Almond, C., Shin, A., Fortescue, E., et al. (2005). Hyponatremia among Runners in the Boston Marathon. The New England Journal of Medicine. 352:1550-1556.
The authors studied a cohort of marathon runners to determine the incidence and risk factors of hyponatremia. They found that considerable weight gain while running, a long racing time, and body-mass-index extremes were associated with hyponatremia.