Muscle force estimation from lower limb EMG signals using novel optimised machine learning techniques

The main objective of this work is to establish a framework for processing and evaluating the lower limb electromyography (EMG) signals ready to be fed to a rehabilitation robot. We design and build a knee rehabilitation robot that works with surface EMG (sEMG) signals. In our device, the muscle forces are estimated from sEMG signals using several machine learning techniques, i.e. support vector machine (SVM), support vector regression (SVR) and random forest (RF). In order to improve the estimation accuracy, we devise genetic algorithm (GA) for parameter optimisation and feature extraction within the proposed methods. At the same time, a load cell and a wearable inertial measurement unit (IMU) are mounted on the robot to measure the muscle force and knee joint angle, respectively. Various performance measures have been employed to assess the performance of the proposed system. Our extensive experiments and comparison with related works revealed a high estimation accuracy of 98.67% for lower limb muscles. The main advantage of the proposed techniques is high estimation accuracy leading to improved performance of the therapy while muscle models become especially sensitive to the tendon stiffness and the slack length.

In Vitro Mitral Valve Model with Unrestricted Ventricular Access: Using Vacuum to Close the Valve and Enable Static Trans-Mitral Pressure

Current in vitro models of the left heart establish the pressure difference required to close the mitral valve by sealing and pressurizing the ventricular side of the valve, limiting important access to the subvalvular apparatus. This paper describes and evaluates a system that establishes physiological pressure differences across the valve using vacuum on the atrial side. The subvalvular apparatus is open to atmospheric pressure and accessible by tools and sensors, establishing a novel technique for experimentation on atrioventricular valves. Porcine mitral valves were excised and closed by vacuum within the atrial chamber. Images were used to document and analyze closure of the leaflets. Papillary muscle force and regurgitant flow rate were measured to be 4.07 N at 120 mmHg and approximately 12.1 ml/s respectively, both of which are within clinically relevant ranges. The relative ease of these measurements demonstrates the usefulness of improved ventricular access at peak pressure/force closure. Graphical abstract

Study on the Release of Muscle Passive Force by Ultrasonic Mechanical Effect and its Related Mechanism

Background: Excessive muscle force impedes physical movement and relaxing passive muscle force substantially improves movement impairment. Ultrasound is an energy carrier with the characteristics of repetitive mechanical stimulation, which may be a feasible method to relieve muscle tension.Methods: We performed stress relaxation experiments on soleus muscle and combine the obtained results with the standard linear solid model to extract information of viscoelastic effect of ultrasound on muscle, and calculated muscle fibril content by histological analysis.Results: Ultrasound can accelerate muscle stress relaxation; the viscosity and elasticity coefficient of the ultrasound group was higher than that of the control group, and there was no significant difference between the three ultrasound intensities; H&E staining showed that muscle fibrillar content decreased and the matrix substance increased.Conclusion: We considered that ultrasound can change the microstructure of muscle, and the matrix substance plays a significant role in the relaxation process. In this paper, the relationship between muscle viscoelasticity and passive muscle force is obtained. The results provide an important theoretical basis and a feasible method for monitoring muscle functional characteristics by measuring muscle viscoelasticity.

The energetic basis for smooth human arm movements

The central nervous system plans human reaching movements with stereotypically smooth kinematic trajectories and fairly consistent durations. Smoothness seems to be explained by accuracy as a primary movement objective, whereas duration seems to economize energy expenditure. But the current understanding of energy expenditure does not explain smoothness, so that two aspects of the same movement are governed by seemingly incompatible objectives. Here we show that smoothness is actually economical, because humans expend more metabolic energy for jerkier motions. The proposed mechanism is an underappreciated cost proportional to the rate of muscle force production, for calcium transport to activate muscle. We experimentally tested that energy cost in humans (N=10) performing bimanual reaches cyclically. The empirical cost was then demonstrated to predict smooth, discrete reaches, previously attributed to accuracy alone. A mechanistic, physiologically measurable, energy cost may therefore explain both smoothness and duration in terms of economy, and help resolve motor redundancy in reaching movements.

Effects of a Single Session of Floss Band Intervention on Flexibility of Thigh, Knee Joint Proprioception, Muscle Force Output, and Dynamic Balance in Young Adults

The floss band (FB) has been correlated with increases in the joint range of motion (ROM). However, the literature on FB effectiveness in knee joint ROM and athletic performance remains sparse. This study investigated the effects of FB on the flexibility of the quadriceps and hamstrings, knee joint proprioception, muscle force output, and dynamic balance in men. Thirty recreationally active men without musculoskeletal disorders were randomized to receive FB (Lime Green; Sanctband flossband) and elastic bandage (EB) intervention on the dominant knee joint. Participants received two interventions on two occasions with 2 days of rest between interventions. The primary outcome was the flexibility of the quadriceps and hamstrings; the secondary outcomes were knee proprioception (joint reposition angle error), knee muscle force output, and dynamic balance. Preintervention and postintervention (immediately following band removal and 20 min later) measurements were obtained. After FB intervention, hamstring flexibility (immediately: p < 0.001; 20 min later: p < 0.001) and quadriceps flexibility (immediately: p < 0.001; 20 min later: p < 0.001), quadriceps muscle force output (immediately: p = 0.007; 20 min later: p < 0.001), and dynamic balance (both immediately and 20 min later, p < 0.001) were significantly improved. Compared with EB intervention, FB intervention significantly improved knee extension ROM (immediately and 20 min later, both p < 0.001), knee flexion ROM (immediately, p = 0.01; 20 min later, p = 0.03), hamstrings muscle force output (20 min later, p = 0.022) and dynamic balance (immediately, p = 0.016; 20 min later, p = 0.004). Regarding proprioception, no significant difference among time points and conditions was observed. In conclusion, FB intervention can significantly improve the flexibility of the quadriceps and hamstrings, quadriceps muscle force output, and dynamic balance without impeding knee proprioception. Physiotherapists or athletic professionals may consider FB intervention as a potential tool as a warmup to enhance the flexibility of the quadriceps and hamstrings, quadriceps muscle force output, and dynamic balance in young adults.

Biomechanical Characteristics of Vertical Jumping of Preschool Children in China Based on Motion Capture and Simulation Modeling

Vertical jumping is one of the basic motor skills, and it is an essential part of many sports. The main purpose of this paper is to investigate characteristics of vertical jumping of children. This paper uses a motion capture system, three-dimensional platforms, and a simulation modeling system to analyze the kinematics and dynamics performance of children’s vertical jumping. The compression time increases from 3 to 4 years old, and flight height and time increases with age and stage gradually. In the compression phase and pushing phase, the hip and knee joint play a major role; in the landing phase, the knee and ankle joint play a major role. Muscle forces are mainly affected by age, and the three types of muscle force had two different trends. The muscle force of the shank and thigh increased with age, and the pelvic girdle muscles showed an “low–high–low” trend. The regression model suggests that the force of GMiP and the hip angular velocity have a great influence on jumping ability. Therefore, if we want to improve the jumping ability of preschool children, we should pay more attention to hip exercises. We should integrate the hip exercises into interesting games, which are more in line with their physical and mental health.

Limb Muscle Reinnervation with the Nerve-Muscle-Endplate Grafting Technique: An Anatomical Feasibility Study

Background. Peroneal nerve injuries results in tibialis anterior (TA) muscle paralysis. TA paralysis could cause “foot drop,” a disabling condition that can make walking difficult. As current treatment methods result in poor functional recovery, novel treatment approaches need to be studied. The aim of this study was to explore anatomical feasibility of limb reinnervation with our recently developed nerve-muscle-endplate grafting (NMEG) in the native motor zone (NMZ). Methods. As the NMEG-NMZ technique involves in nerves and motor endplates (MEPs), the nerve supply patterns and locations of the MEP bands within the gastrocnemius (GM) and TA muscles of rats were investigated using Sihler’s stain and whole-mount acetylcholinesterase (AChE) staining, respectively. Five adult rats underwent TA nerve transaction. The denervated TA was reinnervated by transferring an NMEG pedicle from the ipsilateral lateral GM. At the end of a 3-month recovery period, maximal muscle force was measured to document functional recovery. Results. The results showed that the TA was innervated by the deep peroneal nerve. A single MEP band was located obliquely in the middle of the TA. The GM was composed of two neuromuscular compartments, lateral (GM-l) and medial (GM-m), each of which was innervated by a separate nerve branch derived from the tibial nerve and had a vertically positioned MEP band. The locations of MEP bands in the GM and TA muscles and nerve supply patterns demonstrated that an NMEG pedicle can be harvested from the GM-l and implanted into the NMZ within the TA muscle. The NMEG-NMZ pilot study showed that this technique resulted in optimal muscle force recovery. Conclusion. NMEG-NMZ surgery is feasible for limb reinnervation. Specifically, the denervated TA caused by peroneal nerve injuries can be reinnervated with a NMEG from the GM-l.

The Effect of Lower-Limb Exercise on Pain Management of the Patients Undergoing Posterior Lumbar Fusion Surgery: A Retrospective Case-Control Study

Purpose. The purpose of this study is to investigate the clinical effect of lower-limb exercise, when combined with celecoxib, on pain management of patients undergoing posterior lumbar fusion surgeries. Methods. The patients undergoing posterior lumbar fusion surgeries between 01/2018 and 06/2021 were retrospectively identified, with their data collected. After surgery, some patients took celecoxib for analgesia (celecoxib group, 200 mg/day) while the others took celecoxib together with lower-limb exercise (combined group, celecoxib-200 mg/day). On postoperative days (POD) 1, 3, 7, and 14, data were collected and analyzed regarding the following items: patient satisfaction, lower-limb muscle force, lumbar JOA score (29 points), Oswestry Disability Index (ODI), and visual analog scale (VAS) score. Results. A total of 225 participants were included in this study. Specifically, 120 cases were admitted into in the celecoxib group and 105 were included in the combined group. Comparisons of baseline data did not indicate any difference between the combined group and the celecoxib group. Data analysis showed that patient satisfaction in the combined group was significantly higher than the celecoxib group on POD 3, 7, and 14, respectively (all p < 0.001 ). Moreover, the combined group had less VAS score compared with the celecoxib group on POD 3, 7, and 14, respectively (all p < 0.01 ). In addition, lower-limb muscle force in the combined group was significantly stronger than that in the celecoxib group on POD 3 and POD 7, respectively (both p < 0.01 ). Furthermore, the combined group achieved less ODI score than the celecoxib group on POD 3, 7, and 14, respectively (all p < 0.05 ). Comparisons of the lumbar JOA score did not suggest any statistical difference during the whole follow-up period. Conclusions. In conclusion, postoperative lower-limb rehabilitation exercise can help to release pain after lumbar fusion surgeries. Additionally, postoperative lower-limb exercise can facilitate the recovery of lower-limb muscle force, as well as improving patient satisfaction.