Body fluids and exercise: Influences of nutrition and feeding management

Athletic performance may be initially enabled but then become limited by ch anges in body fluids. This subject is reviewed in three parts: physiologica l responses, replacement strategies, and the influences of nutrition and fe eding management. Emphasis on losses in sweat during strenuous exercise hav e focused attention on replacement of water and electrolytes, but the econo mies of water and energy are intertwined, so our interest should expand to the whole diet and its management. reed balanced for strenuous exercise mus t maximize the conversion of its potential chemical energy into kinetic mec hanical energy, and minimize waste such as feces, acid and heat. Research s uggests five efficiency promoting tentative features: strong cation-anion b alance (200-300 mEq/kg dry matter); modest protein (80-100 g/kg); ample veg etable oil (100- 120 g/kg); specified fibers (difficult to quantify simply) ; and a stress profile of other essential nutrients (tentatively 1.5- to 3- times higher than currently recommended on a digestible energy basis). In e ffect, such an ergogenic feed replaces starch and sugar with fat and fiber. A high fiber intake increases water intake, gut water and net water absorp tion during strenuous exercise. It also increases heat production and water needed for evaporation, bowel ballast and fecal water output. Feeding mana gement before an event involves the timing, size and nature of meals and wa tering. It should be adapted to the individual horse during training. Our l aboratory has developed two complete and balanced ergogenic feeds, one for the stall-kept athlete, the other for the horse on pasture. Use of high-eff iciency feeds like these should enhance the homeostasis of body fluids duri ng strenuous exercise.