The efect of some types of exercise on systolic pressure was studied. The results were as follows.
1. Increased rate of systolic pressure immediately after run of eight distances was greatest in 100 meter run. Such a high level was also observed in both 400 and 1, 500 meter runs.
Further prolongation of the distance, however, induced a sharp reduction of increased rate to 5, 000 meters and in a run of still longer distance the above tendency was weakened.
2. If these results are applicable to the change of systolic pressure during a prolonged exercise, Edward's graphic representation seems to be true. Some of our experiments, however, indicated that Edward's curve was not the only case.
Some features often expected were the following.
a) Generally, the final rise was low if the initial rise was low.
b) However, the final rise would be high in the cases with a faster finish even if the initial rise was low.
c) In general, the final rise was high if the initial rise was high.
d) However, the final rise would be lowering as development of exhaustion even if the initial rise was high, and only this form was considered to analogize with Edward's curve.
3. Blood pressure was determined during short interruption of exercise in 10, 000meter run. The lap time was estimated immediately before the determination of pressure.
Since there was a strong statistical correlation between the increased rate of systolic pressure and the lap time (r=0.698, P<0.01), the fall in systolic pressure increased at early stage in a long continued exercise was supposed to be induced by decreased pace.
Therefore, decreased severity of exercise may be a major factor inhibiting increase of pressure during prolonged exercise. It is undeniable that this type brought about by in-hibiting pressor effect is angmented by some nervous or humoral factors.
4. The longer the distance, the earlier the subnormal phase after exercise tends to start and the deeper the drop of systolic pressure will become.
In all of the four prolonged runs over 5, 000 meters was observed average drop below normal of about 20 per cent and the lowest value of 28 per cent except two cases indicating marked fall. Futhermore, average fall below normal in mean arterial pressure induced after increased pressure by epinephrine was 30 per cent in rabbits. These data showed that in subnormal phase there may be a certain lower limit to sink and that the existense of this protective line of defence would prevent deterioration of the circulation.
5. The systolic pressure rised in the trained higher than in the untrained immediately after a short and sharp effort, but in the former the reduction of the rise with longer distance of run was more slight than the latter.