Gait & Posture - Articles in Press

Indicators of dynamic stability in transtibial prosthesis users - Corrected Proof

C. Kendell, E.D. Lemaire, N.L. Dudek, J. Kofman — 2010-02-08

Abstract: An improved understanding of factors related to dynamic stability in lower-limb prosthesis users is important, given the high occurrence of falls in this population. Current methods of assessing stability are unable to adequately characterize dynamic stability over a variety of walking conditions. F-Scan Mobile has been used to collect plantar pressure data and six extracted parameters were useful measures of dynamic stability. The aim of this study was to investigate dynamic stability in individuals with unilateral transtibial amputation based on these six parameters. Twenty community ambulators with a unilateral transtibial amputation walked over level ground, uneven ground, stairs, and a ramp while plantar pressure data were collected. For each limb (intact and prosthetic) and condition, six stability parameters related to plantar center-of-pressure perturbations and gait temporal parameters, were computed from the plantar pressure data. Parameter values were compared between limbs, walking condition, and groups (unilateral transtibial prosthesis users and able-bodied subjects). Differences in parameters were found between limbs and conditions, and between prosthesis users and able-bodied individuals. Further research could investigate optimizing parameter calculations for unilateral transtibial prosthesis users and define relationships between potential for falls and the dynamic stability measures.

Classifying household and locomotive activities using a triaxial accelerometer - Corrected Proof

2010-02-08

Abstract: The purpose of this study was to develop a new algorithm for classifying physical activity into either locomotive or household activities using a triaxial accelerometer. Sixty-six volunteers (31 men and 35 women) participated in this study and were separated randomly into validation and cross-validation groups. All subjects performed 12 physical activities (personal computer work, laundry, dishwashing, moving a small load, vacuuming, slow walking, normal walking, brisk walking, normal walking while carrying a bag, jogging, ascending stairs and descending stairs) while wearing a triaxial accelerometer in a controlled laboratory setting. Each of the three signals from the triaxial accelerometer was passed through a second-order Butterworth high-pass filter to remove the gravitational acceleration component from the signal. The cut-off frequency was set at 0.7Hz based on frequency analysis of the movements conducted. The ratios of unfiltered to filtered total acceleration (TAU/TAF) and filtered vertical to horizontal acceleration (VAF/HAF) were calculated to determine the cut-off value for classification of household and locomotive activities. When the TAU/TAF discrimination cut-off value derived from the validation group was applied to the cross-validation group, the average percentage of correct discrimination was 98.7%. When the VAF/HAF value similarly derived was applied to the cross-validation group, there was relatively high accuracy but the lowest percentage of correct discrimination was 63.6% (moving a small load). These findings suggest that our new algorithm using the TAU/TAF cut-off value can accurately classify household and locomotive activities.

An analysis of directional changes in the center of pressure trajectory during stance - Corrected Proof

Akinori Nagano, Hisahito Noritake, Zhi-Wei Luo — 2010-02-08

Abstract: This study proposes a new approach of posturography analysis, which enables the evaluation of directional changes in the center of pressure trajectory. The concept is similar to that of so-called “stabilogram diffusion analysis”. Instead of calculating the distance traveled by the center of pressure in a certain time interval, this new method calculates the cosine of the instantaneous velocity vectors of the center of pressure, which corresponds to the amount of change in the sway direction (cosine=1 corresponds to the identical direction; cosine=−1 corresponds to the opposite direction). This method was applied to the analysis of the experimental data in which postural sway was collected under four conditions: open eyes, closed eyes, and two auditory biofeedback conditions. In the biofeedback conditions, auditory signal was given to the subjects when the center of pressure swayed out of a certain area. As results, the differences in the postural reaction under these conditions were clearly shown using the new method. The results indicated that the subjects reacted to the auditory signals by swaying in the opposite direction with biofeedback. It was also found that the eyes open condition exhibited a more random-like profile. As this method analyzes the directional change in the postural sway, this method can be utilized cooperatively together with such a method as stabilogram diffusion analysis, which analyzes the magnitude of sway.

Light curtain for detecting footfall instants during treadmill walking—An exploratory study - Corrected Proof

John W. Chow, Robert J. Hirko, Mark E. Hemleben, Dobrivoje S. Stokic — 2010-02-08

Abstract: Footswitches, instrumented insoles, and forceplates are commonly used for detecting footfall instants during treadmill walking. This study aimed to explore the feasibility of using an optoelectronic light curtain for detecting initial foot contact (FC) and toe-off (TO) instants during treadmill walking. A commercial light curtain comprised of an array of parallel infrared light beams was installed 5mm above the treadmill belt. Ten subjects walked on the treadmill at 0.5, 1.0 and 1.4m/s and their gait was captured using seven optoelectronic cameras. Footswitches were secured over the heel and big toe of the right foot and the corresponding areas of the shoe. Footfall instants from the light curtain, markers, and foot footswitches were compared with the shoe footswitches serving as a criterion. The respective time differences were computed for each step and used to evaluate the agreement with the criterion and variability across subjects. FC instants from foot footswitches were on average within 10ms of the criterion. Both video and light curtain FC instants were detected at least 30ms before the criterion. For TO, both the foot footswitches and video instants preceded the criterion. In contrast, the TO from the light curtain occurred >110ms after the criterion but the variability was the smallest. The results indicated that using a light curtain for detecting footfall instants is feasible. The advantages of light curtain are relatively low cost, no subject preparations, and real-time signals. Greater accuracy is expected with further optimization of the setup.

Measures of frontal plane stability during treadmill and overground walking - Corrected Proof

Noah J. Rosenblatt, Mark D. Grabiner — 2010-02-03

Abstract: Given the consequences of falling to the side by older adults, attention has focused on identifying variables associated with changes in lateral stability and fall risk. Step-width (SW) and step-width variability (SWV) have traditionally been associated with such changes. Recently the “margin of stability” (MOS) has been adopted for describing dynamic stability. Although these measures may be influenced by the conditions during which locomotion occurs, only one published within-subject study has compared SW (but not SWV or MOS) during overground and treadmill walking. Therefore, we compared SW, SWV and minimum MOS (MOSmin) in 10 healthy young subjects walking at self-selected speeds, both overground and on a treadmill. We found SW was significantly larger (p=0.001), and SWV significantly smaller (p=0.001) during treadmill walking, and that these changes were meaningfully correlated between tasks. In contrast, MOSmin was insensitive to treadmill versus overground walking. This suggested first, that SW and SWV only partially reflect frontal plane stability, and second, that the goal of the central nervous system may be to maintain a constant MOSmin regardless of task.

Determination of preferred walking speed on treadmill may lead to high oxygen cost on treadmill walking - Corrected Proof

Ugur Dal, Taner Erdogan, Bora Resitoglu, Hüseyin Beydagi — 2010-02-03

Abstract: The energy consumption of walking relates to the intensity of physical effort and can be affected by the alterations in walking speed. Therefore, walking speed can be accepted as a crucial, determinant of energy consumption measurement for a walking test. We aimed to investigate the differences in preferred walking speed (PWS) determined both on overground and on a treadmill and, to measure walking energy expenditure and spatio-temporal parameters of gait on a treadmill at both, speeds. Participants (n=26) walked on a treadmill at two pre-determined speeds for 7min while, indirect calorimetry measurements were being performed. Spatio-temporal parameters were collected, by video-taping during each walking session on a treadmill. The average overground preferred walking speed (O-PWS) was 85.96±12.82m/min and the average treadmill preferred walking speed (T-PWS), was 71.15±13.85m/min. Although T-PWS was lower, oxygen cost was statistically higher when, treadmill walking at T-PWS (0.158±0.02ml/kg/m) than when the treadmill walking at O-PWS, (0.1480±0.02ml/kg/m). Cadence (127±9.13 steps/min), stride (134.02±14.09cm) and step length (67.02±6.90cm) on the treadmill walking at O-PWS were significantly higher than cadence (119±10 steps/min), stride (117.96±14.38cm) and step length (59.13±7.02cm) on the treadmill walking at TPWS. In conclusion, walking on treadmill using O-PWS is more efficient than walking on treadmill using TPWS, in walking tests. Since using T-PWS for treadmill walking tests overestimates the oxygen cost of walking, O-PWS should be used for oxygen consumption measurement during treadmill walking tests.

Non-linear analysis of the structure of variability in midfoot kinematics - Corrected Proof

M.S. Rathleff, C.G. Olesen, C.M. Moelgaard, K. Jensen, P. Madeleine, J.L. Olesen — 2010-02-03

Abstract: Introduction: Evaluation of structural variability in biological time series through measures such as sample entropy (SaEn) has provided important information in neurology and cardiology. This has contributed to the development of the “loss of complexity hypothesis” where high variability has been described as healthy flexibility and low variability associated with pathology. The purpose of this study was to calculate sample entropy (SaEn) to establish normal values of non-linear variability and to examine which factors are associated with SaEn in midfoot kinematics.Method: Static foot posture was measured using Foot Posture Index. A video sequence analysis system was used to quantify midfoot kinematics during walking in the sagittal plane. SaEn was calculated for navicular drop during stand phase as an expression of the dynamic complexity.Results: A significant difference was observed between the three major foot types and between genders (p<0.001). Mean SaEn in women were 1.10±0.19 (supinated foot posture), 0.96±0.17 (neutral foot posture) and 0.77±0.16 (pronated foot posture) and 1.25±0.24 (supinated foot posture), 1.06±0.23 (neutral foot posture) and 0.86±0.19 (pronated foot posture) in males. The regression model showed that foot posture and dynamic navicular drop (dND) were both associated with SaEn.Conclusion: This study confirmed that non-linear analysis is of relevance in the interpretation of kinematic data. Pronated foot posture, large navicular drop and women were characterized by low values of non-linear variability. Future studies should investigate if measurements of SaEn are capable of identifying subjects with an increased risk of injury.

Natural history of flexed knee gait in diplegic cerebral palsy evaluated by gait analysis in children who have not had surgery - Corrected Proof

G.E. Rose, K.A. Lightbody, R.G. Ferguson, J.C. Walsh, J.E. Robb — 2010-01-29

Abstract: Eighteen children with diplegic cerebral palsy and no history of orthopaedic surgery had two gait analyses a mean of 6.3 years apart to analyse the effects of time on their gait. The mean age of the children at first analysis was 7.7 years (range 4.4–13.3 years). The data was analysed as a whole group (18 children) and as two sub-groups of nine children: those with a shorter follow-up (mean 5.0 years) and those with a longer follow-up (mean 7.5 years) between analyses. The following significant bilateral changes were seen in the whole group and longer follow-up sub-group: deterioration in the range of knee flexion, mid-stance knee flexion, peak knee extension in stance and hamstring length and an improvement in mean and maximum hip rotation. Temporal data showed no significant changes once normalised. There were no bilateral significant changes in data from children evaluated at a mean of 5 years follow-up. GMFCS scores generally improved over time despite the significant increase in flexed knee gait. There was no significant change in gait deviation index in any group over time. There was an increase in body mass index in 16 children but there was no correlation between this and the degree of mid-stance knee flexion. These findings may have implications for longer term follow-up of children with cerebral palsy into adulthood.

Effects of age and walking speed on coactivation and cost of walking in healthy adults - Corrected Proof

Daniel S. Peterson, Philip E. Martin — 2010-01-28

Abstract: Our goal was to determine how age and walking speed affect metabolic cost of walking (Cw), lower, extremity antagonist coactivation, and relationships between coactivation and Cw in healthy, active, individuals. Fourteen young (25±3 years) and 14 older (71±4 years) participants walked on a treadmill at, four speeds (0.89, 1.12, 1.34, and 1.57ms−1) while electromyography (EMG) and oxygen consumption, were measured. Coactivation indices were calculated for musculature about the thigh and shank. Cw, was higher in older adults across all speeds (p<0.001). Coactivation about the thigh was also higher in, older adults (p<0.001), whereas coactivation about the shank was not different between age groups (p=0.60). Total coactivation (thigh coactivation plus shank coactivation) showed significant positive, relationships to Cw at all walking speeds (r=0.46–0.57). Higher Cw and coactivation in older adults, along with the positive relationship between Cw and coactivation implies coactivation contributes to, higher Cw of older adults.

Patterns of muscle coordination vary with stride frequency during weight assisted treadmill walking - Corrected Proof

Taryn Klarner, Henry K. Chan, James M. Wakeling, Tania Lam — 2010-01-25

Abstract: Partial body weight-supported treadmill training is an approach for gait rehabilitation. Variables such as stepping frequency and the amount of body weight support are key parameters manipulated during training. The purpose of this study was to quantify the extent to which body weight support and stride frequency contribute and interact to produce the coordination patterns of the leg muscles. Principal components analysis was used to provide insight into the interaction effects of these factors on electromyographical (EMG) activity during treadmill locomotion. Eight healthy subjects walked on a treadmill at 15 different combinations of weight support (0%, 20%, 40%, 60%, 100%), and stride frequency (0.40, 0.49, 0.57Hz). Treadmill walking was performed with the Lokomat robotic gait orthosis to constrain leg kinematics. Surface EMG data were collected from several lower limb muscles. Results indicate that much of the variance in EMG activity during treadmill locomotion can be attributed to the mechanics of the locomotor task imposed by the level of body weight support and stride frequency. We also showed that body weight support and stride frequency interact in different ways to affect muscle coordination patterns. EMG coordination patterns are similar between conditions of high levels of body weight support and faster stride frequencies vs. lower levels of body weight support and slower stride frequency. Our data suggest that the interaction of body weight support and stride frequency should be taken into consideration for optimizing motor output during locomotor training.

Mechanical work performed by the legs of children with spastic diplegic cerebral palsy - Corrected Proof

Max J. Kurz, Wayne A. Stuberg, Stacey L. DeJong — 2010-01-22

Abstract: The purpose of this investigation was to evaluate the work performed on the center of mass by the legs of children with cerebral palsy. 10 children that were diagnosed as having cerebral palsy with spastic diplegia (Age=9.1±2 years), and 10 healthy children with no walking disabilities participated (Age=9.4±2 years). We collected individual leg ground reaction forces from four force platforms, and calculated the mechanical work performed on the center of mass by the lead and trail legs. The normalized walking speeds were not significantly (p=0.33) different between the children with cerebral palsy (0.26±0.07) and the controls (0.28±0.06). The children with cerebral palsy performed significantly more negative work by the lead leg during double support (p=0.0004), and significantly less positive work by the trail leg (p<0.00001). During single support, the children with cerebral palsy performed significantly more positive work on the center of mass (p<0.00001). No significant differences were found for the amount of negative work performed by the leg in single support (p=0.84). Children with spastic diplegic cerebral palsy show a diminished ability to appropriately perform mechanical work by the legs to lift and redirect the center of mass. The altered mechanical work performed by the legs on the center of mass may play a role in the higher metabolic cost for walking noted in children with cerebral palsy.

An empirical examination of detrended fluctuation analysis for gait data - Corrected Proof

Sotirios Damouras, Matthew D. Chang, Ervin Sejdić, Tom Chau — 2010-01-08

Abstract: Stride interval series exhibit statistical persistence, and detrended fluctuation analysis (DFA) is a routinely employed technique for describing this behavior. However, the implementation of DFA to gait data varies considerably between studies. We empirically examine two practical aspects of DFA which significantly affect the analysis outcome: the box size range and the stride interval series length. We conduct an analysis of their effect using stride intervals from 16 able-bodied adults, for overground walking, treadmill walking while holding a handrail, and treadmill walking without using a handrail. Our goal is to provide general guidelines for these two choices, with the aim of standardizing the application of DFA and facilitating inter-study comparisons. Based on the results of our analysis, we propose the use of box sizes from to , where N is the number of stride intervals. Moreover, for differentiating between normal and pathological walking with reasonable accuracy, we recommend a minimum of stride intervals.

Variability and fluctuation in running gait cycle of trained runners and non-runners - Corrected Proof

Yosuke Nakayama, Kazutoshi Kudo, Tatsuyuki Ohtsuki — 2010-01-07

Abstract: The current study examined variability and fluctuation in the running gait cycle, focusing on differences between trained distance runners and non-runners. The two groups of participants performed treadmill running at 80%, 100%, and 120% of their preferred speed for 10min. Stride-interval time-series were recorded during running using footswitches. The average preferred speed was significantly higher for the trained runners than for the non-runners. The trained runners showed significantly smaller variability of stride interval than did the non-runners, and at the same time the scaling exponent α evaluated by detrended fluctuation analysis tended to be smaller for the trained runners. These results suggest that expert runners can reduce variability in the trained movement without loosing dynamical degrees of freedom for spatiotemporal organization of the gait pattern.

Obstacle stepping in children: Task acquisition and performance - Corrected Proof

J. Michel, C. Grobet, V. Dietz, H.J.A. van Hedel — 2010-01-06

Abstract: The aim of this study was to investigate the locomotor capacity of children during the performance of different lower extremity tasks with increasing difficulty. Two subject groups of children (aged 6–8 and 9–12 years) and adult controls performed several motor tasks from the Zürich Neuromotor Assessment (ZNA) test, as well as a unilateral and bilateral obstacle stepping test during treadmill walking. Performance of ZNA items, changes in foot clearance, and obstacle hits were assessed. Correlations between children's age, ZNA and obstacle measures were calculated. Performance of all motor tasks improved with increasing age. All three groups improved foot clearance during unilateral obstacle stepping, while the younger children achieved a poorer performance level. During bilateral obstacle stepping, only the adult controls and the 9–12 years old children's group further improved foot clearance, while no further improvement occurred in the 6–8 years old children's group. A relationship between items of ZNA and bilateral obstacle stepping was found. It is concluded that children in the mid-childhood range are able to significantly improve performance of a high-precision locomotor task. However, children below 9 years of age have a poorer motor performance compared to older children and adults that becomes more pronounced with increasing complexity of the task. Finally, ZNA tests can improve the prediction of complex adaptive locomotor behaviour compared to calendar age alone.

Falls prediction in elderly people: A 1-year prospective study - Corrected Proof

Jaap Swanenburg, Eling D. de Bruin, Daniel Uebelhart, Theo Mulder — 2010-01-04

Abstract: The aim of the present study was to determine whether force plate variables in single- and dual-task situations are able to predict the risk of multiple falls in a community-dwelling elderly population. Two hundred and seventy elderly persons (225 females, 45 males; age, 73±7 years) performed balance assessment with and without vision. Seven force plate variables were assessed to predict the risk of multiple falls; maximum displacement in the anteroposterior and medial–lateral directions (Max-AP, Max-ML), mean displacement in the medial–lateral direction (MML), the root mean square amplitude in anteroposterior and medial–lateral directions (RMS-AP, RMS-ML), the average speed of displacement (V), and the area of the 95th percentile ellipse (AoE). Falls were prospectively recorded during the following year. A total of 437 registered falls occurred during monitoring period. The force plate variable RMS-ML in the single-task condition (odds ratio, 21.8) predicted multiple falls together with the following covariables: history of multiple falls (odds ratio, 5.6), use of medications (fall-risk medications or multiple medicine use; odds ratio, 2.3), and gender (odds ratio, 0.34). Multiple fallers had a narrower stance width than non-fallers.

Plantar pressure measurements using an in-shoe system and a pressure platform: A comparison - Corrected Proof

Thierry Larose Chevalier, Helen Hodgins, Nachiappan Chockalingam — 2009-12-31

Abstract: This study compared three different foot-pressure measurement methods to investigate whether these measurement methods could or should be used interchangeably. In-shoe pressure measurements using F-Scan system, shod and unshod pressure measurements using the MatScan system were taken for each of the 21 healthy subjects while performing walking trials using a two-step gait initiation protocol. Each foot was separated in three regions: forefoot (40%), midfoot (30%) and rearfoot (30%) for further analysis. The parameters researched include average peak pressure, average peak force, timing and centre of pressure displacement. The in-shoe condition produced the highest values for the average peak force. However, the shod condition showed a trend for the highest average peak pressure. The F-Scan system consistently demonstrated slower timing values for all parameters, except one. Centre of pressure anterior/posterior trajectory was considerably shorter for the in-shoe gait condition. Consequently, the data cannot be extrapolated from one collection method to another. It is therefore recommended that a standardised collection method is utilised when pressure analysis is undertaken and that they are not used interchangeably.

The use of kinematic and parametric information to highlight lack of movement and compensation in the upper extremities during activities of daily living - Corrected Proof

Alessio Murgia, Peter Kyberd, Tom Barnhill — 2009-12-25

Abstract: A problem that is common to the study of upper limb kinematics and gait analysis is the translation of the evidence from kinematic measurements into easily interpretable information on the status of the patient, such as the amount of compensation or lack of motion. In this study parameters that can be helpful in the rapid and clear identification of limited wrist motion and compensation were derived from kinematic data. A group of six subjects (group A) with no hand impairment, average age 32.5ys SD 10.7ys, and another group of five subjects (group B), average age 34.2ys SD 16.8ys, having suffered from distal radius fracture were tested during a cyclic activity of daily living. The activity simulated page turning. Thorax, shoulder, elbow and wrist angles were measured during this task using a motion capture system. Corresponding angle ranges were also calculated.The active range of motion (AROM) found for Group B was generally lower than that of Group A, particularly for elbow supination and wrist movements, with wrist flexion/extension statistically smaller for group B (P=0.02). Additional parameters that took into account lack of movements at the wrist and compensation from shoulder elevation, rotation and elbow pronation/supination proved to be more useful at identifying those subjects of group B outside the normative range and can provide clinicians with a rapid and efficient tool that can shorten the analysis process and help make more informed decisions on therapeutic treatments.

Real-time gait event detection for normal subjects from lower trunk accelerations - Corrected Proof

2009-12-25

Abstract: In this paper we report on a novel algorithm for the real-time detection and timing of initial (IC) and final contact (FC) gait events. We process the vertical and antero-posterior accelerations registered at the lower trunk (L3 vertebra). The algorithm is based on a set of heuristic rules extracted from a set of 1719 steps. An independent experiment was conducted to compare the results of our algorithms with those obtained from a Digimax force platform. The results show small deviations from times of occurrence of events recorded from the platform (13±35ms for IC and 9±54ms for FC). Results for the FC timing are especially relevant in this field, as no previous work has addressed its temporal location through the processing of lower trunk accelerations. The delay in the real-time detection of the IC is 117±39ms and 34±72ms for the FC, improving previously reported results for real-time detection of events from lower trunk accelerations.

Adult age differences in familiarization to treadmill walking within virtual environments - Corrected Proof

2009-12-23

Abstract: We assessed age-related differences in adults in familiarization to treadmill walking within virtual environments (VE), and examined whether treadmill walking after familiarization resembles overground walking. Seventeen younger and 17 older adults walked at preferred speed on an overground walkway and afterwards walked at the same speed for 20min on a treadmill coupled to a VE. A motion capture system was used to measure spatio-temporal gait parameters. On the treadmill, both younger and older adults initially displayed decreased step length and increased step width, cadence, and time in double support relative to overground walking. Except for time in double support, step characteristics approached overground walking-behavior with a negatively accelerated trend. After 15min of treadmill walking, changes became minor corresponding to less than 1% deviations to individuals’ overground walking. At the end of familiarization, average differences in step length, cadence, and double support relative to overground walking were reduced to less than 5 percent in both age groups. For step width, younger adults approximated overground walking after 20min more closely than older adults, probably reflecting larger initial differences between treadmill and overground walking among older adults. We conclude (a) that 20min of familiarization to treadmill walking in a VE are sufficient to reach stable walking patterns resembling those observed in overground walking, but that some differences between the two settings remain, especially in older adults; (b) that sufficient familiarization to the treadmill is needed to ascertain the validity and generalizability of comparisons between younger and older adults.

Ocular dominance and balance performance in healthy adults - Corrected Proof

Revital Gandelman-Marton, Aharon Arlazoroff, Zeevi Dvir — 2009-12-23

Abstract: Purpose: To evaluate the effect of ocular dominance on balance performance in healthy adult subjects.Methods: Ocular dominance was determined in 24 healthy subjects using the hole-in-the-paper test. Balance function was evaluated by computerized dynamic platform posturography (CDPP). Sway index (SI), antero-posterior sway (APS) and lateral sway (LS) were served as outcome parameters.Results: The outcome parameters did not differ significantly between dominant and non-dominant eye fixation both in static and angular balance tests (SI—5.47±0.42, 6.23±0.52, p=0.146 and 18.4±1.07, 19.11±1.15, p=0.142, respectively; APS—−2.26±4.68, −5.1±4.6, p=0.082 and −1.94±3.33, −3.64±2.6, p=0.48, respectively; LS—−1.21±1.46, −1.12±1.66 p=0.94 and −1.98±1.16, −1.55±1.39, p=0.69, respectively).Conclusions: Ocular dominance does not seem to affect postural function in the monovision and far viewing condition.

Effects of a secondary task on postural control in children with Tourette syndrome - Corrected Proof

Martin Lemay, Thanh-Thuan Lê, François Richer, The Montreal Tourette Study Group — 2009-12-21

Abstract: Tourette syndrome (TS) is a neurodevelopmental disorder characterized by involuntary motor and vocal tics. Sub-clinical postural control anomalies have recently been reported in children with TS. The goal of the present study was to determine whether these anomalies interact with attention in postural control. Thirty-two younger (below 10 years) and 21 older (above 10 years) children with TS were compared to 13 younger and 15 older age-matched controls. Postural control was examined during standing with and without a secondary visual attention task. Sway velocity was higher in younger children than older ones and also higher in children with TS than in controls. The secondary task exacerbated the velocity anomalies in younger children with TS. The effects were independent of tic severity, medication, and attention deficit. The results suggest that postural control anomalies in TS are sensitive to attentional requirements.

Differences in self-selected and fastest-comfortable walking in post-stroke hemiparetic persons - Corrected Proof

C.B. Beaman, C.L. Peterson, R.R. Neptune, S.A. Kautz — 2009-12-14

Abstract: Post-stroke hemiparetic walking is typically asymmetric. Assessment of symmetry is often performed at either self-selected or fastest-comfortable walking speeds to gain insight into coordination deficits and compensatory mechanisms. However, how walking speed influences the level of asymmetry is unclear. This study analyzed relative changes in paretic and non-paretic leg symmetry to assess whether one speed is more effective at highlighting asymmetries in hemiparetic walking and whether there is a systematic effect of speed on asymmetry. Forty-six subjects with chronic hemiparesis walked at their self-selected and fastest-comfortable speeds on an instrumented split-belt treadmill. Relative proportions (paretic leg value/(paretic+non-paretic leg value)) were computed at each speed for step length (PSR), propulsion (PP), and joint moment impulses at the ankle and hip. Thirty-six subjects did not change their step length symmetry with speed, while three subjects changed their step length values toward increased asymmetry and seven changed toward increased symmetry. Propulsion symmetry did not change uniformly with speed for the group, with 15 subjects changing their propulsion values toward increased asymmetry while increasing speed from their self-selected to fastest-comfortable and 11 decreasing the asymmetry. Both step length and propulsion symmetry were correlated with ankle impulse proportion at self-selected and fastest-comfortable speed (cf., hip impulse proportion), but ratios (self-selected value/fastest-comfortable value) of the proportion measures (PSR and PP) showed that neither step length nor propulsion symmetry correlated with the ankle impulse proportions. Thus, the individual kinetic mechanisms used to increase speed could not be predicted from PSR or PP.

Center of mass position relative to the ankle during walking: A clinically feasible detection method for gait imbalance - Corrected Proof

Chu-Jui Chen, Li-Shan Chou — 2009-12-11

Abstract: This study examined the effectiveness of using the center of mass (COM)-Ankle inclination angles to identify elderly individuals with gait imbalance. Whole body motions of 12 elderly patients with gait imbalance and 12 healthy elderly controls were captured with an 8-camera motion analysis system. Inclination angles between the line formed between the COM and lateral ankle marker or by the COM and center of pressure (COP) and their respective vertical lines were computed for each frame during the single stance phase of gait. Similar to the results for COM-COP angles, the results showed that COM-Ankle inclination angles during the single stance phase could successfully distinguish elderly individuals with gait imbalance from healthy elderly adults. Examination of the COM-Ankle inclination angles could be an alternative assessment to clinical populations who possess inconsistent gait that hinder the calculation of the COM-COP inclination angles.

Validity and reliability of the Nintendo Wii Balance Board for assessment of standing balance - Corrected Proof

2009-12-11

Abstract: Impaired standing balance has a detrimental effect on a person's functional ability and increases their risk of falling. There is currently no validated system which can precisely quantify center of pressure (COP), an important component of standing balance, while being inexpensive, portable and widely available. The Wii Balance Board (WBB) fits these criteria, and we examined its validity in comparison with the ‘gold standard’—a laboratory-grade force platform (FP). Thirty subjects without lower limb pathology performed a combination of single and double leg standing balance tests with eyes open or closed on two separate occasions. Data from the WBB were acquired using a laptop computer. The test–retest reliability for COP path length for each of the testing devices, including a comparison of the WBB and FP data, was examined using intraclass correlation coefficients (ICC), Bland–Altman plots (BAP) and minimum detectable change (MDC). Both devices exhibited good to excellent COP path length test–retest reliability within-device (ICC=0.66–0.94) and between-device (ICC=0.77–0.89) on all testing protocols. Examination of the BAP revealed no relationship between the difference and the mean in any test, however the MDC values for the WBB did exceed those of the FP in three of the four tests. These findings suggest that the WBB is a valid tool for assessing standing balance. Given that the WBB is portable, widely available and a fraction of the cost of a FP, it could provide the average clinician with a standing balance assessment tool suitable for the clinical setting.