Neural Correlates of Abnormal Cortical Gait Control in Parkinson's Disease: A Whole-Gait-Cycle EEG Study.

OBJECTIVE: Electroencephalography (EEG) with high time-resolution allows for recording dynamic cortical activity during walking and provides new insight into the underlying pathophysiology of gait impairments in PD. However, traditional gait-phase-specific EEG analysis only measures the brain activities in the isolated gait phase, but neglects the between-gait-phase interactions as well as the whole-gait-cycle characteristics, and therefore is unable to effectively reflect the abnormal cortical gait control. METHODS: In this study, we introduced three whole-gait-cycle measures of intra-stride EEG activity (i.e., mean desynchronization, amplitude of fluctuations, and coupling to the gait phase), and investigated their abnormalities in PD and relationships with gait impairments, which were further compared with the traditional gait-phase-specific measures. RESULTS: Compared with healthy controls, PD patients showed overwhelming stronger desynchronizations (ERD) across the whole gait cycle in θ, α and low-ß bands, implying a cortical compensatory strategy in response to the low efficiency of the motor network. Patients also exhibited weaker intra-stride ERD fluctuations in the central area in α and low-ß bands, with reduced amplitude and less coupling to the gait phase, which were correlated with gait impairments in walking speed, gait rhythm and walking stability. However, gait-phase-specific EEG measures did not show any significant correlation with gait impairments in PD. CONCLUSION: Our results demonstrated the efficiency of whole-gait-cycle EEG measures in characterizing the abnormal cortical gait control, and for the first time, associated gait impairments with weak intra-stride electrocortical fluctuations. SIGNIFICANCE: The findings may shed light on the development of cortical-targeted interventions for PD.

Investigation of gait and balance function in cervical spondylotic myelopathy patients using wearable sensors.

BACKGROUND CONTEXT: Cervical spondylotic myelopathy (CSM) is a degenerative disease caused by cervical cord compression and can lead to the significant impairment of motor function including gait and balance disturbances and changes in lower extremity muscle activity. PURPOSE: This study aimed to characterize gait, balance and lower extremity muscle activity in patients with CSM compared to age-matched healthy controls (HCs) using wearable sensors in the clinical setting. STUDY DESIGN: Nonrandomized, prospective cohort study. PATIENT SAMPLE: Ten CSM patients and 10 age-matched HCs were recruited for this study. OUTCOME MEASURES: Gait and balance function parameters contained spatial temporal parameters, step regularity (SR1), stride regularity (SR2) and harmonic ratio (HR). EMG muscle activity parameters included time to peak and peak value during loading, stance, and swing phase. METHODS: In this study, parameters of gait and balance function were extracted using triaxial accelerometer attached to the spinous processes of Lumbar 5 while participants performed an overground walking at a self-preferred speed. Moreover, muscular activity was simultaneously recorded via sEMG sensors attached to tibialis anterior (TA), rectus femoris (RF), bicep femoris (BF), and gastrocnemius lateral (GL). Independent sample t test was used to find the differences between CSM patients and HCs. RESULTS: Gait analysis showed cadence, step length and walking speed were statistically significantly lower in CSM patients than HCs. Stride time was significantly higher for CSM patients in comparison to HCs. Lower root mean square ratio (RMSR) of acceleration in the mediolateral (ML) direction, HR in the anteroposterior (AP) direction, SR1 in the AP direction and SR2 in all three directions were observed in CSM patients. For muscle activity analysis, EMG RMS for TA and RF during loading phase and RMS for GL during midstance phase was significantly lower for CSM patients, while significantly higher value was observed for RF RMS during midstance phase and GL RMS during swing phase in CSM patients. CONCLUSION: Our pilot study shows that wearable sensors are able to detect the changes of gait, balance and lower extremity muscle activities of CSM patients in the clinical setting. This pilot study sets the stage for future researches on the diagnosis and monitor progression of CSM disease using wearable technology.

The effect of visual cues on muscular activation in the lower limbs of Parkinson's disease patients with freezing of gait: a preliminary study.

Freezing of gait (FOG) is a disabling symptom of Parkinson's disease (PD) patients, especially in advanced stages. Visual cues, such as the laser, have been confirmed to improve kinematic performance and alleviate FOG incidences. However, the muscular effect is unknown. In this study, we aim to investigate the effect of visual cues on muscular activity in the lower limbs of PD patients with FOG. Surface EMG signals of the tibialis anterior (TA), lateral gastrocnemius (GL), rectus femoris (RF), and biceps femoris (BF) muscles were collected from eight patients (FOGer) and eight healthy elderly (HC) in both normal walking and walking with laser cues. Results showed that visual cues improved FOGer's muscular activation pattern towards normal. The RMS of TA was significantly increased in the loading response phase (p=0.02) and decreased in the pre-swing phase for FOGer (p=0.005) under visual cue. The RMS of GL in FOGer was considerably reduced in the loading response phase (p<0.001) and increased in the pre-swing phase (p=0.008) of their gait cycle. A significant strong correlation was also observed between the decrement in GL RMS during the loading response phase and the increment in GL RMS during the pre-swing phase (R=-0.952, p<0.001) incurred by visual cue in FOGer. These results indicate that the visual cues can help FOGer to modulate their muscular activation of ankle muscles, especially to normalize GL's activation distribution during stance. For clinical purposes, future rehabilitative strategies aimed at the modulation of ankle muscles are suggested.

Walking stability in patients with benign paroxysmal positional vertigo: an objective assessment using wearable accelerometers and machine learning.

BACKGROUND: Benign paroxysmal positional vertigo (BPPV) is one of the most common peripheral vestibular disorders leading to balance difficulties and increased fall risks. This study aims to investigate the walking stability of BPPV patients in clinical settings and propose a machine-learning-based classification method for determining the severity of gait disturbances of BPPV. METHODS: Twenty-seven BPPV outpatients and twenty-seven healthy subjects completed level walking trials at self-preferred speed in clinical settings while wearing two accelerometers on the head and lower trunk, respectively. Temporo-spatial variables and six walking stability related variables [root mean square (RMS), harmonic ratio (HR), gait variability, step/stride regularity, and gait symmetry] derived from the acceleration signals were analyzed. A support vector machine model (SVM) based on the gait variables of BPPV patients were developed to differentiate patients from healthy controls and classify the handicapping effects of dizziness imposed by BPPV. RESULTS: The results showed that BPPV patients employed a conservative gait and significantly reduced walking stability compared to the healthy controls. Significant different mediolateral HR at the lower trunk and anteroposterior step regularity at the head were found in BPPV patients among mild, moderate, and severe DHI (dizziness handicap inventory) subgroups. SVM classification achieved promising accuracies with area under the curve (AUC) of 0.78, 0.83, 0.85 and 0.96 respectively for differentiating patients from healthy controls and classifying the three stages of DHI subgroups. Study results suggest that the proposed gait analysis that is based on the coupling of wearable accelerometers and machine learning provides an objective approach for assessing gait disturbances and handicapping effects of dizziness imposed by BPPV.

Biomechanical differences before and after arthroscopic partial meniscectomy in patients with semilunar and discoid lateral meniscus injury.

The purpose of the current study was to investigate the differences in knee kinematics and kinetics in patients with semilunar lateral meniscus (SLM) and discoid lateral meniscus (DLM) injuries before and after arthroscopic partial meniscectomy during level walking. Fifteen healthy volunteers (control group), thirteen patients with SLM injury (SLM group) and nine patients with DLM injury (DLM group) were enrolled in our study. Gait analyses were performed pre- and post-operatively during level walking at a self-selected walking speed. Our results showed that compared to the control group before surgery, the SLM and DLM groups showed significantly lower walking speed, shorter stride length, lower maximum knee flexion during stance phase and swing phase, lower first peak knee flexion moment, and smaller adduction-abduction range of motion (ROM) during the gait cycle. Compared to the control group, only the DLM group showed significantly decreased flexion-extension ROM and maximum abduction angle. The first peak knee adduction moment was lower in the SLM group than in the control group. Significant difference was observed in first peak knee flexion moment between SLM and DLM groups. After surgery, there were no significant differences in gait spatiotemporal parameters, knee kinematics, and kinetics between the three groups, indicating that meniscectomy is an effective treatment for both types of injury. By using three-dimensional gait analysis, the current results revealed that lateral meniscus types influence gait patterns after injury, which may further impact clinical treatment choice and long-term prognosis.

Prediction of Freezing of Gait in Patients With Parkinson's Disease by Identifying Impaired Gait Patterns.

Freezing of gait (FoG) prediction, combined with rhythmic laser cues, may help Parkinson's disease (PD) patients overcome FoG episodes. This study aimed to utilize the impaired gait patterns preceding FoG to build a machine-learning-based model for FoG prediction. Acceleration signals were collected using an accelerometer attached to the lower back of 12 PD patients with FoG while they were performing designed FoG-provoking walking tasks. Step-based impaired gait features and conventional FoG detection features were extracted from the signals, based on which two FoG prediction models were built using AdaBoost to validate if the use of the impaired gait features can better predict FoG. For the correct labeling of the gait prior to FoG (pre-FoG), the personalized pre-FoG phase was defined according to the slope of the impaired gait pattern. The impaired gait features were relabeled based on the pre-FoG phase upon which the personalized labeled FoG prediction model was built. This was compared with the model built using unified labeling. Results showed that impaired gait features could better predict FoG than conventional FoG detection features with low time latency, and personalized labeling could further improve the FoG prediction accuracy. Using impaired gait features and personalized labeling, we built a FoG prediction model with 0.93 sec of latency. Compared to using conventional features and unified labeling, our model achieved 5.7% higher accuracy (82.7%) in patient-dependent test and 9.8% higher accuracy (77.9%) in patient-independent test. Therefore, using the impaired gait patterns is a promising approach to accurately predict FoG with low latency.

Quantitative gait analysis for laser cue in Parkinson's disease patients with freezing of gait.

BACKGROUND: The aim of this study was to investigate the gait spatiotemporal, kinematic, and kinetic changes of Parkinson's disease (PD) patient with freezing of gait (FOG) under the laser cue (LC). Such an approach may provide greater insight into the effects of LC on gait. METHODS: Thirty-four PD with FOG (PD + FOG) and 32 healthy controls (HC) were tested in gait laboratory. Patients were tested at their usual self-selected speed in no laser cue (NC) first and then under LC condition. Sagittal plane kinematic and kinetic parameters of the lower-limb joints (hip, knee, and ankle joints) as well as spatiotemporal parameters (velocity, cadence, stride length, single and double support time), were measured. Spatiotemporal parameters and kinematic were submitted to one-way analysis of variance (ANOVA) to explore difference among NC, LC, and HC. Covariance analysis was used to compare kinetic parameters. RESULTS: For PD + FOG, spatiotemporal parameters (stride length, velocity, and cadence) were significantly improved in LC (1.06±0.18, 1.01±0.19, 120±13.26, respectively) compared with NC (0.93±0.20, 0.87±0.17, 131±14.75) (P=0.027, 0.045, 0.035, respectively), and close to HC (1.1±0.12, 1.12±0.13, 116±9.37) (P=0.594, 0.276, 0.084, respectively). In kinematics, LC could significantly ameliorate the amplitude of maximal dorsiflexion in ankle (35.1±3.8), extension in stance in knee (16.8±4.3) and hip (4.43±5.1), as well as the range of motion (ROM) in ankle (33.15±6.1) and hip joints (38.6±3.3). In kinetics, LC also markedly improved power generation in ankle (2.03±1.52) and hip joints (1.08±0.48) and power absorption in pre-swing phase in knee joint (-1.68±0.29) compared with NC (1.37±1.13, 0.899±0.43, -1.31±0.27, respectively). CONCLUSIONS: LC significantly improves gait performance in spatiotemporal parameters as well as kinematics and kinetics performance in ankle and hip joints. LC may be promising when applied as an optional technique in the rehabilitation training in PD + FOG.

Three-Dimensional Porous Scaffolds with Biomimetic Microarchitecture and Bioactivity for Cartilage Tissue Engineering.

Ideal tissue-engineering cartilage scaffolds should possess the same nanofibrous structure as the microstructure of native cartilage as well as the same biological function provided by the microenvironment for neocartilage regeneration. In the present study, three-dimensional composite biomimetic scaffolds with different concentration ratios of electrospun gelatin-polycaprolactone (gelatin-PCL) nanofibers and decellularized cartilage extracellular matrix (DCECM) were fabricated. The nanofibers with the biomimetic microarchitecture of native cartilage served as a skeleton with excellent mechanical properties, and the DCECM served as a biological functionalization platform for the induction of cell response and the promotion of cartilage regeneration. Experimental results showed that the composite nanofiber/DCECM (NF/DCECM) scaffolds had stronger mechanical properties and structural stability in wet state compared with those of DCECM scaffolds. In vitro experiments demonstrated that all scaffolds had good biocompatibility, but the chondrocyte proliferation rate of the composite NF/DCECM scaffolds was higher than that of the NF scaffolds. In vitro and in vivo cartilage regeneration results indicated that the DCECM component of the composite scaffolds facilitated early maturation of the cartilage lacuna and the secretion of collagen and glycosaminoglycan. The macroscopic and histological results at 12 weeks postsurgery exhibited that the composite NF/DCECM scaffolds yielded better cartilage repair outcomes than those of the nontreated group and NF scaffolds group. Overall, the present study demonstrated that the structurally and functionally biomimetic NF/DCECM scaffold is a promising tissue engineering scaffold for cartilage regeneration and cartilage defect repair.

Decellularized cartilage matrix scaffolds with laser-machined micropores for cartilage regeneration and articular cartilage repair.

Decellularized allogeneic and xenogeneic articular cartilage matrix scaffolds (CMS) are considered ideal scaffolds for cartilage regeneration owing to their heterogeneous architecture, and biochemical and biomechanical properties of native articular cartilage. However, the dense structure of the articular cartilage extracellular matrix, particularly the arrangement of collagen fibers, limits cellular infiltration, leading to poor cartilage regeneration. In addition, the incomplete removal of xenograft cells is associated with immunogenic reaction in the host. To facilitate the migration of chondrocytes into scaffolds and the rate of decellularization processing, we applied a carbon dioxide laser technique to modify the surface of porcine CMS while retaining major properties of the scaffold. By optimizing the laser parameters, we introduced orderly, lattice-arranged conical micropores of suitable depth and diameter onto the cartilage scaffold surface without affecting the cartilage shape or mechanical properties. We found that laser-modified CMS (LM-CMS) could enhance the degree of decellularization and were conducive to cell adhesion, as compared with the intact CMS. Decellularized scaffolds were seeded with rabbit-derived chondrocytes and cultured for 8 weeks in vitro. We found that cell-scaffold constructs formed cartilage-like tissue within the micropores and on the scaffold surface. In vivo, we found that cell-scaffold constructs subcutaneously implanted into the flanks of nude mice formed ivory-white neocartilage with high contents of DNA and cartilage matrix components, as well as good mechanical strength as compared with native CMS. Furthermore, scaffolds combined with autogenous chondrocytes induced neocartilage and better structural restoration at 8 weeks after transplantation into rabbit knee articular cartilage defects. In conclusion, decellularized xenogeneic CMS with laser-machined micropores offers an ideal scaffold with high fidelity for the functional reconstruction of articular cartilage.

Local Dynamic Stability of the Locomotion of Lower Extremity Joints and Trunk During Backward Upslope Walking.

Backward slope walking was considered as a practical rehabilitation and training skill. However, its gait stability has been hardly studied, resulting in its limited application as a rehabilitation tool. In this study, the effect of walking direction and slope grade were investigated on the local dynamic stability of the motion of lower extremity joints and trunk segment during backward and forward upslope walking (BUW/FUW). The local divergence exponents (λS) of 16 adults were calculated during their BUW and FUW at grades of 0%, 5%, 10%, and 15%. Mean standard deviation over strides (MeanSD) was analyzed as their gait variability. Backward walking showed larger λS for the abduction-adduction and rotational angles of knee and ankle on inclined surface than forward walking, while λS for hip flexion-extension angle at steeper grades was opposite. No grade effect for any joint existed during BUW, while λS increased with the increasing grade during FUW. As to the trunk, walking direction did little impact on λS. Still, significant larger λS for its medial-lateral and vertical motion were found at the steeper grades during both FUW and BUW. Results indicate that during BUW, the backward direction may influence the stability of joint motions, while the trunk stability was challenged by the increasing grades. Therefore, BUW may be a training tool for the stability of both upper and lower body motion during gait.

Knockdown of Sox2 Inhibits OS Cells Invasion and Migration via Modulating Wnt/ß-Catenin Signaling Pathway.

Osteosarcoma (OS) was a prevalent malignant bone tumor which threatens people's health worldwide. Wnt/ß catenin signaling pathway had been proved significant in various cancers, indicating its possible function in OS as well. Sox2, a crucial member among SOX family could regulate cells biologically. How Sox2 modulated Wnt/ß catenin signaling pathway in OS remained to be discussed. The study aimed to investigate the effects of Sox2 on the invasion and migration of OS cells and the related molecular mechanisms. Twenty-four human OS and adjacent tissue samples were involved in this study. Human OS cell lines MG63 and HOS were selected for further investigation. The liposome carrier si-Sox2 which could interfere with the expression of Sox2 gene was built to transfect MG63 and HOS cells). QRT-PCR assay and western blot were utilized to analyze the expression of mRNA and proteins of Sox2. Transwell assay and wound healing assay were conducted to test the invasion and migration level of cells. The expression of GSK3, ß-catenin, cyclin D1 and c-myc proteins were detected by western blot assay after transfection with si-Sox2. Compared with normal tissues and cells, the expression of Sox2 in OS tissues and cells was significantly higher. The mRNA and protein levels of Sox2 significantly decreased after transfection with si-Sox2. The invasion and migration of OS cells were down-regulated significantly through the inhibition of Sox2 by inactivating Wnt/ß-catenin signaling pathway related proteins. Knockdown of Sox2 could inhibit invasion and migration of OS cells via modulating Wnt/ß-catenin signaling pathway.

MiR-127-3p inhibits cell growth and invasiveness by targeting ITGA6 in human osteosarcoma.

Osteosarcoma (OS) is one of the most universal malignant bone tumors that occur mostly in children and adolescents. This study aimed to investigate the roles of miR-127-3p and integrin subunit-α 6 (ITGA6) in OS proliferation, apoptosis, invasion and migration, and to explore the possible molecular mechanism and target relationship. By conducting quantitative real-time polymerase chain reaction (qRT-PCR) and western blot, the microRNA (miRNA) and protein expressions of miR-127-3p and ITGA6 in both tissues and cells were determined. The expression of apoptosis and migration related were also detected by western blot. The target relationship between miR-127-3p and ITGA6 was predicted by TargetScan and verified by dual-luciferase reporter assay. The biological functions of miR-127-3p and ITGA6 in OS were investigated by following experiments: cell counting kit 8 (CCK-8) and colony formation assays to inspect cell proliferation, flow cytometry, and caspase 3 activity assay to examine apoptosis, and transwell and wound healing assays to analyze invasion and migration. Significant down-regulation of miR-127-3p and up-regulation of ITGA6 was found out in OS tissues and cells. ITGA6 was proved to be the downstream target gene of miR-127-3p and functioned as a tumor promotor in OS, while miR-127-3p restrained deterioration of OS by suppressing cell viability, reducing migration and invasion, and promoting apoptosis. MiR-127-3p suppressed proliferation, invasion, and migration while stimulated apoptosis of OS cells through knocking down ITGA6. © 2018 IUBMB Life, 70(5):411-419, 2018.

Effect of active arm swing to local dynamic stability during walking.

Arm swing is an essential component in regulating dynamic stability of the whole body during walking, while the contribution of active arm swing to local dynamic stability of different motion segments remains unclear. This study investigated the effects of arm swing under natural arm swing condition and active arm swing condition on local dynamic stability and gait variability of the trunk segments (C7 and T10 joint) and lower extremity joints (hip, knee and ankle joint). The local divergence exponents (λs) and mean standard deviation over strides (MeanSD) of 24 young healthy adults were calculated while they were walking on treadmill with two arm swing conditions at their preferred walking speed (PWS). We found that in medial-lateral direction, both λs and MeanSD values of the trunk segments (C7 and T10 joint) in active arm swing condition were significantly lower than those in natural arm swing condition (p<0.05), while no significant difference of λs or MeanSD in lower extremity joints (hip, knee and ankle joint) was found between two arm swing conditions (p>0.05, respectively). In anterior-posterior and vertical direction, neither λs nor MeanSD values of all body segments showed significant difference between two arm swing conditions (p>0.05, respectively). These findings indicate that active arm swing may help to improve the local dynamic stability of the trunk segments in medial-lateral direction.

Local dynamic stability of the trunk segments and lower extremity joints during backward walking.

Backward walking has become a popular training method in physical exercise and clinical rehabilitation. For the sake of safety, it is important to keep a stable gait during backward walking. However, the gait stability during backward walking was rarely studied. This study investigated the effects of walking direction on local dynamic stability of the trunk segments (neck, torso and pelvis) and lower extremity joints (hip, knee and ankle joint). The maximum Lyapunov exponents (λ(s)) of 17 young healthy male adults were calculated while they were walking under three conditions: backward walking with preferred walking speed (BW), forward walking (FW) with the same speed determined by BW, and forward walking with normal speed (FWN). We found that compared with FW, BW showed significant higher values of λ(s) in the trunk segments in vertical (VT) direction (p<0.05). The torso segment also displayed a higher value of λ(s) in anterior-posterior (AP) direction (p<0.01); Higher values of λ(s) during BW were found in the rotation (RT) motion of hip and knee joint (p=0.036, and p=0.009, respectively), and in the abduction/adduction (AB/AD) motion of knee and ankle joint (p=0.013, and p=0.021, respectively). The significant effect of walking speed was found between FW and FWN condition in VT direction (p<0.01). These findings indicate that backward walking did impair the local dynamic stability in trunk segments and lower extremity joints. Especially, the negative effect of BW on the poor gait stability in the AP direction of torso segment, and AB/AD and RT motion of knee joint should not be neglected.

Geraniin suppresses RANKL-induced osteoclastogenesis in vitro and ameliorates wear particle-induced osteolysis in mouse model.

Wear particle-induced osteolysis and subsequent aseptic loosening remains the most common complication that limits the longevity of prostheses. Wear particle-induced osteoclastogenesis is known to be responsible for extensive bone erosion that leads to prosthesis failure. Thus, inhibition of osteoclastic bone resorption may serve as a therapeutic strategy for the treatment of wear particle induced osteolysis. In this study, we demonstrated for the first time that geraniin, an active natural compound derived from Geranium thunbergii, ameliorated particle-induced osteolysis in a Ti particle-induced mouse calvaria model in vivo. We also investigated the mechanism by which geraniin exerts inhibitory effects on osteoclasts. Geraniin inhibited RANKL-induced osteoclastogenesis in a dose-dependent manner, evidenced by reduced osteoclast formation and suppressed osteoclast specific gene expression. Specially, geraniin inhibited actin ring formation and bone resorption in vitro. Further molecular investigation demonstrated geraniin impaired osteoclast differentiation via the inhibition of the RANKL-induced NF-κB and ERK signaling pathways, as well as suppressed the expression of key osteoclast transcriptional factors NFATc1 and c-Fos. Collectively, our data suggested that geraniin exerts inhibitory effects on osteoclast differentiation in vitro and suppresses Ti particle-induced osteolysis in vivo. Geraniin is therefore a potential natural compound for the treatment of wear particle induced osteolysis in prostheses failure.

Kinematic characteristics of gait in middle-aged adults during level walking.

Middle-aged people have shown a high fall incidence and degeneration in gait stability, while few studies concern that. This study aimed to assess the kinematic characteristics of gait in middle-aged people compared with younger and older ones during level walking, and to find sensitive indicators to characterize degenerated gait stability in middle-aged people. 13 middle-aged (mean age=52.1 years), with 13 older (mean age=74.8 years) and 13 young (mean age=23.3 years) healthy adults participated in this study. We assessed following gait parameters of the subjects during their level walking: 1) temporal-spatial gait parameters: normalized gait velocity, stride length, step length and their variability; 2) gait stability parameters: acceleration root mean square (RMS) of COM and its variability; and instantaneous COM-COP inclination angles. Compared with young and older subjects, middle-aged adults showed no significant difference in temporal-spatial gait parameters and their stride-to-stride variability (P>0.050); Compared with young subjects, middle-aged adults showed a significant higher value in medial-lateral (ML) direction of acceleration RMS of COM (P=0.038) and its stride-to-stride variability (P=0.030), as well as in COM-COP inclination angle (P=0.003). There was no significant difference in the above two parameters of gait stability between middle-aged and older subjects (P>0.050). Results illustrated that middle-aged subjects showed similar degenerated pattern in gait stability as the older ones in ML direction. Gait stability parameters, including ML acceleration of COM and its variability, as well as ML COM-COP inclination angle may help to characterize this degenerated gait stability. It's necessary for us to develop early interventions for middle-aged adults to prevent falls during walking.

Development of robust behaviour recognition for an at-home biomonitoring robot with assistance of subject localization and enhanced visual tracking.

Our research is focused on the development of an at-home health care biomonitoring mobile robot for the people in demand. Main task of the robot is to detect and track a designated subject while recognizing his/her activity for analysis and to provide warning in an emergency. In order to push forward the system towards its real application, in this study, we tested the robustness of the robot system with several major environment changes, control parameter changes, and subject variation. First, an improved color tracker was analyzed to find out the limitations and constraints of the robot visual tracking considering the suitable illumination values and tracking distance intervals. Then, regarding subject safety and continuous robot based subject tracking, various control parameters were tested on different layouts in a room. Finally, the main objective of the system is to find out walking activities for different patterns for further analysis. Therefore, we proposed a fast, simple, and person specific new activity recognition model by making full use of localization information, which is robust to partial occlusion. The proposed activity recognition algorithm was tested on different walking patterns with different subjects, and the results showed high recognition accuracy.

Local dynamic stability of lower extremity joints in lower limb amputees during slope walking.

Lower limb amputees have a higher fall risk during slope walking compared with non-amputees. However, studies on amputees' slope walking were not well addressed. The aim of this study was to identify the difference of slope walking between amputees and non-amputees. Lyapunov exponents λS was used to estimate the local dynamic stability of 7 transtibial amputees' and 7 controls' lower extremity joint kinematics during uphill and downhill walking. Compared with the controls, amputees exhibited significantly lower λS in hip (P=0.04) and ankle (P=0.01) joints of the sound limb, and hip joints (P=0.01) of the prosthetic limb during uphill walking, while they exhibited significantly lower λS in knee (P=0.02) and ankle (P=0.03) joints of the sound limb, and hip joints (P=0.03) of the prosthetic limb during downhill walking. Compared with amputees level walking, they exhibited significantly lower λS in ankle joints of the sound limb during both uphill (P=0.01) and downhill walking (P=0.01). We hypothesized that the better local dynamic stability of amputees was caused by compensation strategy during slope walking.

Contribution of arm swing to dynamic stability based on the nonlinear time series analysis method.

It is human nature to swing their arms at the frequency of leg motion during walking, but the contribution of arm swing to dynamic stability of human motion segments was poorly understood. Based on the nonlinear time series analysis method, the objective of this study was to investigate the effects of arm swing in three conditions (natural, active and restricted arm swing) on the dynamic stability of spine and lower extremity joints, and to further assess the contribution of arm swing to the human dynamic stability in relation with age. Gait experiments were carried out for 10 young and 8 middle-aged healthy volunteers while walking with natural, active and restricted arm swing. The maximum finite time lyapunov exponents were calculated to quantify the local dynamic stability of spine and lower extremity joints under three arm swing conditions, and the percentage change of the maximum Lyapunov exponents was compared between two groups to evaluate the effectiveness of active arm swing in relation with age. For both young and middle-aged groups, no significant difference of the maximum lyapunov exponents of all motion segments was found between walking with natural arm swing and with restricted arm swing (P>0.05). However, the maximum lyapunov exponents of all motion segments while walking with active arm swing was significantly lower than those while walking with natural arm swing and restricted arm swing, respectively (P<0.05), and the percentage decrease of the maximum lyapunov exponents for all motion segments while walking with active arm swing was significantly higher in middle-aged group than in young group (P<0.05). These results indicated that active arm swing would help to improve dynamic stability of human motion segments, especially more effective with age.