The relationship between serum creatine phosphokinase (CPK) activity and labor strength was examined.
Our epidemiological study showed thar the serum CPK activity in a group of men who worked over ten hours was significantly higher than that in the other groups who worked less than ten hours. In women, the serum CPK activity in a group who worked over seven hours was significantly higher than that in the other groups. The serum CPK activity in fishermen was significantly higher than that in those engaged in other than fishery.
In a laboratory study, test subjects were divided into 3 groups to perform 3 types (30%, 50%, 70% of VO_2max) of exercise for 6 weeks. A rise in the serum CPK activity was noted in every group during exercise. The mean increase for these groups were 44.0 %, 48.1 % and 67.9 %, respectively.

The effect of daily physical activity on the serum lipid level was examined. This study consisted of two parts, an epidemiological study and a laboratory study.
In the epidemiological study, we investigated the relationship between serum lipids and energy expenditure in young adults females. Significant correlations were found between energy expenditure/body weight and the levels of serum HDL-cholesterol and serum triglyceride, and atherogenic index.
In the laboratory study, we examined the effects of exercise on the serum lipid level. Groups of subjects took part in the programs of physical activity of two different intensities for 6 weeks, and their serum lipid levels before and after these programs were compared. Exercise regimens of increasing intensity caused a significant mean increase in the serum HDL-cholesterol level. However, these regimens did not cause any significant change in serum total cholesterol and serum triglyceride values.
These results suggest that doing even light exercise on a regular basis is effective in producing an optimum serum lipid pattern in young adult females.