Quantification of dance movement by simultaneous measurement of body motion and biophysical information

The purpose of this research is a quantitative analysis of movement patterns of dance,which cannot be analyzed with a motion capture system alone,using simultaneous measurement of body motion and biophysical information.In this research,two kinds of same leg movement are captured by simultaneous measurement;one is a leg movement with given strength,the other is a leg movement without strength on condition of basic experiment using optical motion capture and electromyography (EMG) equipment in order to quantitatively analyze characteristics of leg movement.Also,we measured the motion of the traditional Japanese dance using the constructed system.We can visualize leg movement of Japanese dance by displaying a 3D CG character animation with motion data and EMG data.In addition,we expect that our research will help dancers and researchers on dance through giving new information on dance movement which cannot be analyzed with only motion capture.     

Biomechanical evaluation of bike power saver

Bike power saver (BPS) is a new product that claims to change the angle of pedaling forces and reduce applied power dead range (Chic Sheng Industrial Co., Ltd, Taiwan, China). In order to determine its effectiveness, we quantified how BPS operates through a 3D kinematical study and electromyography (EMG) analysis of leg muscles during pedaling. Ten kinesiology students participated in this study. A 3D motion capture system consisting of nine high-speed cameras (VICON v8i, a capture rate of 120 frames/s) was used to collect the total body and pedal motion with and without BPS at statically determined low, middle and high intensity cycling levels. The short-time test (14s) was applied to all intensity levels while the long-time test (30 min) was applied only to the low wattage level. Wireless EMG was synchronized with the 3D motion capture system to monitor the right and left tibialis anterior, gastrocnemius, quadriceps and hamstring. The results revealed that BPS did not alter hip and knee movement significantly (p>0.05), but it did vary ankle movement. BPS caused a movement change in the pedals, and consequently induced instability in ankle control. The altered pedal movement led to an increase in activity level and presumably also energy expenditure for dominant muscles, resulting in a faster fatigue process. From these data, it is likely that the BPS actually requires more effort than a standard bike.     

The effect on lower spine muscle activation of walking on a narrow beam in virtual reality

To what extent do people behave in immersive virtual environments as they would in similar situations in a physical environment? There are many ways to address this question, ranging from questionnaires, behavioral studies, and the use of physiological measures. Here, we compare the onsets of muscle activity using surface electromyography (EMG) while participants were walking under three different conditions: on a normal floor surface, on a narrow ribbon along the floor, and on a narrow platform raised off the floor. The same situation was rendered in an immersive virtual environment (IVE) Cave-like system, and 12 participants did the three types of walking in a counter-balanced within-groups design. The mean number of EMG activity onsets per unit time followed the same pattern in the virtual environment as in the physical environment-significantly higher for walking on the platform compared to walking on the floor. Even though participants knew that they were in fact really walking at floor level in the virtual environment condition, the visual illusion of walking on a raised platform was sufficient to influence their behavior in a measurable way. This opens up the door for this technique to be used in gait and posture related scenarios including rehabilitation.     

Job enlargement and mechanical exposure variability in cyclic assembly work

Cyclic assembly work is known to imply a high risk for musculoskeletal disorders. To have operators rotate between work tasks is believed to be one way of decreasing this risk, since it is expected to increase variation in mechanical and psychological exposures (physical and mental loads). This assumption was investigated by assessing mechanical exposure variability in three assembly tasks in an electronics assembly plant, each on a separate workstation, as well as in a 'job enlargement' scenario combining all three stations. Five experienced operators worked for 1 h on each station. Data on upper trapezius and forearm extensor muscle activity were obtained by means of electromyography (EMG), and working postures of the head and upper arms were assessed by inclinometry. The cycle-to-cycle variance of parameters representing the three exposure dimensions: level, frequency and duration was estimated using ANOVA algorithms for each workstation separately as well as for a balanced combination of all three. For a particular station, the variability of trapezius EMG activity levels relative to the mean was higher than for extensor EMG: between-cycles coefficients of variation (CV) about 0.15 and 0.10, respectively. A similar relationship between CV applied to the parameter describing frequency of EMG activity. Except for head inclination levels, the between-cycles CV was larger for posture parameters than for EMG. The between-cycles variance increased up to six fold in the job enlargement scenario, as compared to working at only one station. The difference in mean exposure between workstations was larger for trapezius EMG parameters than for forearm extensor EMG and postures, and hence the effect of job enlargement on exposure variability was more pronounced for the trapezius. For some stations, job enlargement even implied less cycle-to-cycle variability in forearm extensor EMG parameters than working at that station only. Whether the changes in exposure variability associated with job enlargement were sufficient to imply a decreased risk for musculoskeletal disorders is not known.     

Job enlargement and mechanical exposure variability in cyclic assembly work

Cyclic assembly work is known to imply a high risk for musculoskeletal disorders. To have operators rotate between work tasks is believed to be one way of decreasing this risk, since it is expected to increase variation in mechanical and psychological exposures (physical and mental loads). This assumption was investigated by assessing mechanical exposure variability in three assembly tasks in an electronics assembly plant, each on a separate workstation, as well as in a ‘job enlargement’ scenario combining all three stations. Five experienced operators worked for 1?h on each station. Data on upper trapezius and forearm extensor muscle activity were obtained by means of electromyography (EMG), and working postures of the head and upper arms were assessed by inclinometry. The cycle-to-cycle variance of parameters representing the three exposure dimensions: level, frequency and duration was estimated using ANOVA algorithms for each workstation separately as well as for a balanced combination of all three. For a particular station, the variability of trapezius EMG activity levels relative to the mean was higher than for extensor EMG: between-cycles coefficients of variation (CV) about 0.15 and 0.10, respectively. A similar relationship between CV applied to the parameter describing frequency of EMG activity. Except for head inclination levels, the between-cycles CV was larger for posture parameters than for EMG. The between-cycles variance increased up to six fold in the job enlargement scenario, as compared to working at only one station. The difference in mean exposure between workstations was larger for trapezius EMG parameters than for forearm extensor EMG and postures, and hence the effect of job enlargement on exposure variability was more pronounced for the trapezius. For some stations, job enlargement even implied less cycle-to-cycle variability in forearm extensor EMG parameters than working at that station only. Whether the changes in exposure variability associated with job enlargement were sufficient to imply a decreased risk for musculoskeletal disorders is not known.     

Muscular fatigue and endurance during intermittent static efforts: effects of contraction level, duty cycle, and cycle time

OBJECTIVE: To determine the effects of intermittent task parameters on muscle fatigue and endurance time during static shoulder abductions, with a long-term goal of establishing relationships between intermittent task parameters and short-term performance. BACKGROUND: Effects of intermittent work on endurance and fatigue development have been reported, and certain combinations of contraction levels and duty cycles have been proposed as design guidelines. These findings, however, were not derived from systematic manipulations of the task parameters. METHOD: Prolonged (1-hr maximum) intermittent shoulder abductions were performed at different combinations of contraction level (12% or 28% of muscle strength), duty cycle (.25 or .75), and cycle time (34 or 166 s). Fatigue was measured based on reductions in muscle strength and indirectly by changes in ratings of discomfort, electromyographic (EMG) amplitude, and EMG spectral distribution. RESULTS: Contraction level and duty cycle significantly affected endurance time and muscle fatigue, and interactive effects between these parameters were observed for some of the measures. Significant effects of cycle time were found only for EMG spectral measures. CONCLUSION: Endurance time and local fatigue were dependent on the comprehensive effects of the different task parameters. APPLICATION: Design changes to reduce the occurrence of localized fatigue during intermittent work need to take into account all the task parameters simultaneously.     

Relationship between limb movement speed and associated contraction of the trunk muscles

Rapid shoulder movement is preceded by contraction of the abdominal muscles to prepare the body for the expected disturbance to postural equilibrium and spinal stability provoked by the reactive forces resulting from the movement. The magnitude of the reactive forces is proportional to the inertia of the limb. The aim of the study was to investigate if changes in the reaction time latency of the abdominal muscles was associated with variation in the magnitude of the reactive forces resulting from variation in limb speed. Fifteen participants performed shoulder flexion at three different speeds (fast, natural and slow). The onset of EMG of the abdominal muscles, erector spinae and anterior deltoid (AD) was recorded using a combination of fine-wire and surface electrodes. Mean and peak velocity was recorded for each limb movement speed for five participants. The onset of transversus abdominis (TrA) EMG preceded the onset of AD in only the fast movement condition. No significant difference in reaction time latency was recorded between the fast and natural speed conditions for all muscles. The reaction time of each of the abdominal muscles relative to AD was significantly delayed with the slow movement compared to the other two speeds. The results indicate that the reaction time latency of the trunk muscles is influenced by limb inertia only with limb movement below a threshold velocity.     

Modeling of the carbon dioxide capture process system using machine intelligence approaches

Improving the efficiency of the carbon dioxide (CO₂) capture process requires a good understanding of the intricate relationships among parameters involved in the process. The objective of this paper is to study the relationships among the significant parameters impacting CO₂ production. An enhanced understanding of the intricate relationships among the process parameters supports prediction and optimization, thereby improving efficiency of the CO₂ capture process. Our modeling study used the 3-year operational data collected from the amine-based post combustion CO₂ capture process system at the International Test Centre (ITC) of CO₂ Capture located in Regina, Saskatchewan of Canada. This paper describes the data modeling process using the approaches of (1) neural network modeling combined with sensitivity analysis and (2) neuro-fuzzy modeling technique. The results from the two modeling processes were compared from the perspectives of predictive accuracy, inclusion of parameters, and support for explication of problem space. We conclude from the study that the neuro-fuzzy modeling technique was able to achieve higher accuracy in predicting the CO₂ production rate than the combined approach of neural network modeling and sensitivity analysis.     

The size of cycle-to-cycle variability in biomechanical exposure among butchers performing a standardised cutting task

The effects of employment duration and pain development on motor variability were investigated during repetitive work. Electromyographic (EMG) and kinematics data from two previous studies were re-analysed. Newly employed butchers were followed prospectively in relation to employment duration and pain development. Healthy butchers with long-term experience were compared with novices. The variability of the cycle time, EMG ratio and arm and trunk movement was expressed as cycle-to-cycle standard deviations. During the first 6 months of employment, cycle time variability decreased, while posture and movement variability increased (p < 0.05). In presence of pain, the variability of the initial arm position decreased while it increased for the trunk (p < 0.05). Experienced butchers showed a larger variability than novices for work cycle and several kinematic variables, but a smaller EMG ratio variability (p < 0.05). These findings indicate that the variability of motor patterns in repetitive work changes with experience and pain. A change towards a more variable motor strategy may protect workers from work-related musculoskeletal disorders.     

The effects of load placement on the EMG activity of the low back muscles during load carrying by men and women

An electromyographic (EMG) study of the lumbar paraspinal muscles during load carrying was undertaken in a group of 24 healthy subjects, 12 male and 12 female. Two different magnitude loads (10% and 20% of the subject's body weight) and four different carrying positions were compared with walking without an external load. Results indicated changes in back muscle activity showing a significant interaction between load magnitude and carrying position. Compared to walking without an external load, lumbar paraspinal EMG activity showed slight decreases when loads were carried in a backpack position or in the hand ipsilateral to the muscle. EMG activity contralateral to the hand carrying the load was significantly increased. Significant increases occurred when loads were carried anterior to the chest with the arms and a significant difference was found between male and female subjects for this carrying position. These findings have implications for the selection of carrying methods.     

Temporal strategy and performance during a fatiguing short-cycle repetitive task

This study investigated temporal changes in movement strategy and performance during fatiguing short-cycle work. Eighteen participants performed six 7-min work blocks with repetitive reaching movements at 0.5 Hz, each followed by a 5.5-min rest break for a total duration of 1 h. Electromyography (EMG) was collected continuously from the upper trapezius muscle, the temporal movement strategy and timing errors were obtained on a cycle-to-cycle basis, and perceived fatigue was rated before and after each work block. Clear signs of fatigue according to subjective ratings and EMG manifestations developed within each work block, as well as during the entire hour. For most participants, timing errors gradually increased, as did the waiting time at the near target. Changes in temporal movement strategy were negatively correlated with changes in the level and variability of EMG, suggesting that an adaptive temporal strategy offset the development of unstable motor solutions in this fatiguing, short-cycle work. PRACTITIONER SUMMARY: Sustained performance of operators is essential to maintain competitiveness. In this study of repetitive work, participants gradually changed their temporal movement strategy, for possibly alleviating the effects of fatigue. This suggests that in order to effectively counteract fatigue and sustain performance, industrial production should allow extensive spatial and temporal flexibility.     

Physiologic responses during rest on a sleep system at varied degrees of firmness in a normal population

This study explores the hypothesis that a high degree of sustained muscle activity associated with a sub-optimal spinal orientation may compromise an individual's ability to relax or initiate sleep. Data from 22 participants who were considered to be part of a normal, back-pain-free population were used in these studies. Participants laid down on a mattress in a foetal position (i.e. on their sides) at three varying bed pressures while EMG activities, heart rates, blood pressures, subjective comfort levels and spinal alignment data were recorded. Minor effects of mattress inflation pressures were associated with changes in EMG activity, heart rate, blood pressure and/or subjective comfort. In contrast, spinal alignment assessment revealed significant differences between the three different inflation pressures studied (827.4, 2413.2 and 3999.0 Pa). It was concluded that in a population of normal participants, although mattress inflation pressure induced significant changes in spinal alignment, these changes were of little physiological consequence. Nevertheless, this data provides baseline information needed to assess similar correlations in a symptomatic population (e.g. those with either acute or chronic neck or back pain).     

Electromyography applied to sport ergonomics

Abstract

The improvement of electromyographic (EMG) devices for the detection of electric potentials produced in voluntary complex movements and the evolution of methodological approaches to data acquisition and computerized analysis of patterns, are responsible for the increased applications of EMG in bioengineering, rehabilitation, sport and occupational biomechanics, physiology and zoology and to a lesser extent in ergonomics. This paper describes three different EMG applications related to a sport environment using three different EMG registration and data acquisition approaches.

The first study examined the relation between the swimming action in water and its simulation using training equipment on land. It was found that with respect to the mechanical aspects of dry-land equipment and to the biomechanical differences in the execution of the front crawl action on dry land and in water, based on EMG activity of the propulsion muscles, the best results were found when using devices with accommodating resistance. Recovery muscles were best imitated using isokinetics, but despite the greater effort on land, lower EMG activity was recorded than in water. It was generally observed that whenever the swimmer acted against a mechanical resistance an important pattern deviation was noted.

Second, a study to determine the influence of ski materials on the EMG muscle activity of skiers showed systematic differences between the use of racing, soft and compact skis. The results supported the idea that the soft ski should be more highly recommended than the compact or racing ski for both general and competive use.

Finally, in a third study we found that there was a very high degree of similarity in the pattern and intensity of muscle activity in both free swimming and swimming against a mechanical resistance (MAD swimming), even though the kinesiological aspects of the movement trajectory were proved different beforehand.     

A Biophysically‐Based Model of the Optical Properties of Skin Aging

This paper presents a time‐varying, multi‐layered biophysically‐based model of the optical properties of human skin, suitable for simulating appearance changes due to aging. We have identified the key aspects that cause such changes, both in terms of the structure of skin and its chromophore concentrations, and rely on the extensive medical and optical tissue literature for accurate data. Our model can be expressed in terms of biophysical parameters, optical parameters commonly used in graphics and rendering (such as spectral absorption and scattering coefficients), or more intuitively with higher‐level parameters such as age, gender, skin care or skin type. It can be used with any rendering algorithm that uses diffusion profiles, and it allows to automatically simulate different types of skin at different stages of aging, avoiding the need for artistic input or costly capture processes. While the presented skin model is inspired on tissue optics studies, we also provided a simplified version valid for non‐diagnostic applications.     

基于迁移QCNN的孪生网络轴承故障诊断方法

轴承故障诊断对于降低旋转机械的损坏风险,进一步提高经济效益具有重要意义。深度学习在轴承故障诊断中应用广泛,但是深度学习模型在训练与测试时容易受到噪声的干扰导致性能下降。并且轴承的工况变化频繁,不同工况下的数据采集困难。对此,提出了一种基于迁移QCNN的孪生网络轴承故障诊断方法,先预训练QCNN获取具有较强判别性的模型参数,将预训练的参数迁移到QCNN作为子网络的孪生网络中,然后正常训练孪生网络获取模型,最后将测试数据与故障数据组成数据对输入模型,即可得到测试数据的故障类型。该方法将QCNN与孪生网络相结合,QCNN中的Quadratic神经元具有强大的特征提取能力,孪生网络共享权重和相对关系的训练方式,使得模型可以缓解噪声和工况数据不平衡问题的影响。实验结果显示,相较与传统机器学习模型和QCNN等模型,所提出方法在面对噪声和工况数据不平衡问题表现更好。     

Estimating vigilance level by using EEG and EMG signals

We developed a new method for estimation of vigilance level by using both EEG and EMG signals recorded during transition from wakefulness to sleep. Previous studies used only EEG signals for estimating the vigilance levels. In this study, it was aimed to estimate vigilance level by using both EEG and EMG signals for increasing the accuracy of the estimation rate. In our work, EEG and EMG signals were obtained from 30 subjects. In data preparation stage, EEG signals were separated to its subbands using wavelet transform for efficient discrimination, and chin EMG was used to verify and eliminate the movement artifacts. The changes in EEG and EMG were diagnosed while transition from wakefulness to sleep by using developed artificial neural network (ANN). Training and testing data sets consist of the subbanded components of EEG and power density of EMG signals were applied to the ANN for training and testing the system which gives three situations for the vigilance level of the subject: awake, drowsy, and sleep. The accuracy of estimation was about 98–99% while the accuracy of the previous study, which uses only EEG, was 95–96%.     

基于函数型数据分析方法的人体动态行为识别

人体运动过程中,肢体的运动是连续的,而对应的运动捕捉数据是离散的.为了更好地分析人体日常运动行为的连续性与周期性,本文提出了一种基于函数型数据分析（Functional data analysis,FDA）的人体动态行为识别方法.首先,利用函数型数据分析方法,将可穿戴式运动捕捉系统采集的人体周期行为数据函数化,通过函数准确地定义数据的连续性与周期性;然后,根据导函数信息确定一个运动周期的起始点,并近似地提取出一个运动周期的数据序列;最后,根据不同行为一个周期内的曲线特征差异,利用支持向量机对动态行为进行分类识别.实验结果表明,本文的算法既能够较好地描述人体动态行为的连续性与周期性,又使得运动数据在标定的统一起始点处对齐,且在WARD数据集与自采集数据集上均取得了较好的识别率,分别达到97.5%与98.75%.     

Online variational inference for state-space models with point-process observations

We present a variational Bayesian (VB) approach for the state and parameter inference of a state-space model with point-process observations, a physiologically plausible model for signal processing of spike data. We also give the derivation of a variational smoother, as well as an efficient online filtering algorithm, which can also be used to track changes in physiological parameters. The methods are assessed on simulated data, and results are compared to expectation-maximization, as well as Monte Carlo estimation techniques, in order to evaluate the accuracy of the proposed approach. The VB filter is further assessed on a data set of taste-response neural cells, showing that the proposed approach can effectively capture dynamical changes in neural responses in real time.     

Enhancing Ergonomic Safety Effectiveness of Repetitive Job Activities: Prediction of Muscle Fatigue in Dominant and Nondominant Arms of Industrial Workers

Work?related musculoskeletal disorders are very common in the workplace, especially with tasks involving repetitive lifting and motions. Repetitive lifting of excessively heavy objects in the workplace could increase the severity and rates of work?related musculoskeletal disorders. In this article, the physiological effect of muscle fatigue on the dominant and nondominant arms of adult industrial workers performing various repetitive tasks was predicted using a muscular endurance model. Twenty?four (n = 24) industrial workers (18–45 years old) were randomly selected for this research. The effects of electromyography (EMG) were observed during incremental loading of 5–40 kg on the muscle of the dominant and nondominant arms of the subjects during static lifting activities. Results of the analysis showed that the endurance time decreased with the application of additional loads on the dominant and nondominant arms of all the subjects. This inverse relationship was used to predict the behavior of muscle fatigue. Additional findings indicated that workers performing repetitive lifting tasks could maintain maximum load capacities ranging from 20 to 30 kg. The acceptable maximum load capacity of 23 kg recommended by the National Institute for Occupational Safety and Health is within this range. The results obtained from this research could be used in the beginning steps of the efforts to reevaluate and reestablish guidelines and limits in the design of industrial jobs involving repetitive motion. © 2014 Wiley Periodicals, Inc.     

Electromyographic fatigue in neck/shoulder muscles and endurance in women with repetitive work.

EMG was recorded with surface electrodes from the trapezius and deltoid muscles during a static endurance test at approximately 20% of maximal voluntary contraction. Objective parameters for localized muscular fatigue were derived from the time course of the root mean square (RMS) and mean power frequency (MPF) of the EMG recordings. Isotonic regression is introduced as a tool for assessment of such parameters. The most pronounced sign of fatigue for trapezius was an increase in the RMS values, while for deltoid it was a decrease in the MPF values. This could be explained by the different functions of the two muscles. The endurance time for a group of 11 women in industrial work with repetitive short-cycled work tasks who were diagnosed with neck/shoulder disorders (tension neck) was significantly shorter (p less than 0.05) than for a group with the same work, but without neck/shoulder disorders (n = 11), and shorter than for a control group (n = 11). Regarding the EMG fatigue measures, there were no significant differences between the three groups. We did not find any relationships between endurance time and the EMG parameters. The results indicate that neck/shoulder disorders were not associated with divergent mechanisms for developing fatigue in the muscles, as recorded with surface EMG.