适用不同Brunnstrom等级患者基于表面肌电信号的动作识别方法

针对不同患病程度的脑卒中患者运动意图识别率低的问题,提出了一种适用于不同Brunnstrom等级患者基于表面肌电信号（sEMG）的动作识别方法．首先将所有等级患者sEMG数据进行融合,使用tsfresh库提取特征,然后基于随机森林（random forest,RF）模型筛选特征,并利用筛选的特征训练动作分类模型．进一步,通过研究动作和康复等级的关系,确定了康复评估动作并设计了康复等级自动评估算法．为了验证所提方法的有效性,在24例患者sEMG数据上进行了测试,实验结果表明所提方法能够将9种动作和6类康复等级的平均识别精度分别提升至89.81%和94%．基于所提方法构建的手部康复机器人系统能够实现康复等级自动评估．     

基于DTW算法的肌电信号手势识别方法

为了提高肌电信号手势识别算法的准确度,增强实时性,提出了一种基于动态时间规整（DTW）算法的手势识别方法,该方法利用肌电信号（EMG）对个体间的手势进行识别。首先,采用滑动平均能量的方法对原始的EMG信号进行数据分割,探测有效动作;其次,对于分割的数据段使用平均绝对值（MAV）来提取信号特征;最后,用DTW算法将8维的EMG信号融合并计算测试样本和模版的相似度,其中采用了DTW算法寻找规整路径的方法进行了模板制作,实现了个体间的手势识别。实验结果表明,使用DTW算法对肌电信号进行手势识别,其动作识别的准确率达到96.09%,该方法计算速度快,实时性强。     

Effect of various foot wedge conditions on the electromyographic activity of lower extremity muscles during load lifting

The level of muscle activity can be decreased with optimized foot wedge condition. The aim of this study was to evaluate the effect of different foot wedge conditions on the activity of selected lower extremity muscles during load lifting. Nine able‐bodied male subjects participated in this study. Electromyography activity of the vastus medialis (VM), vastus lateralis (VL), medialis gastrocnemius (MG), and soleus (SOL) muscles was recorded during dynamic load lifting using the squat technique in 5 conditions: i) non‐wedge (NW), ii) 1 cm heel height increasing (PW1), iii) 3 cm heel height increasing (PW3), iv) 1 cm in front of the feet (AW1), and v) 1 cm inside the feet (MW1). The results showed that the VM activity decreases in the MW1 compared to other conditions and significantly compared to the PW1 and PW3 conditions (p < .05). Decreases in the VL activity in the AW1 as well as in descending and ascending phases of MW1 were observed (p < .05). Also in the descending phase, the SOL activity in AW1 decreased significantly compared to NW condition (p < .05). However, there was no significant difference in MG activity between different conditions (p > .05). It seems that placing wedges in the anterior and medial area of the feet may decrease quadriceps muscles activity and probably can delay reaching time to fatigue during load lifting. These findings may be helpful in designing special shoes for ergonomics fields and work environments.     

Effects of a novel neck balance system on neuromuscular fatigue of neck muscles during repeated flexions and extensions

This study aimed at investigating the effects of a novel neck balance system (NBS), which is a baseball cap with counterweights in the occipital part, on neuromuscular fatigue of neck muscles during and after a full‐range repeated neck flexion‐extension task. Surface electromyography (sEMG) of sternocleidomastoid (SCM) and semispinalis capitis (SC) muscles was recorded in 15 healthy individuals during full‐range flexion‐extension movements of the neck lasting 5 min at a fixed pace (1 Hz), with or without NBS. Maximal isometric force and sEMG were recorded before and after the fatiguing task. During the fatiguing task, the SC muscle showed a higher decline in amplitude of sEMG with NBS than without NBS, while no differences in the SCM muscle emerged between the two conditions. Maximal isometric force of both neck flexor and extensor muscles decreased significantly after the fatiguing task, both with NBS (p < .05) and without NBS (p < .05), with no differences between the two conditions. In conclusion, adopting the NBS promotes an increase of the activation of neck extensor muscles, possibly leading to earlier decline of the neuromuscular performance and to diminished ability to actively stabilize neck structures. For these reasons, the adoption of the NBS during dynamic, fatiguing contractions may not be appropriate.     

Optimal location of the tablet for typing while listening to a song

Tablets are much heavier than smartphones and able to bring more musculoskeletal disorders in the upper extremities. The aim of this study was to understand the effects of tablet location on the recruitment of muscles in the neck and upper extremities. Fifteen healthy volunteers typed the lyrics while listening to a song at three tablet locations for 5 min. An iPad 2 was randomly located at one of the levels with 70, 90, and 130 degrees of elbow flexion in sitting. Typing duration, frequency of typing error, perceived levels of fatigue, and subjective position preferences were recorded and recruitment of muscles in the neck and upper extremities was measured. Muscle recruitment of three parts of the trapezius and biceps brachii decreased and use of the levator scapula increased as the vertical level of the tablet heightened. Self‐reported discomfort increased significantly in the neck, upper back, shoulders, elbows, and wrists over time regardless of the tablet location. The table location affected the self‐reported discomfort only at the elbow joints. Subjective preference was highest at the lowest tablet location with the 130‐degree elbow flexion. The vertical levels of the tablet and typing duration independently affected the muscle recruitment and self‐reported discomfort. Findings of this study can be helpful for tablet users in preventing musculoskeletal disorders in the upper extremities.     

Upper trapezius muscle activity in healthy office workers: reliability and sensitivity of occupational exposure measures to differences in sex and hand dominance

Patterns of cervical muscle activity may contribute to overuse injuries in office workers. The purpose of this investigation was to characterise patterns of upper trapezius muscle activity in pain-free office workers using traditional occupational exposure measures and a modified Active Amplitude Probability Distribution Function (APDF), which considers only periods of active muscle contraction. Bilateral trapezius muscle activity was recorded in 77 pain-free office workers for 1–2 full days in their natural work environment. Mean amplitude, gap frequency, muscular rest and Traditional and Active APDF amplitudes were calculated. All measures demonstrated fair to substantial reliability. Dominant muscles demonstrated higher amplitudes of activity and less muscular rest compared to non-dominant, and women demonstrated less muscular rest with no significant difference in amplitude assessed by Active APDF compared to men. These findings provide normative data to identify atypical motor patterns that may contribute to persistence or recurrence of neck pain in office workers.

Practitioner Summary: Upper trapezius muscle activity was characterised in a large cohort of pain-free workers using electromyographic recordings from office environments. Dominant muscles demonstrated higher activity and less rest than non-dominant, and women demonstrated less rest than men. Results may be used to identify atypical trapezius muscle activity in office workers.     

Effects of the weight configuration of hand load on trunk musculature during static weight holding

The performance of manual material handling tasks is one major cause of lower back injuries. In the current study, we investigated the influence of the weight configuration of hand loads on trunk muscle activities and the associated spinal stability. Thirteen volunteers each performed static weight-holding tasks using two different 9 kg weight bars (with medial and lateral weight configurations) at two levels of height (low and high) and one fixed horizontal distance (which resulted in constant spinal joint moment across conditions). Results of the current study demonstrated that holding the laterally distributed load significantly reduced activation levels of lumbar and abdominal muscles by 9–13% as compared with holding the medially distributed load. We believe such an effect is due to an elevated rotational moment of inertia when the weight of the load is laterally distributed. These findings suggest that during the design and assessment of manual material handling tasks, such as lifting and carrying, the weight configuration of the hand load should be considered.

Practitioner summary: Elevated trunk muscle activities were found when holding a medially distributed load vs. a laterally distributed load (with an equivalent external moment to the spine), indicating a reduced spinal stability due to the reduced rotational moment of inertia. The configuration of the hand load should be considered when evaluating manual material handling tasks.     

基于小波变换的表面肌电信号低功耗压缩滤波算法

针对现有的表面肌电信号采集传输系统,提出三个算法分别对采样、传输、预处理这三个主要过程进行优化:在采集端降低采样功耗,在传输过程中通过低失真高倍率数据压缩减轻传输带宽负荷,从而降低传输功耗,在接收端通过信号预处理滤除工频干扰,同时对算法复杂度进行评估并提出参数的自适应策略.经仿真验证,本文提出的算法对低功耗表面肌电信号系统设计、优化具有较好的实用性.     

上肢经肱骨截肢神经功能重建研究

表面肌电信号是一种安全、非侵入的电生理信息,作为实现直觉控制多功能肌电假肢系统的信息源而被广泛应用。由于经肱骨截肢者截肢的程度较高,残留的肢体肌肉少,缺乏足够的肌电信息源,无法实现多功能肌电假肢的直觉控制。目前现有技术是通过采用靶向肌肉神经功能重建的方法重建缺失肌电信息源。但目前国内尚未有关于截肢者残端神经功能重建方法的相关研究。因此,文章提出一种新型的神经吻合技术——目标神经功能替代术：采用靶向肌肉神经功能重建术与目标神经功能替代术相结合的方法,首次在国内对经肱骨截肢者成功实施了神经功能重建手术,成功建立了经肱骨截肢者神经功能重建模型,重建了因截肢而丧失的肌电信息。并采用高密度肌电技术对术前和术后的手-腕-肘部动作进行肌电信号采集,通过动作分类识别的准确率验证了该手术后肌电信息源重建的可靠性。这些结果初步验证了该方法可以为经肱骨截肢者残肢重建缺失肢体神经功能,并为直觉控制多功能肌电假肢提供潜在的信息源。     

Analysis of sEMG signal for KOA classification

The sEMG signals are collected from the vastus lateralis,vastus medialis,biceps femoris,and semitendinosus of lower extremity during level walking among control subjects and knee osteoarthritis (OA) pa...