Walking In Healthy Subjects Research Articles

DEVELOPMENT OF GAIT TRAINING SYSTEM USING BI-ARTICULAR MUSCLE MODEL

The purpose of this study was to develop a pneumatic gait training system which was consisted by Mckibben type actuators to achieve the normal gait patterns of lower limb joint angular displacements. These actuators were arranged as human musculoskeletal system; mono- and bi-articular muscles. The system provided a proportional directional control valve which controlled antagonistic actuators, and this system had PID controller and joint angular displacement feedback circuit. In the results, the output of the knee joint movement pattern had well validation for the input signal which was recorded from natural treadmill walking in healthy subjects. This system made the orthosis reproduce like the human natural walking. In conclusion, we structured a fundamental bi-articular muscle type of the gait training system using Mckibben type actuators.

Biomechanics of overground vs. treadmill walking in healthy individuals

The goal of this study was to compare treadmill walking with overground walking in healthy subjects with no known gait disorders. Nineteen subjects were tested, where each subject walked on a split-belt instrumented treadmill as well as over a smooth, flat surface. Comparisons between walking conditions were made for temporal gait parameters such as step length and cadence, leg kinematics, joint moments and powers, and muscle activity. Overall, very few differences were found in temporal gait parameters or leg kinematics between treadmill and overground walking. Conversely, sagittal plane joint moments were found to be quite different, where during treadmill walking trials, subjects demonstrated less dorsiflexor moments, less knee extensor moments, and greater hip extensor moments. Joint powers in the sagittal plane were found to be similar at the ankle but quite different at the knee and hip joints. Differences in muscle activity were observed between the two walking modalities, particularly in the tibialis anterior throughout stance, and in the hamstrings, vastus medialis and adductor longus during swing. While differences were observed in muscle activation patterns, joint moments and joint powers between the two walking modalities, the overall patterns in these behaviors were quite similar. From a therapeutic perspective, this suggests that training individuals with neurological injuries on a treadmill appears to be justified.

Study of Human Outdoor Walking with a Low-Cost GPS and Simple Spreadsheet Analysis

To determine whether a low-cost, commercially available global positioning system (GPS) can be used to study outdoor walking of healthy subjects, allowing the detection of walking and resting (nonwalking) periods and the accurate estimation of speed and distance of each walking periods. The same EGNOS-enabled GPS receiver was used for all experiments. In experiment 1, various signal-processing methodologies were tested for the detection of both walking and resting bouts from a prescribed walking protocol (PWP) that was performed 21 times by six healthy subjects on an outdoor athletic track. In experiment 2, the accuracies of these processing methodologies were then tested through a blinded analysis of different PWP for 10 other healthy subjects in a designated public park. In experiment 3, speed and distance calculated by the GPS receiver during series of 100-400 m on an outdoor athletic track were compared with actual speed and distance. Raw data were inaccurate, but the combination of a low-pass filter, an adapted high-pass filter, and artifact processing enabled one to detect walking and resting bouts with an accuracy of 89.8% (95% CI, 84.4-93.4). A manual post-processing methodology, used to complete previous automatic processing results, provided the highest concordance with the PWP, reaching an accuracy of 97.1% (95% CI, 93.5-98.8). There was an excellent relationship both between actual and processed distances (R2=1.000) and between actual and processed speeds (R2=0.947). Low-cost, commercially available GPS may be accurate in studying outdoor walking, provided that simple data processing is applied. Future validation in diseased subjects could allow for the study of free-living walking capacity, such as maximal walking distance in vascular patients.

Implications of increased medio-lateral trunk sway for ambulatory mechanics

The purposes of this study was to test a mechanism to reduce the knee adduction moment by testing the hypothesis that increased medio-lateral trunk sway can reduce the knee adduction moment during ambulation in healthy subjects, and to examine the possibility that increasing medio-lateral trunk sway can produce similar potentially adverse secondary gait changes previously associated with reduced knee adduction moments in patients with knee osteoarthritis. Nineteen healthy adults performed walking trials with normal and increased medio-lateral trunk sway at a self-selected normal walking speed. Standard gait analysis was used to calculate three-dimensional lower extremity joint kinematics and kinetics. Knee and hip adduction moments were lower (−65.0% and −57.1%, respectively) for the increased medio-lateral trunk sway trials than for the normal trunk sway trials. Knee flexion angle at heel-strike was 3° higher for the increased than for the normal trunk sway trials. Knee and hip abduction moments were higher for the increased medio-lateral trunk sway trials, and none of the other variables differed between the two conditions. Walking with increased medio-lateral trunk sway substantially reduces the knee adduction moment during walking in healthy subjects without some of the adverse secondary effects such as increased axial loading rates at the major joints of the lower extremity. This result supports the potential of using gait retraining for walking with increased medio-lateral trunk sway as treatment for patients with degenerative joint disease such as medial compartment knee osteoarthritis.

거골하 관절 현수 테이핑의 생체 역학적 효과 분석

The purpose of this study was to identify the effect of the subtalar sling ankle taping, by measuring changes in peak plantar pressure and subtalar angle during jump landing and walking in healthy subjects with subtalar sling ankle taping applied of the ankle joint. Fifty healthy subjects(8 males and 7 female, aged 22 to 25) were randomly divided into a participated in this study. They were free of musculoskeletal injury and neurologic deficit in lower extremity. The subjects were asked to perform 5M walking and single leg jump landing by under the guidance of physical therapists. Subtalar motions were typically measured as the angle made between the posterior aspect of the calcaneous and the posterior aspect of the lower leg during walking with taping or not. This measurement were made using a video system (30Hz sampling rate, rectified 60 Hz sampling rate). At the same time, peak lateral and vertical pressure were investigated using pressure distribution platforms(MatScan system) under foot during walking and single leg jump landing with taping or not. Statistical analysis was done by paired t-test and intraclass correlation coefficient [ICC(3.1)], using software SPSS. We have recently demonstrated significantly altered patterns of subtalr joint and peak plantar pressure when applied subtalar sling ankle taping(p<.05). Inversion angle of subtalar joint significantly decreased with taping(p<.05). The result suggest that pressure patterns observed in subjects are likely to result due to significant decrease in stress on ankle joint structures during jump landing and walking. Also, the result that the subtalar sling ankle taping procedure provides greater restiction of motion associated with ankle inversion. However, this study involved asymptomatic subjects without history of ankle inversion injury, further research is needed to assess the motion restraining effect of the subtalar sling ankle taping in subjects with lateral ankle instability.

Diffusion entropy analysis on the stride interval fluctuation of human gait

In this paper, the diffusion entropy technique is applied to investigate the scaling behavior of stride interval fluctuations of human gait. The scaling behaviors of the stride interval of human walking at norm, slow, and fast rate are similar; with the scale-invariance exponents in the interval [ 0.663 , 0.955 ] , of which the mean value is 0.821 ± 0.011 . Dynamical analysis of these stride interval fluctuations reveals a self-similar pattern: fluctuation at one time scale are statistically similar to those at multiple other time scales, at least over hundreds of steps, while the healthy subjects walk at their norm rate. The long-range correlations are observed during the spontaneous walking by removal of the trend in the time series with Fourier filter. These findings uncover that the fractal dynamics of stride interval fluctuation of human gait are normally intrinsic to the locomotor systems.

A kinematic and kinetic comparison of overground and treadmill walking in healthy subjects

Introduction Gait evaluation protocols using instrumented treadmills will be increasingly used in the near future. For this reason, it must be shown that using instrumented treadmills will produce measures of the ground reaction force adequate for inverse dynamic analysis, and differences between treadmill and overground gait must be well characterized. Methods Overground walking kinetics were estimated with the subjects walking at their self-selected comfortable walking speed. For the treadmill gait trials, the subjects walked on two treadmills, such that heel-strike occurred on the forward treadmill and toe-off occurred on the trailing treadmill. The treadmill was set to the average overground walking speed. Overground and treadmill data were evaluated using Vicon Plug-in Gait. The differences between the maxima and minima of kinematic and kinetic parameters for overground and treadmill gait were evaluated. Results The kinematics of treadmill and overground gait were very similar. Twelve of 22 kinematic parameter maxima were statistically significantly different ( p < 0.05), but the magnitude of the difference was generally less than 2°. All GRF maxima were found to be statistically significantly smaller for treadmill versus overground gait ( p < 0.05) as were 15 of 18 moment, and 3 of 6 power maxima. However, the magnitude of the differences was comparable to the variability in normal gait parameters. The sagittal plane ankle moments were not statistically different for treadmill and overground gait. Discussion We have shown that treadmill gait is qualitatively and quantitatively similar to overground gait. Differences in kinematic and kinetic parameters can be detected in matched comparisons, particularly in the case of kinetic parameters. However, the magnitudes of these differences are all within the range of repeatability of measured kinematic parameters. Thus, the mechanics of treadmill and overground gait are very similar. Clinical significance Having demonstrated the essential equivalence of treadmill and overground gait, it is now possible for clinical movement analysis to take advantage of treadmill-based protocols.

Reliability and Validity of Bilateral Thigh and Foot Accelerometry Measures of Walking in Healthy and Hemiparetic Subjects

Objective. Measures of walking ability in large clinical trials are usually limited to a timed short-distance walk and the distance walked in a fixed time. A new integrated system of 5 accelerometers was tested for reliability and compared to a footswitch system to determine if the accelerometers offered a practical option for the acquisition of spatiotemporal gait parameters. Methods. Leg accelerations and decelerations were defined in relation to simultaneous kinematic and electromyographic data acquired from a healthy subject. Eight healthy adults and 6 independent ambulators with hemiparetic stroke walked 15 m at 2 different speeds wearing both the accelerometers and footswitches. Twelve healthy subjects walked at 5 different speeds repeated 3 times on each of 2 days wearing the accelerometers. Walking speed, cadence, stride length, and single- and double-limb support, swing, and stance times were calculated. Results. No differences (t test, P > 0.2) were found between footswitch and accelerometer variables when comparing all left or right legs in healthy subjects and all paretic or unaffected legs in stroke subjects. A 2-way nested ANOVA model (speed, left and right legs, trial, and session) with the accelerometers at walking speeds from 0.5 to 1.8 m/s revealed high reproducibility of all measures. Conclusions. The accelerometry system provided reliable and valid spatiotemporal measures of gait for the upper range of speeds likely to be targeted for rehabilitation interventions in ambulatory subjects.

The Reliability and Validity of the Physiological Cost Index in Healthy Subjects While Walking on 2 Different Tracks

Graham RC, Smith NM, White CM. The reliability and validity of the Physiological Cost Index in healthy subjects while walking on 2 different tracks. Objective To investigate the reliability and validity of the Physiological Cost Index (PCI) scores, as a measure of energy expenditure, when healthy subjects walk on 2 different tracks (20-m and 12-m figure eight tracks). Design Intra- and interrater reliability and construct validity. Setting Physiotherapy division of a university in London, UK. Participants Forty healthy subjects (15 men, 25 women; mean age ± standard deviation, 34.5±12.6y). Interventions Not applicable. Main Outcome Measures Heart rate (in beats/min) and speed (in m/min) were used to calculate the PCI (in beats/m). Rate of oxygen consumption (V̇ o 2, in mL·kg −1·min −1) and oxygen cost (E o 2, in mL·kg −1·m −1) were used as criterion estimates of energy cost E o 2. Pearson correlation coefficients between the PCI, components of the PCI, E o 2, and V̇ o 2 were used to quantify validity. Intrarater reliability was assessed in all participants and interrater reliability was assessed on a subset of 13 subjects using intraclass correlation coefficients and Bland-Altman plots. Results Intrarater ( r=.73, r=.79) and interrater ( r=.62, r=.66) reliability were acceptable between PCI scores from 20-m and 12-m tracks, respectively. Correlations between V̇ o 2 and E o 2 with PCI were weak. PCI scores from the 20-m track were significantly lower than those on the 12-m track ( P=.002). Subjects walked significantly faster on the 20-m track ( P<.001). Results suggest a large difference in PCI scores would be necessary to indicate a “true” alteration in performance (52% for 20-m track, 43.4% for the 12-m track). Conclusions The PCI is reliable but not valid as a measure of the energy cost of walking in healthy subjects, on either track. The 20-m track is recommended for clinical use because it enables subjects to walk at a faster pace.

Pendulum efficiency during walking in healthy subjects and hemiparetic patients

Pendulum efficiency during walking in healthy subjects and hemiparetic patients

An improved powered ankle–foot orthosis using proportional myoelectric control

We constructed a powered ankle-foot orthosis for human walking with a novel myoelectric controller. The orthosis included a carbon fiber and polypropylene shell, a metal hinge joint, and two artificial pneumatic muscles. Soleus electromyography (EMG) activated the artificial plantar flexor and inhibited the artificial dorsiflexor. Tibialis anterior EMG activated the artificial dorsiflexor. We collected kinematic, kinetic, and electromyographic data for a naive healthy subject walking with the orthosis. The current design improves upon a previous prototype by being easier to don and doff and simpler to use. The novel controller allows naive wearers to quickly adapt to the orthosis without artificial muscle co-contraction. The orthosis may be helpful in studying human walking biomechanics and assisting patients during gait rehabilitation after neurological injury.

Numerical Validation of Linear Accelerometer Systems for the Measurement of Head Kinematics

The purpose of this study was to analytically exploit the capabilities of head-mounted systems instrumented with linear accelerometers (ACs) for field use in redundant configurations. We simulated different headsets equipped with uni-, bi- or triaxial sensors with a number of axes that lie in the range of 12-24; the ACs were located on a hemispherical surface by adopting a priori criterion while their orientation was randomized. In addition, for a comparative purpose the nine accelerometer scheme (one triaxial AC and three biaxial ACs addressed in the following as "3-2-2-2 configuration") was also analyzed in the present paper. We simulated and statistically assessed the performances of hemispherical headsets in the test case of a healthy subject walking freely at normal pace over level ground. The numerical results indicated that a well designed instrumented headset can retrieve the angular acceleration and (a0-g) component with rms errors of about 2% and 0.5%, respectively, and angular velocity with a drift error of about 20% in a 6 s trial. On the contrary, the pose of the headset cannot be evaluated because of the drift induced by the integration process. In general, we can state that headsets with uni-, bi- or triaxial ACs have comparable performances. The main implications of the above-mentioned observations are (a) neither expensive triaxial ACs nor assembling procedure based on the use of orthogonal mounting blocks are needed; (b) redundant arrays of low-cost uni- or biaxial ACs can effectively be used to reach adequate performances in biomechanical studies where head acceleration and velocity are investigated; (c) while estimates of angular acceleration with accelerometers are accurate, estimations of angular velocities, linear velocities and pose are not.

Evidence for Cognitive Processes Involved in the Control of Steady State of Walking in Healthy Subjects and after Cerebral Damage

Objective. The involvement of cognitive processes in the control of walking at steady state was studied in 10 healthy subjects and 18 subjects after unilateral vascular brain damage. A dual task paradigm was used to compare the performance level of a probe reaction time (RT) in sitting (simple task) and during standing or walking on a treadmill (dual task conditions). In this latter condition, RTs were classified and analyzed in relation to the different phases of the gait cycle. Results. The results show a marked increase in RT while walking compared to sitting and standing only in stroke subjects. Specific changes in RTs related to the gait cycle phases were observed in both healthy subjects and those after brain damage. It is concluded that walking at steady state is attentionally demanding. The phase-dependent modulations of the RTs suggest that cognitive processes may play a role in the control of the step cycle. The increase of attentional demand during walking in subjects who had suffered a stroke varies, depending on severity of impairments of walking but also on a reduced general attentional capacity. The dual task paradigm provides a sensitive tool in the assessment of walking ability in stroke subjects.

Reduction of Common Synaptic Drive to Ankle Dorsiflexor Motoneurons During Walking in Patients With Spinal Cord Lesion

It is possible to obtain information about the synaptic drive to motoneurons during walking by analyzing motor-unit coupling in the time and frequency domains. The purpose of the present study was to compare motor-unit coupling during walking in healthy subjects and patients with incomplete spinal cord lesion to obtain evidence of differences in the motoneuronal drive that result from the lesion. Such information is of importance for development of new strategies for gait restoration. Twenty patients with incomplete spinal cord lesion (SCL) participated in the study. Control experiments were performed in 11 healthy subjects. In all healthy subjects, short-term synchronization was evident in the discharge of tibialis anterior (TA) motor units during the swing phase of treadmill walking. This was identified from the presence of a narrow central peak in cumulant densities constructed from paired EMG recordings and from the presence of significant coherence between these signals in the 10- to 20-Hz band. Such indicators of short-term synchrony were either absent or very small in the patient group. The relationship between the amount of short-term synchrony and the magnitude of the 10- to 20-Hz coherence in the patients is discussed in relation to gait ability. It is suggested that supraspinal drive to the spinal cord is responsible for short-term synchrony and coherence in the 10- to 20-Hz frequency band during walking in healthy subjects. Absence or reduction of these features may serve as physiological markers of impaired supraspinal control of gait in SCL patients. Such markers could have diagnostic and prognostic value in relation to the recovery of locomotion in patients with central motor lesions.

Neural control mechanisms for normal versus Parkinsonian gait

The non-invasive methods which can be applied to the study of the cerebral control mechanisms for human gait are limited because of technical constraints. In particular, the subject's head has to be fixed for most measurements. Despite this problem, SPECT-detected, rCBF activation studies have shown that the cerebral cortex participates in the control of the normal volitional walking of healthy human subjects. The active brain areas include the foot and trunk regions of the primary sensorimotor cortex, and the supplementary motor area (SMA), lateral premotor cortex, and cingulated gyrus. Selected subcortical structures also exhibit walking-related activity, including the dorsal brainstem and cerebellum. These same regions are active in patients with Parkinson's disease (PD), but significantly less so in the right SMA, left precuneus, and right cerebellar hemisphere. For the "kinesie paradoxale" of PD patients, the right lateral premotor area plays an important role in the visually induced gait improvement brought on by adding transverse lines to the walking path.

Energy cost of walking and gait instability in healthy 65- and 80-yr-olds

This study tested whether the lower economy of walking in healthy elderly subjects is due to greater gait instability. We compared the energy cost of walking and gait instability (assessed by stride to stride changes in the stride time) in octogenarians (G80, n = 10), 65-yr-olds (G65, n = 10), and young controls (G25, n = 10) walking on a treadmill at six different speeds. The energy cost of walking was higher for G80 than for G25 across the different walking speeds (P < 0.05). Stride time variability at preferred walking speed was significantly greater in G80 (2.31 +/- 0.68%) and G65 (1.93 +/- 0.39%) compared with G25 (1.40 +/- 0.30%; P < 0.05). There was no significant correlation between gait instability and energy cost of walking at preferred walking speed. These findings demonstrated greater energy expenditure in healthy elderly subjects while walking and increased gait instability. However, no relationship was noted between these two variables. The increase in energy cost is probably multifactorial, and our results suggest that gait instability is probably not the main contributing factor in this population. We thus concluded that other mechanisms, such as the energy expenditure associated with walking movements and related to mechanical work, or neuromuscular factors, are more likely involved in the higher cost of walking in elderly people.

Functional coupling of motor units is modulated during walking in human subjects.

Time- and frequency-domain analysis of the coupling between pairs of electromyograms (EMG) recorded from leg muscles was investigated during walking in healthy human subjects. For two independent surface EMG signals from the tibialis anterior (TA) muscle, coupling estimated from coherence measurements was observed at frequencies </=50 Hz, with identifiable peaks occurring in two frequency bands ranging approximately from 8 to 15 and 15 to 20 Hz. The coherence between TA recordings was greatest toward the end of swing, reduced in early swing, and largely absent in midswing. In time-domain estimates constructed from paired TA EMG recordings, a short-lasting central peak indicative of motor-unit synchronization was observed. This feature of motor-unit coupling was also reduced in mid swing. In paired recordings made among triceps surae, quadriceps, and hamstring muscles, a similar pattern of correlation to that for paired TA recordings was observed. However, no significant coupling was observed in recordings for which one EMG recording was made from an ankle flexor/extensor muscle and the other from a knee extensor/flexor muscle. These results demonstrate that for TA a modulation exists in the functional coupling of motor units recruited during swing. The data also indicate that human motoneurons belonging to different muscles are only weakly coupled during walking. This absence of widespread short-term synchronization between the activities of muscles of the leg may provide a basis for the highly adaptive nature of human gait patterns.

The energy expenditure in walking and stair locomotion of healthy elderly subjects

The energy expenditure in walking and stair locomotion of healthy elderly subjects

Nonlinear time series analysis of normal and pathological human walking.

Characterizing locomotor dynamics is essential for understanding the neuromuscular control of locomotion. In particular, quantifying dynamic stability during walking is important for assessing people who have a greater risk of falling. However, traditional biomechanical methods of defining stability have not quantified the resistance of the neuromuscular system to perturbations, suggesting that more precise definitions are required. For the present study, average maximum finite-time Lyapunov exponents were estimated to quantify the local dynamic stability of human walking kinematics. Local scaling exponents, defined as the local slopes of the correlation sum curves, were also calculated to quantify the local scaling structure of each embedded time series. Comparisons were made between overground and motorized treadmill walking in young healthy subjects and between diabetic neuropathic (NP) patients and healthy controls (CO) during overground walking. A modification of the method of surrogate data was developed to examine the stochastic nature of the fluctuations overlying the nominally periodic patterns in these data sets. Results demonstrated that having subjects walk on a motorized treadmill artificially stabilized their natural locomotor kinematics by small but statistically significant amounts. Furthermore, a paradox previously present in the biomechanical literature that resulted from mistakenly equating variability with dynamic stability was resolved. By slowing their self-selected walking speeds, NP patients adopted more locally stable gait patterns, even though they simultaneously exhibited greater kinematic variability than CO subjects. Additionally, the loss of peripheral sensation in NP patients was associated with statistically significant differences in the local scaling structure of their walking kinematics at those length scales where it was anticipated that sensory feedback would play the greatest role. Lastly, stride-to-stride fluctuations in the walking patterns of all three subject groups were clearly distinguishable from linearly autocorrelated Gaussian noise. As a collateral benefit of the methodological approach taken in this study, some of the first steps at characterizing the underlying structure of human locomotor dynamics have been taken. Implications for understanding the neuromuscular control of locomotion are discussed. (c) 2000 American Institute of Physics.

A kinematic comparison of overground and treadmill walking

Objective. To compare overground and treadmill ambulation for possible differences in gait temporal variables and leg joint kinematics. Design. A human subject trial of walking in two conditions. Background. The treadmill is frequently used to simulate overground ambulation; however, the literature shows a wide difference of opinion as to whether the treadmill replicates the overground environment. Methods. A total of 17 uninjured subjects walked overground at their preferred velocity. The treadmill was then set at the average velocity obtained in overground walking. Gait temporal variables and leg joint kinematics were analysed using the three dimensional (3D) Kinemetrix Motion Analysis System. The data were analysed separately for the two gender groups and for the groups combined. Results. In the females, only the maximum hip flexion angle was significantly different in the two conditions with greater flexion occurring on the treadmill. For males, significant differences were noted between the two conditions for cadence and maximum knee flexion angle with greater values in the treadmill walking. When all subjects were compared, significant increases were seen during treadmill walking in hip range of motion, maximum hip flexion joint angle and cadence, while a significant decrease was observed in stance time. Conclusions. Statistically significant differences exist between overground and treadmill walking in healthy subjects for some joint kinematic and temporal variables.