The effects of maternal physical exercise during eary pregnancy upon the embryonic development of mice were studied as follows: A/Jax female mice at 10 to 16 weeks of age were imposed daily compulsory running at the speed of 15 meter/min. using a tread mill for 100 min. for the period from zero to 6th day of gestation (called severe exercise group) and for 50 min. from zero to 13th day of gestation (called mild exercise group) respectively. All mice together with the control group without the exercise were sacrificed at 18th day of gestation and the states of concep.uses as well as external and skeletal development of fetuses were observed. The results may be summarized as follows:
1.Significant pregnancy-blocking effect was found in the severe exercise group and it is presumed that the treatment caused obstruction of implantation or maintaince of early pregnancy after implantation in most cases.
2. No significant differences were observed in litter size, fetal mortality, fetal body weight and frequency of the malformed fetuses between pregnant mothers of each of experimental group and control group.
3. The progress of ossification in the mild exercise group was slightly superior in some part of the skeleton to that of the control group.

The relationship between exercise habit and physical fitness in aged individuals was studied in 179 urban residents aged 60-89 years (82 males and 97 females) by a battery of physical performance tests. Eighty-seven point eight percent of the males and 88, 5% of the females were regularly engaged in some kind of exercise, most frequently walking (45.8% of the males and 37.7% of the females), followed by tending plants, croquet, and light exercise (about 30% each) . More strenuous exercise such as swimming, tennis, and jogging was done by 2-3%. The results of the tests were better in individuals who exercised regularly than those who did not, and the differences were significant in grip strength, breath holding, and total score in the males and in all items except grip strength in the females. Physical performance also differed among those who exercised according to the frequency, duration, and intensity of the exercise, but the differences were smaller than between those who exercised and those who did not. From these findings, relatively mild exercise is considered to be effective for preventing (or delaying) the decline of physical fitness in aged individuals.