Comparison of kinematics and joint moments calculations for lower limbs during gait using markerless and marker-based motion capture.

Objective: This study aimed at quantifying the difference in kinematic and joint moments calculation for lower limbs during gait utilizing a markerless motion system (TsingVA Technology, Beijing, China) in comparison to values estimated using a marker-based motion capture system (Nokov Motion Capture System, Beijing, China). Methods: Sixteen healthy participants were recruited for the study. The kinematic data of the lower limb during walking were acquired simultaneously based on the markerless motion capture system (120 Hz) and the marker-based motion capture system (120 Hz). The ground reaction force was recorded synchronously using a force platform (1,200 Hz). The kinematic and force data were input into Visual3D for inverse dynamics calculations. Results: The difference in the lower limb joint center position between the two systems was the least at the ankle joint in the posterior/anterior direction, with the mean absolute deviation (MAD) of 0.74 cm. The least difference in measuring lower limb angles between the two systems was found in flexion/extension movement, and the greatest difference was found in internal/external rotation movement. The coefficient of multiple correlations (CMC) of the lower limb three joint moments for both systems exceeded or equaled 0.75, except for the ad/abduction of the knee and ankle. All the Root Mean Squared Deviation (RMSD) of the lower limb joint moment are below 18 N·m. Conclusion: The markerless motion capture system and marker-based motion capture system showed a high similarity in kinematics and inverse dynamic calculation for lower limbs during gait in the sagittal plane. However, it should be noted that there is a notable deviation in ad/abduction moments at the knee and ankle.

A contactless monitoring system for accurately predicting energy expenditure during treadmill walking based on an ensemble neural network.

The monitoring of treadmill walking energy expenditure (EE) plays an important role in health evaluations and management, particularly in older individuals and those with chronic diseases. However, universal and highly accurate prediction methods for walking EE are still lacking. In this paper, we propose an ensemble neural network (ENN) model that predicts the treadmill walking EE of younger and older adults and stroke survivors with high precision based on easy-to-obtain features. Compared with previous studies, the proposed model reduced the estimation error by 13.95% and 66.20% for stroke survivors and younger adults, respectively. Furthermore, a contactless monitoring system was developed based on Kinect, mm-wave radar, and ENN algorithms, and the treadmill walking EE was monitored in real time. This ENN model and monitoring system can be combined with smart devices and treadmill, making them suitable for evaluating, monitoring, and tracking changes in health during exercise and in rehabilitation environments.

The deer play in Wuqinxi and four-point hand-knee kneeling positions for training core muscle function and spinal mobility.

The four-point kneeling exercise is a core stabilization exercise that provides the spine with dynamic stability and neuromuscular control. In the traditional Chinese exercise Wuqinxi, deer play is performed in a hand-foot kneeling (HFK) position, which is remarkably similar to the four-point hand-knee kneeling (HKK) position. However, the differences in spinal function promotion between these two positions are poorly understood. The aim of this study was to investigate muscle activation patterns and spinal kinematics during specific core stabilization training to provide evidence for selecting specific exercises. A total of 19 healthy adults were recruited to perform HFK and HKK. The rotation angle of the C7-T4 vertebra and the surface EMG signals of abdominal and lumbar muscles on both sides were collected. The paired t-test showed that the vertebral rotation angles were significantly higher during HKK than HFK, and the intra-group differences mainly occurred at the level of the thoracic vertebra. The muscle activation of both sides of the rectus abdominis and external oblique in HFK was significantly higher than in HKK when the upper limb was lifted (p < 0.05). The activation of the ipsilateral lumbar multifidus and erector spinae muscles was significantly higher during the HKK position than during HFK when the lower limb was lifted (p < 0.05). HFK provided more training for strengthening abdominal muscles, while HKK could be recommended for strengthening lumbar muscles and increasing spine mobility. These findings can be used to help physiotherapists, fitness coaches, and others to select specific core exercises and develop individualized training programs.

Subcutaneous Fat Thickness Remarkably Influences Contact Pressure and Load Distribution of Buttock in Seated Posture.

Spinal cord injury patients are prone to develop deep tissue injury (DTI) as they may spend half their time per day in sitting postures, which produce excessive load in their buttocks. However, the impact of fat thickness on the biomechanical response of buttock in sitting posture remained unclear. This study aimed to investigate the influence of subcutaneous fat thickness on the interface pressure and load distribution of buttock of seated humans. To achieve this goal, a 3-dimensional finite element model of male buttock was constructed and the contact pressure on a rigid cushion was evaluated against experimental results. The modified models, which had various fat thicknesses under ischial tuberosity, were built and used to simulate the sitting conditions with different cushion stiffnesses. In the models simulating sitting on the rigid cushion, the peak contact pressure ranges from 0.052 MPa to 0.149 MPa. In the simulation of sitting on the soft cushion, the peak stress of muscle underneath ischial tuberosity in the model with the thickest fat tissue was slightly higher than that of the other models. The results demonstrate that the fat tissue in the buttock could reduce the contact pressure when sitting on the rigid seat. However, contact pressure solely could not be used to estimate the internal tissue stress of seated buttock, especially in subjects with thicker fat tissue.

[Biomechanical analysis of ankle-foot complex during a typical Tai Chi movement-Brush Knee and Twist Step].

The purpose of this study is to analyze the biomechanics of ankle cartilage and ligaments during a typical Tai Chi movement-Brush Knee and Twist Step (BKTS). The kinematic and kinetic data were acquired in one experienced male Tai Chi practitioner while performing BKTS and in normal walking. The measured parameters were used as loading and boundary conditions for further finite element analysis. This study showed that the contact stress of the ankle joint during BKTS was generally less than that during walking. However, the maximum tensile force of the anterior talofibular ligament, the calcaneofibular ligament and the posterior talofibular ligament during BKTS was 130 N, 169 N and 89 N, respectively, while it was only 57 N, 119 N and 48 N during walking. Therefore, patients with arthritis of the ankle can properly practice Tai Chi. Practitioners with sprained lateral ligaments of the ankle joint were suggested to properly reduce the ankle movement range during BKTS.

Muscle Fatigue Enhance Beta Band EMG-EMG Coupling of Antagonistic Muscles in Patients With Post-stroke Spasticity.

There is a significant influence of muscle fatigue on the coupling of antagonistic muscles while patients with post-stroke spasticity are characterized by abnormal antagonistic muscle coactivation activities. This study was designed to verify whether the coupling of antagonistic muscles in patients with post-stroke spasticity is influenced by muscle fatigue. Ten patients with chronic hemipare and spasticity and 12 healthy adults were recruited to participate in this study. Each participant performed a fatiguing isometric elbow flexion of the paretic side or right limb at 30% maximal voluntary contraction (MVC) level until exhaustion while surface electromyographic (sEMG) signals were collected from the biceps brachii (BB) and triceps brachii (TB) muscles during the sustained contraction. sEMG signals were divided into the first (minimal fatigue) and second halves (severe fatigue) of the contraction. The power and coherence between the sEMG signals of the BB and TB in the alpha (8-12 Hz), beta (15-35 Hz), and gamma (35-60 Hz) frequency bands associated with minimal fatigue and severe fatigue were calculated. The coactivation ratio of the antagonistic TB muscle was also determined during the sustained fatiguing contraction. The results demonstrated that there was a significant decrease in maximal torque during the post-fatigue contraction compared to that during the pre-fatigue contraction in both stroke and healthy group. In the stroke group, EMG-EMG coherence between the BB and TB in the alpha and beta frequency bands was significantly increased in severe fatigue compared to minimal fatigue, while coactivation of antagonistic muscle increased progressively during the sustained fatiguing contraction. In the healthy group, coactivation of the antagonistic muscle showed no significant changes during the fatiguing contraction and no significant coherence was found in the alpha, beta and gamma frequency bands between the first and second halves of the contraction. Therefore, the muscle fatigue significantly increases the coupling of antagonistic muscles in patients with post-stroke spasticity, which may be related to the increased common corticospinal drive from motor cortex to the antagonistic muscles. The increase in antagonistic muscle coupling induced by muscle fatigue may provide suggestions for the design of training program for patients with post-stroke spasticity.

Short-Step Adjustment and Proximal Compensatory Strategies Adopted by Stroke Survivors With Knee Extensor Spasticity for Obstacle Crossing.

Stroke survivors adopt cautious or compensatory strategies for safe and successful obstacle crossing. Although knee extensor spasticity is a common independent secondary sensorimotor disorder post-stroke, few studies have examined the step adjustment and compensatory strategies used by stroke survivors with knee extensor spasticity during obstacle crossing. This study aimed to compare the differences in the kinematics and kinetics during obstacle crossing between stroke survivors with and without knee extensor spasticity, and to identify knee extensor spasticity-related differences in step adjustment and compensatory strategies. Twenty stroke subjects were divided into a spasticity group [n = 11, modified Ashworth scale (MAS) ≥ 1] and a non-spasticity group (n = 9, MAS = 0), based on the MAS score of the knee extensor. Subjects were instructed to walk at a self-selected speed on a 10-m walkway and step over a 15 cm obstacle. A ten-camera 3D motion analysis system and two force plates were used to collect the kinematic and kinetic data. During the pre-obstacle phase, stroke survivors with knee extensor spasticity adopted a short-step strategy to approach the obstacle, while the subjects without spasticity used long-step strategy. During the affected limb swing phase, the spasticity group exhibited increased values that were significantly higher than those seen in the non-spasticity group for the following measurements: pelvic lateral tilt angle, trunk lateral tilt angle, medio-lateral distance between the ankle and ipsilateral hip joint, hip work contributions, the inclination angles between center of mass and center of pressure in anterior-posterior and medio-lateral directions. These results indicate that the combined movement of the pelvic, trunk lateral tilt, and hip abduction is an important compensatory strategy for successful obstacle crossing, but it sacrifices some balance in the sideways direction. During the post-obstacle phase, short-step and increase step width strategy were adopted to reestablish the walking pattern and balance control. These results reveal the step adjustment and compensatory strategies for obstacle crossing and also provide insight into the design of rehabilitation interventions for fall prevention in stroke survivors with knee extensor spasticity.

Body weight support-Tai Chi footwork for balance of stroke survivors with fear of falling: A pilot randomized controlled trial.

BACKGROUND AND PURPOSE: Balance impairment is the predominant risk factor for falls in stroke survivors. This study examined the effects of body weight support-Tai Chi (BWS-TC) footwork on balance control among stroke survivors with fear of falling (FOF). MATERIALS AND METHODS: Twenty-eight stroke survivors with FOF were randomly allocated to either control or BWS-TC groups. Those in BWS-TC underwent Tai Chi training for 12 weeks. Outcomes were assessed in all participants by evaluation of the limits of stability test, modified clinical test of sensory integration of balance, fall risk index, and Fugl-Meyer assessment of lower limbs at baseline and 12 weeks. RESULTS: The BWS-TC group displayed significant enhancement in dynamic control and vestibular and somatosensory integration. CONCLUSION: BWS-TC may enhance dynamic control and sensory integration of balance and reduce the risk of fall in stroke survivors with FOF.