[Multivariate analysis on the relationship between subjective symptoms and risk factors for the development of symptoms including working conditions, life habits and physical status in forestry workers using chain saw].
ABSTRACT To determine the risk factors of the subjective symptoms experienced by chain saw workers, we surveyed 206 forestry workers using this device in their work. The strength of the relationship between their symptoms and such potential risk factors as occupational, behavioral, and physical factors was evaluated by a multiple logistic regression model. It was found that many years of chain saw operation, and numerous hours of chain saw operation per day, increased the risk of white finger, numbness of hands and arms, chillness of hands and arms and difficulty in joint movement, indicating that these symptoms were closely related to vibration exposure. Many years of forestry work before chain saw work also increased the risk of joint pain, suggesting that bone and joint disorders are related to heavy manual work not using a chain saw. A second job involving manual labor increased the risk of weakness in the arms, stiffness of the shoulders, and lumbago. Infrequent bathing was associated with increased risk of pain in hands and arms and lumbago. Older workers had a higher prevalence of stomach discomfort. No risk factor was found to significantly increase the risk of easy fatigability, forgetfulness and sleep disorder. It was found that not only exposure to vibration but also other factors contributed to the prevalence of pain in hands and arms, joint pain, weakness in arms, stiffness of shoulder, and lumbago. Second job and infrequent bathing appeared to be related to the occurrence of certain subjective symptoms. These contributory factors should be taken into account when evaluating subjective symptoms encountered in field studies of forestry workers.
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ABSTRACT: Four rats obtained food pellets by poking a key and 5-s presentations of the discriminative stimuli by pressing a lever. Every 1 or 2 min, the prevailing schedule of reinforcement for key poking alternated between rich (either variable-interval [VI] 30 s or VI 60 s) and lean (either VI 240 s, VI 480 s, or extinction) components. While the key was dark (mixed-schedule stimulus), no exteroceptive stimulus indicated the prevailing schedule. A lever press (i.e., an observing response), however, illuminated the key for 5 s with either a steady light (S+), signaling the rich reinforcement schedule, or a blinking light (S-), signaling the lean reinforcement schedule. One goal was to determine whether rats would engage in selective observing (i.e., a pattern of responding that maintains contact with S+ and decreases contact with S-). Such a pattern was found, in that a 5-s presentation of S+ was followed relatively quickly by another observing response (which likely produced another 5-s period of S+), whereas exposure to S- resulted in extended breaks from observing. Additional conditions demonstrated that the rate of observing remained high when lever presses were effective only when the rich reinforcement schedule was in effect (S+ only condition), but decreased to a low level when lever presses were effective only during the lean reinforcement component (S- only condition) or when lever presses had no effect (in removing the mixed stimulus or presenting the multiple-schedule stimuli). These findings are consistent with relativistic conceptualizations of conditioned reinforcement and extend the generality of selective observing to procedures in which the experimenter controls the duration of stimulus presentations, the schedule components both offer intermittent food reinforcement, and rats serve as subjects.Journal of the Experimental Analysis of Behavior 04/2002; 77(2):171-87. · 1.48 Impact Factor