Researchers in Japan have studied the effects of underwater exercise upon relaxation. Using 8 healthy young men between the ages of 20-26. Three different forms of exercise were used in warm water (34° ) to gauge the effect on relaxation.

Comparing the power values of the electroencephalogram alpha bands and the profile of mood states, it was found that both measured significant increases in the strength, positive mood and vigour. This study showed that underwater exercise improved and increased the physiological and psychological effects of relaxation on those that took part.