Annals of Occupational and Environmental Medicine

Original Article

Usefulness of Power Spectral Analysis for Measurement of Local Muscle Fatigue during Keyboard Task: Soon Young Kwon, Chung Yill Park, Jung Wan Koo, Hyeon Woo Yim, Kang Sook Lee; Korean Journal of Occupational and Environmental Medicine 1999;11(4):449-459. Published online December 31, 1999; DOI: https://doi.org/10.35371/kjoem.1999.11.4.449

Abstract PDF: OBJECTIVES
Work-related upper extremity disorders of the tendons, nerves, and musdes associated with. repetitive motion represent an increasing proportion of occupational illnesses, medical services, and workers' compensation costs. Severe local muscle fatigue may be a precursor of repetition strain injuries. The demand for objective and quantitative assessment of local muscle fatigue is now increasing. The purpose of this study is to determine the usefulness of power spectral analysis of individual muscle as one of the objective spectral parameters in quantification of local muscle fatigue.
METHODS
From 10 normal male without neuromuscular dysfuction, motor unit action potentials (MUAPs) of three muscles (upper trapezius, infraspinatus, and anterior deltoid) of left shoulder girdle were obtained. The surface electrodes were used and the changes of power spectrum according to frequency components were calculated per minute during the keyboard task for 30-minute period by power spectral analysis of MUAPs signal.
RESULTS
There was a linear relationship between median frequency (MF) and time flow in the upper trapezius muscle, however the same was not observed in other muscles. The MF slope of the upper trapezius muscle showed a decline of the MF over time and reflected the fatigue rate. Other spectral parameters, such as mean frequency and total power were not significantly correlated to time flow during the keyboard task in all three muscles. And no significant correlation was observed between keying rate and slope of median frequency of upper trapezius muscle.
CONCLUSIONS
Above results suggested that the power spectral analysis on median frequency in upper trapezius muscle would be useful in quantification of local muscle fatigue during the keyboard task and local muscle fatigue of shoulder was affected by static posture, not by keying rate.

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Original Article

A Survival Case Sustained Pulmonary Damage After Paraquat Ingestion: Won Oh Choo, Se Hoon Lee; Korean Journal of Occupational and Environmental Medicine 1996;8(2):223-227. Published online September 30, 1996; DOI: https://doi.org/10.35371/kjoem.1996.8.2.223

Abstract PDF: The rapid quantification of paraquat in body fluids is of undoubted value in both initial assesment as well as the immediate prognosis of acutely poisoned patients. A 20-year-old woman ingested a mouthful of paraquat. Serum and urine paraquat levels were measured colorimetrically for 48 hours after identifying the presence of paraquat in her urine by a Paraquat test kit. At that time her survivability was considerd to be over 50% according to Proudfoot's scale of time related measured serum paraquat levels. Five days after admission, she began to cough but her chest x-ray picture was normal. However, she persisted to cough and subsequent chest x-rays showed fine reticulonodular densities in both upper and lower lobes. Twenty days after admission, she .was clinically well, and not deteriorated radiologically. Therefore, respiratory function tests were under-taken. They showed reduced lung volume, moderate reduction in ventilatory capacity, and a diffusion defect (DLco: 27% predicted value). Twenty four days after admission, the patient was discharged in good condition except for the sequale of lung involvement. Six months later, she was re-examined and found to be healthy with a large regression of lung lesions on her chest x-ray.

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