Search Results (40)

The volitional control of powered assistive devices is commonly performed by mapping the electromyographic (EMG) activity of the lower limb to joints’ angular kinematics, which are then used as the input for regulation. However, during walking, the ground reaction force (GRF) plays a central role in the modulation of the gait, providing dynamic stability and propulsion during the stance phase. Including this information within the control loop of prosthetic devices can improve the quality of the final output, providing more physiological walking dynamics that enhances the usability and patient comfort. In this work, we explored the feasibility of the estimation of the ground reaction force vertical component (VGRF) by using only the EMG activities of the thigh and shank muscles. We compared two deep learning models in three experiments that involved different muscular configurations. Overall, the outcomes show that the EMG signals could be leveraged to obtain a reliable estimation of the VGRF during walking, and the shank muscles alone represent a viable solution if a reduced recording setup is needed. On the other hand, the thigh muscles failed in providing performance enhancements, either when used alone or together with the shank muscles. The results outline the feasibility of including GRF information within an EMG-driven control scheme for prosthetic and assistive devices. Full article

Inclusive design does not stop at removing physical obstacles such as staircases. It also involves identifying architectural features that impose sensory burdens, such as repetitive visual patterns that are known to potentially cause dizziness or visual discomfort. In order to assess their influence on human gait and its stability, three repetitive patterns—random dots, repetitive stripes, and repetitive waves (Lisbon pattern)—were displayed in a coloured and greyscale variant in a virtual reality (VR) environment. The movements of eight participants were recorded using a motion capture system and electromyography (EMG). During all test conditions, a significant increase in the muscular activity of leg flexor muscles was identified just before touchdown. Further, an increase in the activity of laterally stabilising muscles during the swing phase was observed for all of the test conditions. The lateral and vertical centre of mass (CoM) deviation was statistically evaluated using a linear mixed model (LMM). The patterns did cause a significant increase in the CoM excursion in the vertical direction but not in the lateral direction. These findings are indicative of an inhibited and more cautious gait style and a change in control strategy. Furthermore, we quantified the induced discomfort by using both algorithmic estimates and self-reports. The Fourier-based methods favoured the greyscaled random dots over repetitive stripes. The colour metric favoured the striped pattern over the random dots. The participants reported that the wavey Lisbon pattern was the most disruptive. For architectural and structural design, this study indicates (1) that highly repetitive patterns should be used with care in consideration of their impact on the human visuomotor system and its behavioural effects and (2) that coloured patterns should be used with greater caution than greyscale patterns. Full article

Aim and Background: To determine whether occupational physical activity (OPA) and physical fitness (Fitscore) predict cardiovascular disease (CVD) mortality and its components. Methods: Among middle-aged men (N = 5482) of seven cohorts of the Seven Countries Study (SCS), several baseline risk factors were measured, and there was a follow-up for 60 years until virtual extinction. OPA was estimated from the type of work while Fitscore was derived from linear combinations of levels of arm circumference, heart rate and vital capacity computed as a factor score by principal component analysis. The predictive adjusted power of these characteristics was obtained by Cox models for coronary heart disease (CHD), heart diseases of uncertain etiology (HDUE), stroke and CVD outcomes. Results: Single levels of the three indicators of fitness were highly related to the three levels of OPA and Fitscore. High levels of both OPA and Fitscore forced into the same models were associated with lower CVD, CHD, HDUE and stroke mortality. When assessed concomitantly in the same models, hazard ratios (high versus low) for 60-year CVD mortality were 0.88 (OPA: 95% CI: 0.78–0.99) and 0.68 (Fitscore 95% CI: 0.61–0.75), and the predictive power of Fitscore outperformed that of OPA for CHD, HDUE and stroke outcomes. Similar results were obtained in individual outcome models in the presence of risk factors. Segregating the first 30 from the second 30 years of follow-up indicated that people dying earlier had lower arm circumference and vital capacity, whereas heart rate was higher for CVD and most of its major components (all p < 0.0001). Conclusions: OPA was well related to the indicators of fitness involving muscular mass, cardio-circulatory and respiratory functions, thus adding predictive power for CVD events. The Fitscore derived from the above indicators represents another powerful long-term predictor of CHD, HDUE and stroke mortality. Full article

Virtual reality (VR) is continuing to grow as more affordable technological devices become available. Video games are one of the most profitable applications, while rehabilitation has the most significant social impact. Both applications require a proper user evaluation to provide personalized experiences that avoid boring or stressful situations. Despite the successful applications, there are several opportunities to improve the field of human–machine interactions, one of the most popular ones being the use of affect detection to create personalized experiences. In that sense, this study presents the implementation of two dynamic difficulty adaptation strategies. The person’s affective state is estimated through a machine learning classification model, which later serves to adapt the difficulty of the video game online. The results show that it is possible to maintain the user at a given difficulty level, which is analogous to achieving the well-known flow state. Among the two implemented strategies, no statistical differences were found in the workload induced by the users. However, more physical demands and a higher frustration were induced by one of the strategies, validated with the recorded muscular activity. The results obtained contribute to the state of the art of DDA strategies in virtual reality driven by affective data. Full article

Glyphosate, a widely used herbicide, is linked to a plethora of deleterious effects in both clinical and preclinical studies. Nevertheless, the effects of its main metabolite, aminomethylphosphonic acid (AMPA), whose half-life in soil is even longer than that of glyphosate, have been little explored. On this basis, as a first approach, in this work, we report that intraperitoneal (i.p.) administration of AMPA or glyphosate (at 10, 56, and 100 mg/kg) decreased, to a similar extent, plasma cholinesterase (ChE) activity in acutely exposed rats. Moreover, we designed an experimental protocol to analyze and compare the effects of AMPA and glyphosate on human plasma ChE activity; this protocol consisted of adding these compounds to human plasma to subsequently test the effects of this plasma on the contraction to acetylcholine (ACh) in the frog rectus abdominis muscle (an indirect estimate of ChE activity). Accordingly, this muscular contraction to ACh was evaluated before and after pre-incubation of ACh with (i) plasma alone, (ii) plasma with AMPA, and (iii) plasma with glyphosate. Our results indicate that AMPA, like glyphosate, decreased ChE activity in the plasma of rats (when given i.p.) and humans (when added in vitro), suggesting that both xenobiotics may exert similar toxicological effects. Full article

Adults do not engage in enough physical activity. Investigating cognitive and physiological factors related to improving this behavior—and reducing health risks—remains a public health priority. Our objective was to assess whether cognitive flexibility influenced perceptions and choice of exercise programs and whether flexibility was associated with cardiovascular disease (CVD) risk factors. Independent sample groups of college-aged adults (18–24 yrs) participated in two studies. Data were collected on individuals’ degree of cognitive flexibility (both self-reported and objectively measured), perceptions and choice of exercise programs, and health status markers known to be associated with CVD (vascular function, muscular strength, and body composition). Vascular function was assessed with a near-infrared spectroscopy device, strength was defined as handgrip, and body composition was estimated via digital circumferences. Self-reported flexibility reliably predicted individuals’ choice of exercise program and perceptions of effort required for success on an exercise program. The relationships among CVD risk factors and objectively measured cognitive flexibility were not significant, demonstrating that identifying a healthy individual’s degree of performance-based cognitive flexibility does not predict health status. Furthermore, although greater self-reported trait flexibility (rigidity) is known to predict higher (lower) likelihood of physical activity, this finding should not be extrapolated to also assume that flexibility (rigidity), as measured by objective cognitive tests, is associated with reduced CVD risk in healthy adults. We posit a rationale for how understanding cognitive flexibility and rigidity can play an impactful role in improving adherence to exercise prescriptions targeted to reducing risks. Full article

Mechanical scooter riding is a popular physical activity among children, but little is known about the differences in muscle loading between the dominant and non-dominant sides during this activity. The objective of this study was to identify the muscle activation patterns in children’s dominant and non-dominant legs as they rode scooters on the convenient and inconvenient sides. The study included nine healthy children aged 6–8. The participants rode 20 m on a mechanical scooter at a self-selected pace using both the convenient and inconvenient sides. Electromyography was used to measure the muscle activity in the dominant and non-dominant legs during the pushing and gliding phases. A 20 m sprint run was used as a control exercise to estimate the typical differences in muscle activation between the dominant and non-dominant legs. In the pushing phase, the symmetry index for five of the eight analyzed muscles exceeded 50% (p < 0.05); four of these muscles were more active in the pushing leg, and one was more active in the standing leg. In the gliding phase, four muscles were more active in the standing leg, and one was more active in the pushing leg (p < 0.05). Upon observing children who changed sides while riding a scooter, it was found that the pattern of muscle activation displayed a reverse trend that resembled the initial pattern. Our study indicated notable differences in muscle activity patterns between the dominant and non-dominant sides of individual leg muscles during children’s scooter riding. These patterns were reversed when children switched sides on the scooter. These findings suggest that using both legs and switching sides while riding a scooter may be a viable strategy for promoting balanced muscular development. Full article

We aimed to investigate the relationship between physical fitness and motivation in adolescents and analyze if the associations of physical fitness with volitional exercise intensity in adolescents are mediated by motivation. The participants were 108 adolescents (58 girls 16.0 ± 0.92 years). Cardiorespiratory fitness (CRF) was assessed using the Yo-YoITL1, and the push-up test was used to evaluate strength. Body composition was measured by bioelectrical impedance analysis. The intervention was applied in the first 10–15 min of each Physical Education class (PEC), twice a week, for 16 weeks and ranged from 14 to 20 all-out bouts intervals, adopting a 2:1 work to rest ratio. A cut-point of ≥90% of the maximal heart rate (HR) was used as a criterion for satisfactory compliance with high-intensity exercise. Volition intensity was assessed through a forearm wearable plethysmography heart rate sensor to ensure compliance with the exercise stimulus at the predetermined target HR zone. Motivation was estimated with a validated questionnaire (BREQ-3). Mediation effects were estimated using bootstrapped 95% confidence intervals and were deemed significant if zero was not included in the intervals, and values below 0.05 were considered to indicate statistical significance. The mediation analysis revealed a non-significant indirect effect of physical fitness through motivation on exercise intensity, specifically on CRF (B = −0.0355, 95% BootCI [−0.5838; 0.4559]), muscular fitness (B = −0.7284, 95% BootCI [−2.0272; 0.2219]) and body fat (B = 0.5092, 95% BootCI [−0.4756; 1.6934]). These results suggest that high or low values of motivation did not increase or decrease volitional high-intensity exercise, and lower levels of fitness (CRF, muscular and body fat) were associated with higher volitional exercise intensity. These findings highlight the need for regular moderate-to-vigorous physical exercise for maintaining or improving physical fitness, regardless of motivation regulations, and emphasize the importance of new strategies in PEC with acute vigorous-intensity activities that retain the health-enhancing effects. Full article

Estimation of the force exerted by muscles from their electromyographic (EMG) activity may be useful to control robotic devices. Approximating end-point forces as a linear combination of the activities of multiple muscles acting on a limb may lead to an inaccurate estimation because of the dependency between the EMG signals, i.e., multi-collinearity. This study compared the EMG-to-force mapping estimation performed with standard multiple linear regression and with three other algorithms designed to reduce different sources of the detrimental effects of multi-collinearity: Ridge Regression, which performs an L2 regularization through a penalty term; linear regression with constraints from foreknown anatomical boundaries, derived from a musculoskeletal model; linear regression of a reduced number of muscular degrees of freedom through the identification of muscle synergies. Two datasets, both collected during the exertion of submaximal isometric forces along multiple directions with the upper limb, were exploited. One included data collected across five sessions and the other during the simultaneous exertion of force and generation of different levels of co-contraction. The accuracy and consistency of the EMG-to-force mappings were assessed to determine the strengths and drawbacks of each algorithm. When applied to multiple sessions, Ridge Regression achieved higher accuracy (R² = 0.70) but estimations based on muscle synergies were more consistent (differences between the pulling vectors of mappings extracted from different sessions: 67%). In contrast, the implementation of anatomical constraints was the best solution, both in terms of consistency (R² = 0.64) and accuracy (74%), in the case of different co-contraction conditions. These results may be used for the selection of the mapping between EMG and force to be implemented in myoelectrically controlled robotic devices. Full article

The present study describes the development of a wearable device designed to assist those who work in an unstructured posture. In the manufacturing sector, industrial accidents have been steadily on the rise due to poor work environments and excessive workloads imposed on workers. Against this backdrop, the present study aimed to analyze various types of work, especially those performed in unstructured postures by heavy industry workers, who are frequently exposed to high workloads and poor work environments. Based on the analysis results, an attempt was made to develop a shoulder muscle-assistive wearable device capable of assisting a wearer who is working using their shoulder muscles. Various types of unstructured posture work are performed in heavy industries, including activities such as the welding and grinding of ship components and plant structures. They are typically conducted in narrow spaces with limited postures, causing many workers to suffer muscle fatigue. In the present study, as the first step of developing a shoulder muscle-assistive wearable device, different working scenarios were simulated, and the corresponding motion data and required torque values were estimated using motion capture devices. The obtained motion data and required torque values were reflected in the design of the wearable device. The main structural body of the shoulder muscle-assistive wearable device was made of a carbon fiber-reinforced composite to be lightweight. This shoulder muscle-assistive wearable device was designed to fully cover the range of motion for workers working in unstructured postures while generating the torque required for a given job, thereby enhancing the muscular endurance of the workers. The gravity compensation module of the designed shoulder muscle-assistive wearable device generates a support force of 4.47 Nm per shoulder. The shoulder muscle assistive wearable device was developed to provide support for approximately 30% of the shoulder joint’s maximum torque generated in overhead tasks. This shoulder muscle-assistive wearable device is expected to contribute to improving the productivity of field workers, while reducing the occurrence of musculoskeletal injuries arising from the aging of the working-age population. Full article

Cardiovascular calcifications (CVC) are frequently observed in chronic kidney disease (CKD) patients and contribute to their cardiovascular mortality. The aim of the present study was to investigate the impact of osteoprotegerin (OPG)/Receptor Activator of NF-κΒ (RANK)/RANK ligand (RANKL) pathway in the development and evolution of CVCs in hemodialysis patients. In total, 80 hemodialysis patients were assessed for the presence of vascular (abdominal aorta and muscular arteries) calcifications and results were correlated to serum OPG and RANKL levels and the OPG/RANKL ratio. Traditional cardiovascular risk factors and mineral bone disease parameters were also estimated. The presence of VCs was also evaluated 5 years after the initiation of the study, and results were correlated to the initial serum OPG levels. Age, diabetes mellitus, coronary artery disease and OPG levels (p < 0.001) were associated with VCs, whereas RANKL levels were not. Multivariate analysis though revealed that only OPG levels were significantly associated with abdominal aorta calcifications (p = 0.026), but they were not correlated with the progression of VCs. Serum OPG levels are positively and independently associated with VCs in HD patients, but not with their progression. RANKL levels did not show any associations, whereas further studies are needed to establish the significance of OPG/RANKL ratio. Full article

The present study aimed to assess the function of muscular and nervous systems in high-maneuvering jet fighters with the chosen method of clinical neurophysiology, which methodologically has not yet been presented in detail. Fifteen pilots with the experience of more than 1700 flying hours at 7G overloading on average and fifteen healthy subjects for the comparison of health status declared to participate in this study. The dermatomal perception from C4 to S1 was examined using von Frey’s filaments tactile method. Surface electromyography (sEMG) recordings examined the activity of proximal and distal muscles in the upper and lower extremities, the transmission of motor nerve impulses peripherally was diagnosed by electroneurography (ENG), the efferent transmission from C5–C7 and L4–L5 spinal centers to muscles was entirely verified with recordings of motor-evoked potentials induced oververtebrally with the magnetic field (MEP). The pilots estimated more lumbosacral than cervical pain at about 2 on the 10-point visual analog scale (VAS). Sensory perception studies did not reveal abnormal symptoms in the C2–S1 dermatomes innervation. Clinical neurophysiology studies indicated, in general, the lack of pathology during sEMG tests in comparison to healthy subjects or even better muscle motor unit contractile properties in pilots, both in the upper and lower extremities. In pilots, the parameters of ENG and MEP examinations show a statistically significant sensitivity for detecting the slight changes and their consequences in the transmission of neural impulses within L4–L5 ventral root fibers. The research results enable specifying the algorithm of future preventing rehabilitative treatment in high-maneuvering jet fighters with an average flight experience of 2000 h and working conditions at 7G on average. This study, for the first time, describes the application of a set of diagnostic neurophysiological methods with the particular importance of MEPs in the clinical evaluation of the jet fighters’ health status. Full article

Surface electromyography (sEMG) is the acquisition, from the skin, of the electrical signal produced by muscle activation. Usually, sEMG is measured through electrodes with electrolytic gel, which often causes skin irritation. Capacitive contactless electrodes have been developed to overcome this limitation. However, contactless EMG devices are still sensitive to motion artifacts and often not comfortable for long monitoring. In this study, a non-invasive contactless method to estimate parameters indicative of muscular activity and fatigue, as they are assessed by EMG, through infrared thermal imaging (IRI) and cross-validated machine learning (ML) approaches is described. Particularly, 10 healthy participants underwent five series of bodyweight squats until exhaustion interspersed by 1 min of rest. During exercising, the vastus medialis activity and its temperature were measured through sEMG and IRI, respectively. The EMG average rectified value (ARV) and the median frequency of the power spectral density (MDF) of each series were estimated through several ML approaches applied to IRI features, obtaining good estimation performances (r = 0.886, p < 0.001 for ARV, and r = 0.661, p < 0.001 for MDF). Although EMG and IRI measure physiological processes of a different nature and are not interchangeable, these results suggest a potential link between skin temperature and muscle activity and fatigue, fostering the employment of contactless methods to deliver metrics of muscular activity in a non-invasive and comfortable manner in sports and clinical applications. Full article

Although the older population has been rapidly growing, the availability of formal caregivers remains limited. Assistance provided by care robots has helped lower this burden; however, whether using a care robot while providing excretion care (EC) is quantitatively increasing or decreasing caregivers’ physical care burden has not been extensively studied. This study aimed to quantitatively compare the physical burden experienced by caregivers while providing manual excretion care (MC) using a paper diaper versus robot-aided care (RC). Ten formal caregivers voluntarily participated in the experiment. MC and RC tasks were structuralized according to phases and classified by characteristics. The experiment was conducted in a smart care space. The physical load of formal caregivers was estimated by muscular activity and subjective rating of perceived physical discomfort. The results demonstrated that although the physical load on the lower back and upper extremities during the preparation and post-care phases were greater in RC than MC, RC markedly alleviated caregivers’ physical load when performing front tasks. In the preparation-care phases, the physical loads on the lower back and upper extremities were approximately 40.2 and 39.6% higher in the case of RC than MC, respectively. Similar to the preparation-care phases, the physical loads on the lower back and upper extremities during post-care phases were approximately 39.5 and 61.7% greater in the case of RC than MC, respectively. On the other hand, in the front-care phases, the physical loads on the lower back and upper extremities were approximately 25.6 and 34.9% lower in the case of RC than MC, respectively. These findings can quantitatively explain the effectiveness and features of a care robot to stakeholders and provide foundational research data for the development of EC robots. This study emphasizes the implementation and promotion of the dissemination, popularization, and development of care robots to fulfill formal caregiving needs. Full article

(1) Background: This study presents a new method for the motion quantitative analysis of Duchenne muscular dystrophy patients (DMD) performing functional tasks in clinical conditions. (2) Methods: An experimental study was designed to define how different levels of external mass (light and heavy) influence the performance of the upper limbs of a tested DMD and reference subject (RS) during horizontal movements (level of the waist) under natural conditions (NC) and passive manipulator conditions (PMC); the kinematic data and muscle activity of four chosen superficial muscles (EMG) were recorded. (3) Results: A piecewise linear multi-regression analysis revealed high statistically significant results (R² ≥ 0.75) between the tested muscle activities and kinematic data in the tested DMD patient and RS. These results were used to define whether the neural control of the four tested muscles (processed EMG data) was correlated more with the displacement of the wrist joint or the center of mass of the tested upper limb while performing functional tests with a given external weight in a horizontal plane under NC or PMC. (4) Conclusions: The proposed approach can be used to estimate the contributions of the tested muscles to patients’ motion performance and define whether this contribution is correlated with the kinematics or dynamics of the tested arm. Full article