Effects of treadmill walking speed on lateral gastrocnemius muscle firing

OBJECTIVE: To study the electromyographic profile--including ON, OFF, and peak timing locations--of the lateral gastrocnemius muscle over a wide range of walking speeds (0.5-2.1 m/sec) in healthy young adults. DESIGN: We studied gastrocnemius muscle-firing patterns using an electromyographic surface electrode in 15 healthy subjects ambulating on a treadmill at their normal walking speed and at three paced walking speeds (0.5, 1.8, and 2.1 m/sec). Initial heel contact was determined from a force-sensitive switch secured to the skin over the calcaneous. RESULTS: For all speeds, the gastrocnemius firing pattern was characterized by a main peak, occurring 40-45% into the gait cycle, that increased in amplitude with walking speed. Speeds of > or =1.3 m/sec produced a common electromyographic timing profile, when the profile is expressed relative to the stride duration. However, at 0.5 m/sec (a speed typical of individuals with upper-motor neuron lesions), the onset of gastrocnemius firing was significantly delayed by 3-6% of the gait cycle and was prolonged by 8-11% of the gait cycle. CONCLUSION: Many patients with upper motor neuron lesions (e.g., stroke and traumatic brain injury) walk at speeds much slower than those commonly described in the literature for normal gait. At the slow walking speed of 0.5 m/sec, we have measured noticeable changes in the electromyographic timing profile of the gastrocnemius muscle. Given the importance of appropriate plantar flexor firing patterns to maximize walking efficiency, understanding the speed-related changes in gastrocnemius firing patterns may be essential to gait restoration.     

The use of the 6-min walk test as a proxy for the assessment of energy expenditure during gait in individuals with lower-limb amputation

The objective of this study was to determine, and compare, the utility of the 6-min walk test (6 MWT) and self-selected walking speed over 15 m as proxies for the assessment of energy expenditure during gait in individuals with lower-limb amputation. Patients with unilateral, transfemoral amputation (n=6) and patients with unilateral, transtibial amputation (n=10) from community-based support groups participated in this study. Age-matched and body mass index-matched able-bodied controls (n=28) from a sample of convenience also participated. The main outcome measures were as follows: (a) distance, heart rate, oxygen consumption and oxygen cost during the 6 MWT and (b) self-selected walking speed over 15 m. Oxygen cost did not correlate significantly with self-selected walking speed over 15 m (ρ=-0.329) or average walking speed during the 6 MWT (ρ=-0.350). Significant correlations were not present between oxygen cost and the walking speed during the 6 MWT (range, ∣ρ∣: 0.210-0.531), although walking speeds at particular times of the 6 MWT demonstrated stronger correlations than others. Walking speed in the third min of walking during the 6 MWT recorded the strongest correlation with peak oxygen cost (ρ=-0.531). The 6 MWT is a submaximal measure in persons with lower-limb amputation. Self-selected walking speed over 15 m was not an appropriate proxy for the assessment of the energy cost of gait. Individuals with a lower-limb amputation require approximately 3 min of continuous walking to re-establish homoeostasis in heart rate, oxygen consumption and oxygen cost. The nonsignificant correlation between walking speeds during the 6 MWT and oxygen cost suggest that the 6 MWT can provide an indication of oxygen cost, but caution should be exercised when using it as a sole proxy for the measurement of oxygen cost in individuals with lower-limb amputation.     

Gait impairments in persons with multiple sclerosis across preferred and fixed walking speeds

Remelius JG, Jones SL, House JD, Busa MA, Averill JL, Sugumaran K, Kent-Braun JA, Van Emmerik RE. Gait impairments in persons with multiple sclerosis across preferred and fixed walking speeds.ObjectivesTo investigate (1) whether previously observed changes in gait parameters in individuals with multiple sclerosis (MS) are the result of slower preferred walking speeds or reflect adaptations independent of gait speed; and (2) the changes in spatiotemporal features of the unstable swing phase of gait in people with MS.DesignCross-sectional study assessing changes in gait parameters during preferred, slow (0.6m/s), medium (1.0m/s), and fast (1.4m/s) walking speeds.SettingGait laboratory with instrumented walkway and motion capture system.ParticipantsMS group with mild to moderate impairment (n=19, 16 women) with a median Expanded Disability Status Scale score of 3.75 (range, 2.5–6), and a sex- and age-matched control group (n=19).InterventionsNot applicable.Main Outcome MeasuresGait speed, stride length, stride width, cadence, dual support time, swing time, and timing of swing foot and body/head center of mass during swing phase.ResultsIndividuals with MS walked at slower preferred speeds with longer dual support times compared with controls. In fixed-speed conditions, dual support times were longer and swing times were shorter in MS compared with controls. Stride width was wider for all speed conditions in the MS group. In fixed-speed conditions, the MS group positioned their head and body centers of mass closer to the anterior base of support boundary when entering the unstable equilibrium of the swing phase.ConclusionsLonger dual support time is part of a gait strategy in MS that is apparent even when controlling for the confounding effect of slower preferred speed. However, a gait strategy featuring longer dual support times may have limitations if potentially destabilizing swing dynamics exist, which especially occur at walking speeds other than preferred for people with MS.     

Effect of increases in plantarflexor and hip flexor muscle strength on the levels of effort during gait in individuals with hemiparesis

BACKGROUND: Following a stroke, strength gain of the trained affected lower-limb muscles has been observed to result in a change in gait speed, but its effect on other variables related to gait performance has scarcely been studied. The aim of this study was to assess the effect of strength gain of the affected plantarflexors and hip flexors on bilateral levels of effort during gait, in the sagittal plane of movement. METHODS: The levels of effort of 24 chronic hemiparetic participants (mean (standard deviation (SD)): 57.3 (SD 15.5) years), who had strength gains in the ankle and hip muscles following a strengthening programme, were estimated with the muscular utilization ratio during self-selected and maximal speeds. The ratio relates the net moment in gait relative to the muscle's maximal capability. The peak value and the area under the curve of the ratio were used as main outcome measures. FINDINGS: Regardless of speed, strength gains have been noted to cause a significant 12-17% decrease in the peak value of the ratio of the affected plantarflexors and hip flexors with a reduction of the area under the curve of the affected hip flexors' ratio and a trend toward a decrease for the affected plantarflexors at maximal speed. A significant, albeit small increase in self-selected and maximal gait speeds (P<0.05) was also observed post-training. Regardless of assessment time, the peak value of the affected plantarflexors' ratio was greater than that of the affected hip flexors at self-selected speed (P=0.006) and the area under the curve of the affected hip flexors' ratio was greater than that of the affected plantarflexors (P=0.007) at maximal speed. Generally, negative associations (-0.32-0.83) were noted between the changes in the peak value of the ratio and strength but not between the changes in gait speed. INTERPRETATION: The decrease in the peak value of the ratio could be explained by the increase in strength. Becoming stronger, hemiparetic participants favoured a reduction of their levels of effort during walking instead of substantially increasing their gait speed.     

The kinematics of idiopathic gait disorder. A comparison with healthy young and elderly females

In this study the kinematic gait parameters of healthy young and elderly subjects were compared with those of a group of patients with idiopathic gait disorder of the elderly (IGDE), a condition characterized by dysfunctional walking for which no underlying cause can be determined. The velocity and the temporal/distance gait kinematics were measured for self-selected fast, medium and slow speeds of walking. The elderly walk with a more cautious gait pattern than younger adults. This pattern is characterized by a slow walking speed and a reduced single support phase, with shorter but more frequent strides, and is even more marked in persons with IGDE. The slower the walking speed the more cautious this pattern becomes. The patients with IGDE not only walk far slower than a group of healthy age matched individuals but the range of speeds, from self-selected slow to fast, is much reduced and does not overlap that of the healthy elderly. With objective gait measurements this group might be better identified.     

A biomechanical comparison of powered robotic exoskeleton gait with normal and slow walking: An investigation with able-bodied individuals

BackgroundOverground lower-limb robotic exoskeletons are assistive devices used to facilitate ambulation and gait rehabilitation. Our understanding of how closely they resemble comfortable and slow walking is limited. This information is important to maximise the effects of gait rehabilitation. The aim was to compare the 3D gait parameters of able-bodied individuals walking with and without an exoskeleton at two speeds (self-selected comfortable vs. slow, speed-matched to the exoskeleton) to understand how the user's body moved within the device.MethodsEight healthy, able-bodied individuals walked along a 12-m walkway with and without the exoskeleton. Three-dimensional whole-body kinematics inside the device were captured. Temporal-spatial parameters and sagittal joint kinematics were determined for normal and exoskeleton walking. One-way repeated measures ANOVAs and statistical parametric mapping were used to compare the three walking conditions (P < .05).FindingsThe walking speeds of the slow (0.44[0.03] m/s) and exoskeleton (0.41[0.03] m/s) conditions were significantly slower than the comfortable walking speed (1.54[0.07] m/s). However, time in swing was significantly greater (P < .001, d = −3.64) and double support was correspondingly lower (P < .001, d = 3.72) during exoskeleton gait than slow walking, more closely resembling comfortable speed walking. Ankle and knee angles were significantly reduced in the slow and exoskeleton conditions. Angles were also significantly different for the upper body.InterpretationAlthough the slow condition was speed-matched to exoskeleton gait, the stance:swing ratio of exoskeleton stepping more closely resembled comfortable gait than slow gait. The altered upper body kinematics suggested that overground exoskeletons may provide a training environment that would also benefit balance training.     

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.     

Coordination of the non-paretic leg during hemiparetic gait: Expected and novel compensatory patterns

Background

Post-stroke hemiparesis is usually considered a unilateral motor control deficit of the paretic leg, while the non-paretic leg is assumed to compensate for paretic leg impairments and have minimal to no deficits. While the non-paretic leg electromyography (EMG) patterns are clearly altered, how the non-paretic leg acts to compensate remains to be established.

Methods

Kinesiological data were recorded from sixty individuals with chronic hemiparesis (age: 60.9, SD = 12.6 years, 21 females, 28 right hemiparetic, time since stroke: 4.5 years, SD 3.9 years), divided into three speed-based groups, and twenty similarly aged healthy individuals (age: 65.1, SD = 10.4 years, 15 females). All walked on an instrumented split-belt treadmill at their self-selected speed and control subjects also walked at slower speeds matching those of the persons with hemiparesis. We determined the differences in magnitude and timing of non-paretic EMG activity relative to healthy control subjects in four pre-defined regions of stance phase of the gait cycle.

Findings

Integrated EMG activity and EMG timing in the non-paretic leg were different in many muscles. Multiple compensatory patterns identified included: increased EMG output when the muscle was typically active in controls and novel compensatory EMG patterns that appeared to provide greater propulsion or support with little evidence of impaired motor performance.

Interpretation

Most novel compensations were made possible by altered kinematics of the paretic and non-paretic leg (i.e., early stance plantarflexor activity provided propulsion due to the decreased advancement of the non-paretic foot) while others (late single limb stance knee extensor and late stance hamstring activity) appeared to be available mechanisms for increasing propulsion.     

Prosthetic gait of unilateral lower-limb amputees with current and novel prostheses: A pilot study

BackgroundNovel lower-limb prostheses aim to improve the quality of locomotion of individuals with an amputation. This study evaluates the biomechanics of a novel bionic foot during walking.MethodsAble-bodied individuals (n = 7) and individuals with a transfemoral (n = 6) or transtibial amputation (n = 6) were included. Able-bodied individuals conducted one experimental trial, whereas individuals with transtibial and transfemoral amputations conducted a familiarization (with current prosthesis) and two experimental trials using a passive and bionic prosthesis. Each trial consisted of 3 bouts of 2 min of treadmill walking at different speeds. Biomechanical data were gathered using a force platform and motion capture system and analysed using Statistical Parametric Mapping and (non)-parametric tests.FindingsConventional prosthetic feet alter gait patterns and induce locomotion difficulties. While walking at a normal speed with the passive prosthesis, transtibial amputees display reduced maximum heel forces, increased ankle and trunk angular velocities at midstance, and increased knee angle during stance and swing phases on their effected side (P ≤ 0.026). Improved lower-limb kinematics was demonstrated during slow and normal speed walking with the bionic prosthesis; however, dynamic trunk stability was negatively impacted during this condition. The bionic prosthesis did not benefit transfemoral amputees at any walking speed.InterpretationTranstibial amputees can better approximate typical movement patterns at slow and normal walking speeds using the novel bionic prosthesis; however the same benefit was not observed in transfemoral amputees.     

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.     

Angular movements of the lumbar spine and pelvis can be reliably measured after 4 minutes of treadmill walking

OBJECTIVE: To determine the familiarization period required to obtain consistent measurements of the angular movements of the lumbar spine and pelvis during treadmill walking. DESIGN: An in vivo study with repeated measures every 2 min over 10 min. BACKGROUND: Walking on a treadmill can initially be an unfamiliar experience. No data were available to indicate the length of time required for treadmill familiarization prior to taking measurements of the angular movements of the lumbar spine and pelvis. The familiarization period has implications for the use of this technique in clinical testing. METHODS: The angular movements of the lumbar spine and pelvis were examined by thePEAK 3D motion measurement system in 16 untrained, normal subjects walking for 10 min on a treadmill at either self-selected or 60% of self-selected speed. RESULTS: The reliability of the angular measurements of the spine and pelvis were all greater than 0.83 (ICC) after 4 min of treadmill walking and did not appear to increase after 4 min. No changes in the amplitudes of the angular movements of the lumbar spine and pelvis could be detected after 4 min of treadmill walking, or of the absolute difference scores beyond 2 min of treadmill walking, in either normal or slow-speed walking groups. CONCLUSIONS: Angular movements of the lumbar spine and pelvis were consistent after 4 min of treadmill walking by normal subjects, both at self-selected and slow walking speeds, indicating that reliable measurements of these parameters could be taken at that time.     

Differences in gait parameters between healthy subjects and persons with moderate and severe knee osteoarthritis: A result of altered walking speed?

Background

While knee osteoarthritis has been shown to affect a multitude of kinematic, kinetic and temporo-spatial gait parameters, few investigations have examined the effect of increasing levels of radiographic osteoarthritis severity on these gait parameters. Fewer still have investigated the effect of walking speed on gait variables in persons with knee osteoarthritis. The objective of this study was to investigate the influence of walking speed on biomechanical variables associated with joint loading in persons with varying severities of medial compartment knee osteoarthritis.

Methods

Twenty-one persons with moderate osteoarthritis (Kellgren–Lawrence score 2–3) and 13 persons with severe osteoarthritis (Kellgren–Lawrence score of 4) participated. Twenty-two persons without knee pain or radiographic evidence of arthritis comprised a healthy control group. Sagittal plane kinetics, knee adduction moment, sagittal plane knee excursion, ground reaction forces and knee joint reaction forces were calculated from three-dimensional motion analysis at 1.0 m/s, self-selected and fastest tolerable walking speeds. Differences were analyzed using multivariate analysis of variance and multivariate analysis of covariance with speed as a covariate.

Findings

Persons with knee osteoarthritis showed significantly lower knee and ankle joint moments, ground reaction forces, knee reaction force and knee excursion when walking at freely chosen speeds. When differences in walking speed were accounted for in the analysis, the only difference found at all conditions was decreased knee joint excursion.

Interpretation

Compared to a healthy control group, persons with knee OA demonstrate differences in joint kinetics and kinematics. Except for knee excursion, these differences in gait parameters appear to be a result of slower freely chosen walking speeds rather than a result of disease progression.     

Gait characteristics of elderly people with a history of falls: a dynamic approach

BACKGROUND AND PURPOSE: This study investigated changes in the kinematics of elderly people who experienced at least one fall 6 months prior to data collection. The authors hypothesized that, in order to decrease variability of walking, people with a history of falls would show different kinematic adaptations of their walking patterns compared with elderly people with no history of falls. SUBJECTS AND METHODS: Twenty-one elderly people who had fallen within the previous 6 months ("fallers"; mean age=72.1 years, SD=4.9) and 27 elderly people with no history of falls ("nonfallers"; mean age=73.8 years, SD=6.4) walked at their preferred stride frequency (STF) as treadmill speed was gradually increased (from 0.18 m/s to 1.52 m/s) and then decreased in steps of 0.2 m/s. Gait parameter measurements were recorded, and statistical analysis was applied using walking speed and STF as independent variables. RESULTS: Fifty-seven percent of the fallers were unable to walk at the fastest speed, whereas all nonfallers walked comfortably at all walking speeds. Although the fallers showed significantly greater STF, smaller stride lengths, smaller center-of-mass lateral sway, and smaller ankle plantar flexion and hip extension during push-off, they showed increased variability of kinematic measures in their coordination of walking compared with the nonfallers. DISCUSSION AND CONCLUSION: Although the fallers' adaptations were expected to reduce variability in the coordination of walking, they showed less stable gait patterns (ie, greater variability) compared with the nonfallers. Increased variability of walking patterns may be an important gait risk factor in elderly people with a history of falls.     

行走和跑步两种步态模式的实验分析

目的 :分析行走和跑步运动两种模式下人体步态的特征。方法及结果 :使用自行研制的三维运动检测分析系统对 5名健康男性在跑步机上进行了不同速率下行走和跑步 2种步态模式的比较实验。结论 :行走和跑步两种步态模式的参数具有明显差异 ,步速对步态参数的影响要小于步态模式的影响。     

Comparison of angular lumbar spine and pelvis kinematics during treadmill and overground locomotion

OBJECTIVE: To determine the differences between angular oscillation curves of the lumbar spine and pelvis during walkway and treadmill ambulation. DESIGN: An in vivo observation of walking in overground and treadmill conditions. BACKGROUND: Angular movements of the lumbar spine and pelvis have been obtained during overground and treadmill walking. No data are available to indicate whether lumbar spine treadmill findings may be compared or generalized to overground readings. METHODS: Nine male subjects walked at their natural cadence along an 8 m walkway positioned over a motorized treadmill. During each of 20 walking trials, kinematic data of one full gait cycle were collected in the middle segment of the walkway. Following the overground readings the walkway was removed and treadmill recordings were taken at the subjects' preferred walking speed and at an imposed speed of 1.25 m/s. Movement patterns and maximum oscillation angles were calculated in each plane. RESULTS: Cross-correlation values of pairwise comparisons demonstrated almost comparable movement patterns between walking conditions (r > or =0.891; p<0.001) except for the movement in the sagittal plane (r=0.642, p<0.01). ANOVA for repeated measures revealed significant (p<0.05) differences in the gait cycle duration as well as reductions in oscillation amplitudes of the upper lumbar region and the pelvis in both the frontal and transverse plane during treadmill walking compared to walkway locomotion. CONCLUSIONS: Statistically significant differences exist for some angular lumbar spine movement parameters between walkway and treadmill locomotion. RELEVANCE: The observed differences between overground and treadmill locomotion should be taken in account when treadmill-based lumbar spine and pelvis kinematics want to be extended or compared to overground recordings.     

Gait adaptation during walking on an inclined pathway following spinal cord injury

Background

Individuals with incomplete spinal cord injury need to be assessed in different environments. The objective of this study was to compare lower-limb power generation in subjects with spinal cord injury and healthy subjects while walking on an inclined pathway.

Methods

Eleven subjects with spinal cord injury and eleven healthy subjects walked on an inclined pathway at their natural gait speed and at slow gait speed (healthy subjects only). Ground reaction forces were recorded by force plates embedded in the inclined pathway and a 3-D motion analysis system recorded lower-limb motions. Data analysis included gait cycle parameters and joint peak powers. Differences were identified by student t-tests.

Findings

Gait cycle parameters were lower in spinal cord injury subjects compared to healthy subjects at natural speed but similar at slow gait speed. Subjects with spinal cord injury presented lower power at the ankle, knee and hip compared to healthy subjects at natural gait speed while only the power generation at push-off remained lower when the two groups performed at similar speed.

Interpretation

The most important differences are associated with the fact that individuals with spinal cord injury walk at a slower speed, except for the ankle power generation. This study demonstrated that, even with a good motor recovery, distal deficits remain and may limit the ability to adapt to uphill and downhill walking. Inclined pathways are indicated to train patients with spinal cord injury. Clinicians should focus on the speed of uphill and downhill walking and on the use of plantar flexors.     

Frontal plane compensatory strategies associated with self-selected walking speed in individuals post-stroke

Background

Approximately two out of three individuals post-stroke experience walking impairments. Frontal plane compensatory strategies (i.e. pelvic hiking and circumduction) are observed in post-stroke gait in part to achieve foot clearance in response to reduced knee flexion and ankle dorsiflexion. The objective of this study was to investigate the relationship between self-selected walking speed and the kinematic patterns related to paretic foot clearance during post-stroke walking.

Methods

Gait analysis was performed at self-selected walking speed for 21 individuals post-stroke. Four kinematic variables were calculated during the swing phase of the paretic limb: peak pelvic tilt (pelvic hiking), peak hip abduction (circumduction), peak knee flexion, and peak ankle dorsiflexion. Paretic joint angles were analyzed across self-selected walking speed as well as between functionally relevant ambulation categories (Household < 0.4 m/s, Limited Community 0.4–0.8 m/s, Community > 0.8 m/s).

Findings

While all subjects exhibited similar foot clearance, slower walkers exhibited greater peak pelvic hiking and less knee flexion, ankle dorsiflexion, and circumduction compared to faster walkers (P < .05). Additionally, four of the fastest walkers compensated for poor knee flexion and ankle dorsiflexion through large amounts of circumduction.

Interpretation

These findings suggest that improved gait performance after stroke, as measured by self-selected walking speed, is not necessarily always accomplished through gait patterns that more closely resemble healthy gait for all variables. It appears the ability to walk fast is achieved by either sufficient ankle dorsiflexion and knee flexion to achieve foot clearance or the employment of circumduction to overcome a deficit in either ankle dorsiflexion or knee flexion.     

Walking speed modifies spasticity effects in gastrocnemius and soleus in cerebral palsy gait

Background

The calf muscles of children with cerebral palsy are often spastic, which can lead to an equinus gait pattern. Although spasticity is defined as a velocity-dependent increase in muscle tone, very little is known about the effect of walking speed on muscle–tendon behavior of spastic muscles during gait. The aim of this study was to investigate gastrocnemius and soleus length and lengthening velocity during gait in spastic muscles with and without static contractures compared to non-spastic muscles, as well as the effect of walking speed, and the interacting effect of walking speed and spasticity on muscle–tendon length and lengthening velocity.

Methods

Seventeen ambulatory children with spastic cerebral palsy and 11 typically developing children, aged 6–12, walked at comfortable, slow, and fast walking speeds. 3D kinematic data were collected and muscle–tendon lengths and velocities were calculated using musculoskeletal modeling. Spasticity and contractures of calf muscles were measured during standardized physical examination.

Findings

Spastic calf muscles showed a deviating muscle–tendon length pattern with two peaks in stance, which was found to be irrespective of muscle contracture. This deviating pattern became more pronounced as walking speed increased. In swing, spastic calf muscles were stretched approximately one third slower than normal, while in stance, spastic calf muscles were stretched twice as fast as normal, with peak velocity occurring earlier in the gait cycle.

Interpretation

The increasingly deviating muscle–tendon length pattern at faster walking speed indicates a velocity-dependent spasticity effect. This impairs walking especially at faster speeds, and may therefore limit comfortable walking speed.     

Initial development and testing of a novel foam-based pressure sensor for wearable sensing

Background

The ability to maintain a steady gait rhythm is impaired in patients with Parkinson's disease (PD). This aspect of locomotor dyscontrol, which likely reflects impaired automaticity in PD, can be quantified by measuring the stride-to-stride variability of gait timing. Previous work has shown an increase in both the variability of the stride time and swing time in PD, but the origins of these changes are not fully understood. Patients with PD also generally walk with a reduced gait speed, a potential confounder of the observed changes in variability. The purpose of the present study was to examine the relationship between walking speed and gait variability.

Methods

Stride time variability and swing time variability were measured in 36 patients with PD (Hoehn and Yahr stage 2–2.5) and 30 healthy controls who walked on a treadmill at four different speeds: 1) Comfortable walking speed (CWS), 2) 80% of CWS 3) 90% of CWS, and 4) 110% of CWS. In addition, we studied the effects of walking slowly on level ground, both with and without a walker.

Results

Consistent with previous findings, increased variability of stride time and swing time was observed in the patients with PD in CWS, compared to controls. In both groups, there was a small but significant association between treadmill gait speed and stride time variability such that higher speeds were associated with lower (better) values of stride time variability (p = 0.0002). In contrast, swing time variability did not change in response to changes in gait speed. Similar results were observed with walking on level ground.

Conclusion

The present results demonstrate that swing time variability is independent of gait speed, at least over the range studied, and therefore, that it may be used as a speed-independent marker of rhythmicity and gait steadiness. Since walking speed did not affect stride time variability and swing time variability in the same way, it appears that these two aspects of gait rhythmicity are not entirely controlled by the same mechanisms. The present findings also suggest that the increased gait variability in PD is disease-related, and not simply a consequence of bradykinesia.     

Changes in three dimensional lumbo-pelvic kinematics and trunk muscle activity with speed and mode of locomotion

BACKGROUND: Control of the trunk is critical for locomotor efficiency. However, investigations of trunk muscle activity and three-dimensional lumbo-pelvic kinematics during walking and running remain scarce. METHODS: Gait parameters and three-dimensional lumbo-pelvic kinematics were recorded in seven subjects. Electromyography recordings of abdominal and paraspinal muscles were made using fine-wire and surface electrodes as subjects walked on a treadmill at 1 and 2 ms(-1) and ran at 2, 3, 4 and 5 ms(-1). FINDINGS: Kinematic data indicate that the amplitude but not timing of lumbo-pelvic motion changes with locomotor speed. Conversely, a change in locomotor mode is associated with temporal but not spatial adaptation in neuromotor strategy. That is, peak transverse plane lumbo-pelvic rotation occurs at foot strike during walking but prior to foot strike during running. Despite this temporal change, there is a strong correlation between the amplitude of transverse plane lumbo-pelvic rotation and stride length during walking and running. In addition, lumbo-pelvic motion was asymmetrical during all locomotor tasks. Trunk muscle electromyography occurred biphasically in association with foot strike. Transversus abdominis was tonically active with biphasic modulation. Consistent with the kinematic data, electromyography activity of the abdominal muscles and the superficial fibres of multifidus increased with locomotor speed, and timing of peak activity of superficial multifidus and obliquus externus abdominis was modified in association with the temporal adaptation in lumbo-pelvic motion with changes in locomotor mode. INTERPRETATION: These data provide evidence of the association between lumbo-pelvic motion and trunk muscle activity during locomotion at different speeds and modes.