Short-Term Effect of Prosthesis Transforming Sensory Modalities on Walking in Stroke Patients with Hemiparesis.

Sensory impairments caused by neurological or physical disorders hamper kinesthesia, making rehabilitation difficult. In order to overcome this problem, we proposed and developed a novel biofeedback prosthesis called Auditory Foot for transforming sensory modalities, in which the sensor prosthesis transforms plantar sensations to auditory feedback signals. This study investigated the short-term effect of the auditory feedback prosthesis on walking in stroke patients with hemiparesis. To evaluate the effect, we compared four conditions of auditory feedback from plantar sensors at the heel and fifth metatarsal. We found significant differences in the maximum hip extension angle and ankle plantar flexor moment on the affected side during the stance phase, between conditions with and without auditory feedback signals. These results indicate that our sensory prosthesis could enhance walking performance in stroke patients with hemiparesis, resulting in effective short-term rehabilitation.

Differences in kinetic factors affecting gait speed between lesion sides in patients with stroke.

The differences in kinetic mechanisms of decreased gait speed across brain lesion sides have not been elucidated, including the arrangement of motor modules reflected by kinetic interjoint coordination. The purpose of this study was to elucidate the differences in the kinetic factors of slow gait speed in patients with stroke on the lesion sides. A three-dimensional motion analysis system was employed to assess joint moment in the lower limb and representative gait parameters in 32 patients with right hemisphere brain damage (RHD) and 38 patients with left hemisphere brain damage (LHD) following stroke as well as 20 healthy controls. Motor module composition and timing were determined using principal component analysis based on the three joint moments in the lower limb in the stance phase, which were the variances accounted for principal components (PCs) and the peak timing in the time series of PCs. A stepwise multiple linear regression analysis was performed to identify the most significant joint moment and PC-associated parameter in explaining gait speed. A negligible difference was observed in age, weight, height, and gait speed among patients with RHD and LHD and controls. The following factors contributed to gait speed: in patients with RHD, larger ankle plantarflexion moment on the paretic (p = 0.001) and nonparetic (p = 0.002) sides and ankle dorsiflexion moment on the nonparetic side (p = 0.004); in patients with LHD, larger ankle plantarflexion moment (p < 0.001) and delayed peak timing of the first PC (p = 0.012) on the paretic side as well as ankle dorsiflexion moment on the nonparetic side (p < 0.001); in the controls, delayed peak timing of the first PC (p = 0.002) on the right side and larger ankle dorsiflexion moment (p = 0.001) as well as larger hip flexion moment on the left side (p = 0.023). The findings suggest that the kinetic mechanisms of gait speed may differ among patients with RHD following patients with stroke with LHD, and controls.

Effects of ankle-foot orthosis with dorsiflexion resistance on the quasi-joint stiffness of the ankle joint and spatial asymmetry during gait in patients with hemiparesis.

BACKGROUND: Reduced ankle quasi-joint stiffness affects propulsion in the paretic side of patients with hemiparesis, contributing to gait asymmetry. We investigated whether the use of an ankle-foot orthosis with dorsiflexion resistance to compensate for reduced stiffness would increase quasi-joint stiffness and spatiotemporal symmetry in patients with hemiparesis. METHODS: Seventeen patients walked along a 7-m walkway in both ankle-foot orthosis with dorsiflexion resistance and control (i.e., ankle-foot orthosis) conditions. Dorsiflexion resistance by spring and cam was set to increase linearly from zero-degree ankle dorsiflexion. Gait data were analyzed using a three-dimensional motion analysis system. FINDINGS: Ankle-foot orthosis with dorsiflexion resistance significantly increased the quasi-joint stiffness in the early and middle stance phase (P = 0.028 and 0.040). Furthermore, although ankle power generation in the ankle-foot orthosis with dorsiflexion resistance condition was significantly lower than in the control condition (P = 0.003), step length symmetry significantly increased in the ankle-foot orthosis with dorsiflexion resistance condition (P = 0.016). There was no significant difference in swing time ratio between conditions. INTERPRETATION: Applying dorsiflexion resistance in the paretic stance phase increased quasi-joint stiffness but did not lead to an increase in ankle power generation. On the other hand, applying dorsiflexion resistance also resulted in a more symmetrical step length, even though the ankle joint power generation on the paretic side did not increase as expected. Future research should explore whether modifying the magnitude and timing of dorsiflexion resistance, considering the biomechanical characteristics of each patients' ankle joint during gait, enhances ankle joint power generation.

Differences in kinematic parameters during gait between the patients with knee osteoarthritis and healthy controls using an insole with a single inertial measurement unit: A case-control study.

BACKGROUND: An inertial measurement unit is small and lightweight, allowing patient measurements without physical constraints. This study aimed to determine the differences in kinematic parameters during gait using an insole with a single inertial measurement unit in healthy controls and on both sides in patients with knee osteoarthritis. METHODS: Twenty patients with knee osteoarthritis and 13 age-matched controls were included in this study. The participants walked at a self-selected speed and foot kinematics were measured during gait using an insole with a single inertial measurement unit. The right side of the healthy controls and both the affected and contralateral sides of patients with KOA were analyzed separately. FINDINGS: The foot extension angular velocity at toe-off was significantly reduced on the affected side than on the contralateral side (P < 0.001) and in healthy controls (P < 0.001). During the swing phase, foot posterior-anterior acceleration was significantly lower on the affected side than on the healthy controls (P = 0.005). Furthermore, despite a decrease in walking speed, foot superior-inferior acceleration at initial contact in patients was significantly lower on the contralateral side than in healthy controls (P = 0.0167), but not on the affected side (P = 0.344). INTERPRETATION: An insole with a single inertial measurement unit can detect differences in foot kinematics during gait between healthy controls and patients with knee osteoarthritis. Our findings indicate that patients with knee osteoarthritis exhibit dysfunction of push-off at toe-off and shock absorption at initial contact on the affected side.

Gait classification of knee osteoarthritis patients using shoe-embedded internal measurement units sensor.

BACKGROUND: Knee osteoarthritis negatively affects the gait of patients, especially that of elderly people. However, the assessment of wearable sensors in knee osteoarthritis patients has been under-researched. During clinical assessments, patients may change their gait patterns under the placebo effect, whereas wearable sensors can be used in any environment. METHODS: Sixty patients with knee osteoarthritis and 20 control subjects were included in the study. Wearing shoes with an IMU sensor embedded in the insoles, the participants were required to walk along a walkway. The sensor data were collected during the gait. To discriminate between healthy and knee osteoarthritis patients and to classify different subgroups of knee osteoarthritis patients (patients scheduled for surgery vs. patients not scheduled for surgery; bilateral knee osteoarthritis diagnosis vs. unilateral knee osteoarthritis diagnosis), we used a machine learning approach called the support vector machine. A total of 88 features were extracted and used for classification. FINDINGS: The patients vs. healthy participants were classified with 71% accuracy, 85% sensitivity, and 56% specificity. The "patients scheduled for surgery" vs. "patients not scheduled for surgery" were classified with 83% accuracy, 83% sensitivity, and 81% specificity. The bilateral knee osteoarthritis diagnosis vs. unilateral knee osteoarthritis diagnosis was classified with 81% accuracy, 75% sensitivity, and 79% specificity. INTERPRETATION: Gait analysis using wearable sensors and machine learning can discriminate between healthy and knee osteoarthritis patients and classify different subgroups with reasonable accuracy, sensitivity, and specificity. The proposed approach requires no complex gait factors and is not limited to controlled laboratory settings.

Effects of Wearing Slippers While Obstacle Crossing in Healthy Young Adults: Strategy for Toe Clearance Enhancement and Prevention of Slipper Loss.

Wearing loose footwear, such as slippers, poses a risk factor for tripping. Previous studies have examined obstacle crossing to find strategies to avoid tripping. However, the effect of wearing slippers on the likelihood of tripping remains unclear. Therefore, this study aimed to determine whether wearing slippers while level walking and obstacle crossing affects kinematic characteristics and muscle activity. Sixteen healthy, young adults performed two tasks (a) while wearing slippers and (b) while barefoot: (1) level walking and (2) crossing a 10-cm obstacle. Toe clearance, joint angles, muscle activity, and cocontraction were measured for both the leading and trailing lower limbs. In the slipper-wearing condition, knee flexion and hip flexion angles were significantly increased in the swing phase for the leading limb (p < .001 and p < .001, respectively) and trailing limb (p < .001 and p = .004, respectively) compared with the barefoot condition. Tibialis anterior activity (p = .01) and muscle cocontraction of the tibialis anterior and the medial head of the gastrocnemius (p = .047) were significantly increased in the swing phase of the trailing limb for the slipper-wearing condition compared with the barefoot condition in the obstacle crossing task. Wearing slippers increased knee and hip flexion angles, and muscle cocontraction of the tibialis anterior and medial head of gastrocnemius increased during obstacle crossing. The results revealed that obstacle crossing while wearing slippers would require foot fixation adjustment in addition to increased knee and hip flexion to avoid toe collision.

Postural adjustment in standing position when catching a ball under unpredictable conditions of the direction to be caught.

Background: Balanced postural control of the body is associated with two mechanisms: anticipatory postural adjustment and compensatory postural adjustment. Previous studies reported changes in body postural control under unpredictable conditions (interference with closed eyes). Research question: To ascertain whether in contrast with predictable disturbances, there is a difference in muscle activity and center of pressure displacement changes when the direction of the disturbance is unpredictable. Methods: Three examiners stood at 45° to the left, the front, and 45° to the right of the participant to throw the ball to him. 11 healthy young participants were required to maintain their balance in the standing position after receiving the ball in conditions with and without known catching directions. The anticipatory postural adjustment and compensatory postural adjustment integral changes of the muscle activity in the lower limbs and trunk bilaterally and at the center of pressure displacement in the known and unknown conditions were observed. Two-way ANOVA was used to compare the differences in muscle activity and displacement changes. Results: Results showed that the center of pressure in the anticipatory postural adjustment and compensatory postural adjustment in the posterior direction with known catching direction was significantly shorter than those without. Integration of electromyogram in anticipatory postural adjustment of the right soleus (p = 0.023) was associated with higher muscle activities in the unknown than known conditions. Integration of electromyogram in compensatory postural adjustment of the right tibial anterior (p = 0.004), right rectus femoris (p = 0.023) and left rectus abdominis (p = 0.038) in unknown catching direction had significantly greater muscle activity than those without. When the direction of the perturbation is unpredictable, the central nervous system may initiate and induce greater center of pressure changes in the posterior direction with changes in several muscular activities to ensure postural control.

Effects of aging on whole-body center of mass movement and lower limb joint kinematics and kinetics during deep-squat movement.

Deep-squat movement is one of the most important activities for independent living. Although a large range of motion of lower extremity joints in the sagittal plane is required for deep-squat movement, older individuals exhibit reduced mobility of lower limb joints. However, the effect of aging on deep-squat movement remains unclear. The purpose of this study was to investigate the age-related changes in the whole-body movement and lower extremity joint kinematics and kinetics during deep-squat movement. Twelve older and nineteen younger individuals performed the deep-squat movement, with knee flexion exceeding 100 degrees, and a motion analysis system and force plates collected their motion data. The median (interquartile range) age of older and younger individuals was 76.5 (3.3) and 30.0 (9.0) years, respectively. The deep-squat depth was significantly shallower in older individuals than in younger individuals (P < 0.05). Furthermore, older individuals exhibited smaller ankle dorsiflexion and knee flexion angles, larger trunk flexion angles, and greater forward displacement of the whole-body center of mass during deep-squat movement (P < 0.05). In terms of kinetic variables, older individuals exhibited smaller contributions of knee extension moment and larger contributions of hip extension moment to the support moment in the timing of the maximum support moment during deep-squat movement (P < 0.05). Our results indicated that older individuals have greater difficulty with deeper-squat movement and smaller contribution of knee extension moment to support body weight using trunk, hip, and ankle movements during deep-squat movement.

Effect of Walking Adaptability on an Uneven Surface by a Stepping Pattern on Walking Activity After Stroke.

Real-world walking activity is important for poststroke patients because it leads to their participation in the community and physical activity. Walking activity may be related to adaptability to different surface conditions of the ground. The purpose of this study was to clarify whether walking adaptability on an uneven surface by step is related to daily walking activity in patients after stroke. We involved 14 patients who had hemiparesis after stroke (age: 59.4 ± 8.9 years; post-onset duration: 70.7 ± 53.5 months) and 12 healthy controls (age: 59.5 ± 14.2 years). The poststroke patients were categorized as least limited community ambulators or unlimited ambulators. For the uneven surface, the study used an artificial grass surface (7 m long, 2-cm leaf length). The subjects repeated even surface walking and the uneven surface walking trials at least two times at a comfortable speed. We collected spatiotemporal and kinematic gait parameters on both the even and uneven surfaces using a three-dimensional motion analysis system. After we measured gait, the subjects wore an accelerometer around the waist for at least 4 days. We measured the number of steps per day using the accelerometer to evaluate walking activity. Differences in gait parameters between the even and uneven surfaces were calculated to determine how the subjects adapted to an uneven surface while walking. We examined the association between the difference in parameter measurements between the two surface properties and walking activity (number of steps per day). Walking activity significantly and positively correlated with the difference in paretic step length under the conditions of different surface properties in the poststroke patients (r = 0.65, p = 0.012) and step width in the healthy controls (r = 0.68, p = 0.015). The strategy of increasing the paretic step length, but not step width, on an uneven surface may lead to a larger base of support, which maintains stability during gait on an uneven surface in poststroke patients, resulting in an increased walking activity. Therefore, in poststroke patients, an increase in paretic step length during gait on an uneven surface might be more essential for improving walking activity.

Two-Week Rehabilitation with Auditory Biofeedback Prosthesis Reduces Whole Body Angular Momentum Range during Walking in Stroke Patients with Hemiplegia: A Randomized Controlled Trial.

Walking rehabilitation is challenging in stroke patients with sensory impairments. In this study, we examined the two-week effect of an auditory biofeedback prosthesis, Auditory Foot (AF), on the change in the frontal whole body angular momentum (WBAM) range, before and after a two-week walking rehabilitation. We conducted a pilot randomized controlled trial (RCT). We employed statistical Bayesian modeling to understand the mechanism of the rehabilitation effect and predict the expected effect in new patients. The best-performing model indicated that the frontal WBAM range was reduced in the AF group by 12.9-28.7%. This suggests that the use of kinesthetic biofeedback in gait rehabilitation contributes to the suppression of frontal WBAM, resulting in an improved walking balance function in stroke patients.

Classification of Ankle Joint Stiffness during Walking to Determine the Use of Ankle Foot Orthosis after Stroke.

Categorization based on quasi-joint stiffness (QJS) may help clinicians select appropriate ankle foot orthoses (AFOs). The objectives of the present study were to classify the gait pattern based on ankle joint stiffness, also called QJS, of the gait in patients after stroke and to clarify differences in the type of AFO among 72 patients after stroke. Hierarchical cluster analysis was used to classify gait patterns based on QJS at least one month before the study, which revealed three distinct subgroups (SGs 1, 2, and 3). The proportion of use of AFOs, articulated AFOs, and non-articulated AFOs were significantly different among SGs 1-3. In SG1, with a higher QJS in the early and middle stance, the proportion of the patients using articulated AFOs was higher, whereas in SG3, with a lower QJS in both stances, the proportion of patients using non-articulated AFOs was higher. In SG2, with a lower QJS in the early stance and higher QJS in the middle stance, the proportion of patients using AFOs was lower. These findings indicate that classification of gait patterns based on QJS in patients after stroke may be helpful in selecting AFO. However, large sample sizes are required to confirm these results.

Effects of seat height on whole-body movement and lower limb muscle power during sit-to-stand movements in young and older individuals.

Sit-to-stand (STS) movements from low seat height are not easily executed by older individuals. Although young individuals increase their lower limb muscle power (LLMP) based on the product of the ground reaction force (GRF) and center of mass velocity (CoMv) during STS movement from a low seat height, it remains unclear whether seat height has an effect on LLMP during STS movement in older individuals. The present study aimed to investigate differences in the LLMP during STS movements when seat height is lowered between young and older individuals. Twelve older and twelve height-matched young individuals were instructed to perform STS movements from low (20 cm), middle (40 cm), and high (60 cm) seat heights. STS movement and GRF were obtained by a motion analysis system and force plates. In the low-seat-height condition, the forward and upward LLMPs and the upward CoMv were significantly lower in older individuals than those in young individuals, but the forward CoMv was not. The completion time of STS movement from a low seat height was significantly longer in older individuals than in young individuals. Our findings suggest that the slower upward CoMv due to the lower upward LLMP extends the completion time of STS movement from a low seat height in older individuals. Furthermore, in the low-seat-height condition, older individuals may move their center of mass (CoM) forward in a different way when compared with young individuals, and they may not use forward LLMP for moving CoM forward.

Comparison of handrail reaction forces between two different handrails during sit-to-stand movement in the elderly.

BACKGROUND: The handrail is an effective means of assisting sit-to-stand movements. As some elderly people need force to support their body during sit-to-stand movements because of instability and weakness; however, few handrails are specifically shaped to generate more force and support the body. This study aimed to investigate the effect of a newly designed curved-angled handrail on the reaction force during sit-to-stand movements in the elderly. METHODS: Twenty-one elderly subjects (age range, 72-84 years) participated in the study. They performed sit-to-stand movements using a conventional vertical handrail and then the curved-angled handrail five times each. For each subject, body coordinate data were acquired and the handrail reaction force was measured using motion analysis and load sensors on the handrail. FINDINGS: The reaction forces generated in the anterior-posterior and upward-downward directions during sit-to-stand movements using the curved-angled handrail were significantly greater than those generated using the conventional vertical handrail (p < .001). INTERPRETATION: Compared with using the conventional vertical handrail, using the curved-angled handrail enhances the generated force during sit-to-stand movements.

Finite element analysis of load transition on sacroiliac joint during bipedal walking.

The sacroiliac joint (SIJ) is burdened with variant loads. However, no methods have allowed to measure objectively how the SIJ deforms during bipedal walking. In this study, in-vivo walking conditions were replicated in a kinematic model combining the finite element method with 3D walking analysis data divided into five phases in order to visualize the load transition on the SIJ and clarify the role of the SIJ. Both models with and without inclusion of the SIJ were investigated. In models with bilateral SIJs, the displacement differed greatly between the sacrum and both hip bones on the SIJ as the boundary. The movements of the sacrum involved a nutation movement in the stance phase and a counter-nutation in the swing phase relative to the ilium. In models without SIJs, the displacement of the pelvis and loads of pelvic ligaments decreased, and the equivalent stress of the SIJs increased compared to the model with SIJs. The walking loads cause distortion of the entire pelvis, and stress concentration at the SIJ are seen due to the morphology of the pelvic ring. However, the SIJs help dissipate the resulting stresses, and the surrounding ligaments are likewise involved in load transmission.

Ankle-foot orthosis with dorsiflexion resistance using spring-cam mechanism increases knee flexion in the swing phase during walking in stroke patients with hemiplegia.

BACKGROUND: Ankle-foot orthoses with plantarflexion resistance (AFO-Ps) improve knee flexion in the stance phase on the paretic side in patients with hemiparesis. However, AFO-Ps decrease ankle power generation in the late stance phase and do not improve the knee flexion in the swing phase based on insufficient push-off at the late stance, resulting in lower toe clearance. RESEARCH QUESTION: This study sought to investigate the effect of an AFO with dorsiflexion resistance, which was implemented by our developed device with spring-cam mechanism attached to the AFO-P (Gait Solution; Pacific Supply Co., Ltd., Japan), on kinetics and kinematics in the lower limb during gait in patients with hemiparesis. METHODS: Eleven patients with hemiparesis due to stroke walked on a 7-m walkway at a self-selected comfortable pace in the following conditions: (a) walking using the AFO-P with the proposed device with a spring-cam mechanism (AFO-PCAM), (b) walking using the AFO-P without our device (AFO-P), and (c) walking using no device (barefoot condition). Gait kinematics and kinetics were collected using a three-dimensional motion analysis system and four ground-reaction force plates. Changes in all parameters from the barefoot to AFO-PCAM and AFO-P conditions were compared using the Wilcoxon signed-rank test. RESULTS: In the AFO-PCAM condition, decrease in the maximum ankle power generation in the late-stance phase was significantly smaller than that in the AFO-P condition (p = 0.041). We noted a significant higher change in knee flexion in the paretic swing phase in the AFO-PCAM condition relative to that in the AFO-P condition (p = 0.016). The effect size for the comparisons of change was large (r ≧ 0.5). SIGNIFICANCE: Our device facilitated the realization of the ankle plantarflexion power in the late-stance phase because of dorsiflexion resistance, increasing the knee flexion angle during the swing phase.

Difference in Pain and Discomfort of Comparable Wrist Movements Induced by Magnetic or Electrical Stimulation for Peripheral Nerves in the Dorsal Forearm.

PURPOSE: Both repetitive peripheral magnetic stimulation (rPMS) and transcutaneous electrical current stimulation (TES) could elicit the limb movements; it is still unclear how subjective sensation is changed according to the amount of limb movements. We investigated the pain and discomfort induced by newly developed rPMS and TES of peripheral nerves in the dorsal forearm. METHODS: The subjects were 12 healthy adults. The stimulus site was the right dorsal forearm; thus, when stimulated, wrist dorsiflexion was induced. The rPMS was delivered by the new stimulator, Pathleader at 10 stimulus intensity levels, and TES intensity was in 1-mA increments. The duration of each stimulation was 2 s. The analysis parameters were subjective pain and discomfort, measured by a numerical rating scale. The rating scale at corresponding levels of integrated range of movement (iROM) induced by rPMS or TES was compared. The subjective values were analyzed by two-way repeated measures ANOVA with the stimulus conditions (rPMS, TES) and the seven levels of iROM (20-140 ºs). RESULTS: In the rPMS experiments, stimuli were administered to all subjects at all stimulus intensities. In the TES experiments, none of the subjects dropped out between 1 and 16 mA, but there were dropouts at each of the intensities as follows: 1 subject at 17 mA, 20 mA, 22 mA, 23 mA, 27 mA, 29 mA and 2 subjects at 21 mA, 24 mA, 26 mA. The main effects of the stimulus conditions and iROM were significant for pain and discomfort. Post hoc analysis demonstrated that pain and discomfort in rPMS were significantly lower compared to TES when the iROM was above 60 ºs and 80 ºs, respectively. CONCLUSION: New rPMS stimulator, Pathleader, caused less pain and discomfort than TES, but this was only evident when comparatively large joint movements occurred.

Effects of shelf bar assistance on kinetic control during sit-to-stand in healthy young and elderly subjects.

This study aimed to determine the kinetic effects of using unilateral shelf bar, vertical grab bar (GB), and horizontal GB during sit-to-stand (STS) in young and elderly subjects. Twenty young adults aged 20-40 years and eighteen healthy elderly people aged ≥ 65 years old were recruited. The subjects performed STS with and without using the three types of bars. Bar reaction force (BRF) and maximum power (MP) defined as the maximal product calculated by multiplying the GRF and the velocity of the center of mass in each direction were measured using three-dimensional motion analysis, two load sensors of GB, and four force plates. The use of the shelf bar generated a significantly larger BRF in the vertical direction than the other bars (p < 0.05) and lower MP in the vertical direction than the horizontal bar (p < 0.05) and no bar (p < 0.05). In the younger subjects, only the use of the vertical bar generated a significantly larger BRF (p < 0.05) and negative MP (p < 0.05) in the forward direction than those in elderly subjects. The use of the shelf bar may assist the decreased MP in the vertical direction during STS in elderly people, resulting in decrease of failed STS in daily living. In contrast, the use of the vertical bar in the elderly may not generate sufficient BRF in the forward direction because of lack of eccentric control in the whole body in the forward direction during STS.

The differences in sagittal plane whole-body angular momentum during gait between patients with hemiparesis and healthy people.

Regulation of whole-body angular momentum (WBAM) is essential for maintaining dynamic balance during gait. Patients with hemiparesis frequently fall toward the anterior direction; however, whether this is due to impaired WBAM control in the sagittal plane during gait remains unknown. The present study aimed to investigate the differences in WBAM in the sagittal plane during gait between patients with hemiparesis and healthy individuals. Thirty-three chronic stroke patients with hemiparesis and twenty-two age- and gender-matched healthy controls walked along a 7-m walkway while gait data were recorded using a motion analysis system and force plates. WBAM and joint moment were calculated in the sagittal plane during each gait cycle. The range of WBAM in the sagittal plane in the second half of the paretic gait cycle was significantly larger than that in the first and second halves of the right gait cycle in the controls (P = 0.015 and P = 0.011). Furthermore, multiple regression analysis revealed the slower walking speed (P < 0.001) and larger knee extension moment on the non-paretic side (P = 0.003) contributed to the larger range of WBAM in the sagittal plane in the second half of the paretic gait cycle. Our findings suggest that dynamic stability in the sagittal plane is impaired in the second half of the paretic gait cycle. In addition, the large knee extension moment on the non-paretic side might play a role in the dynamic instability in the sagittal plane during gait in patients with hemiparesis.

Three-dimensional GRF and CoP Estimation during Stair and Slope Ascent/Descent with Wearable IMUs and Foot Pressure Sensors.

Wearable systems for gait analysis in daily living have been recently developed. Previous studies have demonstrated the significant potential of these systems; however, most of them focused on the level-walking condition, which is a limited portion of daily activities. To provide a new contribution to the gait analysis field, we have developed the first models for estimating three-dimensional (3D) ground reaction force (GRF) and center of pressure (CoP) during stair and slope ascent/descent with wearable sensors. Our system comprises light weight inertial measurement units (IMUs) and foot pressure sensors. We modeled the correlation between the measurements obtained with the wearable sensors and the ground truth of GRF/CoP from force plates, on the basis of linear regression models. Twenty healthy subjects completed a collection of ascent/descent tasks on stairs or slopes. We tested our models using cross-validation to evaluate the estimation accuracy in terms of the root mean square error (RMSE), the normalized RMSE (NRMSE), and the Pearson's correlation coefficient between the estimated GRF/CoP and those obtained from force plates. The experimental results showed practical estimation accuracy was obtained for GRF (RMSE ≤ 44.94 N) and CoP (RMSE ≤19.43 mm). Our system promises to contribute to clinical and sports medicine research by serving as a novel tool for assessing stair and slope ascent/descent outside laboratory environments.

Influence of thoracic posture on scapulothoracic and glenohumeral motions during eccentric shoulder external rotation.

BACKGROUND: Throwing injuries to the shoulder joint often occur during shoulder external rotation. An appropriate combination of thoracic, scapular, and humeral motion during throwing is important to prevent such injuries, but it is unclear how thoracic posture contributes to shoulder motion during throwing. RESEARCH QUESTION: The purpose of this study, therefore, was to clarify the influence of thoracic posture on scapulothoracic and glenohumeral motion during shoulder external rotation. METHODS: Eccentric external rotation at 90° of shoulder abduction in thoracic flexion and extension postures was performed by 15 asymptomatic participants. Three-dimensional scapulothoracic and glenohumeral movements were measured with an electromagnetic tracking device at 75°, 80°, 85°, and maximum shoulder external rotation. The thoracic angle and maximum shoulder external rotation in absolute coordination were measured with a three-dimensional motion capture system. RESULTS: The results showed that scapular posterior tilting and external rotation in the thoracic extension posture were significantly greater than those in the flexion posture (p < 0.05). Glenohumeral horizontal extension was significantly less in the thoracic extension posture than in the flexion posture (p < 0.05), whereas maximum shoulder external rotation was significantly greater (p < 0.01). Thus, thoracic extension increased scapulothoracic posterior tilting and external rotation and reduced glenohumeral horizontal extension during shoulder external rotation, as well as increasing maximum shoulder external rotation. SIGNIFICANCE: These findings suggest that thoracic extension may contribute to reduction of mechanical demand in the glenohumeral joint during throwing, potentially reducing shoulder injuries.