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In this experimental comparative study between a prototype lever-propelled wheelchair and conventional hand rim wheelchair, trunk muscles activity in able-bodied subjects was examined using surface electromyography (SEMG). Fifteen healthy males and non-wheelchair users were recruited in Tripoli, Lebanon. Participants successfully performed two propulsion trials on both types of wheelchair: conventional (hand rim; CHr) and non-conventional (lever-propelled prototype; NCLP) at a preselected speed of 0.9 m/s. Variables measured included muscle activity, frequencies, fatigability and the intensity of muscle contractions on two types of propulsion. Results showed that both abdominal and back muscle groups revealed significantly lower activation during NC-LP compared to the C-Hr propulsion. Results showed also muscle activation profile of the trunk musculature at two type of wheelchair propulsion. Our results suggested a necessity of a future study design methodology including wheelchair users with spinal cord injury.

Low Back Pain (LBP) affects the vast majority of the population at some point in their lives. People with LBP show altered trunk muscle activity and enhanced fatigability of trunk muscles is associated with the development and future risk of LBP. Therefore, a system that can forecast trunk muscle activity and detect fatigue can help subjects, practitioners and physiotherapists in the diagnosis, monitoring and recovery of LBP. In this paper, we present a novel approach in order to determine whether subjects are fatigued, or transitioning to fatigue, 25 seconds ahead of time using surface Electromyography (sEMG) from 14 trunk muscles. This is achieved using a three-step approach: A) extracting features related to fatigue from sEMG, B) forecasting the features using a real-time adaptive filter and C) performing dimensionality reduction (from 70 to 2 features) and then classifying subjects using a supervised machine learning algorithm. The forecasting classification accuracy across 13 patients is 99.1% ± 0.004 and the area under the micro and macro ROC curve is 0.935 ± 0.036 and 0.940 ±0.034 as determined by 10-fold cross validation. The proposed approach enables a computationally efficient solution which could be implemented in a wearable device for preventing muscle injury.

BACKGROUND: Sitting nowadays is typical working position and causes various harmful effects which could be minimized by regular changes of position implemented due to periodical activation of corresponding muscles. OBJECTIVE: To determine changes of trunk muscles activity and posture after prolonged sitting on unstable chairs. METHODS: 20 office workers participated in the study. Posture and movements of their torso and pelvis were measured by 3D MoCap system and four trunk muscles activities - by electromyograph. Three different unstable chairs were tested when performing three different tasks while sitting on teach of them. RESULTS: Trunk muscles activity significantly increased after 6 weeks sitting on unstable chairs: Multifidus muscles - 8.88 %, Transversus abdominis muscle - 5.19 %. Measurements of C7, Th7, L3 spine angle showed that it increased by 2 degrees when sitting on Back app and Human Tool unstable chairs. CONCLUSIONS: Sitting on unstable surfaces for 6 weeks significantly increased Multifidus and Transversus abdominis muscles activity, which are responsible for spine stabilization. Unstable chairs, especially Back app and Human Tool, have positive influence on the posture of participants. It means that chairs, mentioned above, it is proper for prolonged sitting position at workplace due to improvement of the posture and muscles activity.

Weight gain and stretched and weakens abdominal muscles by an enlarging gravid uterus are remarkable features during pregnancy. These changes elicit postural and movement instability and place strain on various body segments. In general, agonist and antagonist muscles of body segments act simultaneously to increase joint stabilization during human movements. The co-contraction might be well observed in pregnant women because of their unstable body joints. Musculoskeletal models are well used to investigate muscle load. However, very few studies have been conducted on the model for pregnant women. Additionally, it is difficult to estimate the co-contraction of muscles by using musculoskeletal models. Therefore, the purpose of this study is to construct musculoskeletal model for pregnant women and estimate co-contraction of trunk muscles. At first, motion analysis of sit-to-stand for a pregnant woman was conducted to obtain the motion and force data for inputting to musculoskeletal model. Simultaneously, muscle activation of rectus abdominis and longissimus were measured by using surface electromyography. On the other hand, the size and mass of body segment of a musculoskeletal model were changed to meet pregnant women. Then, stretched abdominal muscle was modeled. At last, the co-contraction of rectus abdominis and longissimus was estimated from EMG data and joint torque that was calculated from the musculoskeletal model using genetic algorithm.

The recruitment pattern of trunk muscles is determined using a three-dimensional model of the spine with two joints and six symmetric pairs of muscles in which both equilibrium and stability requirements are satisfied. Model predictions are verified using Anybody Modeling System (AMS) and Abaqus. The model is used to test the hypothesis that antagonistic muscle activities are necessary for the spinal stability. The model with stability constraints predicts muscle activities greater than those predicted without stability consideration. In agreement with experimental data, the stability-based model predicts antagonistic muscle activities. It is shown that spinal stability increases with trunk flexion and further improves at heavier tasks.

Flexed postural tasks are frequently involved in daily activities, this paper evaluated a wide range of trunk muscle electromyogram (EMG) features to find the best feature spaces that discriminate among different trunk flexion angles. Using Davies-Bouldin index (DBI) and Calinski-Harabasz index (CHI) it was found that zero crossings, mean power frequency, median power frequency, and second order cumulants of extensor muscles' EMG, independent of holding load level and electrode location (right or left side of muscle) are the most sensitive features to trunk flexion angle variation.

In this study, posture and spinal stability were evaluated during a manual task in a standing posture on a movable scaffold at two levels of heights, with and without safety handrails between experts and novice construction workers using insole pressure transducers and muscle activities of trunk muscles. Eight construction workers (4 experts and 4 novices) working at a construction site participated in the experiment for ergonomic assessment. A significant difference was found in postural stability, spinal stability with regard to career (p

This paper studies the time-frequency analysis of trunk response based on surface electromyography (EMG) under an experimental protocol of sudden load release. Due to difficulties in feature extraction of surface EMG in short-time muscular reflex using conventional time-frequency analysis algorithms, a novel method called adaptive Lomb periodogram (ALP) is employed to improve the time and frequency resolutions by adaptively selecting the window sizes. Experimental results demonstrate the improved time-frequency resolution of the ALP in analyzing the EMG signals compared with conventional methods using scalogram. The findings of this study would provide important information in devising objective and quantitative protocol for neuromuscular function assessment, which are applicable to rehabilitation of low back pain patients, motor control and training, elderly fall prevention and ergonomic studies.

The ability of individuals with trans-tibial amputations and trans-femoral amputations to perform a lifting task using different weights was compared to able-bodied individuals (ABI). Overall, the three subject groups showed very similar lifting styles and dynamics. Differences were observed that suggest that amputees rely more on shoulder and trunk muscles than ABI and have less lateral stability.

The relationship between the electromyographic activity of erector spinae at L/sub 3/ level and hand force during isometric and multispeed isokinetic (20 cm S/sup -1/, 60 cm S/sup -1/, and 100 cm S/sup -1/) arm lift and back lift was investigated among ten normal male subjects. The magnitude of the EMG (electromyogram) signals at the intervals of one-tenth of the activity cycle were significantly different during isokinetic back lifts (p >

In urological surgery on 4 surgeons the electro-myograms of several shoulder and trunk muscles were studied during 29 endoscopic operations. Two operation methods were compared: 1. use of a look-through endoscope (direct endoscopy) and 2. use of a video camera mounted on the top of the endoscope and a monitor (monitor endoscopy). The studies reveal a significant decrease in the myoelectrical activity of both trapezius muscles due to the use of a video system. In the course of the operations an increase in the myoelectrical activity of the trapezius and deltoideus muscles is observed which is interpreted as a sign of muscle fatigue. It is concluded that the last part of the operation has to be performed when the shoulder muscles are already fatigued.