[Body acceleration measurement and oxygen uptake during jumping].

The integral of the positive acceleration per unit time was defined as physical activity. The device that measured physical activity during jumping was developed and the relationship between physical activity by acceleration measurement and energy expenditure was evaluated. Acceleration wave forms of back were measured with strain gauge type accelerometer. After amplification and rectification, the positive acceleration wave forms integrated. When the output of the integrator reached the threshold of comparator, the output of the comparator contained trigger signal. The physical activity was determined by the total counts of the trigger signal. 10 males jumped at four jumping cycles (20, 40, 60 min-1 and random) and 24 children jumped at random jumping. Oxygen uptake, physical activity and heart rate were simultaneously measured. The results showed the oxygen uptake, physical activity and heart rate of males were linearly related to jumping cycle. However, oxygen uptake of random jumping was less than one of 60 min-1 jumping in spite of the greater physical activity. This result indicated that the random jumping was operated efficiency due to the effect of elastic bounce. The oxygen uptake/body weight of males had good correlation to physical activity (r = 0.922), and heart rate (r = 0.902). Also the oxygen uptake/body weight of males and children had good correlation to physical activity (r = 0.953). The difference of ages and weights was not significant during jumping. These results mentioned to be useful in providing an objective evaluation of the physical activity of human subjects during jumping.