Quality-sorting jobs in four fruit-sorting plants and one rice-processing plant in Niigata Prefecture were investigated as well as experimental simulations on colour-sorting jobs of plastic marvel and kidney bean, to have a closer look at characteristics of physiological load in so-called conveyor work, which kind of work tends to increase recently in Japanese farming, Results obtained are as follows:
1. Complaints of subjective symptoms on monotonous feeling varied depending on work conditions. However, the complaints ratio of negative feeling was generally found more in quality-sorters than in workers in other jobs at the same plants, in experimental conveyor work than in table work, and also in relatively higher conveyor speed than in lower speed.
2. Increase rate of expiration during work to that in rest period was almost less than 50%. There were no definite relations between this rate and work conditions.
3. During one work session of 90min or more, heart rate mostly increased at the beginning, then decreased a little into settled condition in the middle period and slightly increased again toward the end of work. This successive change was almost similar to the typical pattern in nervous work
4. Increase of heart rate during work was almost below 25%. Most investigated and experimented jobs were assumed to be classified into light class in terms of relative metabolic rate. There was low positive correlation between this increase rate and work output (r=+0.46, 90% level significant). So, heart rate is assumed to increase proportionally to frequency of picking-up movement of arms.
5. Coefficient of variation of heart beat interval (sinus arrhythmia) during work more or less decreased compared with that in rest period except for in case of the lowest conveyor speed, and the ratio of the former coefficient to the latter significantly decreased and reflected raise-up of nervous load almost in proportion to the increase of conveyor speed. Putting subjective and objective symptoms together, the lowest speed in the experiment seemed to be optimum for picking up small materials. However, further problems should be studied on the relations between properties of materials, belt speed and work load.
6. Ratio of expiration increase rate to that of heart rate was obviously lower in conveyor work than in step-test. This ratio may roughly and relatively indicate which factor seems to be more dominant in work load, muscular or nervous.
7. Critical flicker fusion frequency decreased after a session of work and recovered after each recess, especially in the afternoon and in the evening. But, no definite tendencies were found between the decrease rate and work conditions.

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