1. The concentration of potassium in the erythrocytes and the plasma of forty-one normal subjects and twenty-five diabetic patients was measured and the results were used to calculate the total amount of potassium in the erythrocyte mass and the total amount of potassium in the plasma. The total body potassium was measured in a whole-body monitor. 2. In normal subjects a close correlation was found between total erythrocyte potassium and total body potassium and also between total plasma potassium and total body potassium. 3. The regression relation between total body potassium and total erythrocyte potassium in normal subjects was used to predict the total body potassium in diabetic patients. There was reasonable agreement between the measured and predicted total body potassium but there was poor agreement between the measured total body potassium and that predicted from the patient's height and age or height, weight and age.
1. Total body potassium was measured in professional football players before the football season began and at approximately mid-season. The values obtained were significantly higher than in healthy subjects taking only average exercise. There was a significant increase in body potassium as the season progressed. 2. Lean body mass was estimated by four methods and the results were compared. The values of lean body mass, as a percentage of body weight, were significantly higher than in healthy control subjects taking only average exercise and they also increased significantly over the period of the study. 3. The mean erythrocyte potassium concentration was lower pre-season than at mid-season and the pre-season value was also significantly less than in healthy controls. The values before and after vigorous exercise were not significantly different. 4. Conversely, the pre-season mean plasma potassium concentration was significantly higher than in control subjects and than the mid-season value. The mean plasma potassium concentration was higher before vigorous exercise than immediately afterwards. 5. The leucocyte count increased significantly after vigorous exercise, correlating with a decrease in leucocyte ascorbic acid content.