Characteristics of the gait adaptation process due to split-belt treadmill walking under a wide range of right-left speed ratios in humans.

The adaptability of human bipedal locomotion has been studied using split-belt treadmill walking. Most of previous studies utilized experimental protocol under remarkably different split ratios (e.g. 1:2, 1:3, or 1:4). While, there is limited research with regard to adaptive process under the small speed ratios. It is important to know the nature of adaptive process under ratio smaller than 1:2, because systematic evaluation of the gait adaptation under small to moderate split ratios would enable us to examine relative contribution of two forms of adaptation (reactive feedback and predictive feedforward control) on gait adaptation. We therefore examined a gait behavior due to on split-belt treadmill adaptation under five belt speed difference conditions (from 1:1.2 to 1:2). Gait parameters related to reactive control (stance time) showed quick adjustments immediately after imposing the split-belt walking in all five speed ratios. Meanwhile, parameters related to predictive control (step length and anterior force) showed a clear pattern of adaptation and subsequent aftereffects except for the 1:1.2 adaptation. Additionally, the 1:1.2 ratio was distinguished from other ratios by cluster analysis based on the relationship between the size of adaptation and the aftereffect. Our findings indicate that the reactive feedback control was involved in all the speed ratios tested and that the extent of reaction was proportionally dependent on the speed ratio of the split-belt. On the contrary, predictive feedforward control was necessary when the ratio of the split-belt was greater. These results enable us to consider how a given split-belt training condition would affect the relative contribution of the two strategies on gait adaptation, which must be considered when developing rehabilitation interventions for stroke patients.

Rhythmic arm swing enhances patterned locomotor-like muscle activity in passively moved lower extremities.

The use of driven gait orthosis (DGO) has drawn attention in gait rehabilitation for patients after central nervous system (CNS) lesions. By imposing a passive locomotor-like kinematic pattern, the neural mechanisms responsible for locomotion can be activated as in a normal gait. To further enhance this activity, discussions on possible intervention are necessary. Given the possible functional linkages between the upper and lower limbs, we investigated in healthy subjects the degree of modification in the lower limb muscles during DGO-induced passive gait by the addition of swing movement in the upper extremity. The results clearly showed that muscle activity in the ankle dorsiflexor TA muscle was significantly enhanced when the passive locomotor-like movement was accompanied by arm swing movement. The modifications in the TA activity were not a general increase through the stride cycles, but were observed under particular phases as in normal gaits. Voluntary effort to swing the arms may have certain effects on the modification of the muscle activity. The results provide clinical implications regarding the usefulness of voluntary arm swing movement as a possible intervention in passive gait training using DGO, since ordinary gait training using DGO does not induce spontaneous arm swing movement despite its known influence on the lower limb movement.

Anti-phase action between the angular accelerations of trunk and leg is reduced in the elderly.

Quiet standing posture in humans has often been modeled as a single inverted pendulum pivoting around the ankle joint. However, recent studies have suggested that anti-phase action between leg and trunk segments plays a significant role in stabilizing posture by reducing the acceleration of the center of mass (COM) of the body. The aim of this study is to test the hypothesis that anti-phase action is attenuated in the elderly compared to the young. The anterior-posterior movements of leg and trunk segments were measured using 4 laser displacement sensors from 22 healthy young subjects (age range, 20-35 years) and 38 healthy elderly subjects (age range, 57-80 years) standing quietly for 30s twice. To focus on the segmental action between trunk and legs, we applied constraints (i.e., wooden splints) on each segment. We found that the velocity and acceleration of the COM (standard deviation of the time series was evaluated) were significantly higher for the elderly subjects than for young subjects. The increase in the acceleration of the COM resulted not only from an increase in the angular acceleration of the segments but also from the reduction of their anti-phase relationship, as demonstrated by an index that quantifies the degree of cancelation between both segments. We conclude that the degree of anti-phase action between trunk and leg segments during quiet standing is smaller for elderly subjects than for young subjects, and that this change of the anti-phase action due to aging resulted in increased COM acceleration in the elderly subjects.

The precise adjustment of coil location for transcranial magnetic stimulation during dynamic motion.

Transcranial magnetic stimulation (TMS) to the cerebral cortex is a major in vitro technique that is used in the field of neurophysiology. The magnitude of the motor-evoked potentials (MEP) that are elicited by TMS to the primary motor cortex reflect the excitability of the corticospinal pathway. MEPs are very sensitive to the scalp location of the stimulus coil, especially when corticospinal excitability is recorded during walking or other dynamic motions. In this study, we created a coil navigational system that consisted of three-dimensional motion analysis cameras, rigid bodies on the head and coil, and programming software. In order to evaluate the feasibility of the use of our system, pseudo TMS was applied during treadmill walking with or without the navigational system. As a result, we found that the variances due to coil location and/or distance from the target site were reduced with our system. This technique enabled us to realize high precision and accuracy in coil placement, even during dynamic motion.

Effect of sensory inputs on the motor evoked potentials in the wrist flexor muscle during the robotic passive stepping in humans.

The purpose of this study was to reveal whether the stepping-related afferent feedback modulates the motor evoked potentials (MEPs) in the wrist flexor muscle in humans. MEPs generated in flexor carpi radialis muscle (FCR) by transcranial magnetic stimulation (TMS) were recorded during robotic-assisted passive stepping and standing conditions. TMS were applied at fifteen scalp sites (3 × 5 cm grid in anterior-posterior direction and medial-lateral direction, respectively) centered on the "hot spot" which was defined as an optimal site for eliciting the MEP in FCR during passive standing task, The MEP amplitudes were measured for each stimulus sites, and then compared between different conditions. During passive stepping, the MEP amplitudes in FCR muscle were significantly increased in six adjacent stimulus sites of the hot spot, This result suggests that stepping-related afferent feedback induces expansion of excitatory area in motor cortex for FCR muscle.

Automatic detection method of muscle fiber movement as revealed by ultrasound images.

The objective of this study was to develop a method of muscle structure measurement based on the automatic analysis of muscle fibers, proximal fascias, and distal aponeurosis movements as revealed by a time-series of ultrasound images. This method was designed to detect changes in the length of muscle fiber movements, and its validity was demonstrated in a time-series of muscle movement, slow ankle dorsiflexion (10 degrees/s), by comparison to manual measurement. The results showed that, when this method was used, the changes in the length of the muscle fiber under slow muscle movement were smaller than those in manual operations by novice individuals. However, with the proposed method, it was possible to obtain a sufficient degree of validity and reliability for the changes in the length of the muscle fiber length compared with those in manual operations, since the correlation coefficients exceeded 0.8 which was tested by the linear regression. The proposed method suggests that automation reduces the errors caused by manual operations and makes the processing of data possible in an acceptable amount of time.

Robotic gait trainer in water: development of an underwater gait-training orthosis.

PURPOSE: To develop a robotic gait trainer that can be used in water (RGTW) and achieve repetitive physiological gait patterns to improve the movement dysfunctions. METHOD: The RGTW is a hip-knee-ankle-foot orthosis with pneumatic actuators; the control software was developed on the basis of the angular motions of the hip and knee joint of a healthy subject as he walked in water. Three-dimensional motions and electromyographic (EMG) activities were recorded in nine healthy subjects to evaluate the efficacy of using the RGTW while walking on a treadmill in water. RESULTS: The device could preserve the angular displacement patterns of the hip and knee and foot trajectories under all experimental conditions. The tibialis anterior EMG activities in the late swing phase and the biceps femoris throughout the stance phase were reduced whose joint torques were assisted by the RGTW while walking on a treadmill in water. CONCLUSION: Using the RGTW could expect not only the effect of the hydrotherapy but also the standard treadmill gait training, in particular, and may be particularly effective for treating individuals with hip joint movement dysfunction.

Somatosensory graviception inhibits soleus H-reflex gain in humans during walking.

To investigate the effects of gravity-related somatosensory information on spinal human reflexes, the soleus H-reflex was recorded in ten healthy subjects walking on a treadmill at 2.0 km/h on land and in water. The modulation pattern of the soleus H-reflex was determined in ten different phases of the step cycle. While the subjects were walking in water, the background electromyographic activity (BGA) of the soleus was lower than that on land; on the other hand, the soleus H-reflex amplitude while the subjects were walking in water showed no significant differences throughout the step cycle compared with that while the subjects were on land; the phase-dependent soleus H-reflex modulation pattern was well preserved while walking in water. There was a linear relationship between the BGA and the H-reflex amplitude in each condition; however, the soleus H-reflex gain while walking in water was significantly higher than that on land. These findings suggest that the somatosensory graviception can markedly reduce the spinal reflex excitability. Our findings are discussed in relation to human gait; therefore, further studies are needed to clarify the effect of somatosensory graviception on human neural mechanisms.

Functional roles of lower-limb joint moments while walking in water.

OBJECTIVE: To clarify the functional roles of lower-limb joint moments and their contribution to support and propulsion tasks while walking in water compared with that on land. DESIGN: Sixteen healthy, young subjects walked on land and in water at several different speeds with and without additional loads. BACKGROUND: Walking in water is a major rehabilitation therapy for patients with orthopedic disorders. However, the functional role of lower-limb joint moments while walking in water is still unclear. METHODS: Kinematics, electromyographic activities in biceps femoris and gluteus maximums, and ground reaction forces were measured under the following conditions: walking on land and in water at a self-determined pace, slow walking on land, and fast walking in water with or without additional loads (8 kg). The hip, knee, and ankle joint moments were calculated by inverse dynamics. RESULTS: The contribution of the walking speed increased the hip extension moment, and the additional weight increased the ankle plantar flexion and knee extension moment. CONCLUSIONS: The major functional role was different in each lower-limb joint muscle. That of the muscle group in the ankle is to support the body against gravity, and that of the muscle group involved in hip extension is to contribute to propulsion. In addition, walking in water not only reduced the joint moments but also completely changed the inter-joint coordination. RELEVANCE: It is of value for clinicians to be aware that the greater the viscosity of water produces a greater load on the hip joint when fast walking in water.

Development of quantitative neuropsychological tests for diagnosis of subclinical hepatic encephalopathy in liver cirrhosis patients and establishment of diagnostic criteria-multicenter collaborative study in Japanese.

At present, there are no generally accepted diagnostic criteria or methods for subclinical hepatic encephalopathy (SHE) associated with liver cirrhosis. We therefore developed an easily conducted computer-aided quantitative neuropsychiatric function test system for use in routine medical practice. We established normal values in healthy Japanese subjects and determined differences between healthy persons and liver cirrhosis patients without clinical encephalopathy in a multi-center clinical trial. The test system consists of eight tests: number connection tests A and B, a figure position test, a digit symbol test, a block design test, and reaction time tests A, B and C. The test results were affected by age, but not by gender or facility. No learning effect was noted. The results were therefore reported by 5-year quartile ranges and differences were evaluated between 542 healthy subjects and 292 cirrhotic patients. When the cut-off value was set at the 10th/90th percentile of the results in healthy subjects, the results of each of the 8 tests were abnormal in about 25% of cirrhotic patients, and at least 1 of the 8 tests gave values greater than the 10th/90th percentile cut-off value in 58.2% of the 292 liver cirrhosis patients. SHE patients were thought to be included in these 58.2% of patients. The developed test makes it possible to quantitatively assess neuropsychiatric function, and the results obtained can be used as a basis for the diagnosis of SHE.

Effect of the walking speed to the lower limb joint angular displacements, joint moments and ground reaction forces during walking in water.

PURPOSE: The purpose of this study was to compare the changes in ground reaction forces (GRF), joint angular displacements (JAD), joint moments (JM) and electromyographic (EMG) activities that occur during walking at various speeds in water and on land. METHOD: Fifteen healthy adults participated in this study. In the water experiments, the water depth was adjusted so that body weight was reduced by 80%. A video-motion analysis system and waterproof force platform was used to obtain kinematics and kinetics data and to calculate the JMs. RESULTS: Results revealed that (1) the anterior-posterior GRF patterns differed between walking in water and walking on land, whereas the medio-lateral GRF patterns were similar, (2) the JAD patterns of the hip and ankle were similar between water- and land-walking, whereas the range of motion at the knee joint was lower in water than on land, (3) the JMs in all three joints were lower in water than on land throughout the stance phase, and (4) the hip joint extension moment and hip extensor muscle EMG activity were increased as walking speed increase during walking in water. CONCLUSIONS: Rehabilitative water-walking exercise could be designed to incorporate large-muscle activities, especially of the lower-limb extensor muscles, through full joint range of motion and minimization of joint moments.

Lower limb joint moment during walking in water.

PURPOSE: Walking in water is a widely used rehabilitation method for patients with orthopedic disorders or arthritis, based on the belief that the reduction of weight in water makes it a safer medium and prevents secondary injuries of the lower-limb joints. To our knowledge, however, no experimental data on lower-limb joint moment during walking in water is available. The aim of this study was to quantify the joint moments of the ankle, knee, and hip during walking in water in comparison with those on land. METHOD: Eight healthy volunteers walked on land and in water at a speed comfortable for them. A video-motion analysis system and waterproof force platform were used to obtain kinematic data and to calculate the joint moments. RESULTS: The hip joint moment was shown to be an extension moment almost throughout the stance phase during walking in water, while it changed from an extension- to flexion-direction during walking on land. The knee joint moment had two extension peaks during walking on land, whereas it had only one extension peak, a late one, during walking in water. The ankle joint moment during walking in water was considerably reduced but in the same direction, plantarflexion, as that during walking on land. CONCLUSIONS: The joint moments of the hip, knee, and ankle were not merely reduced during walking in water; rather, inter-joint coordination was totally changed.

Sympathetic nervous activity and myocardial damage immediately after subarachnoid hemorrhage in a unique animal model.

BACKGROUND AND PURPOSE: Obvious cardiac dysfunction, including ECG abnormalities and left ventricular asynergy, is known to develop after subarachnoid hemorrhage (SAH). To clarify the close relationship between myocardial damage and sympathetic nervous activity immediately after SAH, a novel experimental animal model was used. METHODS: SAH was provoked by perforation of the basilar artery with the use of a microcatheter inserted through the femoral artery in 18 beagle dogs. Hemodynamic changes were recorded, and plasma concentrations of noradrenaline, adrenaline, and 3-methoxy-4-hydroxy-phenylethylene glycol (MHPG) and serum levels of creatine kinase-MB (CK-MB) and troponin T were measured at 0, 5, 15, 30, 60, 120, and 180 minutes after SAH. RESULTS: Noradrenaline (pg/mL), adrenaline (pg/mL), and MHPG (ng/mL) increased abruptly from 120+/-70, 130+/-70, and 1.3+/-0.5 before SAH to 1700+/-1200, 5600+/-3500, and 3.2+/-1.2 at 5 minutes after SAH, respectively. Aortic pressure, left ventricular wall motion, and cardiac output increased by 60%, 40%, and 30%, respectively (P<0.001) at 5 minutes and then decreased by 50%, 55%, and 40%, respectively (P<0.001) >60 minutes after SAH compared with baseline values. The peak value of CK-MB correlated positively with the peak values of noradrenaline and adrenaline (r=0.730 and r=0.611, respectively). The peak value of troponin T also correlated positively with the peak values of noradrenaline and adrenaline (r=0.828 and r=0.792, respectively). CONCLUSIONS: These results suggest that the elevated activity of the sympathetic nervous system observed in the acute phase of SAH induced myocardial damage and contributed to the development of cardiac dysfunction.