Trienke IJmker

Gait and cognition: The relationship between gait stability and variability with executive function in persons with and without dementia

Besides cognitive decline, dementia is characterized by gait changes and increased fall risk, also in early stages of the disease. The aim of this study was to investigate differences in the relationship between executive function and gait variability and stability during single task and dual task walking in persons with and without dementia. The study sample consisted of three groups: fifteen dementia patients (aged 75-87), fourteen healthy elderly (aged 75-85), and twelve relatively younger elderly (aged 55-70). Participants underwent neuropsychological testing and tests of single and dual task walking while wearing an accelerometer. Outcome measures include stride related measures such as mean and coefficient of variation of stride time, and dynamic measures regarding the magnitude, smoothness, predictability and local stability of trunk accelerations. Patients with dementia exhibited a significantly (p<.05) less variable, but more irregular trunk acceleration pattern than cognitively intact elderly on single and dual task walking. The walking pattern during dual tasking for the whole group became increasingly unstable, even though participants modified their gait pattern by slowing their walking speed, and decreasing the magnitude of trunk accelerations. Moderate to high correlations (r>.51) were found between executive tasks and gait parameters. In conclusion, these findings indicate that decreased executive function plays an important role in increased gait variability in dementia patients; a fact that should be considered when designing fall risk interventions for this population. Furthermore, results indicate that measures of gait variability and stability should be deemed worthwhile in the diagnosis of dementia.

Energy cost of balance control during walking decreases with external stabilizer stiffness independent of walking speed

Human walking requires active neuromuscular control to ensure stability in the lateral direction, which inflicts a certain metabolic load. The magnitude of this metabolic load has previously been investigated by means of passive external lateral stabilization via spring-like cords. In the present study, we applied this method to test two hypotheses: (1) the effect of external stabilization on energy cost depends on the stiffness of the stabilizing springs, and (2) the energy cost for balance control, and consequently the effect of external stabilization on energy cost, depends on walking speed. Fourteen healthy young adults walked on a motor driven treadmill without stabilization and with stabilization with four different spring stiffnesses (between 760 and 1820 Nm(-1)) at three walking speeds (70%, 100%, and 130% of preferred speed). Energy cost was calculated from breath-by-breath oxygen consumption. Gait parameters (mean and variability of step width and stride length, and variability of trunk accelerations) were calculated from kinematic data. On average external stabilization led to a decrease in energy cost of 6% (p<0.005) as well as a decrease in step width (24%; p<0.001), step width variability (41%; p<0.001) and variability of medio-lateral trunk acceleration (12.5%; p<0.005). Increasing stabilizer stiffness increased the effects on both energy cost and medio-lateral gait parameters up to a stiffness of 1260 Nm(-1). Contrary to expectations, the effect of stabilization was independent of walking speed (p=0.111). These results show that active lateral stabilization during walking involves an energetic cost, which is independent of walking speed.

Effect of balance support on the energy cost of walking after stroke

OBJECTIVE To examine the influence of balance support on the energy cost of treadmill and overground walking in ambulatory patients with stroke. DESIGN Cross-sectional. SETTING Research laboratory at a rehabilitation center. PARTICIPANTS Patients with stroke depending on a walking aid in daily life (n=12; walking aid dependent ambulators) and walking aid independent ambulators (n=12), all able to walk for at least 5 minutes. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Energy cost (J·kg(-1)·m(-1)) and temporal gait parameters (walking speed, mean and coefficient of variation of stride time, and symmetry index) were obtained during 4 walking trials at preferred walking speed: overground with and without a cane and on a treadmill with and without handrail support. RESULTS On the treadmill, handrail support resulted in a significant decrease in energy cost of 16%, independent of the group. Although walking aid dependent ambulators had on average a larger reduction in energy cost than walking aid independent ambulators (19% vs 14%), this interaction did not reach statistical significance (P=.11). Interestingly, overground walking with support resulted in an 8% reduction in energy cost for walking aid dependent ambulators, but a 6% increase for walking aid independent ambulators. The reduction in energy cost with support was accompanied by changes in temporal gait parameters, most notably an increase in stride time and symmetry and a decrease in stride time variability. CONCLUSIONS Balance support can result in a significant reduction in the energy cost of walking in stroke patients, the magnitude of which depends on walking ability and the walking task. Impaired balance control should not be overlooked as a contributing factor to the increased energy cost of walking in patients with stroke, and improving or assisting balance control should be considered to reduce the energy cost of hemiplegic gait.

Can external lateral stabilization reduce the energy cost of walking in persons with a lower limb amputation

The aim of this study was to examine whether impaired balance control is partly responsible for the increased energy cost of walking in persons with a lower limb amputation (LLA). Previous studies used external lateral stabilization to evaluate the energy cost for balance control; this caused a decrease in energy cost, with concomitant decreases in mean and variability of step width. Using a similar set-up, we expected larger decreases for LLA than able-bodied controls. Fifteen transtibial amputees (TT), 12 transfemoral amputees (TF), and 15 able-bodied controls (CO) walked with and without external lateral stabilization provided via spring like cords attached to the waist. Effects of this manipulation on energy cost, step parameters, and pelvic motion were evaluated between groups. TT (-5%) and CO (-3%) showed on average a small reduction in energy cost when walking with stabilization, whereas TF exhibited an increase in energy cost (+6.5%) The difference in the effect of stabilization was only significant between TT and TF. Step width, step width variability, and medio-lateral pelvic displacement decreased significantly with stabilization in all groups, especially in TT. Contrary to expectations, external lateral stabilization did not result in a larger decrease in the energy cost of walking for LLA compared to able-bodied controls, suggesting that balance control is not a major factor in the increased cost of walking in LLA. Alternatively, the increased energy cost with stabilization for TF suggests that restraining (medio-lateral) pelvic motion impeded necessary movement adaptations in LLA, and thus negated the postulated beneficial effects of stabilization on the energy cost of walking.

Postural threat during walking: effects on energy cost and accompanying gait changes

BackgroundBalance control during walking has been shown to involve a metabolic cost in healthy subjects, but it is unclear how this cost changes as a function of postural threat. The aim of the present study was to determine the influence of postural threat on the energy cost of walking, as well as on concomitant changes in spatiotemporal gait parameters, muscle activity and perturbation responses. In addition, we examined if and how these effects are dependent on walking speed.MethodsHealthy subjects walked on a treadmill under four conditions of varying postural threat. Each condition was performed at 7 walking speeds ranging from 60-140% of preferred speed. Postural threat was induced by applying unexpected sideward pulls to the pelvis and varied experimentally by manipulating the width of the path subjects had to walk on.ResultsResults showed that the energy cost of walking increased by 6-13% in the two conditions with the largest postural threat. This increase in metabolic demand was accompanied by adaptations in spatiotemporal gait parameters and increases in muscle activity, which likely served to arm the participants against a potential loss of balance in the face of the postural threat. Perturbation responses exhibited a slower rate of recovery in high threat conditions, probably reflecting a change in strategy to cope with the imposed constraints. The observed changes occurred independent of changes in walking speed, suggesting that walking speed is not a major determinant influencing gait stability in healthy young adults.ConclusionsThe current study shows that in healthy adults, increasing postural threat leads to a decrease in gait economy, independent of walking speed. This could be an important factor in the elevated energy costs of pathological gait.

Effects of handrail hold and light touch on energetics, step parameters, and neuromuscular activity during walking after stroke

BackgroundHolding a handrail or using a cane may decrease the energy cost of walking in stroke survivors. However, the factors underlying this decrease have not yet been previously identified. The purpose of the current study was to fill this void by investigating the effect of physical support (through handrail hold) and/or somatosensory input (through light touch contact with a handrail) on energy cost and accompanying changes in both step parameters and neuromuscular activity. Elucidating these aspects may provide useful insights into gait recovery post stroke.MethodsFifteen stroke survivors participated in this study. Participants walked on a treadmill under three conditions: no handrail contact, light touch of the handrail, and firm handrail hold. During the trials we recorded oxygen consumption, center of pressure profiles, and bilateral activation of eight lower limb muscles. Effects of the three conditions on energy cost, step parameters and neuromuscular activation were compared statistically using conventional ANOVAs with repeated measures. In order to examine to which extent energy cost and step parameters/muscle activity are associated, we further employed a partial least squares regression analysis.ResultsHandrail hold resulted in a significant reduction in energy cost, whereas light touch contact did not. With handrail hold subjects took longer steps with smaller step width and improved step length symmetry, whereas light touch contact only resulted in a small but significant decrease in step width. The EMG analysis indicated a global drop in muscle activity, accompanied by an increased constancy in the timing of this activity, and a decreased co-activation with handrail hold, but not with light touch. The regression analysis revealed that increased stride time and length, improved step length symmetry, and decreased muscle activity were closely associated with the decreased energy cost during handrail hold.ConclusionHandrail hold, but not light touch, altered step parameters and was accompanied by a global reduction in muscle activity, with improved timing constancy. This suggests that the use of a handrail allows for a more economic step pattern that requires less muscular activation without resulting in substantial neuromuscular re-organization. Handrail use may thus have beneficial effects on gait economy after stroke, which cannot be accomplished through enhanced somatosensory input alone.

Shotgun approaches to gait analysis: insights & limitations

BackgroundIdentifying features for gait classification is a formidable problem. The number of candidate measures is legion. This calls for proper, objective criteria when ranking their relevance.MethodsFollowing a shotgun approach we determined a plenitude of kinematic and physiological gait measures and ranked their relevance using conventional analysis of variance (ANOVA) supplemented by logistic and partial least squares (PLS) regressions. We illustrated this approach using data from two studies involving stroke patients, amputees, and healthy controls.ResultsOnly a handful of measures turned out significant in the ANOVAs. The logistic regressions, by contrast, revealed various measures that clearly discriminated between experimental groups and conditions. The PLS regression also identified several discriminating measures, but they did not always agree with those of the logistic regression.Discussion & conclusionExtracting a measure’s classification capacity cannot solely rely on its statistical validity but typically requires proper post-hoc analysis. However, choosing the latter inevitably introduces some arbitrariness, which may affect outcome in general. We hence advocate the use of generic expert systems, possibly based on machine-learning.