Physiological changes and gastro-intestinal complaints as a result of ultra-endurance running. - Rehrer,N.J.; Brouns,F.; Beckers,E.J.; Frey,W.O.; Villiger,B.; Riddoch,C.J.; Menheere,P.PCA.; Saris,W.HM. (Eur J Appl Physiol, 1992)