Effects of walking speed on asymmetry and bilateral coordination of gait

The mechanisms regulating the bilateral coordination of gait in humans are largely unknown. Our objective was to study how bilateral coordination changes as a result of gait speed modifications during over ground walking. 15 young adults wore force sensitive insoles that measured vertical forces used to determine the timing of the gait cycle events under three walking conditions (i.e., usual-walking, fast and slow). Ground reaction force impact (GRFI) associated with heel-strikes was also quantified, representing the potential contribution of sensory feedback to the regulation of gait. Gait asymmetry (GA) was quantified based on the differences between right and left swing times and the bilateral coordination of gait was assessed using the phase coordination index (PCI), a metric that quantifies the consistency and accuracy of the anti-phase stepping pattern. GA was preserved in the three different gait speeds. PCI was higher (reduced coordination) in the slow gait condition, compared to usual-walking (3.51% vs. 2.47%, respectively, p = 0.002), but was not significantly affected in the fast condition. GRFI values were lower in the slow walking as compared to usual-walking and higher in the fast walking condition (p < 0.001). Stepwise regression revealed that slow gait related changes in PCI were not associated with the slow gait related changes in GRFI. The present findings suggest that left–right anti-phase stepping is similar in normal and fast walking, but altered during slow walking. This behavior might reflect a relative increase in attention resources required to regulate a slow gait speed, consistent with the possibility that cortical function and supraspinal input influences the bilateral coordination of gait.     

Dynamic stability of superior vs. inferior segments during walking in young and older adults

Active control of trunk motion is believed to enable humans to maintain stability during walking, suggesting that stability of the trunk is prioritized over other segments by the nervous system. We investigated if superior segments are more stable than inferior segments during walking and if age-related differences are more prominent in any particular body segments. Eighteen healthy older adults and 17 healthy young adults walked on a treadmill for two trials of 5 min each at their preferred speed. 3D kinematics of the trunk, pelvis, and left thigh, shank, and foot were recorded. Local divergence exponents and maximum Floquet multipliers (FM) were calculated to quantify each segment's responses to small inherent perturbations during walking. Both older and younger adults walked with similar preferred walking speeds (p = 0.86). Local divergence exponents were larger in inferior segments (p < 0.001), and larger in older adults (p < 0.001). FM was larger in the superior segments (p < 0.001), and larger in older adults (p < 0.001). The age-associated difference in local divergence exponents was larger for trunk motion (interaction p = 0.02). Thus, superior segments exhibited less local instability but greater orbital instability. Trunk motion was more sensitive to age-associated differences in dynamic stability during gait. Trunk motion should be considered in studying age-related deterioration of gait.     

Gait variability and disability in multiple sclerosis

Gait variability is clinically relevant in some populations, but there is limited documentation of gait variability in persons with multiple sclerosis (MS). This investigation examined average and variability of spatiotemporal gait parameters in persons with MS and healthy controls and subsequent associations with disability status. 88 individuals with MS (age 52.4 ± 11.1) and 20 healthy controls (age 50.9 ± 8.7) performed two self-paced walking trials on a 7.9-m electronic walkway to determine gait parameters. Disability was indexed by the Expanded Disability Status Scale (EDSS) and ranged between 2.5 and 6.5. Gait variability was indexed by standard deviation (SD) and coefficient of variation (CV = SD/mean) of step time, step length, and step width. Average gait parameters were significantly correlated with EDSS (ρ = 0.756–0.609) and were significantly different in individuals with MS compared to controls (p ≤ 0.002). Also, step length (p < 0.001) and step time (p < 0.001) variability were both significantly greater in MS compared to controls. EDSS was positively correlated with step length variability and individuals with MS who used assistive devices to walk had significantly greater step length variability than those who walked independently (p's < .05). EDSS was correlated with step time and length variability even when age was taken into account. Additionally, Fisher's z test of partial correlations revealed that average gait parameters were more closely related to disability status than gait variability in individuals with MS. This suggests that focusing on average gait parameters may be more important than variability in therapeutic interventions in MS.     

The relationship between pelvis–trunk coordination and low back pain in individuals with transfemoral amputations

Low back pain (LBP) is common in individuals with transfemoral amputation and may result from altered gait mechanics associated with prosthetic use. Inter-segmental coordination, assessed through continuous relative phase (CRP), has been used to identify specific patterns as risk factors. The purpose of this study was to explore pelvis and trunk inter-segmental coordination across three walking speeds in individuals with transfemoral amputations with and without LBP. Nine individuals with transfemoral amputations with LBP and seven without pain were compared to twelve able-bodied subjects. Subjects underwent a gait analysis while walking at slow, moderate, and fast speeds. CRP and CRP variability were calculated from three-dimensional pelvis and trunk segment angles. A two-way ANOVA and post hoc tests assessed statistical significance. Individuals with transfemoral amputation demonstrated some coordination patterns that were different from able-bodied individuals, but consistent with previous reports on persons with LBP. The patient groups maintained transverse plane CRP consistent with able-bodied participants (p = 0.966), but not sagittal (p < 0.001) and frontal plane CRP (p = 0.001). Sagittal and frontal CRP may have been re-optimized based on new sets of constraints, such as protective rigidity of the segments, muscular strength limitations, or prosthesis limitations. Patients with amputations and without LBP exhibited few differences. Only frontal and transverse CRP shifted toward out-of-phase as speed increased in the patient group with LBP. Although a cause and effect relationship between CRP and future development of back pain has yet to be determined, these results add to the literature characterizing biomechanical parameters of back pain in high-risk populations.     

The relationship between pelvis–trunk coordination and low back pain in individuals with transfemoral amputations

Low back pain (LBP) is common in individuals with transfemoral amputation and may result from altered gait mechanics associated with prosthetic use. Inter-segmental coordination, assessed through continuous relative phase (CRP), has been used to identify specific patterns as risk factors. The purpose of this study was to explore pelvis and trunk inter-segmental coordination across three walking speeds in individuals with transfemoral amputations with and without LBP. Nine individuals with transfemoral amputations with LBP and seven without pain were compared to twelve able-bodied subjects. Subjects underwent a gait analysis while walking at slow, moderate, and fast speeds. CRP and CRP variability were calculated from three-dimensional pelvis and trunk segment angles. A two-way ANOVA and post hoc tests assessed statistical significance. Individuals with transfemoral amputation demonstrated some coordination patterns that were different from able-bodied individuals, but consistent with previous reports on persons with LBP. The patient groups maintained transverse plane CRP consistent with able-bodied participants (p = 0.966), but not sagittal (p < 0.001) and frontal plane CRP (p = 0.001). Sagittal and frontal CRP may have been re-optimized based on new sets of constraints, such as protective rigidity of the segments, muscular strength limitations, or prosthesis limitations. Patients with amputations and without LBP exhibited few differences. Only frontal and transverse CRP shifted toward out-of-phase as speed increased in the patient group with LBP. Although a cause and effect relationship between CRP and future development of back pain has yet to be determined, these results add to the literature characterizing biomechanical parameters of back pain in high-risk populations.     

Foot-related pain and disability and spatiotemporal parameters of gait during self-selected and fast walking speeds in people with gout: A two-arm cross sectional study

ObjectivesTo examine gait parameters in people with gout during different walking speeds while adjusting for body mass index (BMI) and foot-pain, and to determine the relationship between gait parameters and foot-pain and disability.MethodGait parameters were measured using the GAITRite™ walkway in 20 gout participants and 20 age- and sex-matched controls during self-selected and fast walking speeds. Foot-pain and disability was measured using the Manchester Foot Pain and Disability Index (MFPDI) which contains four domains relating to function, physical appearance, pain and work/leisure.ResultsAt the self-selected speed, gout participants demonstrated increased step time (p = 0.017), and stance time (p = 0.012), and reduced velocity (p = 0.031) and cadence (p = 0.013). At the fast speed, gout participants demonstrated increased step time (p = 0.007), swing time (p = 0.005) and stance time (p = 0.019) and reduced velocity (p = 0.036) and cadence (p = 0.009). For participants with gout, step length was correlated with total MFPDI (r = −0.62, p = 0.008), function (r = −0.65, p = 0.005) and physical appearance (r = −0.50, p = 0.041); stride length was correlated with total MFPDI (r = −0.62, p = 0.008), function (r = −0.65, p = 0.005) and physical appearance (r = −0.50, p = 0.041); and velocity was correlated with total MFPDI (r = −0.60, p = 0.011), function (r = −0.63, p = 0.007) and work/leisure (r = −0.53, p = 0.030).ConclusionGait patterns exhibited by people with gout are different from controls during both self-selected and fast walking speeds, even after adjusting for BMI and foot-pain. Additionally, gait parameters were strongly correlated with patient-reported functional limitation, physical appearance and work/leisure difficulties, while pain did not significantly influence gait in people with gout.     

Sleep quality is associated with walking under dual-task,but not single-task performance

ObjectivesThe objective of this study was to assess the relationship between sleep behavior and gait performance under single-task (ST) and dual-task (DT) walking conditions in community- dwelling older adults.MethodsWalking under ST and DT conditions was evaluated in 34 community-dwelling older adults, 64.7% women, mean age 71.5 (SD ± 5.8). Gait-speed and gait-variability data were collected using the OPAL wearable sensors of the Mobility Lab. Sleep behavior (sleep efficiency [SE] and sleep latency [SL]) was assessed using actigraphy, over 5 consecutive nights.ResultsLower SE was associated with decreased gait speed and increased stride-length variability during DT (rs = 0.35; p = 0.04; rs = −0.36; p = 0.03, respectively), whereas longer SL was associated with increased stride-length variability during DT (rs = 0.38; p = .03). After controlling for age and cognition, SE accounted for 24% and 33% of the variability in stride length and stride time. No associations were found between sleep and gait measures under ST walking.ConclusionsLower SE is associated with decreased gait speed and increased gait variability under DT conditions that are indicative of an increased risk for falls in older adults. Our findings support clinical recommendations to incorporate the evaluation of sleep quality in the context of risk assessment for falls.     

Conflicting and non-conflicting visual cues lead to error in gait initiation and gait inhibition in individuals with freezing of gait

IntroductionWe asked whether conflicting visual cues influences gait initiation, gait inhibition and postural control in Parkinson’s disease (PD) between freezers, non-freezers and healthy older adults.MethodsTwenty-five PD participants on dopaminergic medication and 17 healthy older adults were asked to initiate or refrain gait depending on visual cues: green GO (GG), green STOP (GS), red GO (RG), red STOP (RS). Center of pressure (CoP) displacement, variability and mean velocity (VCoP) in the anterior-posterior (AP) and medial-lateral (ML) directions and movement time (MT) were measured.ResultsGait initiation: Both freezers and non-freezers were different from controls in GG and GS. In GS, freezers had smaller CoP displacement and velocity in both directions (p < 0.01), while non-freezers had smaller VCoP in AP and ML (p < 0.01). AP CoP displacement in GS was smaller in freezers compared to non-freezers (p < 0.05). Freezers had longer MT compared to controls in GG and compared to both groups in GS (p < 0.01). Gait inhibition: Controls and freezers had larger CoP displacement variability (p < 0.05) and velocity (p < 0.01) in both directions in RG compared to RS. No differences were seen in non-freezers. Three freezers initiated walking during the RG or RS conditions.ConclusionFreezers were in general slower at initiating gait, displayed a more restrictive postural strategy and were more affected by the conflicting conditions compared to both controls and non-freezers. In freezers, the conflicting visual cues may have increased the cognitive load enough to provoke delays in processing the visual information and implementing the appropriate motor program.     

Selective motor control correlates with gait abnormality in children with cerebral palsy

Children with bilateral cerebral palsy (CP) commonly have limited selective motor control (SMC). This affects their ability to complete functional tasks. The impact of impaired SMC on walking has yet to be fully understood. Measures of SMC have been shown to correlate with specific characteristics of gait, however the impact of SMC on overall gait pattern has not been reported. This study explored SMC data collected as part of routine gait analysis in children with bilateral CP.As part of their clinical assessment, SMC was measured with the Selective Control Assessment of the Lower Extremities (SCALE) in 194 patients with bilateral cerebral palsy attending for clinical gait analysis at a single centre. Their summed SCALE score was compared with overall gait impairment, as measured by Gait Profile Score (GPS).Score on SCALE showed a significant negative correlation with GPS (r_s = −0.603, p < 0.001). Cerebral injuries in CP result in damage to the motor tracts responsible for SMC. Our results indicate that this damage is also associated with changes in the development of walking pattern in children with CP.     

Further evidence of validity of the Gait Deviation Index

In this paper, the relationship of the Gait Deviation Index (GDI) to gross motor function and its ability to distinguish between different Gross Motor Function Classification System (GMFCS) levels was determined. A representative sample of 184 ambulant children with CP in GMFCS levels I (n = 57), II (n = 91), III (n = 22) and IV (n = 14) were recruited as part of a population-based study. Representative gait cycles were selected following a 3D gait analysis and gross motor function was assessed using the Gross Motor Function Measure (GMFM). GDI scores were calculated in Matlab. Valid 3D kinematic data were obtained for 173 participants and both kinematic and GMFM data were obtained for 150 participants. A substantial relationship between mean GDI and GMFM-66 scores was demonstrated (r = 0.70; p < 0.001) with significant differences in mean GDI scores between GMFCS levels (p < 0.001) indicating increasing levels of gait deviation in subjects less functionally able. The relationship between the GDI, GMFM and GMFCS in a representative sample of ambulators, lends further weight to the validity of the GDI scoring system. Furthermore it suggests that the subtleties of gait may not be wholly accounted for by gross motor function evaluation alone. Gait specific tools such as the GDI more likely capture both the functional and aesthetic components of walking.     

The influence of divided attention on walking turns: Effects on gait control in young adults with and without a history of low back pain

The cognitive control of gait is altered in individuals with low back pain, but it is unclear if this alteration persists between painful episodes. Locomotor perturbations such as walking turns may provide a sensitive measure of gait adaptation during divided attention in young adults. The purpose of this study was to investigate changes in gait during turns performed with divided attention, and to compare healthy young adults with asymptomatic individuals who have a history of recurrent low back pain (rLBP). Twenty-eight participants performed 90° ipsilateral walking turns at a controlled speed of 1.5 m/s. During the divided attention condition they concurrently performed a verbal 2-back task. Step length and width, trunk-pelvis and hip excursion, inter-segmental coordination and stride-to-stride variability were quantified using motion capture. Mixed-model ANOVA were used to examine the effect of divided attention and group, and interaction effects on the selected variables. Step length variability decreased significantly with divided attention in the healthy group but not in the rLBP group (post-hoc p = 0.024). Inter-segmental coordination variability was significantly decreased during divided attention (main effect of condition p < 0.000). There were small but significant reductions in hip axial and sagittal motion across groups (main effect of condition p = 0.044 and p = 0.040 respectively), and a trend toward increased frontal motion in the rLBP group only (post-hoc p = 0.048). These findings suggest that the ability to switch attentional resources during gait is altered in young adults with a history of rLBP, even between symptomatic episodes.     

Non-traditional wearing positions of pedometers: Validity and reliability of the Omron HJ-203-ED pedometer under controlled and free-living conditions

ObjectivesTo test the validity and intra-instrument reliability of the HJ-203 Omron pedometer when worn in different positions, under controlled and free-living conditions.DesignCross-sectional.MethodsForty healthy adults (20 men, 29.5 ± 7.7 years) participated in three controlled tests, i.e. 20 step test, stair climbing (up and down), and treadmill walking (five bouts at different speeds). All participants wore a HJ-203 pedometer in the pants pocket, in a carrier bag, and around the neck. Fifty-four adults (23 men, 33.9 ± 11.1 years) participated in a free-living conditions test, wearing a HJ-203 in the pants pocket and around the neck during one day.ResultsDuring controlled tests, absolute percentage error ranged between 0.1% and 14.0%. Accuracy was influenced by wearing position (p < 0.001), walking speed (p < 0.001), and wearing position × walking speed (p = 0.001). Accuracy was poor for pedometers worn in the pants pocket, especially at slower speeds; and best when worn around the neck. During free-living conditions, APE ranged between 30.7% and 36.9% and did not differ statistically between pants pocket and neck position. Intra-instrument reliability varied for controlled tests (ICC = 0.14–0.96) and was acceptable during free-living conditions (ICC = 0.94).ConclusionsThe HJ-203 Omron pedometer showed acceptable accuracy for all wearing positions during stairs walking and treadmill walking at higher speeds; but limited accuracy during free-living conditions when worn at non-traditional wearing positions (necklace and pants pocket). Reliability was acceptable during treadmill walking at higher speeds and free-living conditions.     

Effects of toe-out and toe-in gait with varying walking speeds on knee joint mechanics and lower limb energetics

Toe-out/-in gait has been prescribed in reducing knee joint load to medial knee osteoarthritis patients. This study focused on the effects of toe-out/-in at different walking speeds on first peak knee adduction moment (fKAM), second peak KAM (sKAM), knee adduction angular impulse (KAAI), net mechanical work by lower limb as well as joint-level contribution to the total limb work during level walking.Gait analysis of 20 healthy young adults was done walking at pre-defined normal (1.18 m/s), slow (0.85 m/s) and fast (1.43 m/s) walking speeds with straight-toe (natural), toe-out (15° > natural) and toe-in (15° < natural). Repeated measure ANOVA (p < 0.05) with post-hoc Tukey’s test was applied for statistical analysis.Toe-out gait increased fKAM at all walking speeds (highest at normal speed) while toe-in gait reduced fKAM at all speeds (highest at fast walking speed). Toeing-in reduced KAAI at all speeds while toeing-out affected KAAI only at normal speed. Increasing walking speed generally increased fKAM for all foot positions, but it did not affect sKAM considerably. Slowing down the speed, increased KAAI significantly at all foot positions except for toe-in. At slow walking speed, hip and knee joints were found to be major energy contributors for toe-in and toe-out respectively. At higher walking speeds, these contributions were switched. The ankle joint remained unaffected by changing walking speeds and foot progression angles.Toe-out/-in gait modifications affected knee joint kinetics and lower limb energetics at all walking speeds. However, their effects were inconsistent at different speeds. Therefore, walking speed should be taken into account when prescribing toe-out/-in gait.     

Energy cost of walking,symptomatic fatigue and perceived exertion in persons with multiple sclerosis

A higher energy cost of walking (Cw) is sometimes observed in MS, and could contribute to fatigue. The purpose of this study was to compare Cw at three speeds in MS and controls, and determine the effects of walking speed on fatigue and perceived exertion. We hypothesized that MS would have higher Cw, fatigue and exertion during walking than controls. Ten persons with MS and 14 controls of similar age and physical activity levels were studied. Oxygen consumption (VO₂) was obtained at rest and during treadmill walking at 0.6 and 1.4 m s⁻¹, and preferred speed. Cw was calculated as net VO₂:velocity. Fatigue and exertion were assessed using the visual analog fatigue and modified Borg scales, respectively. Preferred treadmill speed was not different between groups. Cw was higher in MS than controls across walking speeds (p = 0.003), with a group-by-speed interaction indicating higher Cw in MS at 0.6 m s⁻¹ (p = 0.001), but not at preferred speed or 1.4 m s⁻¹. MS reported greater fatigue (p = 0.001) and exertion (p = 0.004) at all speeds. Despite similar preferred speeds, and Cw at preferred and fast speeds, MS exhibited higher fatigue and exertion at all walking speeds. These results suggest that increased energy demands in MS are most notable at low speeds such as those used in everyday activities, which may contribute to fatigue over the day.     

A comparison of two walking while talking paradigms in aging

BackgroundOur study aimed to [1] compare dual-task costs in gait and cognitive performance during two dual-task paradigms: walking while reciting alternate letters of the alphabet (WWR) and walking while counting backward by sevens (WWC); [2] examine the relationship between the gait and cognitive interference tasks when performed concurrently.ScopeGait and cognitive performance were tested in 217 non-demented older adults (mean age 76 ± 8.8 years; 56.2% female) under single and dual-task conditions. Velocity (cm/s) was obtained using an instrumented walkway. Cognitive performance was assessed using accuracy ratio: [correct responses]/[total responses]. Linear mixed effects models revealed significant dual-task costs, with slower velocity (p < .01) and decreased accuracy ratio (p < .01) in WWR and WWC compared to their respective single task conditions. Greater dual-task costs in velocity (p < .01) were observed in WWC compared to WWR. Pearson correlations revealed significant and positive relationships between gait and cognitive performance in WWR and WWC (p < .01); increased accuracy ratio was associated with faster velocity.ConclusionsOur findings suggested that dual-task costs in gait increase as the complexity of the cognitive task increases. Furthermore, the positive association between the gait and cognitive tasks suggest that dual-task performance was not influenced by task prioritization strategies in this sample.     

Manipulating walking path configuration influences gait variability and six-minute walk test outcomes in older and younger adults

This study determined whether manipulations to walking path configuration influenced six-minute walk test (6MWT) outcomes and assessed how gait variability changes over the duration of the 6MWT in different walking path configurations. Healthy older (ODR) and younger (YNG) (n = 24) adults completed familiarisation trials and five randomly ordered experimental trials of the 6MWT with walking configurations of; 5, 10 and 15 m straight lines, a 6 m by 3 m rectangle (RECT), and a figure of eight (FIG8). Six-minute walk distance (6MWD) and walking speed (m.s⁻¹) were recorded for all trials and the stride count recorded for experimental trials. Reflective markers were attached to the sacrum and feet with kinematic data recorded at 100 Hz by a nine-camera motion capture system for 5 m, 15 m and FIG8 trials, in order to calculate variability in stride and step length, stride width, stride and step time and double limb support time. Walking speeds and 6MWD were greatest in the 15 m and FIG8 experimental trials in both groups (p < 0.01). Step length and stride width variability were consistent over the 6MWT duration but greater in the 5 m trial vs. the 15 m and FIG8 trials (p < 0.05). Stride and step time and double limb support time variability all reduced between 10 and 30 strides (p < 0.01). Stride and step time variability were greater in the 5 m vs. 15 m and FIG8 trials (p < 0.01). Increasing uninterrupted gait and walking path length results in improved 6MWT outcomes and decreased gait variability in older and younger adults.     

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.     

Insights into gait disorders: Walking variability using phase plot analysis,Huntington's disease

Huntington's disease (HD) is a progressive inherited neurodegenerative disorder. Identifying sensitive methodologies to quantitatively measure early motor changes have been difficult to develop. This exploratory observational study investigated gait variability and symmetry in HD using phase plot analysis. We measured the walking of 22 controls and 35 HD gene carriers (7 premanifest (PreHD)), 16 early/mid (HD1) and 12 late stage (HD2) in Oxford and Cardiff, UK. The unified Huntington's disease rating scale-total motor scores (UHDRS-TMS) and disease burden scores (DBS) were used to quantify disease severity. Data was collected during a clinical walk test (8.8 or 10 m) using an inertial measurement unit attached to the trunk. The 6 middle strides were used to calculate gait variability determined by spatiotemporal parameters (co-efficient of variation (CoV)) and phase plot analysis. Phase plots considered the variability in consecutive wave forms from vertical movement and were quantified by SD_A (spatiotemporal variability), SD_B (temporal variability), ratio ∀ (ratio SD_A:SD_B) and Δangleβ (symmetry). Step time CoV was greater in manifest HD (p < 0.01, both manifest groups) than controls, as was stride length CoV for HD2 (p < 0.01). No differences were found in spatiotemporal variability between PreHD and controls (p > 0.05). Phase plot analysis identified differences between manifest HD and controls for SD_B, Ratio ∀ and Δangle (all p < 0.01, both manifest groups). Furthermore Ratio ∀ was smaller in PreHD compared with controls (p < 0.01). Ratio ∀ also produced the strongest correlation with UHDRS-TMS (r = −0.61, p < 0.01) and was correlated with DBS (r = −0.42, p = 0.02). Phase plot analysis may be a sensitive method of detecting gait changes in HD and can be performed quickly during clinical walking tests.     

Dynamic instability during post-stroke hemiparetic walking

Falls and fall-related injuries cause extremely costly and potentially fatal health problems in people post-stroke. However, there is no global indicator of walking instability for detecting which individuals will have increased risk of falls. The purposes of this study were to directly quantify walking stability in stroke survivors and neurologically intact controls and to determine which stability measures would reveal the changes in walking stability following stroke. This study thus provided an initial step to establish objective measures for identifying potential fallers. Nine post-stroke individuals and nine controls walked on a treadmill at four different speeds. We computed short-term local divergence exponent (LDE) and maximum Floquet multiplier (maxFM) of the trunk motion, average and variability of dynamic margins of stability (MOS) and step spatiotemporal measures. Post-stroke individuals demonstrated larger short-term LDE (p = 0.002) and maxFM (p = 0.041) in the mediolateral (ML) direction compared to the controls but remained orbitally stable (maxFM < 1). In addition, post-stroke individuals walked with greater average step width (p = 0.003) but similar average ML MOS (p = 0.154) compared to the controls. Post-stroke individuals also exhibited greater variability in all MOS and step measures (all p < 0.005). Our findings indicate that post-stroke individuals walked with greater local and orbital instability and gait variability than neurologically intact controls. The results suggest that short-term LDE of ML trunk motion and the variability of MOS and step spatiotemporal measures detect the changes in walking stability associated with stroke. These stability measures may have the potential for identifying those post-stroke individuals at increased risk of falls.