Relaxation effects in humans of underwater exercise of moderate intensity.

In this study we investigated the effects of underwater exercise in warm water (34 degrees C) on physiological and psychological relaxation. Eight healthy young men (aged 20-26 years) volunteered for the experiment. The experiment consisted of the following three successive segments: a pre-exercise period of 20 min, during which the subjects rested in a semi-supine posture with their eyes closed for the final 10 min; an underwater exercise period of approximately 60 min, during which the subjects performed gymnastic exercises or aerobic dancing with occasional movements or jumping; a post-exercise recovery of 20 min, which was similar to the pre-exercise rest period. We compared the relative power values (power %) of the electroencephalogram alpha bands (8-13 Hz) and profile of moods states (POMS) before and after the underwater exercise. We also estimated the percentage of maximal heart rate (%HRmax) throughout the experiment to ascertain the intensity of the underwater exercise. The results of %HRmax indicated that the intensity of underwater exercises practised in the experiments ranged from low to moderate. The power % of EEG alpha bands had increased significantly after the underwater exercise compared with the pre-exercise rest (P<0.05). From the POMS results, we observed that positive mood (vigour) increased and negative mood (tension and anxiety, depression and dejection) decreased significantly after the underwater exercise (P<0.05). This study found that the subjects showed increased physiological and psychological indices of relaxation after underwater exercise.