A compalative study of maximal aerobic power (MAP) with special reference to age were carried out as a basic study for determing the optimal physical load for successful living in modern society or in future ages. 169 males who have a sedentary living style profoundly affected by the motorization, 10-69 years of age, in suburban district of Fukuoka City (JAPAN) and 54 males who have a natural living style, 16-55 years of age, in rural districts of Nepal were selected as subjects. Measurement of MAP was made indirectly following to the method of Margaria et al.. Each subject were given two different intensity step up and down exercises, and MAP was calculated from heart rates immediately after exercises and individual's estimated maximal heart rate. % Fat was estimated from skinfold thickness according to the method of Nagamine.
Statistically significant correlations were found both of Japanese group (r= -0.554, P<0.001) and Nepalese group (r=0.561, P<0.001), and each regression equation etween MAP (ml/kg/min) and Age (yr) were as follows :
MAP=-0.350 Age +52.121 in the case of Japanese group.
MAP=-0.446 Age +63.395 in the case of Nepalese group.
However, difference of the regression coefficient was not significant.
Mean MAP per kilogram of body weight or per kilogram of lean body mass of every Japanese age groups wese lower than those of Nepalese groups with coincidental age, respectively. Generally, it is said that the socio-economical condition of Nepal today is a similar to that of Japan in the Meiji era. Therefore, it may be considered that modernization or urbanization have lowerd the system of Japanese people.
According to the review of literatures concerning to the living style and MAP in a evolutional and comparative point of view, it may be considerd that human races have maintained the relatively high MAP like Nepalese group today. Therefore, it is said conclusionally that the maintenance of mean MAP like Nepalese group is desirable in modern society or in future ages to prevent the degeneration of functions attributing the new health problem of modern society.

The relations between the power output during exercise and its maximal duration have been investigated on three young male subjects throughout the performance of heavy constant loaded cycling exercises with different intensities, all of which lead to exhaustion during the period from about 20 seconds to about 100 minutes.
The Aerobic Power output (mean total oxygen intake during exercise) develops rapidly with the increase of the maximal duration of exercise amounting to a few minutes in every case, and then, levels off approximately in one case, but declines steadily in the other cases.
The Anaerobic Power output (oxygen debt per endurance time of exercise) decreases rapidly with the increase of the maximal duration of exercise amounting to about 5 minutes, and then decreases slowly.
The relation between the Total Power output (sum of the Aerobic Power output plus the Anaerobic Power output) and its maximal duration is summarized as the two equations : log P = a - b logt, in the case of the t shorter than about 5 minutes, and log P =a′ - b′log t, in the case of the t longer than about 5 minutes. Here, P is the Total Power, tis the maximal duration, and a, b, a′ and b′ are constants. In each subject, the values of the constants a and b respectively. are greater than the a′ and b′
The present investigation was supported by a Grant in Aid for the Miscellaneous Scientific Research from the Ministry of Education.

“Power-Duration Curves” had been measured on three middle aged subjects through-out the performance of heavy constant loaded cycling exercise with different intensities. And the results were compared with the results of previous investigation on young subjects for the purpose to know the properties of the physical work capacity of middle aged man.
The relations between the Total Power output (TP) and its maximal duration (t) is summarized as the following two equations: log TP=a-b·log t, in the case of the t shorter than about 5-6 minutes, and log TP=a′-b′·log t, in the case of the t longer than about 5-6 minutes. The relations between the Anaerobic Power output (AnP) and its maximal duration (t) is also summarized as the two equations: log AnP=c-d·log t, in the case of the t shorter than about 1-4 minutes, and log AnP=c′-d′·log t, in the case of the t longer than about 1-4 minutes. The above equations are applicable to the results of every subjects in each age group, then, the age difference in quality is hardly found. However, the values of the constants a, a′, c and c′ in the above regression equations are respectively lower in the middle aged subjects, the other hand, the age difference is scarcely found in the values of the constants b, b′, d and d. It is also said that the endurance time of the certain Aerobic Power output of the middle aged subjects are shorter than young ones within the experimental region.
It is considered that the one of the reasons, both of the endurance times of the certain Aerobic Power output and Anaerobic Power output are shorter in the middle aged subjects than young ones, is the maximal aerobic power and the maximal anaerobic capacity of the middle aged subjects are lower than young ones.
In this paper, the Aerobic Power is a mean total oxygen intake during exercise, the Anaerobic Power is a oxygen debt per endurance time of exercise. The term of the “Anaerobic” is not most suitable one, however it is used for convenience. The Total Power is defined as the sum of the Aerobic Power plus the Anaerobic Power.