C₅₇-Black and Strong A mice were forced for physical exercise of five minutes to two and a half hours long running on treadmill or swimming just before the irradiation, then the influence of these exercises upon the radiation sensitivity was investigated, getting the results as follows:
1) The concentration of lactic acid or pyruvic acid was the highest in relatively short time after the beginning of the exercise (about 10 minutes by running and about 5 minutes by swimming).
2) Brief execise (in which lactic or pyruvic acid was assumed to be in the highest concentration level) was not observed to be effective for protection on suvival rate (30 days), average survival span or the change of body weight.
3) It was assumed that optimal preirradiation exercise functioned as a protective mechanism against lethal dose of irradiation. But it seemed to need more time than the one descrived in the item 2). In this experiment, lactic acid level was quite low when measured at the end of the apparent effective exercise.
4) It was concluded that accumulation of lactic acid had no relationship with protective effect against radiation injuries.
5) Consequently, oxygen debt seemed not to be related with the mechanism of modification of the sensitivity against irradiation.