Papers by Keyword: Muscle Activity

Abstract: In the recent years, Advance Manufacturing Technology (AMT) has been widely used in manufacturing industry to increase manufacturing process capability. However, Computer Numerical Control (CNC) machine designs have only focused on its operational capability. The harmonious coordination between users and CNC machines is often neglected, which can contribute to hazardous working practices that can affect the health of users. Bending posture while loading the work piece to the machine can cause fatigue and discomfort to the users. Thus, the focus of this preliminary study is to analyse the effect of CNC machine work piece loading on muscle activity levels and to determine the effectiveness of roller conveyor in reducing muscle activity levels. Muscle activity has been analysed using surface electromyography (sEMG) technique. Erector spinae, biceps and trapezius muscles were concurrently measured during the work piece loading. Five male subjects (n=5) participated in the pre-intervention study and two subjects (n=2) in the post-intervention study (roller conveyor implementation) participated to test the effectiveness of the roller conveyor. Result pre-intervention study found that muscle activity level of biceps was the highest followed by trapezius and erector spinae. Based on the post-intervention study involving the roller conveyor, muscle activity of the erector spinae was reduced meanwhile the muscle activity of biceps and trapezius increased for both subjects.

Abstract: The paper focused on the effects of vibration exposure on muscle activity and grip strength. The study was conducted on eighteen subjects, required to drill wood material using electric drill for 5 and 15 minutes. Electromyography (EMG), Vernier Labpro with 3 axis accelerometer and hand dynamometer were used in the experiment. The results showed that right extensor carpi radialis muscle had the highest percentage of Maximum Voluntary Contraction (MVC) with values of 21.8%MVC-23.5%MVC. The mean vibration level was 10.45 m/s² (5 minutes) and 10.69 m/s² (15 minutes). Drilling wood material for 15 minutes resulted in higher percentage MVC (7.79%), vibration levels (2.29%), and percentage decrease ratio (11.17%) than using 5 minutes for the extensor carpi radialis muscle. The findings of the study indicated that as the level of vibration and exposure duration increase the muscular activity and the percentage decrease ratio of grip strength would also increase.

Abstract: Main causes for discomfort experienced by vehicle drivers during driving were investigated using a rigid-body model originally developed in the AnyBody Modeling System [. The interactions between the human body and the car-seat in various combinations of seat-pan/backrest inclinations and the effect of pedal spring stiffness were analyzed using an inverse dynamics approach. To deal with the muscle redundancy problem, (i.e. the problem with the human-body containing more muscles than necessary to drive its degrees of freedom) a minimum-fatigue criterion [ was utilized. The results show that various seat adjustments (e.g., seat-pan and backrest inclinations) and the pedal spring stiffness have complex influences on the muscle activation and spinal joint forces of the human body. From the results, an optimal adjustment for the car-seat is proposed, i.e. the backrest inclination is 10° and the seat-pan inclination is between 0o to 5 o. This study can in general capture the overall interactions between human body and environment (i.e. the maximum muscle activity and spine forces), which is thought to be the factors of driving fatigue.

Abstract: In industry, manual lifting still a prevalent choice even though mechanized and automated equipment are provided. Mismatch between workers' capability and lifting height, twist angle, and load mass in manual lifting can contribute to occupational injuries such as back pain. The purpose of this study is to investigate the effects of lifting height, twist angle, and load mass on psychophysical experience, muscle activity, and heart rate while performing manual lifting activities. Subjective method associated with Likert Scale was applied to assess the psychophysical experience. Meanwhile, surface Electromyography and heart rate monitor were utilized to measure the muscle activity and heart rate respectively. Main findings of this study show that the rating of psychophysical experience, muscle activity, and heart rate increased when the lifting height and load mass increased. This study concluded that the psychophysical experience and muscle activity were affected when the lifting height, twist angle, and load mass were set at maximum level.

Abstract: Few studies have investigated sitting posture and muscle activity during computer work. This study aims to determine sitting postural angle and its influence on neck and low back muscle activity in ageing women workforce during computer task. Seventeen female workers aged 50 and above participated. Surface electromyography activity was recorded from cervical erector spinae, lumbar multifidus, longgisimus and iliocostalis in 20 minutes computer task. Concurrently inclinometer recordings from upper trunk and pelvis were used to determine back posture. The results for the upper trunk angle show that the posture deviates from the sagittal plane in range-10 to 10 degree during the task. While the pelvic rotated forward and backward in range-15 to 15 degree.Neutral sitting posture with slight extension or flexion of the upper trunk and pelvic posture performed by ageing women workforce during computer work cause reduction in muscle activity. Higher level of muscle activity was indicated in back flexion rather than back extension.

Abstract: This study was conducted to investigate changes in gait pattern that appear after somatosensory stimulation evoked by applying mechanical vibration to the ankle. The gait pattern was observed in a real time using a footswitch mounted on the soles of the feet in order to increase the effectiveness of vibration stimulation. Based on the observed gait pattern, the application site and time of vibration stimulation were determined. The changes in the gait pattern that appear after the application of vibration stimulation were analyzed by comparing the percentage of the gait cycle and the activation of the lower extremity muscles. This study was conducted on young adults, and the result showed that the gait cycle was changed according to the application site of vibrating stimulation, and that the vibration stimulation with intensity less than the threshold, induced a similar effect as shown in vibration stimulation with threshold intensity. The result of this study shows that vibration stimulation could be effectively utilized for gait correction and rehabilitation. It can be also used as basic data for inferring the correlation of the characteristics of vibration stimulation with gait variability.

Abstract: The present study was conducted to determine the strength of somatosensory stimuli applied to the human body as a method for recovery of musculoskeletal function deterioration vibration, to perform a mutual comparison of the threshold-measuring methods which allow physical quantification of the vibration sense, and to verify the accuracy and reliability of the measured threshold through the activity of the muscles. According to the results of experiments conducted on men, the threshold intensity obtained via the ascent and descent methods showed a 1.09-fold difference in size and a 0.43-fold deviation. In addition, the difference in muscular activity found through the comparison of EMG and ultrasound imaging, a 1.43-fold activity difference was observed. The results of the present study can be utilized for the threshold intensity setting of the sensory stimulation vibration and can be used as the basis for the integration of various thresholds measurements.

Abstract: Standing for long periods of time has been recognized as a potential contributor to muscle fatigue. When a person is performing activities in prolonged standing and wearing ineffective material of shoe insole, not only lead to muscle fatigue but can even cause injuries in the long term. The objective of this study is to determine the effects of two types of shoe insole materials; Ethylene Vinyl Acetate (EVA) and a combination of polyurethane (PU) and poron on muscle activity and foot pressure. The analysis of muscle fatigue was performed using surface electromyography (sEMG) while pressure under the foot was measured using FScan device. Results of comparison found that the two types of shoe insole materials showed significant difference (p-value < 0.05) in electromyography signals (µV) in the left and right gastrocnemius muscle while there are significant reductions on the peak pressure measured from the foot pressure measurement. It can be concluded that the combination of PU and poron is an effective material to be used a shoe insole for a person who is exposed to prolonged periods of standing.

Abstract: For the recognition of action sEMG signal, the muscle activity detection is the elementary work, and the morphological filter was explored to achieve the target in this paper. To reduce the noise interference in the collected sEMG signal, the band-pass filter and spectrum interpolation method were applied. Based on two structuring elements, the morphological filter was utilized to separate the action signal from the background signal. Then, the amplitude envelope which could indicate the muscle activity was acquired. The experimental results showed that the satisfying muscle activity detection performance could be implemented by the morphological filter.

Abstract: The purpose of this paper is to observe the ergonomic advantages of different car seats and how the driver is constrained to them during the drive. The study was conducted by taking in to consideration the dynamical characteristics of a standard vehicle and subjecting the human body model provided by the AnyBody Modelling System, to inertia and centrifugal forces, in three different driving posture cases. The model proved to be viable and offered an image of different car seats advantages from ergonomic point of view.