Gait Conditions Research Articles

Corticospinal input in human gait: modulation of magnetically evoked motor responses

Transcranial magnetic stimulation (TMS) of the motor cortex was applied during locomotion to investigate the significance of corticospinal input upon the gait pattern. Evoked motor responses (EMR) were studied in the electromyogram (EMG) of tibialis anterior (TA), gastrocnemius (GM) and, for reference, abductor digiti minimi (AD) muscles by applying below-threshold magnetic stimuli during treadmill walking in healthy adults. Averages of 15 stimuli introduced randomly at each of 16 phases of the stride cycle were analysed. Phase-dependent amplitude modulation of EMR was present in TA and GM which did not always parallel the gait-associated modulation of the EMG activity. No variation of onset latency of the EMR was observed. The net modulatory response was calculated by comparing EMR amplitudes during gait with EMR amplitudes obtained (at corresponding background EMG activities) during tonic voluntary muscle contraction. Large net responses in both muscles occurred prior to or during phasic changes of EMG activity in the locomotor pattern. This facilitation of EMR was significantly higher in leg flexor than extensor muscles, with maxima in TA prior to and during late swing phase. A comparison of this facilitation of TA EMR prior to swing phase and prior to a phasic voluntary foot dorsiflexion revealed a similar onset but an increased amount of early facilitation in the gait condition. The modulated facilitation of EMR during locomotion could in part be explained by spinal effects which are different under dynamic and static motor conditions. However, we suggest that changes in corticospinal excitability during gait are also reflected in this facilitation. This suggestion is based on: (1) the similar onset yet dissimilar size of facilitatory effects in TA EMR prior to the swing phase of the stride cycle and during a voluntary dynamic activation, (2) the inverse variation of EMR and EMG amplitudes during this phase, and (3) the occurrence of this inversion at stimulation strengths below motor threshold (motor threshold was determined during weak tonic contraction and EMR were facilitated during gait). It is hypothesized that the facilitation is phase linked to ensure postural stability and is most effective during the phases prior to and during rhythmical activation of the leg muscles resulting in anticipatory adjustment of the locomotor pattern.

A functional knee brace alters joint torque and power patterns during walking and running

Individuals with anterior cruciate ligament (ACL) injury use greater extensor torques at the hip and ankle and lower extensor torques and joint power at the knee during gait compared to healthy subjects. These adaptations may be mediated by (1) altered neuromuscular strategies due to the injury, (2) training effects produced by rehabilitation protocols, and (3) training effects due to the functional knee brace (FKB) used during rehabilitation. The purpose of the study was to test the hypothesis that a FKB can cause individuals to walk and run with the torque and power patterns observed in rehabilitated ACL-injured individuals. Ten healthy subjects were tested walking and running with and without a FKB. Kinematic and ground reaction data were collected and combined with inverse dynamics to estimate the joint torques and powers. Data were analyzed with a two-way repeated measures ANOVA (gait vs knee condition). In walking, the hip and ankle extensor torques were 14.3% ( p < 0.038) and 5.1% ( p < 0.003) greater with FKB. In running, the hip extensor torque was 17.0% greater with FKB ( p < 0.023). Knee torque was not different between conditions. In walking, the work performed at the hip and knee were 11.6% greater ( p < 0.013) and 17.7% lower with FKB ( p < 0.025), respectively. Results supported the hypothesis and it was concluded that a FKB may be one causative factor in the development of the unique joint torque and power patterns seen in ACL-injured gait.

Anti-inflammatory effects of kappa-opioids in adjuvant arthritis

Current therapies for arthritis are unsatisfactory and cause serious side effects and morbidity. It has been postulated that opioid drugs may block inflammatory mediators and attenuate the joint damage in adjuvant arthritis. However, the importance of opioid receptor subtypes involved in inflammation remains to be determined because data are conflicting in this regard. The present investigation was designed to test the effects of both a kappa-agonist, (±)U50488H and a kappaantagonist, MR2266 on the progression of experimental arthritis. To produce adjuvant arthritis, male Lewis rats were innoculated subcutaneously (s.c.) with 0.05 ml of Freund's complete adjuvant (10 mg/ml) into the right hind paw. The kappa-opioid agonist, (±)U50488H (20 mg/kg/d s.c.) and the kappa-opioid antagonist, MR2266 (20 mg/kg/d s.c.) were administered for 3 days during the primary inflammatory phase of adjuvant arthritis. There were four treatment groups; group I were non-arthritic controls and received paraffin oil vehicle and opioid injections; group II were arthritic controls and received adjuvant and saline injections; group III received adjuvant and agonist and group IV received adjuvant and antagonist. The progression of adjuvant arthritis from day 0 to 24 was monitored by body weight change, hind limb size (ipsilateral and contralateral) and a total severity score for each clinical observation of gait, coat and limb condition. On day 24 histology and radiography of the contralateral limb was performed. There was less soft-tissue swelling, as judged by time-averaged % change in the volume of the contralateral limb, in both agonist (mean ± se: 82 ± 5) and antagonist (77 ± 4) treated rats compared to untreated arthritic controls (99 ± 5, p < 0.05). Other clinical measures of severity were not different between untreated and opioidtreated arthritic rats. However, the joint damage as judged by radiography was lower in kappa agonist treated rats (2.6 ± 0.5, p < 0.05) compared to untreated controls (4.1 ± 0.5) and antagonist treatment (4.4 ± 0.5). Microscopic pathological scores were also significantly lower in agonist (2.8 ± 0.3, p < 0.05) compared to both antagonist treated rats (4.2 ± 0.1) and vehicle-treated controls (3.6 ± 0.2). The results of this study show that kappa-opioid receptor agonists but not antagonists attenuate the progression of experimental arthritis. These observations have important implications for the evaluation and use of kappa-opioid agents in the management of arthritis.

Wall Gait: A Standard Gait for the Quadruped Wall-Climbing Robot.

The development of a wall-climbing robot which is able to move on a "3-dimensional terrain", including floor, wall, ceiling is in high demand in many industries. Thus the authors have developed a quadruped wall-climbing robot, named "Ninja". However, the gait control method specific for the quadruped wall-climbing robot is not at all known yet. As the first step toward consideration of a general gait problem of a quadruped wall-climbing robot, this paper investigates the standard gait on a vertical and smooth wall. The gait is analyzed with a criterion that maximizes the locomotion speed under the constraints which mainly prevent the turning over motion of the robot. As a result, the optimal standard gait, named "wall gait", is shown to maintain foot arrangement of A shape and to move the legs in the order of front-left, rear-left, front-right, rear-right, in static gait and the order of "pace" in dynamic gait. Wall gait realizes fast locomotion and stable sucking motion using a specific motion generated by its own weight when only two legs are sucking the wall.

Development of a balance context indicator during gait

Abstract This work represents the first stage in the designing of a ‘balance pattern’. This one is defined, with a balance instantaneous indicator (Bll) and a balance context indicator (BCl) taken into consideration, and from data provided by an original wearable plantar dynamics analysis system The present paper describes the features extraction method for the BCl, leading to definition of a set of descriptors. These descriptors are tested on a population of non-pathological subjects under normal and simulated abnormal gait conditions. The first results showed the feasibility of an automatic system for recognition of abnormal patterns related to dysfunction of various biomechanical components.

Dynamic and static fusion gait of a quadruped walking vehicle on a winding path

A quadruped walking vehicle has the potential both to walk, conserving the conditions of smoothness and static stability, and to run, where the ride will be bumpy but fast and dynamically stable. The authors have already proposed the concept of 'dynamic and static fusion gait control' and discussed a basic control scheme for the purpose of adaptive selection of these gaits during continuous walking. This paper extends the concept to walking at variable speeds along a winding path. The motion scheme is discussed on the basis of a generalized trot gait and incorporating stability control based on feedforward and feedback control; trajectory modification is based on the concept of zero moment point. The validity of the motion schemes was verified in walking experiments using the quadruped walking vehicles TITAN IV and TITAN VI.

Design and development of an unconstrained dynamic knee simulator.

A dynamic knee simulator has been developed to allow in-vitro investigation of the mechanical response of the joint corresponding to dynamic functional activities, e.g., walking. In the simulator, the controlled inputs are the time-histories of three parameters of a given dynamic activity: the flexion angle, and the flexion/extension moment and tibial axial force components of the foot-to-floor reaction. A combination of stepping motors and electro-hydraulic actuators is used to apply to a knee specimen, simultaneously and independently, the specified load and/or displacement inputs while allowing unconstrained relative motion between the joint members. Satisfactory performance of the simulator has been established for walking gait conditions based on measurements on three fresh-frozen specimens.

Lower extremity moments of force during three gait conditions

Lower extremity moments of force during three gait conditions

Legendre polynomial coefficients in the analysis of the horizontal and lateral component of the force plate measurements for an osteoarthritic gait

The assessment of force plate measurement obtained from subjects with a pathological gait, normally carried out by visual examination of the force-time data, can be augmented by consideration of Legendre polynomial coefficients. The first seven coefficients are evaluated and presented for the horizontal (forwards) and lateral (sideways) components of the force-time curves. It is shown that for an accurate assessment of specific osteoarthritic abnormalities it is necessary to consider the horizontal and lateral component data in addition to that previously presented for the vertical component. Relevance The Legendre analysis identifies the major gait factors from the shape of the curves and gives a reliable method of reducing the dynamic data to a simple set of numerical values by formalizing the classic approach of visual examination of the force-time curves. The method is particularly suitable for assessing the clinical gait condition in respect of heel-strike, toe-off, and stability.

Evaluation of Gait using Physiological Cost Index for Hemiplegia

Gait conditions of forty-three hemiplegic patients were evaluated by Physiological Cost Index (P.C.I.). Then, the correlations between P.C.I. and Brunnstrom stage, ADL, walking speed, and steps per day were investigated. Results obtained were as follows : 1) Hemiplegic patients showed higher P.C.I. and slower walking speed than the healthy adults did. 2) From the standpoint of Brunnstrom stage, P.C.I. indicated higher value and walking speed tended to be slower in stage III than stages IV, V, and VI. 3) The close relationships between P.C.I. and acquired rate of ADL, steps per day, and APDL were observed. In case physical therapy is performed on hemiplegic patients, it might be important that improvement in daily activity should be realized by not only trainings under the impairment level such as ROM training and reeducation of neuromuscle, but also those under the disability level, ADL training, and walking exercise.

Quantitative approach to osteoarthritic gait assessment.

Measurements of the gait of 42 patients with osteoarthritis of the hip are made using only a pair of small force plates with computer interfacing. The use of more complex and expensive television systems is thus avoided. The force between the foot and plate is measured during gait, resolved into vertical, horizontal, and lateral force components, and graphs of the time variations of these components produced. It is shown that an accurate on-line assessment of pre- and post-operative gait can be made, but only by reference to all three force component curves. A numerical assessment of the gait condition is obtained as the total of scores for clearly identified separate features of each curve. This helps the clinician to arrive at a firm value and should reduce subjective variations arising from attempts to assign a single overall number for the ‘quality’ of each curve.

A biomechanical analysis of racewalking gait

The purpose of this study was to investigate the kinetic and kinematic properties of the lower extremity during the phases of the racewalking gait as defined by the rules and compare these to normal walking and running. Cinematographic and force plate data were gathered from 10 competitive racewalkers under four gait conditions. Temporal parameters, angular displacements of the lower extremity, ground reaction forces, path of the center of pressure, and the joint forces during the four gait conditions were compared using a repeated measures analysis of variance. Racewalkers exhibited significantly increased (P less than 0.01) maximal ankle dorsiflexion, maximal knee extension, angular displacements of the pelvis, medial ground-foot reaction forces, peak plantar flexion moment, and external peak knee hyperextension moment than did walking or running. Based upon the results of this investigation, it was determined that the gait of racewalking exhibits some biomechanical characteristics which are different from the gaits of walking or running.

Cerebral evoked potentials associated with the compensatory reactions following stance and gait perturbation

We have studied the gastrocnemius electromyographic (EMG) responses and the cerebral potentials evoked in normal subjects by perturbations of stance and gait in the form of short treadmill acceleration impulses. In the stance condition a small EMG response (LM1; latency around 40 ms) was followed by a strong muscle activation (LM2; latency 75–90 ms). Following perturbation during gait, LM1 was lacking and LM2 appeared a little earlier (65–75 ms). In the stance condition, the cerebral potentials appeared with shorter latency (42 ms as compared to 83 ms) and a larger amplitude (41 μV as compared to 21 μV) than those seen in the gait condition. These changes can be explained by a presynaptic inhibition of group I afferent signals during gait, which are assumed to be responsible for the early EMG and EEG responses. It is suggested that the LM2 and the cerebral responses evoked by gait perturbation are mediated by signals from group II and III afferents.

Development of gait at slow, free, and fast speeds in 3- and 5-year-old children.

The purpose of this study was to describe and statistically analyze 3- and 5-year-old children's gait at slow, free, and fast speeds in terms of stride length, step length (adjusted for leg length), stride width, included angle of feet, and cadence. The study also correlated gait factors and motor development. Gait patterns were recorded with a clinical, footprint method. In general, stride length and cadence were significantly different for age and speed, and step length and stride width were significantly different only for speed. Included angle of feet was not significant for age or speed. Motor ability as measured by the McCarthy Scales of Children's Abilities correlated only with stride length and cadence. It was concluded that gait patterns in 3- and 5-year-old children are not fully mature. Perhaps the interrelationship between gait factors, age, and speed, as well as the relationships among gait factors, present a more realistic analysis of gait in these children than if the variables were considered in isolation. Further research is needed to determine how variability of a child's gait decreases and which gait factors and conditions can be used appropriately to determine gait maturity.

An optimality criterion for processing electromyographic (EMG) signals relating to human locomotion.

Emphasizing consistency and repeatability of acquired data, we have studied the characteristics of surface EMG signals from m. vastus lateralis and m. rectus femoris during several steps of level walking under controlled repeatable gait conditions at three different speeds for several subjects. The variance ratio, a statistical descriptor for repeatability, has been devised. Our findings indicate that the variance ratio offers a simple means for selecting an optimal envelope processor of full-wave rectified EMG signals. It is of value also in determining an optimal location for surface electrodes on a muscle.