Effect of exercise on Na and K concentrations in human saliva and serum

The effect of exercise on the salivary Na, K, and protein concentrations and on the serum Na and K concentrations has been studied in young men. The exercise consisted of a march of 2-hr duration. The exercise had no marked effect on the serum Na and K. The salivary Na concentration increased nearly twofold during exercise, and had decreased to its initial value within 2-hr recovery. No noteworthy changes in the salivary K concentration occurred during the experiment. The salivary protein concentration increased during exercise, and this increase was positively correlated with the increase in the salivary Na/K ratio in the same man. These results are ascribed to the increased permeability of the plasma-saliva barrier during the exercise.