Electromyography (EMG) is known as complex bioelectricity signals that representing the contraction of the muscle in humanbody. The EMG signal offers useful information that can help to understand the human movement. Many techniques have been proposed by various researchers such as fast Fourier transforms (FFT). However, the technique only gives temporal information of the signal and does not suitable for EMG that consists of magnitude and frequency variation. In this paper,the analysis of EMG signal is presented using timefrequency distribution (TFD) which is spectrogram with different window size. Since the spectrogram represent the theEMG signal in time-frequency representation (TFR), it is very appropriate to analyze the signal. The EMG signals from Biceps muscle of two subjects are collected for body position of 0° and 90°. From the TFR, parameters of the signal such as instantaneous fundamental root mean square (RMS) voltage (Vrms) are estimated. To identify the suitable windows size, spectrogram with size window of 64, 256, 512 and 1024 is used to analyze the signal and the performance of the TFR are evaluated. The results show that spectrogram with window size of 512 gives optimal TFR of the EMG signals and suitable to characterize the signal.
Back pain is one of the prevalent injuries that occurs among Malaysian industrial workers. This is due to manual lifting task. Minimal studies have been conducted to determine the effects of manual lifting on psychophysical experience and heart rate of Malaysian population. The objective of this study is to analyze the psychophysical experience and heart rate of Malaysian in manual lifting task. The lifting task was experimented at various lifting heights (55 cm, 75 cm and 140 cm); loads with masses of 5 kg, 10 kg and 13 kg; and twist angles (0°, 45° and 90°). Six male and six female Malaysian students participated as subjects in the experiment. The Likert Scale was used to evaluate the psychophysical experience; meanwhile the heart rate monitor (Polar FT2, Finland) was applied to measure the heart rate. This study discovered that the psychophysical experience recorded the highest rating when performing lifting test at maximum load mass (13 kg), lifting height of 130 cm, and twist angle of 90°. Furthermore, the subjects experienced the highest heart rate after performing lifting test at maximum lifting height (130 cm) and load mass of 13 kg. This study concluded that the load mass, lifting height, and twist angle are proportional to the level of psychophysical experience. Additionally, when the load mass and lifting height were increased, the heart rate was also increased.
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.
Upper body discomfort has become one of the issues to drivers nowadays. In this modern era, majority of Malaysian workers drive to work daily. This paper aims to find the most uncomfortable upper body part, as well as the effect of time, body mass index (BMI) and length of arm towards upper body discomfort for drivers. Sixteen volunteers were requested to complete the questionnaire soon after they completed driving the car simulator for three duration of times (30 minutes, 60 minutes and 90 minutes). Time is proven to be the main factor affecting the upper body comfort level, with the upper arm and lower arm being the most affected part during driving, [F(2,237) =14.37, p<0.01] compared to BMI and length of arm. It can be concluded that the upper body discomfort can be caused by driving for a long time. Nevertheless, the BMI and length of arm is not the issue for upper body discomfort.
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.
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