In the control group the haematocrit value dropped from a very high level immediately after effort to much below the resting value in the 1st hour, and returned in the 4th hour to the resting value. In subjects submitted to hydromassage between the 15th minute and 45th minute of rest this value decreased slightly below the resting value only in the 2nd hour of rest. Immediately after the exercise a very high plasma potassium concentration was found in both groups, in the 15th minute of rest it decreased below the resting level, and then it increased in the control group reaching a high second peak in the 2nd hour of rest. On the other hand, in subjects having hydromassage no second significant rise of potassium level was observed. In the 2nd hour of rest the potassium level increased only to the initial level and in the 4th hour it remained at that level. The high concentration of plasma lactic acid immediately after the exercise decreased gradually in the subsequent periods of rest reaching the resting level in the control group only in the 4th hour, and in the hydromassage group in the 2nd hour. No significant changes were found in the remaining determined parameters between the studied groups.