Daily physical activities of 27 children aged from 10 months to 11 years (13 boys and 14 girls) were studied by monitoring 24 h heart rate and deriving the heart activity index (HAI), and their demands to physical activities were evaluated by questionnaires to their parents. The perspective relative activity on the day of HR recording and the observational activity judged from the children's general vividness containing physical fitness were determined in quantity from the questionnaire. The HAI was compared with total daily heart rates, waking average heart rates, sleeping average heart rates, difference of average heart rates between waking and sleeping, age, and the observational activity.
　General heart rates informations as total heart rates, sleeping heart rates, and waking heart rates showed the rapid decreasing pattern with growth. But the difference of average heart rates between waking and sleeping and the HAI had not showed any conclusive change with development.
　They showed some relationships with the individual relative physical activities of the every day.
　The HAI showed that it was avalable to evaluate the young children's physical activity even like a baby aged around 1 year. And the HAI suggested that the individual difference of children in the degree of demands and the quantity of the physical activity might started already in 1-year-after birth. It may induce the early appearance of the individual difference of the physical performance in childhood.

DESCENTE SPORTS SCIENCE Vol.12/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE