Stride Time Coefficient Of Variation Research Articles

Risk of using smartphones while walking for digital natives in realistic environments: Effects of cognitive–motor interference

The effect of using smartphones while walking on the cognitive and physical abilities of the “digital native” generation, i.e., individuals who have grown up in a digital media–centric environment, remains poorly understood. This study evaluated the effects of cognitive–motor interference on the use of smartphones while walking in children and young adults. The study involved 50 individuals from the digital age generation, including 24 children and 26 young adults. The study encompassed three experimental conditions, in which participants were instructed to traverse a distance of 60 m. The initial condition functioned as a control, wherein the participants walked without supplementary stimuli. In the second condition, the participants were provided with explicit instructions to grasp the smartphone device and position it in front of their chest by using both hands. This manipulation introduced a postural component into the experimental setup. The third condition required participants to be ambulatory while concurrently engaging in a cognitive task, namely, participating in a game that necessitated focused attention. Gait parameters were obtained by using inertial measurement unit sensors. Subsequently, the acquired gait characteristics were converted into dual-task costs (DTC). In the cognitive condition, children exhibited significantly greater DTC values for gait speed (76%), stride length (79%), stride time (102%), and stride length coefficient of variation (CV) than the young adults (p < 0.025). Moreover, as shown by the increased CV, a significant association exists between poor performance in smartphone games among children and increased variability in stride length. In children, the DTC of stride time CV decreased as smartphone game scores increased (R2 = 16.5%), and the DTC of stride length CV decreased more markedly as smartphone game scores increased (R2 = 28.2%). In conclusion, children are at a higher risk of pedestrian accidents when using smartphones while walking compared to young adults.

Validation of Linear and Nonlinear Gait Variability Measures Derived From a Smartphone System Compared to a Gold-Standard Footswitch System During Overground Walking.

Smartphones, with embedded accelerometers, may be a viable method to monitor gait variability in the free-living environment. However, measurements estimated using smartphones must first be compared to known quantities to ensure validity. This study assessed the validity and reliability of smartphone-derived gait measures compared to a gold-standard footswitch system during overground walking. Seventeen adults completed three 8-minute overground walking trials during 3 separate visits. The stride time series was calculated as the time difference between consecutive right heel contact events within the footswitch and smartphone-accelerometry signals. Linear (average stride time, stride time standard deviation, and stride time coefficient of variation) and nonlinear (fractal scaling index, approximate entropy, and sample entropy) measures were calculated for each stride time series. Bland-Altman plots with 95% limits of agreement assessed agreement between systems. Intraclass correlation coefficients assessed reliability across visits. Bland-Altman plots revealed acceptable limits of agreement for all measures. Intraclass correlation coefficients revealed good-to-excellent reliability for both systems, except for fractal scaling index, which was moderate. The smartphone system is a valid method and performs similarly to gold-standard research equipment. These findings suggest the development and implementation of an inexpensive, easy-to-use, and ubiquitous telehealth instrument that may replace traditional laboratory equipment for use in the free-living environment.

Usefulness of gait parameters obtained from inertial sensors attached to the lower trunk and foot for assessment of gait performance in the early postoperative period after total knee arthroplasty

BackgroundThis study was performed to (i) compare gait parameters obtained from inertial sensors attached to the lower trunk and foot between patients in the early postoperative period after total knee arthroplasty (TKA) and healthy age- and sex-matched controls and (ii) elucidate the association between the gait parameters and patient-reported outcome measures (PROMs). MethodThe gait performance of 19 patients who had undergone TKA was assessed using inertial sensors and PROMs obtained from the Knee Injury and Osteoarthritis Outcome Score (KOOS) 1 week before hospital discharge. The patients walked along a 15-m walkway and we calculated the following gait parameters: walking speed, coefficient of variation (CV) of stride time, unbiased autocorrelation coefficient (AC), harmonic ratio (HR), and symmetry index (SI). The same gait parameter data from 19 age- and sex-matched healthy adults (controls) were obtained from our past study. ResultsThe TKA group demonstrated slower walking speed, larger CV of stride time, lower HR in all three directions, lower AC in the vertical direction, and higher SI in the vertical direction than the healthy control group (all p < 0.05). Correlation analysis revealed that the SI in the anteroposterior direction was significantly correlated with the KOOS symptoms subscore and ADL subscore (p < 0.05). ConclusionsPatients in the early postoperative period after TKA exhibited worse gait performance as assessed by inertial sensors compared with healthy controls. Gait symmetry was correlated with PROMs. These results indicate the usefulness of assessing gait parameters after TKA.

Age related changes in gait variability, asymmetry, and bilateral coordination – When does deterioration starts?

BackgroundGait pattern coordination is affected by several factors (e.g., neurodegeneration), while aging is known to have a significant negative impact. Various gait parameters, such as gait asymmetry (GA) and stride time coefficient of variation (CV), are widely used in both research and clinical settings in order to evaluate human locomotion. Another parameter is the phase coordination index (PCI), which specifically assesses bilateral coordination of gait (BCG), by quantifying the consistency and accuracy of the anti-phased stepping pattern. ObjectiveIn this study we hypothesized that there is a steady deterioration in the bilateral coordination of walking through ageing, and in gait rhythmicity, which would be evident by an increase in the values of the coordination parameters which are examined. MethodsWe analyzed gait cycles of 66 healthy participants in ages between 40 and 85 years which were divided into five age groups (40–44; 45–54; 55–64; 75 +). The participants performed corridor walking (i.e., back and forth) wearing a computerized motion sensor-based gait analysis system. PCI, CV and GA parameters were calculated for the straight-line walking segments. ResultsPCI values remained relatively stable between the ages of 40–75 (3.16 ± 1.11%), while in the age group of 75 + years old we observed a significant increase (i.e., deterioration in BCG) in PCI values (5.68 ± 2.01%, p < 0.047). Same pattern was seen for the CV parameter. However, GA was not statistically significantly different between all age groups. ConclusionIt appears that PCI and CV are more sensitive measures to detect changes in gait through the aging process. The results suggest that potential screening to detect salient gait deterioration should start from the age of 70. On the other hand, GA may be used to identify neurological impairments if found increased at any age.

Using the loading response peak for defining gait cycle timing: A novel solution for the double-belt problem

Split-belt treadmills (SBTM) contain force plates under each belt that measure ground reaction force (GRF). Initial contact (IC) detection for each gait cycle obtained from the GRF is used for calculating temporal gait parameters (e.g., gait variability, step time, stride time). Occasionally, the participant steps with one leg on the contralateral belt (i.e., crossing) making the IC undetectable and the calculation of temporal gait parameters are compromised. We term this the double-belt problem (DBP). Objective: here we developed a complementary detection method using the loading response peak (LRP), anchor point for calculating gait parameters. Methods: we used GRF gait data from twenty adults (age 56.45 ± 4.81 y; 6 males) who walked on an SBTM. First, we used no-crossing gait periods free of the DBP to calculate stride time, step time, and stride time to stride time coefficient of variation and evaluated the true error and the normalized true error of the LRP detection method. Then, we used multiple comparisons between no-crossing data and crossing data. Results: we found that normalized errors (in comparison to the IC method) are ≤5.1%. Strong correlations were found between gait parameters computed based on the two detection methods (Intraclass correlation coefficient ≥0.97; p ≤ 0.001). Conclusion: detecting gait cycle timing based on the LRP detection method is reliable for estimating temporal gait parameters, demonstrating high correspondence with the gold standard IC detection method.

Selection of gait parameters for differential diagnostics of patients with de novo Parkinson’s disease

Background: Gait disturbances are an integral part of clinical manifestations of Parkinson’s disease (PD), even in the initial stages of the disease. Our goal was to identify the set of spatio-temporal gait parameters that bear the highest relevance for characterizing de novo PD patients.Methods: Forty patients with de novo PD and forty healthy controls were recorded while walking over an electronic walkway in three different conditions: (1) base walking, (2) walking with an additional motor task, (3) walking with an additional mental task. Both groups were well balanced concerning age and gender. To select a smaller number of relevant parameters, affinity propagation clustering was applied on parameter pairwise correlation. The exemplars were then sorted by importance using the random forest algorithm. Classification accuracy of a support vector machine was tested using the selected parameters and compared to the accuracy of the model using a set of parameters derived from literature.Results: Final selection of parameters included: stride length and stride length coefficient of variation (CV), stride time and stride time CV, swing time and swing time CV, step time asymmetry, and heel-to-heel base support CV. Classification performed using these parameters showed higher overall accuracy (85%) than classification using the common parameter set containing: stride time, stride length, swing time and double support time, along with their CVs (78%).Conclusion: In early stages of PD, double support time and its CV appear to be weak indicators of the disease. We instead found step time asymmetry and support base CV to significantly contribute to classification accuracy.

Noisy vestibular stimulation improves dynamic walking stability in bilateral vestibulopathy.

To examine the effects of imperceptible levels of white noise galvanic vestibular stimulation (nGVS) on dynamic walking stability in patients with bilateral vestibulopathy (BVP). Walking performance of 13 patients with confirmed BVP (mean age 50.1 ± 5.5 years) at slow, preferred, and fast speeds was examined during walking with zero-amplitude nGVS (sham trial) and nonzero-amplitude nGVS set to 80% of the individual cutaneous threshold for GVS (nGVS trial). Eight standard gait measures were analyzed: stride time, stride length, base of support, double support time percentage as well as the bilateral phase coordination index, and the coefficient of variation (CV) of stride time, stride length, and base of support. Compared to the sham trial, nGVS improved stride time CV by 26.0% ± 8.4% (p < 0.041), stride length CV by 26.0% ± 7.7% (p < 0.029), base of support CV by 27.8% ± 2.9% (p < 0.037), and phase coordination index by 8.4% ± 8.8% (p < 0.013). The nGVS effects on walking performance were correlated with subjective ratings of walking balance (ρ = 0.79, p < 0.001). Effect of nGVS on walking stability was most pronounced during slow walking. In patients with BVP, nGVS is effective in improving impaired gait performance, predominantly during slower walking speeds. It primarily targets the variability and bilateral coordination characteristics of the walking pattern, which are linked to dynamic walking stability. nGVS might present an effective treatment option to immediately improve walking performance and reduce the incidence of falls in patients with BVP. This study provides Class IV evidence that in patients with BVP, an imperceptible level of nGVS improves dynamic walking stability.

Anti-dementia drugs-related changes in gait performance while single and dual tasking in patients with Alzheimer disease: a meta-analysis.

The effects of anti-dementia drugs on gait performance in Alzheimer disease (AD) are questionable. The objective of this meta-analysis was to examine the effects of anti-dementia drugs on the mean value and the coefficient of variation (CoV) of stride time among patients with AD while taking into account the type of drugs (i.e., acetylcholinesterase inhibitors [AChEIs] versus memantine) and the walking conditions (i.e., single versus dual-task). An English and French Medline search was conducted in March 2015, with no limit of date, using the Medical Subject Headings terms "pharmaceutical preparations" combined with terms "Pharmaceutical preparations" OR "Therapeutic uses" OR "Drug substitution" OR "Drugs essential" OR "Drugs, Generic" OR "Psychotropic drugs" combined with "Delirium" OR "Dementia" OR "Amnestic" OR "Cognitive disorders" AND "Gait" OR "Gait Ataxia" OR "Gait disorders, Neurologic" OR "Gait apraxia". Fixed-effects meta-analyses were used to examine anti-dementia drugs-related changes in mean value and CoV of stride time. Of the 66 identified abstracts, 5 (7.6%) were included in the meta-analysis. Inter-group comparison of between-visit change underscored a significant decrease in CoV of stride time (P<0.004) in intervention group compared to control group, whatever the pooled analysis considered, but no significant change in the mean value (P>0.06). Intra-group changes in stride time parameters following the use of anti-dementia drugs showed a significant decrease for memantine (P<0.001) and while pooling AChEIs and memantine (P<0.001) under single task condition. Under dual task condition, only AChEIs improved significantly stride time parameters (P=0.002). Anti-dementia drugs demonstrated a significant improvement of gait performance with specific class effect depending on the walking conditions and on the type of stride time parameters considered.

Noise-Enhanced Vestibular Input Improves Dynamic Walking Stability in Healthy Subjects.

White noise galvanic vestibular stimulation (GVS) is thought to enhance the sensitivity of vestibular organs. To examine the effects of noise-enhanced vestibular input on the walking performance in healthy subjects walking with eyes closed. Walking performance of 17 healthy subjects (mean age 28.8 ± 1.7 years) at slow, preferred, and fast speeds was examined during three different conditions: (1) walking with eyes open (EO) as baseline condition, (2) walking with eyes closed and sham noisy GVS (EC), and (3) walking with eyes closed and non-zero amplitude noisy GVS set to 80% of the individual sensory threshold for GVS (EC-GVS). Ten gait parameters were examined: stride time, stride length, base of support, swing time percentage, double support time percentage as well as gait asymmetry, bilateral phase coordination and the coefficient of variation (CV) of stride time, stride length and base of support. Noisy GVS improved stride time CV by 36% (p < 0.034), stride length CV by 31% (p < 0.037), base of support CV by 14% (p < 0.009), and bilateral phase coordination by 23% (p < 0.034). The ameliorating effects of noisy GVS on locomotion function were primarily observable during slow walking speeds. Noise-enhanced vestibular input is effective in improving locomotion function and is accompanied by a subjectively felt improvement of walking balance. It predominantly targets the variability and bilateral coordination characteristics of the walking pattern, which are critically linked to dynamic walking stability. Noisy GVS might present an effective treatment option to improve walking performance in patients with bilateral vestibular dysfunction.

Episodic memory and executive function impairments in non-demented older adults: which are the respective and combined effects on gait performances?

Gait control depends in part on cognition. This study aims to examine the separate and combined effects of episodic memory and executive function impairments on the mean value and the coefficient of variation (CoV) of stride time among non-demented older community dwellers. Based on a cross-sectional design, 1458 older community dwellers without dementia (70.6 ± 4.9 years; 49.2 % female) were recruited and separated into cognitively healthy individuals (CHI) and individuals with cognitive impairment. A score ≤5/6 on the Short Mini-Mental State Examination defined episodic memory impairment. Impaired executive function was defined by errors on the clock-drawing test. Mean value and CoV of stride time were measured by the GAITRite® system. A total of 517 participants (35.5 %) had cognitive impairment in at least one cognitive domain. Participants with memory impairment (P = 0.006) and those with combined cognitive impairments (P < 0.001) had greater (i.e., worse gait performance) mean value of stride time (P = 0.006) compared to CHI. Participants with combined cognitive impairment had a greater CoV of stride time (i.e., worse gait performance) compared to CHI (P = 0.004) and to those with separate memory impairment (P = 0.037). Among participants with combined cognitive impairments, mean value and CoV of stride time had the highest effect size (respectively, effect size = 0.49 [95 % confidence interval (CI) 0.27;0.71] and effect size = 0.40 [95 %CI 0.18;0.62]). Participants with episodic memory or executive impairments had a greater mean value and CoV of stride time compared to those with no cognitive impairment. Combined episodic memory and executive impairments exceeded the sum of separate impairments on gait performances, suggesting a complex interplay going beyond a simple additive effect.

Factors affecting the coefficient of variation of stride time of the elderly without falling history: a prospective study.

[Purpose] The purpose of this study was to investigate the factors affecting the coefficient of variation (CV) of stride time in an exercise intervention for the elderly without falling history. [Subjects and Methods] The subjects were 42 elderly women who had participated in a care prevention program for 12 weeks. Stride time CV, motor function, movement ability, balance, Modified Falls Efficacy Scale (MFES) score, and Life-space Assessment (LSA) score before and after the intervention were examined for significant differences using the paired t-test. Multiple regression analysis was used to determine the factors that changed in the stride time CV. [Results] There were significant differences in muscle strength, sit-and-reach flexibility, the one-leg standing time (eyes open), the maximum walking speed, local stability of trunk acceleration, The Timed Up and Go Test (TUG-T), the MFES score, and the LSA score between the pre-intervention and post-intervention. Stepwise multiple regression analysis revealed that improvement of quadriceps muscle strength, sit-and-reach flexibility, the one-leg standing time, TUG-T, local stability of trunk acceleration (vertical direction) and MFES score were independent variables explaining the reduction in stride time CV. [Conclusion] The results was suggested that it might be possible to reduce the stride time CV by improving strength, flexibility and dynamic balance, and reducing fear of falls through interventions.

The association between fear of falling and gait variability in both leg and trunk movements

The aim of this study was to explore whether FoF was associated with variability in both leg and trunk movements during gait in community-dwelling elderly. Ninety-three elderly people participated in this study. Each participant was categorized into either Fear or No-Fear group on the basis of having FoF. The participants walked 15m at their preferred speed. The wireless motion recording sensor units were attached to L3 spinous process and right posterior surface of heel during gait. Gait velocity, stride time and stride length were calculated. Variability in lower limb movements was represented by coefficient of variation (CV) of stride time. Trunk variability was represented by autocorrelation coefficients (AC) in three directions (vertical: VT, mediolateral: ML and anteroposterior: AP), respectively. Gait parameters were compared between groups, and further analyses were performed using generalized linear regression models after adjustment of age, sex, fall experience, height, weight, and gait velocity. Although gait velocity, mean stride time and stride length did not differ significantly between groups, stride time CV and all ACs were significantly worse in the Fear group after adjustment for variables, even including gait velocity (stride time CV: p=0.003, β=−0.793; AC-VT: p=0.011, β=0.053; AC-ML: p=0.044, β=0.075; AC-AP: p=0.002, β=0.078). Our results suggest that fear of falling is associated with variability in both leg and trunk movements during gait in community-dwelling elderly. Further studies are needed to prove a causal relationship.

Patterns of optimization in single- and inter-leg gait dynamics

IntroductionWe examined the influence of walking speed on the fluctuation and synchronization dynamics of stride intervals and ground reaction force (GRF) profiles. Our aim was to identify patterns of optimization in the single-leg and inter-leg dynamics at preferred walking speed (PWS). PWS is thought to bring about the most stable walking pattern in terms of the attractor dynamics of the locomotion system. MethodsTwenty healthy subjects (29.1±1.8 years; 10 women) walked on a treadmill for 5-min periods at their PWS and at 20, 40, 70, and 80% of maximal walking speed. The coefficient of variation (CV) and long-range correlations α of GRF profile and stride time fluctuations as well as the phase synchronization ρ of inter-leg stride timing were analyzed. ResultsGRF profile α increased with increasing walking speed (p<0.001). In contrast, stride time CV and α showed a U-shaped speed-dependency with lowest values at PWS (p<0.05). The speed-dependency of single-leg stride time fluctuations was mirror-inverted in the speed-dependency of inter-leg stride timing ρ; its highest values occurred at PWS (p<0.001). ConclusionsFluctuations in GRF profiles become more consistent with increasing walking speed. In contrast, the dynamics of single-leg and inter-leg timing show a collective pattern of optimization at PWS. Less correlated noise in single-leg timing at PWS, imposed on the two coupled oscillating legs, increases the phase synchronization of bilateral timing, thereby enhancing gait stability at the attractor of self-paced walking. Thus, the attractor dynamics of locomotion appear to rely on the interaction of single- and inter-leg timing.

Cognitive motor interference during dual-task gait in essential tremor

BackgroundFunctional ambulation requires concurrent performance of motor and cognitive tasks, which may create interference (degraded performance) in either or both tasks. People with essential tremor (ET) demonstrate impairments in gait and cognitive function. In this study we examined the extent of interference between gait and cognition in people with ET and controls during dual-task gait. MethodsWe tested 62 controls and 151 ET participants (age range: 72–102). ET participants were divided into two groups based on median score on the modified Mini Mental State Examination. Participants walked at their preferred speed, and performed a verbal fluency task while walking. We analyzed gait velocity, cadence, stride length, double support time, stride time, step width, step time difference, coefficient of variation (CV) of stride time and stride length. ResultsVerbal fluency performance during gait was similar across groups (p=0.68). Velocity, cadence and stride length were lowest whereas step time difference (p=0.003), double support time (p=0.009), stride time (p=0.002) and stride time CV (p=0.007) were highest for ET participants with lower cognitive scores (ETp-LCS), compared with ET participants with higher cognitive scores (ETp-HCS) and controls. ETp-LCS demonstrated greatest interference for double support time (p=0.005), step time difference (p=0.013) and stride time coefficient of variation (p=0.03). ConclusionsETp-LCS demonstrated high levels of cognitive motor interference. Gait impairments during complex tasks may increase risk for falls for this subgroup and underscore the importance of clinical assessment of gait under simple and dual-task conditions.

Age-Related Changes in the Auditory Reaction Time of Healthy Elderly Person while Walking

[Purpose] This study aimed to investigate the age-related changes in the attentional demand of walking in healthy elderly people by assessing auditory reaction time during walking in several age groups. [Subjects] The participants were 59 healthy elderly people with no history of falls in the previous 12 months, who were divided into 4 age groups (65-69, 70-74, 75-79, and 80-84). [Methods] In the dual-task condition, participants were asked to perform an auditory reaction time task while walking indoors; the Timed Up-and-Go Test, 10-meter walk time and Trail Making Test Part A were also measured. We compared the reaction times and the stride-to-stride time coefficients of variation between the single- and dual-task conditions. [Results] We found that mean reaction time and stride time coefficient of variation increased significantly in the dual task. However, in both task conditions, neither the reaction time nor stride-to-stride time coefficient of variation differed significantly among the age groups. [Conclusion] These findings indicate that an auditory reaction time task can affect walking as a second task in the healthy elderly, and that aging has minimal effects on the attentional demand of walking in this population.

Targeting dopa‐sensitive and dopa‐resistant gait dysfunction in Parkinson's disease: Selective responses to internal and external cues

Independence of certain gait characteristics from dopamine replacement therapies highlights its complex pathophysiology in Parkinson's disease (PD). We explored the effect of two different cue strategies on gait characteristics in relation to their response to dopaminergic medications. Fifty people with PD (age 69.22 ± 6.6 years) were studied. Participants walked with and without cues presented in a randomized order. Cue strategies were: (1) internal cue (attention to increase step length) and (2) external cue (auditory cue with instruction to take large step to the beat). Testing was carried out two times at home (on and off medication). Gait was measured using a Stride Analyzer (B&L Engineering). Gait outcomes were walking speed, stride length, step frequency, and coefficient of variation (CV) of stride time and double limb support duration (DLS). Walking speed, stride length, and stride time CV improved on dopaminergic medications, whereas step frequency and DLS CV did not. Internal and external cues increased stride time and walking speed (on and off dopaminergic medications). Only the external cue significantly improved stride time CV and DLS CV, whereas the internal cue had no effect (on and off dopaminergic medications). Internal and external cues selectively modify gait characteristics in relation to the type of gait disturbance and its dopa-responsiveness. Although internal (attention) and external cues target dopaminergic gait dysfunction (stride length), only external cues target stride to stride fluctuations in gait. Despite an overlap with dopaminergic pathways, external cues may effectively address nondopaminergic gait dysfunction and potentially increase mobility and reduce gait instability and falls.

Running injury and stride time variability over a prolonged run

Locomotor variability is inherent to movement and, in healthy systems, contains a predictable structure. In this study, detrended fluctuation analysis (DFA) was used to quantify the structure of variability in locomotion. Using DFA, long-range correlations (α) are calculated in over ground running and the influence of injury and fatigue on α is examined. An accelerometer was mounted to the tibia of 18 runners (9 with a history of injury) to quantify stride time. Participants ran at their preferred 5k pace±5% on an indoor track to fatigue. The complete time series data were divided into three consecutive intervals (beginning, middle, and end). Mean, standard deviation (SD), coefficient of variation (CV) and α of stride times were calculated for each interval. Averages for all variables were calculated per group for statistical analysis. No significant interval, group or interval×group effects were found for mean, SD or CV of stride time. A significant linear trend in α for interval occurred with a reduction in α over the course of the run (p=0.01) indicating that over the run, stride times of runners became more unpredictable. This was likely due to movement errors associated with fatigue necessitating frequent corrections. The injured group exhibited lower α (M=0.79, CI95=0.70, 0.88) than the non-injured group (p=0.01) (M=0.96, CI95=0.88, 1.05); a reduction hypothesized to be associated with altered complexity. Overall, these findings suggest injury and fatigue influence neuromuscular output during running.

Decrease in gait variability while counting backward: a marker of “magnet effect”?

Counting backward (CB) and walking are both rhythmic tasks. An improvement of CB performance has been reported while walking, and has been interpreted as a "magnet effect" which is the tendency of biological oscillators to attract each other. The objective of this study was to compare the coefficient of variation (CoV) of stride time (ST) and the number of enumerated figures while single- and dual-tasking between older adults who increased and decreased their CoV of ST while CB. The number of enumerated figures and the CoV of ST under single-task (i.e., CB while sitting or walking alone) and dual-task (i.e., CB while walking) were measured among 100 community-dwelling older subjects (mean, 69.8 ± 0.07 years). Subjects were separated into two groups according to the dual-task-related changes in CoV of ST (i.e., either above or below the mean value of CoV of ST under single-task). Seventeen participants decreased their CoV of ST while CB compared to usual walking (2.6 ± 1.6% vs. 2.0 ± 1.3%, P < 0.001), while 83 increased their CoV of ST (1.7 ± 0.6% vs 3.4 ± 2.3%, P < 0.001). The subjects who decreased their CoV of ST had a tendency to enumerate more figures while walking compared to sitting (20.9 ± 6.3 vs 19.4 ± 4.7, P = 0.046) unlike those who increased their CoV of ST (20.3 ± 5.0 vs 21.8 ± 6.0 while sitting, P = 0.001). We found that most of subjects had worse gait and CB performance while dual-tasking. Conversely, a limited number of subjects improved significantly their gait performance and simultaneously had a tendency to improve their CB performance while walking compared to sitting. This behavior was observed only among subjects with the highest gait variability and could be interpreted as an implicit strategy based on the "magnet effect".

Changes in gait while backward counting in demented older adults with frontal lobe dysfunction

Background Gait disorders caused by dementia have been associated with frontal lobe dysfunction. Dual-tasking is used to explore the involvement of cortical level in gait control. It has been shown that dual-task induced gait changes that could be related to (1) the efficiency of executive function, (2) the level of difficulty involved in the walking-associated task, or (3) the articulo-motor components comprised in the walking-associated task. A better understanding of dual-task related changes in demented subjects with frontal lobe dysfunction could help us to clarify the role of the frontal lobe in motor gait control. Objective To assess and compare the effects of two mental arithmetic tasks involving similar articulo-motor components but different level of difficulty on the mean values and coefficient of variation (CV) of stride time among demented older adults with impaired executive function. Methods The mean values and coefficients of variation of stride time were measured using a GAITRite ®-System among 16 demented older adults with impaired executive function while walking with and without forward counting (FC) and backward counting (BC). Results The mean values and CV of stride time were significantly higher under both dual-task conditions than during a simple walking task ( p < 0.05). The change in CV of stride time during BC was significantly higher when compared with the change during FC ( p = 0.015), whereas the change in mean value was not significant ( p = 0.056). There was no difference between the dual-task and single task condition as far the number of enumerated figures were concerned ( p = 0.678 for FC and p = 0.069 for BC), but significantly fewer figures were enumerated while BC compared with FC ( p < 0.001). Conclusion BC provoked more changes in gait parameters than FC with major modification in gait variability related to an inappropriate focusing of attention. These findings suggest that the CV may be a suitable criterion for the assessment of gait control.