The reductions in gastrointestinal (GI) blood flow, gastric emptying rate, intestinal absorption, and GI barrier function, accompanying increases in GI symptoms, can occur, and dehydration likely exacerbates these problems. Intestinal perfusion studies in humans have found that exercise at intensities below -70%-80% maximal oxygen consumption (VO2max) appear to affect intestinal absorption of infused solutions. Very little research has studied the direct effect of dehydration during exercise on intestinal absorption. The overall effect during exercise would likely be a greater degree of hyper-thermia, increased cardiovascular strain, altered metabolic function, and central nervous system dysfunction. Increased GI temperature and reductions in GI blood flow will likely be exacerbated by dehydration further decreasing gastric emptying and, thus, intestinal absorption rates. GI symptoms can result from reduced gastric emptying, intestinal absorption, and GI barrier dysfunction that will likely inhibit fluid intake, also promoting higher core body temperatures and modified metabolism.