Research Activities on Aerospace Medicine in Japan: Past, Present, and Future

Introduction Research activities on aerospace medicine are increasing in these years and getting more and more unportance in Japan. We have rather long history of researches on aviation medicine, but have only short history of researches on space medicine. In this paper, I would like to present a brief review on past, present and future of research activities on aerospace medicine in Japan, expecting to have more cooperations between Korea in this field of research in the near future.

Enhanced performance of maximum vertical jump by arm movement / 体力科学

The effects of an arm lifting movement (ALM) on maximum vertical jumps with all but the ankle joints fixed (propelled only by plantar flexion) were studied in five subjects. ALM increased flight time, but did not alter maximum angular velocity of the ankle before takeoff. Holding 4kg dumbbells in their hands enhanced the effect of ALM on flight time. ALM increased the maximum force and the force at the onset of plantar flexion. Elbow angle recordings showed that both arms were accelerated before or around plantar flexion onset, and decelerated mainly after takeoff. In another series of experiments, we measured the vertical component of head and hand acceleration with accelerometers. ALM produced positive acceleration of the head after takeoff, which was related to negative acceleration of the hand. The results suggest that ALM increased flight time by enhancing plantar flexion torque under suppression of ankle angular velocity before takeoff. We discussed the relationship between this suppression and different acceleration between the arms and the body except the arms.

Anticipation of exercise and response in skin and muscle sympathetic nerve activity / 体力科学

A study was conducted to determine whether anticipation of exercise alters the responses of sympathetic nerve activity to muscle contraction. Sympathetic nerve activity leading to the skin (SSA) and muscle (MSA) was recorded from the tibial nerve in the left and right legs using tungsten microelectrodes. Heart rate and blood pressure (oscillometric method) were also measured during the experiment. Seven healthy subjects, who gave informed consent, participated in the experiment. They were asked to exert a static handgrip (SHG) for 2 min at a tension of 30% of maximal voluntary handgrip. Two different situations were set before the commencement of exercise. One was that after several minutes of controlled rest, a countdown was started 2 min before the exercise, and then the handgrip was applied (Cond. 1) . The other was that a preparation time of between 7 and 5 min was set prior to the handgrip exercise while no information regarding the starting time of exercise was given to the subjects (Cond. 2) . SSA for 30 s just before the exercise was increased in comparison with the control value at rest in Cond. 1, but not in Cond. 2. There was no difference in the SSA response patterns to SHG between the two conditions. Before the commencement of SHG, MSA did not alter from the control value at rest in either condition. The magnitudes of the increase in MSA during SHG were almost identical under both conditions. Heart rate for 30s before SHG in Cond. 1 was increased significantly from the control value, whereas there was no significant change in Cond. 2. The magnitude of the heart rate response to SHG was the same in both conditions. The mean blood pressure showed no significant change before SHG, but increased significantly during SHG in both conditions. The increases in SSA and heart rate prior to the commencement of exercise may be related to the anticipatory response to the exercise, although this response was not significant in MSA. These results confirm that anticipation of exercise increases sympathetic outflow to the skin. This may be advantageous in adapting the body to exercise.