscular coherence changes during and after split-belt walking. We thus investigated the time-series changes of intramuscular coherence in the ankle dorsiflexor muscle associated with split-belt locomotor adaptation by coherence analysis using paired electromyography (EMG) signals. Twelve healthy males walked on a split-belt treadmill. Surface EMG signals were recorded from two parts of the tibialis anterior (TA) muscle in both legs to calculate intramuscular coherence. Each area of intramuscular coherence in the beta and gamma bands in the slow leg gradually decreased during split-belt walking. Significant differences in the area were observed from 7 min compared to the first minute after the start of split-belt walking. Meanwhile, the area of coherence in both beta and gamma bands in the fast leg for the first minute of normal walking following split-belt walking was significantly increased compared with normal walking before split-belt walking, and then immediately returned to the normal walking level. These results suggest that cortical involvement in TA muscle activity gradually weakens when adapting from a normal walking pattern to a new walking pattern. On the other hand, when re-adapting from the newly adapted walking pattern to the normal walking pattern, cortical involvement might strengthen temporally and then weaken quickly.

Muscle size of individual hip extensors in sprint runners: Its relation to spatiotemporal variables and sprint velocity during maximal velocity sprinting.

Hip extensor muscle size is related to sprint running performance. However, the mechanisms underlying this relationship remain unclear. To gain insights into this issue, the present study examined the relationships between the individual hip extensor sizes, spatiotemporal variables (step frequency and length, and their determinants), and sprint velocity during maximal velocity sprinting. Magnetic resonance images of the hip and right thigh were obtained from 26 male sprinters to determine the volumes of the gluteus maximus, individual hamstrings and adductors, and gracilis. Muscle volumes were normalized to their respective body mass and recorded as relative muscle volumes. The sprinters performed a 100-m sprint with their maximal effort. Their sprint motions were recorded using cameras to calculate the mean sprint velocity and the spatiotemporal variables at 50-60 m interval. The sprint velocity was significantly correlated with the relative volume of the semitendinosus (r = 0.497, P = 0.010), but not with the volumes of the other examined muscles. The relative volume of semitendinosus significantly correlated with the stance distance (r = 0.414, P = 0.036) and the stance distance adjusted by the stance time (r = 0.490, P = 0.011). Moreover, there were significant correlations between the stance distance and step length (r = 0.592, P = 0.001), and between the step length and sprint velocity (r = 0.509, P = 0.008). These results suggest that the semitendinosus contributes to attaining long stance distance and thereby high sprint velocity during maximal velocity sprinting.

Short-Term Plasticity in a Monosynaptic Reflex Pathway to Forearm Muscles after Continuous Robot-Assisted Passive Stepping.

Both active and passive rhythmic limb movements reduce the amplitude of spinal cord Hoffmann (H-) reflexes in muscles of moving and distant limbs. This could have clinical utility in remote modulation of the pathologically hyperactive reflexes found in spasticity after stroke or spinal cord injury. However, such clinical translation is currently hampered by a lack of critical information regarding the minimum or effective duration of passive movement needed for modulating spinal cord excitability. We therefore investigated the H-reflex modulation in the flexor carpi radialis (FCR) muscle during and after various durations (5, 10, 15, and 30 min) of passive stepping in 11 neurologically normal subjects. Passive stepping was performed by a robotic gait trainer system (Lokomat(®)) while a single pulse of electrical stimulation to the median nerve elicited H-reflexes in the FCR. The amplitude of the FCR H-reflex was significantly suppressed during passive stepping. Although 30 min of passive stepping was sufficient to elicit a persistent H-reflex suppression that lasted up to 15 min, 5 min of passive stepping was not. The duration of H-reflex suppression correlated with that of the stepping. These findings suggest that the accumulation of stepping-related afferent feedback from the leg plays a role in generating short-term interlimb plasticity in the circuitry of the FCR H-reflex.

Development of a portable gait rehabilitation system for home-visit rehabilitation.

This paper describes the development of a gait rehabilitation system with a locomotion interface (LI) for home-visit rehabilitation. For this purpose, the LI should be compact, small, and easy to move. The LI has two 2 degree-of-freedom (DOF) manipulators with footpads to move each foot along a trajectory. When the user stands on the footpads, the system can move his or her feet while the body remains stationary. The footpads can have various trajectories, which are prerecordings of the movements of healthy individuals walking on plane surfaces or slopes. The homes of stroke patients may have not only flat surfaces but also some slopes and staircases. The quadriceps femoris muscle is important for walking up and down slopes and staircases, and the eccentric and concentric contractions of this muscle are, in particular, difficult to train under normal circumstances. Therefore, we developed a graded-walking program for the system used in this study. Using this system, the user can undergo gait rehabilitation in their home, during visits by a physical therapist. An evaluation of the results of tests showed that the vastus medialis muscles of all the subjects were stimulated more than by walking on real slopes.

Velocity-dependent suppression of the soleus H-reflex during robot-assisted passive stepping.

The amplitude of the Hoffmann (H)-reflex in the soleus (Sol) muscle is known to be suppressed during passive stepping compared with during passive standing. The reduction of the H-reflex is not due to load-related afferent inputs, but rather to movement-related afferent inputs from the lower limbs. To elucidate the underlying neural mechanisms of this inhibition, we investigated the effects of the stepping velocity on the Sol H-reflex during robot-assisted passive stepping in 11 healthy subjects. The Sol H-reflexes were recorded during passive standing and stepping at five stepping velocities (stride frequencies: 14, 21, 28, 35, and 42 min(-1)) in the air. The Sol H-reflexes were significantly inhibited during passive stepping as compared with during passive standing, and reduced in size as the stepping velocity increased. These results indicate that the extent of H-reflex suppression increases with increasing movement-related afferent inputs from the lower limbs during passive stepping. The velocity dependence suggests that the Ia afferent inputs from lower-limb muscles around the hip and knee joints are most probably related to this inhibition.

Pilot study of locomotion improvement using hybrid assistive limb in chronic stroke patients.

BACKGROUND: Locomotor training using robots is increasingly being used for rehabilitation to reduce manpower and the heavy burden on therapists, and the effectiveness of such techniques has been investigated. The robot suit Hybrid Assistive Limb (HAL) has been developed to rehabilitate or support motor function in people with disabilities. The HAL provides motion support that is tailored to the wearer's voluntary drive. We performed a pilot clinical trial to investigate the feasibility of locomotor training using the HAL in chronic stroke patients, and to examine differences between two functional ambulation subgroups. METHODS: Sixteen stroke patients in the chronic stage participated in this study. All patients were trained with the HAL over 16 sessions (20-30 min/day within 2 days/week). Primary outcomes were walking speed, cadence, and number of steps recorded during a 10-meter walk test (10MWT). Berg balance scale (BBS) and timed up and go (TUG) were also measured. All outcome measures were evaluated without wearing HAL assistance before and after the intervention in all patients as well as in the dependent ambulatory and independent ambulatory subgroups. RESULTS: All participants completed the intervention with no adverse events. Gait speed, cadence, number of steps during the 10MWT, and BBS increased significantly from 0.41 m/s to 0.45 m/s (P = 0.031), from 68.6 steps/min to 72.0 steps/min (P = 0.020), from 37.5 steps to 33.1 steps (P = 0.017), and from 40.6 to 45.4 (P = 0.004) respectively. The TUG test score improved, although this difference was not statistically significant. The findings in the dependent ambulatory subgroup primarily contributed to the significant differences observed in the group as a whole. CONCLUSIONS: This pilot study showed that locomotor training using the HAL is feasible for chronic stroke patients. Randomized controlled trials are now required to demonstrate the effectiveness of HAL-based rehabilitation over conventional therapies. TRIAL REGISTRATION: UMIN000002969.

Feasibility of rehabilitation training with a newly developed wearable robot for patients with limited mobility.

OBJECTIVE: To investigate the feasibility of rehabilitation training with a new wearable robot. DESIGN: Before-after clinical intervention. SETTING: University hospital and private rehabilitation facilities. PARTICIPANTS: A convenience sample of patients (N=38) with limited mobility. The underlying diseases were stroke (n=12), spinal cord injuries (n=8), musculoskeletal diseases (n=4), and other diseases (n=14). INTERVENTIONS: The patients received 90-minute training with a wearable robot twice per week for 8 weeks (16 sessions). MAIN OUTCOME MEASURES: Functional ambulation was assessed with the 10-m walk test (10MWT) and the Timed Up & Go (TUG) test, and balance ability was assessed with the Berg Balance Scale (BBS). Both assessments were performed at baseline and after rehabilitation. RESULTS: Thirty-two patients completed 16 sessions of training with the wearable robot. The results of the 10MWT included significant improvements in gait speed, number of steps, and cadence. Although improvements were observed, as measured with the TUG test and BBS, the results were not statistically significant. No serious adverse events were observed during the training. CONCLUSIONS: Eight weeks of rehabilitative training with the wearable robot (16 sessions of 90min) could be performed safely and effectively, even many years after the subjects received their diagnosis.

Aftereffects of robotic-assisted treadmill walking on the locomotor pattern in humans.

We investigated the possible aftereffects on the locomotor pattern of treadmill walking after walking with the assistance of a robot suit HAL in nine healthy subjects. After walking on a treadmill at a speed of 3.5 km/h for 180 s as a pre-condition, each subject walked with robotic assistance to the hip and knee joints of both legs at the same speed for 600 s. The subjects performed normal walking for 300 s as a post-condition after the assisted walking. Compared with normal walking in the pre-condition, gait cycle duration and step length increased significantly during the assisted walking period. The increased gait cycle duration and step length during the assisted walking period returned to that of the pre-condition period soon after the start of the post-condition. In contrast, the range of motion (ROM) within one step cycle during the initial 60 s of the post-condition period gradually increased in the hip joint, but not in the knee joint. Compared with the mean hip ROM in the initial 10 s of the post-condition, significant increases in mean ROM every 10 s were observed in 4 phases of 20-60 s each in the right leg and in 3 phases of 20-50 s each in the left leg. Although strong aftereffects of the robotic assistance on the locomotor pattern were not observed in the present study, small adaptive changes were seen only in hip ROM during the initial normal walking phase immediately after assisted walking.

Robotic-assisted stepping modulates monosynaptic reflexes in forearm muscles in the human.

Although the amplitude of the Hoffmann (H)-reflex in the forelimb muscles is known to be suppressed during rhythmic leg movement, it is unknown which factor plays a more important role in generating this suppression-movement-related afferent feedback or feedback related to body loading. To specifically explore the movement- and load-related afferent feedback, we investigated the modulation of the H-reflex in the flexor carpi radialis (FCR) muscle during robotic-assisted passive leg stepping. Passive stepping and standing were performed using a robotic gait-trainer system (Lokomat). The H-reflex in the FCR, elicited by electrical stimulation to the median nerve, was recorded at 10 different phases of the stepping cycle, as well as during quiet standing. We confirmed that the magnitude of the FCR H-reflex was suppressed significantly during passive stepping compared with during standing. The suppressive effect on the FCR H-reflex amplitude was seen at all phases of stepping, irrespective of whether the stepping was conducted with body weight loaded or unloaded. These results suggest that movement-related afferent feedback, rather than load-related afferent feedback, plays an important role in suppressing the FCR H-reflex amplitude.

Changes in input-output relations in the corticospinal pathway to the lower limb muscles during robot-assisted passive stepping.

We investigated input (stimulus)-output (response) relations of the corticospinal pathway in the lower limb muscles during passive stepping using a robotic driven gait orthosis. Nine healthy adult subjects passively stepped with 40% body weight unloading (ground stepping) and 100% body weight unloading in the air (air stepping). During passive stepping, the motor evoked potentials (MEPs) of the lower limb muscles elicited by transcranial magnetic stimulation (TMS) were recorded at late-stance, early-, and late-swing phases of 2 stepping conditions. The input-output relation at each phase of the stepping conditions was obtained by increasing stimulus intensity in 5% increments from 40% to 70% of maximal stimulator output. The slopes of input-output relations were steeper at the early-swing phase in the rectus femoris muscle and at the late-stance and late-swing phases in the biceps femoris muscle in both stepping conditions. There were no significant differences in the MEP responses of the rectus femoris and biceps femoris muscles at each phase between the 2 conditions. Low muscle activity was seen at the late-stance phase of ground stepping in the soleus muscle and the MEP amplitude at this phase became larger. The slopes in the tibialis anterior muscle were steep at the early- and late-swing phases of ground stepping. There was a significant difference in the MEPs of the tibialis anterior muscle between the late-swing phases in ground and air stepping. The present study indicates that corticospinal excitability to the lower limb muscles is modulated by sensory inputs elicited by passive stepping.

Voluntary motion support control of Robot Suit HAL triggered by bioelectrical signal for hemiplegia.

Our goal is to enhance the quality of life of patients with hemiplegia by means of an active motion support system that assists the impaired motion such as to make it as close as possible to the motion of an able bodied person. We have developed the Robot Suit HAL (Hybrid Assistive Limb) to actively support and enhance the human motor functions. The purpose of the research presented in this paper is to propose the required control method to support voluntarily motion using a trigger based on patient's bioelectrical signal. Clinical trials were conducted in order to investigate the effectiveness of the proposed control method. The first stage of the trials, described in this paper, involved the participation of one hemiplegic patient who is not able to bend his right knee. As a result, the motion support provided by the HAL moved the paralyzed knee joint according to his intention and improved the range of the subject's knee flexion. The first evaluation of the control method with one subject showed promising results for future trials to explore the effectiveness for a wide range of types of hemiplegia.

Effect of sensory inputs on the soleus H-reflex amplitude during robotic passive stepping in humans.

We investigated the modulation of the soleus (Sol) Hoffmann (H-) reflex excitability by peripheral sensory inputs during passive stepping using a robotic-driven gait orthosis in healthy subjects and spinal cord-injured patients. The Sol H-reflex was evoked at standing and at six phases during passive stepping in 40 and 100% body weight unloaded conditions. The Sol H-reflex excitability was significantly inhibited during passive stepping when compared with standing posture at each unloaded condition. During passive stepping, the H-reflex amplitude was significantly smaller in the early- and mid-swing phases than in the stance phase, which was similar to the modulation pattern previously reported for normal walking. No significant differences were observed in the H-reflex amplitude between the two unloaded conditions during passive stepping. The reflex depression observed at the early part of the swing phase during passive stepping might be attributed to the sensory inputs elicited by flexion of the hip and knee joints. The present study provides evidence that peripheral sensory inputs have a significant role in phase-dependent modulation of the Sol H-reflex during walking, and that the Sol H-reflex excitability might be less affected by load-related afferents during walking.