Sodium Loss Varies By Runner

Physiologically speaking, we are all a little different. We respond to the stimulus of exercise in our own unique ways, and this includes how much sodium is lost through perspiration. A study published in the Journal of the International Society of Sports Nutrition shows the differences among 157 marathoners.
 
The 141 men and 16 women had patches on their arms to monitor sodium loss during the event. Women lost less sodium than men, and 20% of the male marathoners lost enough sodium to create an electrolyte imbalance. However, sweat electrolyte concentrations did not correlate with sweat rate, runner age, experience or training.